Alexander Szabo and Oscar Engle - Svenskt Vatten
Alexander Szabo and Oscar Engle - Svenskt Vatten
Alexander Szabo and Oscar Engle - Svenskt Vatten
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___________________________________________________________________________________<br />
Water <strong>and</strong> Environmental Engineering<br />
Department of Chemical Engineering<br />
<br />
Upgrading alternatives for a waste water<br />
treatment pond in Johor Bahru, Malaysia<br />
Master’s Thesis by<br />
<strong>Alex<strong>and</strong>er</strong> <strong>Szabo</strong> <strong>and</strong> <strong>Oscar</strong> <strong>Engle</strong><br />
August 2010<br />
<br />
<br />
__________________________________________________________________<br />
<strong>Vatten</strong>försörjnings- och Avloppsteknik<br />
Institutionen för Kemiteknik<br />
Lunds Universitet<br />
Water <strong>and</strong> Environmental Engineering<br />
Department of Chemical Engineering<br />
Lund University, Sweden<br />
Upgrading alternatives for a waste water treatment<br />
pond in Johor Bahru, Malaysia<br />
Master Thesis number: 2010-13<br />
<strong>Alex<strong>and</strong>er</strong> <strong>Szabo</strong> <strong>and</strong> <strong>Oscar</strong> <strong>Engle</strong><br />
Water <strong>and</strong> Environmental Engineering<br />
Department of Chemical Engineering<br />
April 2010<br />
Supervisor: Associate Professor Dr. Karin Jönsson<br />
Co-Supervisor: Associate Professor Dr. Azmi Bin Aris<br />
Examiner: Professor Jes la Cour Jansen<br />
Picture on Front Page:<br />
Inlet distribution pipe at Treatment Pond during de-sludging operation, UTM, Johor Bahru, Malaysia.<br />
_________________________________________________________________________________<br />
Postal address: Visiting address: Telephone:<br />
P.O. Box 124 Getingevägen 60 +46 46-222 82 85<br />
SE-221 00 Lund +46 46-222 00 00<br />
Sweden<br />
Telefax:<br />
+46 46-222 45 26<br />
Web address:<br />
www.vateknik.lth.se<br />
<br />
<br />
List of abbreviations<br />
BOD – Biochemical Oxygen Dem<strong>and</strong><br />
CFU – Coliform Forming Units<br />
COD – Chemical Oxygen Dem<strong>and</strong><br />
DO – Dissolved Oxygen<br />
HRT – Hydraulic Retention Time<br />
IWK – Indah Water Konsortium<br />
MLSS – Mixed liquor suspended solid<br />
P.E. – Population Equivalent<br />
UTM – Universiti Teknologi Malaysia<br />
TSS – Total Suspended Solids<br />
WSP – Waste Stabilization Pond<br />
i <br />
ii <br />
Summary<br />
Malaysia is developing fast <strong>and</strong> is striving to become a fully developed country by 2020. After<br />
independence in 1957 from Great Britain, Malaysia has gradually set up goals for its waste water<br />
management, which often goes together with economical development <strong>and</strong> growth. Most of the waste<br />
water treatment facilities built so far have been made simple <strong>and</strong> in form of treatment ponds, septic tanks<br />
<strong>and</strong> low flushing latrines. In this project a treatment pond at UTM in Johor Bahru has been analyzed. At<br />
present, the management of UTM is not satisfied with the treatment efficiency <strong>and</strong> is looking for options<br />
to upgrade the pond or replace it with an activated sludge system. The objective of this study is to propose<br />
an upgraded waste water treatment facility to the current treatment pond.<br />
The treatment pond consists today of two parallel lines, each line with a facultative pond followed by a<br />
maturation pond. After treatment the water is discharged to a stream close to the treatment pond. At two<br />
occasions in November 2009 <strong>and</strong> one occasion in January 2010 sampling <strong>and</strong> flow measurements were<br />
performed at the treatment pond. During each occasion sampling <strong>and</strong> flow measurements were made<br />
every second hour for 24 hours. This was made to get the characteristics <strong>and</strong> behavior of the waste water<br />
quality <strong>and</strong> the waste water flow. The samples were analyzed <strong>and</strong> the amount of Chemical Oxygen<br />
Dem<strong>and</strong> (COD), Biological Oxygen Dem<strong>and</strong> (BOD) <strong>and</strong> Total Suspended Solids (TSS) were measured.<br />
The analysis of the data shows that the concentration of COD, BOD <strong>and</strong> TSS is low. It seems there is a<br />
significant infiltration into the sewer network at UTM. This was confirmed by the flow measurements<br />
done at the inlet into the treatment pond. During rain events the influent flow is more than doubled <strong>and</strong><br />
this is something that must be considered when dimensioning a new treatment facility. It seems there is a<br />
possible misconnection between the stormwater network <strong>and</strong> the sewer network at UTM. During these<br />
peaks, the concentration of COD is more than doubled compare to the average COD entering the<br />
treatment pond. The high COD-values are confirmed by higher TSS values during these rain events. The<br />
exact reason for this is unknown but one possible explanation could be that the increased flow in the<br />
waste water pipes will catch <strong>and</strong> carry with it deposits from the sewage pipe. Another explanation could<br />
be that somewhere a stormwater channel is connected to the sewer pipes <strong>and</strong> the stormwater is carrying<br />
organic material from the ground into the pipes which ends up in the treatment pond.<br />
At late night the COD value is low but there is still a significant influent flow. This leads to the<br />
conclusion that the pipe is also taking in groundwater. Together with the increased influent flow during<br />
rain events <strong>and</strong> the high flow at night, the total infiltration is estimated to 60-90% of the total influent<br />
flow.<br />
From the data collected <strong>and</strong> analyzed three different solutions for better treatment efficiency have been<br />
proposed. One solution is an activated sludge system; another is upgrading the current pond by<br />
rearranging the water flow so that it flows in a series through all four treatment ponds. The third<br />
alternative is to add aeration to the upgraded treatment pond as calculations shows that the area is not<br />
sufficient <strong>and</strong> therefore it is overloaded. A review of the sewer <strong>and</strong> stormwater network should also be<br />
considered in order to find the possible misconnection between the stormwater <strong>and</strong> the sewer water.<br />
iii <br />
According to assumptions <strong>and</strong> calculations the activated sludge system will give the best treatment<br />
efficiency in terms of BOD, nitrogen <strong>and</strong> phosphorous removal. An activated sludge system will achieve<br />
st<strong>and</strong>ard A requirements according to Malaysian recommendations <strong>and</strong> according to Malaysian st<strong>and</strong>ard<br />
the activated-sludge system will have an footprint area of around 1 ha if the system receives water from<br />
more than 10 000 people. The current pond received waste water from around 10 500 people at the time<br />
this report was written.<br />
The treatment technology will however be comparatively expensive to build <strong>and</strong> run. An activated sludge<br />
system is also less effective, compared to the other suggested alternatives, in removing pathogens <strong>and</strong><br />
there may be a need for some pathogen removal device after activated-sludge treatment.<br />
The second suggestion to upgrade the current treatment pond does not achieve the same treatment<br />
efficiency as the activated sludge system. On the other h<strong>and</strong> it is less expensive to run <strong>and</strong> easier to<br />
maintain. It will also reduce pathogens more effectively than an activated sludge system. According to<br />
assumptions <strong>and</strong> calculations it will be wise to install oxygen generators as the upgraded treatment pond<br />
system is overloaded <strong>and</strong> the oxygen the algae produce is not sufficient for organic breakdown. If<br />
conservative assumptions <strong>and</strong> calculations are made the treated water will barely fulfill the requirements<br />
for Malaysian st<strong>and</strong>ard A, but at a low price. If optimistic assumptions are made, the treatment result will<br />
reach down just below st<strong>and</strong>ard A.<br />
Our recommendations are for financing reasons <strong>and</strong> for simplicity to keep the old treatment plant,<br />
improve it by installing screening, installing aeration <strong>and</strong> baffles <strong>and</strong> redirecting the flow from parallel<br />
flow to serial flow through all four treatment ponds.<br />
iv <br />
Acknowledgements<br />
This report is a result of a project which has been carried out both in Sweden <strong>and</strong> in Malaysia. In Sweden<br />
we were part of the Water <strong>and</strong> Environmental Engineering at the Department of Chemical Engineering<br />
where we started <strong>and</strong> completed our project. In Malaysia where the field study of our project was<br />
performed we were part of the Environmental Engineering at the Department of Chemical Engineering<br />
(IPASA).<br />
We are proud to participate in the cooperation between LTH in Sweden <strong>and</strong> UTM in Malaysia. We are<br />
only the “second generation” of Swedish students going away to this friendly <strong>and</strong> multicultural country.<br />
Therefore we would like to give our sincere greetings to Prof. Dato’ Ir. Dr. Zaini bin Ujang for<br />
introducing us to his university from his guest lectures in Sweden, spring 2009.<br />
A warm thanks goes to our supervisor in Sweden, Ass. Pr. Karin Jönsson, for her professional support<br />
<strong>and</strong> guidance during the whole project. Your help <strong>and</strong> feedback has made this project a lot easier <strong>and</strong> the<br />
project would not have been possible without your co-operation between LTH <strong>and</strong> UTM in Malaysia.<br />
We would like to give our supervisor in Malaysia Ass. Pr. Azmi Bin Aris our sincere greetings for his<br />
relentless help at IPASA in Malaysia. Your help <strong>and</strong> support at UTM was necessary for us in a<br />
completely new country <strong>and</strong> environment. We hope to see you again in the future, both in Malaysia <strong>and</strong> in<br />
Sweden.<br />
We are also very grateful to Civ. Eng. Rozlan Md Shariff for his support with maps <strong>and</strong> data of the<br />
treatment pond. A special thanks goes to PhD student Chow Ming Fai at IPASA for his help <strong>and</strong> support<br />
at the laboratory. We thank PhD student Mohd Noor Asyraf bin Amirruddin for his help with<br />
precipitation data from the university area. Another special thanks goes to the staff at IPASA for your<br />
service <strong>and</strong> helpfulness when we needed it the most.<br />
We are grateful to our examiner Prof. Jes la Cour Jansen for his useful viewpoints during our project.<br />
We wish to express our warm gratitude to Prof. Dr. Zulkifli Yusop for professional help <strong>and</strong> for<br />
introducing us further into the Malaysian gastronomy with its very tasteful dishes, especially the Satay<br />
chicken.<br />
Finally, we would like to thank Ångpanneföreningen, Helsingkrona nation, Rotary Ängelholm <strong>and</strong><br />
Lundabygdens sparbanks stiftelse for your financial support. Without your help this project would never<br />
had been possible to carry out.<br />
<strong>Alex<strong>and</strong>er</strong> <strong>Szabo</strong> <strong>and</strong> <strong>Oscar</strong> <strong>Engle</strong><br />
Lund, April 2010<br />
v <br />
vi <br />
Contents <br />
List of abbreviations...........................................................................................................................................iii<br />
Summary.............................................................................................................................................................iii<br />
Acknowledgements .............................................................................................................................................v<br />
1. Introduction ...................................................................................................................................................12<br />
1.2 Background .................................................................................................................................................12<br />
1.3 Objective......................................................................................................................................................15<br />
2. Waste Water Treatment Ponds Technology...............................................................................................16<br />
2.1 Introduction to Waste water treatment ponds ...........................................................................................16<br />
2.2 Pretreatment.................................................................................................................................................17<br />
Screening ...................................................................................................................................................17 <br />
Grit removal ..............................................................................................................................................17 <br />
2.3 Pond Types ..................................................................................................................................................17<br />
Anaerobic ponds .......................................................................................................................................17 <br />
Facultative Ponds......................................................................................................................................18 <br />
Maturation ponds ...................................................................................... Error! Bookmark not defined. <br />
Mechanically aerated ponds ..................................................................... Error! Bookmark not defined. <br />
2.4 Degradation processes ................................................................................................................................18<br />
Removal of pollutants in Waste water treatment ponds ......................................................................18 <br />
Aerobic degradation .................................................................................................................................18 <br />
Anaerobic degradation .............................................................................................................................19 <br />
Sedimentation...........................................................................................................................................19 <br />
Disinfection................................................................................................................................................19 <br />
3. Pond Hydraulics ............................................................................................................................................21<br />
3.1 Retention time .............................................................................................................................................21<br />
3.2 Complete-mix model ................................................................................ Error! Bookmark not defined.<br />
3.3 Plug flow.................................................................................................... Error! Bookmark not defined.<br />
3.4 Dispersed flow........................................................................................... Error! Bookmark not defined.<br />
3.5 Hydraulic design ....................................................................................... Error! Bookmark not defined.<br />
Short Circuiting........................................................................................... Error! Bookmark not defined. <br />
Building several ponds in series................................................................ Error! Bookmark not defined. <br />
Baffles ......................................................................................................... Error! Bookmark not defined. <br />
vii <br />
4. Activated sludge process technology......................................................... Error! Bookmark not defined.<br />
Introduction to activated sludge process technology............................. Error! Bookmark not defined. <br />
Primary treatment ..................................................................................... Error! Bookmark not defined. <br />
Biological treatment .................................................................................. Error! Bookmark not defined. <br />
Nitrification <strong>and</strong> denitrification ................................................................ Error! Bookmark not defined. <br />
Chemical treatment ................................................................................... Error! Bookmark not defined. <br />
Activated sludge system – arrangements ................................................ Error! Bookmark not defined. <br />
Sludge treatment ......................................................................................................................................21 <br />
5. Previous studies on WSP systems...............................................................................................................23<br />
5.1 Example of computer simulation of WSP geometry ................................................................................23<br />
5.2 Facultative <strong>and</strong> maturation ponds in Sri Pulai, Johor Bahru, Malaysia. .................................................25<br />
5.3 Previous Study on the studied treatment pond at UTM............................................................................26<br />
6. Study Area ....................................................................................................................................................27<br />
6.1 Climate.........................................................................................................................................................27<br />
6.2 The waste water treatment facilities at UTM ............................................................................................27<br />
6.3 Recipient......................................................................................................................................................28<br />
Introduction...............................................................................................................................................28 <br />
Sampling procedure for lake water .........................................................................................................29 <br />
Results <strong>and</strong> discussion ..............................................................................................................................30 <br />
7. Sampling <strong>and</strong> analysis methods ...................................................................................................................31<br />
Sampling <strong>and</strong> flow measurements....................................................................................................................31<br />
COD ...................................................................................................................................................................31<br />
BOD 5 ..................................................................................................................................................................32<br />
8. Water flow <strong>and</strong> quality .................................................................................................................................37<br />
Sampling procedure for effluent water...................................................................................................37 <br />
De‐sludging conditions .............................................................................................................................37 <br />
BOD 5 <strong>and</strong> COD in effluent.........................................................................................................................37 <br />
TSS in effluent ...........................................................................................................................................38 <br />
Average effluent values............................................................................................................................40 <br />
Algae in effluent........................................................................................................................................40 <br />
Reduction in pond system........................................................................................................................40 <br />
Survey of waste water producers at UTM campus ................................................................................41 <br />
viii <br />
Waste water production in the catchment area ....................................................................................42 <br />
Water velocity measurements.................................................................. Error! Bookmark not defined. <br />
Influent water flow ...................................................................................................................................45 <br />
Total influent water flow..........................................................................................................................46 <br />
Infiltration..................................................................................................................................................46 <br />
Conclusions concerning infiltration .......................................................... Error! Bookmark not defined. <br />
Sampling procedure for influent water...................................................................................................48 <br />
BOD 5 <strong>and</strong> COD in influent water..............................................................................................................48 <br />
Total Suspended Solids in influent water................................................................................................50 <br />
Dimensioning values.................................................................................................................................51 <br />
Degradation rate of BOD ..........................................................................................................................53 <br />
9. Proposals for upgrading of the treatment system........................................................................................56<br />
Alternative 1: Upgrading of existing WSP......................................................................................................56<br />
Alternative 2: Upgrading of existing WSP – Partly aerated pond ............... Error! Bookmark not defined.<br />
Alternative 3: Conventional activated-sludge treatment plant ..................... Error! Bookmark not defined.<br />
Screening device ........................................................................................ Error! Bookmark not defined. <br />
Grit chamber .............................................................................................. Error! Bookmark not defined. <br />
Equalization tank........................................................................................ Error! Bookmark not defined. <br />
Primary settling tank.................................................................................. Error! Bookmark not defined. <br />
Activated sludge tank ................................................................................ Error! Bookmark not defined. <br />
Secondary settling tank ............................................................................. Error! Bookmark not defined. <br />
Sludge h<strong>and</strong>ling.......................................................................................... Error! Bookmark not defined. <br />
Sludge to energy ........................................................................................ Error! Bookmark not defined. <br />
Disinfection................................................................................................. Error! Bookmark not defined. <br />
10. Discussion on the upgrading alternatives ................................................ Error! Bookmark not defined.<br />
11. Conclusion................................................................................................. Error! Bookmark not defined.<br />
12. Future work ............................................................................................... Error! Bookmark not defined.<br />
13. References ................................................................................................. Error! Bookmark not defined.<br />
14. Appendix ................................................................................................... Error! Bookmark not defined.<br />
<br />
ix <br />
x <br />
XI <br />
1. Introduction<br />
1.2 Background<br />
Malaysia is developing rapidly <strong>and</strong> the government has set up goals for becoming a fully<br />
developed country by 2020. This will put more strains on the environment <strong>and</strong> the keyword is<br />
therefore sustainable development (Liew, 2008). With an increasing population <strong>and</strong> a more waterdem<strong>and</strong>ing<br />
society more waste water is produced. Waste water can have a negative impact on the<br />
population, the economy <strong>and</strong> the environment if it is not managed in a wise way. Therefore<br />
Malaysia is trying to develop a system for waste water h<strong>and</strong>ling which is both sustainable <strong>and</strong><br />
suitable for the country’s specific conditions. The complexities <strong>and</strong> unique environment of<br />
Malaysia prevent the adoption of a “carbon copy” development that has been successful in other<br />
countries.<br />
Malaysia is considered to be a good case study example for other developing countries because of<br />
its many experiences with different waste water solutions. The government <strong>and</strong> the authorities<br />
have tried to implement decentralized on-site systems such as septic tanks <strong>and</strong> latrines in rural<br />
<strong>and</strong> semirural areas. Other implemented systems have been centralized conventional treatment<br />
plants in urban areas (Ujang & Henze, 2006). The development of institutions <strong>and</strong> financial<br />
solutions for waste water systems in Malaysia could also serve as a good study example for many<br />
developing countries.<br />
The first sewerage policy in Malaysia was created during the British occupation at the end of the<br />
19 th century. During this period the so-called Sanitary Boards were organized in Malaysia’s major<br />
cities <strong>and</strong> provided services like water supply, latrines, irrigation etc. The Boards were however<br />
only responsible for waste water <strong>and</strong> sanitary problems concerning British settlers (Ujang &<br />
Henze, 2006). After Independence in 1957, sewerage facilities were administrated by the<br />
Environmental Health <strong>and</strong> Engineering unit. The unit belonged to the Ministry of Health created<br />
in the 1960’s (Ujang & Henze, 2006). The unit initiated a successful program in which pour-flush<br />
latrines were implemented in rural <strong>and</strong> semirural areas. A pour-flush toilet utilize small amounts<br />
of water (around 2-3 litres) to pour down human excreta deposit in a pit latrine (UNEP, n.d.). The<br />
excreta are poured down into a tank where the organic material is decomposed. The sludge<br />
collected in the tank has to be emptied on a regular basis.<br />
Pour-flushed toilets were also installed in urban areas but in these areas the unit tried to adopt a<br />
more conventional sewage approach found in the industrialized world. Due to a lack of finances<br />
<strong>and</strong> a well developed national framework for waste water management the implementation was<br />
slow. In many cases the drawings <strong>and</strong> plans for the treatment plants remained on the bookshelves.<br />
A significant step in Malaysia’s waste water management was taken in 1974 when the<br />
government established the Environmental Quality Act which was the first national legal<br />
framework for regulating the quality of effluent water from sewage <strong>and</strong> industries (Ujang &<br />
Henze, 2006). In 1980 the Malaysian Parliament implemented a new law where developers of<br />
new housing areas with more than 30 houses were required to provide proper sewage treatment. It<br />
was favored to keep the new treatment facilities as simple as possible. In order to keep the<br />
<br />
12
treatment facilities simple, treatment ponds or Imhoff tanks were usually implemented. The idea<br />
was that after one year of utilization, the responsibility for running <strong>and</strong> maintaining the treatment<br />
facilities was transferred to the municipal authorities. However, not every local authority had the<br />
resources to run the centralized treatment facilities <strong>and</strong> as a result centralized treatment systems<br />
grew only from 3.5% in 1970 to 5% in 1990. This can be compared to septic tanks coverage in<br />
urban areas which grew from 17.2% in 1970 to 37.3% in 1990 (Ujang & Henze, 2006).<br />
In 1993 a new law, the Sewage Service Act, was implemented <strong>and</strong> a new Federal agency, the<br />
Sewage Service Department was established. The main task of the new agency was to plan,<br />
regulate <strong>and</strong> control sewage water treatment. Since 1993 the agency has been responsible for the<br />
national privatization project <strong>and</strong> in 1993 Indah Water Konsortium (IWK) was given the task to<br />
operate <strong>and</strong> maintain existing treatment facilities (Ujang & Henze, 2006). The reason for<br />
privatizing was to assist the Sewage Service Department with maintenance of existing sewage<br />
systems, refurbishment of old systems <strong>and</strong> constructions of new sewage systems in urban areas<br />
(Ujang & Henze, 2006).<br />
At the moment there are two st<strong>and</strong>ards for treated waste water quality, according to the<br />
Environmental Quality Act from 1974. Every treatment system must comply with either st<strong>and</strong>ard<br />
A or st<strong>and</strong>ard B. St<strong>and</strong>ard A is used if the water is discharged upstream of any raw water intake<br />
<strong>and</strong> St<strong>and</strong>ard B is used when water is discharged downstream of a raw water intake (Sewerage<br />
Services Department, 1998). The most important parameters of treated waste water to be<br />
followed are Biochemical Oxygen Dem<strong>and</strong> over a period of 5 days (BOD 5 ) <strong>and</strong> total suspended<br />
solids (TSS). No discharge of treated waste water higher than the absolute values are permitted by<br />
the law. Because of fluctuations in the quality of the treated waste water, the effluent waste water<br />
quality should be designed to reach a lower “design” value (Table 1.1). This is to ensure that the<br />
effluent waste water quality never reach above the absolute values. The permitted limits for<br />
St<strong>and</strong>ard A <strong>and</strong> St<strong>and</strong>ard B can be seen in Table 1.1 below.<br />
Table 1.1: Malaysian Design values for BOD 5 <strong>and</strong> TSS for treated effluent waste water quality. (redrawn<br />
from Sewerage Services Department, 1998)<br />
Parameter St<strong>and</strong>ard A St<strong>and</strong>ard B<br />
Absolute Design Absolute Design<br />
BOD 5 (mg/l)<br />
TSS 2 (mg/l)<br />
20 10<br />
50 20<br />
50 20<br />
100 40<br />
During the project the effluent st<strong>and</strong>ard from 1974 was changed. It came to our knowledge after<br />
all the sampling from the pond was done that a new st<strong>and</strong>ard was introduced in December 2009.<br />
The new st<strong>and</strong>ard is similar to the one of 1974. The permitted limits for BOD 5 <strong>and</strong> TSS levels are<br />
unchanged. The main difference is the introduction of nitrogen <strong>and</strong> phosphorous removal<br />
(Department of Environment, 2009). Because no measurements of nitrogen <strong>and</strong> phosphorous was<br />
not done we will mostly use St<strong>and</strong>ard A <strong>and</strong> St<strong>and</strong>ard B from 1974 throughout the report. For<br />
more information about the new effluent st<strong>and</strong>ard see Table C.1 in Appendix C.<br />
<br />
13
In this project, a treatment pond built in 1985 at the Universiti Teknologi Malaysia (UTM) has<br />
been studied. Figure 1.1 below shows where UTM is situated. The treatment pond was originally<br />
built for a population of 8 000 P.E. but is currently treating waste water from around 10 500 P.E.<br />
from the university area. The treatment pond consists of two parallel lines each treating equal<br />
amounts of waste water. The treated water is discharged to a small stream next to the treatment<br />
pond. The current discharged waste water is not complying with St<strong>and</strong>ard A according to<br />
Malaysian requirements. At the moment the pond is only complying with st<strong>and</strong>ard B quality<br />
which is a lower quality st<strong>and</strong>ard for treated waste water. The university would like to upgrade<br />
the treatment facility so that it can comply with Malaysian St<strong>and</strong>ard A requirements as the water<br />
downstream is used for canoeing by UTM students. The idea is that a new treatment facility could<br />
also be used for educational purposes for students from the university. Moreover, an improved<br />
treatment facility at the university also goes h<strong>and</strong> in h<strong>and</strong> with Malaysia’s national goals to reach<br />
a more effective <strong>and</strong> better management of waste water.<br />
In order to get a deeper underst<strong>and</strong>ing of the water quality <strong>and</strong> its flow characteristics to the<br />
current treatment pond, sampling <strong>and</strong> different kinds of measurements have been performed. The<br />
obtained information is important as the result of the samples <strong>and</strong> measurements will be used as a<br />
basis when designing an improved <strong>and</strong> more effective treatment facility.<br />
Figure 1.1: Map of Malaysia <strong>and</strong> the location of UTM, Johor Bahru. (Reuterwall & Thorén, 2009)<br />
<br />
14
1.3 Objective<br />
The objective of this master thesis project is to propose <strong>and</strong> evaluate upgraded waste water<br />
treatment facilities which can improve the treated effluent waste water quality at Universiti<br />
Teknologi Malaysia. A new treatment facility should have a footprint area of 25% compared to<br />
the present treatment pond, as the area around the current treatment pond is planned for<br />
recreation. The upgraded treatment facilities must also be able to perform a better treatment of the<br />
waste water compared to the system used today. The requirement is that the effluent can comply<br />
with an effluent of St<strong>and</strong>ard A quality according to Malaysian directives.<br />
<br />
15
2. Waste Water Treatment Ponds Technology<br />
2.1 Introduction to Waste water treatment ponds<br />
Waste water treatment ponds are used around the world for treatment of municipal waste water.<br />
They can offer a good alternative where l<strong>and</strong> prices are low <strong>and</strong> where the climate is beneficial.<br />
Since there is a general relationship between growth rate of bacteria <strong>and</strong> algae that contribute to<br />
the treatment of waste water, pond systems in a warmer climate benefit from high temperatures.<br />
A pond system can be built easily <strong>and</strong> does not require much maintenance. Since it can hold large<br />
quantities of water, it has a good resistance to shock loads <strong>and</strong> hazardous substances that may<br />
enter the system.<br />
A typical arrangement of waste water treatment ponds consists of a primary facultative pond<br />
followed by one or multiple maturation ponds. Under some conditions it is also possible to use an<br />
anaerobic pond before the facultative pond (see Figure 2.1).<br />
Figure 2.1: In this figure three possible arrangements for pond system are illustrated. The first two<br />
series illustrates a primary facultative pond (F) followed by one or two maturation ponds (M). The<br />
third pond series illustrates an anaerobic pond (A) followed by a facultative pond <strong>and</strong> finally a<br />
maturation pond (<strong>Szabo</strong> & <strong>Engle</strong>, 2010).<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
16
2.2 Pretreatment<br />
<br />
Screening<br />
The purpose of a screening device, which is located before the treatment pond, is to remove<br />
coarse materials like pieces of plastic <strong>and</strong> woods etc. The material caught <strong>and</strong> removed from the<br />
screen is often of inorganic characteristics <strong>and</strong> hard to break down biologically in the treatment<br />
pond. The coarse material can also damage pumps <strong>and</strong> aerators used in the subsequent treatment<br />
stages.<br />
It is recommended that the water velocity through the screen should be less than 1 m/s so coarse<br />
material will be able to stick between the screens (Mara, 2003). The space between the bars<br />
should be between 15-25 mm (Mara, 2003). If the flow is above 1000 m 3 /day mechanical screens<br />
which automatically remove the captured objects should be used instead of screens that have to<br />
be maintained manually. This is because mechanical screens can be cleaned more frequently. It is<br />
although wise to have a screen that could be cleaned by h<strong>and</strong> as a back-up for the mechanical<br />
screen in case the mechanical screen would stop working. The waste products collected from the<br />
screen can be taken to the nearest l<strong>and</strong>fill or be incinerated.<br />
Grit removal<br />
Grit is made up of heavier <strong>and</strong> smaller particles (often of inorganic characteristics) like glass,<br />
s<strong>and</strong> eggshells etc. Grit can damage pumps <strong>and</strong> aerators in the subsequent treatment steps <strong>and</strong><br />
should be removed before the treatment pond if the waste water contains large quantities.<br />
Before water enters the screen <strong>and</strong> the treatment pond, the waste water may flow in long grit<br />
channels where the water passes through at a desired velocity. The heavier grit particles will settle<br />
in the channel as the waste water flows through. The grit channels are made up of two parallel<br />
channels so one of the channels can be closed for grit removal. A possible problem with a grit<br />
channel is that it is difficult to keep the velocity at a constant level (Mara, 2003). <br />
2.3 Pond Types<br />
Anaerobic ponds<br />
Anaerobic ponds operate without the presence of algae or oxygen, <strong>and</strong> have an advantage over<br />
the facultative pond since they can deal with higher organic loading. They can reduce the organic<br />
load by 40 to 70% with a retention time of only a few days (Shilton et al., 2005).<br />
Methane (CH 4 ) <strong>and</strong> sulphide (H 2 S) are gasses that are produced under anaerobic conditions.<br />
Methane gas may be considered as a fuel resource if collected, but if not collected as a<br />
greenhouse gas, contributing to the climate change as it escapes into the atmosphere from the<br />
pond. If sulphide is produced <strong>and</strong> released, it is not appreciated since it is releases a bad odor. If<br />
the anaerobic pond is not properly design, or when overloaded, the release of sulphide may be<br />
problematic for people living in the surroundings (Mara, 2003). This is confirmed by a study at<br />
Lee Summit WSP, Missouri, where odor nuisance occurred after the load was increased above the<br />
pond capacity (McKinney, 1968).<br />
<br />
17
Facultative Ponds<br />
The main features of the facultative ponds are that they are horizontally divided into two layers,<br />
with <strong>and</strong> without oxygen presence. In the top layer (down to 20 - 30 centimeters of depth)<br />
photosynthesis makes micro-algae produce oxygen during daytime, the oxygen is then used by<br />
aerobic bacteria to degrade organic substrate. Some of the oxygen in the top layer has its origin<br />
from surface mass transfer, but it has been estimated that more than 80% of the oxygen is<br />
produced by algae (Shilton et al., 2005). The depth of oxygen presence in the water is changing<br />
<strong>and</strong> depends on many factors such as sunlight, water turbidity <strong>and</strong> organic loading (Shilton et al.,<br />
2005). In the bottom of the pond, no dissolved oxygen is available, which gives anaerobic<br />
bacteria opportunities to degrade substrate. The retention time of facultative ponds is relatively<br />
large, up to several weeks. The long retention time <strong>and</strong> the shallow design, typically depth is 1.5<br />
meters, make the ponds consume relatively large l<strong>and</strong> areas (Mara, 2003).<br />
Since the light needed for the algae arrives through the surface, facultative ponds are usually<br />
designed by surface loading. In temperate climates, algae are more productive in terms of oxygen<br />
production <strong>and</strong> the pond may therefore receive a higher loading of BOD. Eq. 2.1 (Mara, 2003) is<br />
used to calculate the maximum possible BOD loading per area:<br />
λ = 350∗(rtial-mix system (EPA, 2002). Since the aeration in a complete mix pond keeps large<br />
quantities of suspended solids mixed in the pond, a following post-settling pond should be<br />
installed. Partial-mix aeration may be installed into an existing facultative pond to improve the<br />
overall treatment efficiency.<br />
2.4 Degradation processes<br />
<br />
Removal of pollutants in Waste water treatment ponds<br />
The nature is capable to degrade human waste water when it is released into waterways. Problems<br />
occur when the load on our natural environment is bigger than the self-cleansing mechanisms<br />
available in our lakes <strong>and</strong> rivers. The more populated the world becomes, the higher the stress on<br />
our environment. The waste water treatment ponds are cleaning the water using the same<br />
processes as in nature. The task of the waste water treatment ponds is to optimize <strong>and</strong> isolate the<br />
processes, so that the cleaning has been done before the water is released in our waterways. In<br />
nature several processes are responsible for the treatment of polluted water, <strong>and</strong> these processes<br />
should be used <strong>and</strong> optimized as much as possible. Some of nature’s processes will be discussed<br />
in this section.<br />
Aerobic degradation<br />
When oxygen is present in water, aerobic microorganisms will use oxygen to oxidize organic<br />
compounds <strong>and</strong> produce carbon dioxide (CO 2 ), water <strong>and</strong> biomass (sludge). Since oxygen is<br />
consumed by the degradation, the process will be limited by the presence of oxygen. If large<br />
quantities of organic material are to be degraded, large amounts of oxygen must be supported. In<br />
<br />
18
the case of waste water treatment ponds, the algae are the main producers of oxygen (Shilton et<br />
al., 2005). Since the algae are only present in the upper part of a pond, it is difficult to achieve<br />
aerobic decomposition through an entire pond. There are however more advanced pond systems<br />
where algae are mixed through the water to oxygenate larger volumes. In mechanically aerated<br />
ponds, oxygen is pumped or mixed into the water which will achieve high dissolved oxygen<br />
levels. The disadvantage of mechanical oxygen support is that it consumes large amounts of<br />
energy.<br />
Aerobic degradation in waste water treatment ponds requires larger volumes <strong>and</strong> a longer<br />
retention time then the conventional activated sludge-systems, because the concentrations of<br />
active biomass, containing the microorganisms, are much lower.<br />
Anaerobic degradation<br />
When no oxygen is available, anaerobic degradation may occur by anaerobic microorganisms.<br />
The benefit of anaerobic digestion is that it can deal with highly concentrated waste water <strong>and</strong> can<br />
achieve good purification results within short retention times. The process is temperature<br />
dependent <strong>and</strong> will, if properly designed, reduce the BOD concentrations by 40% at 10°C, 60% at<br />
20°C <strong>and</strong> 70% at 25°C (Shilton et al., 2005). The anaerobic pond should be installed as the first<br />
treatment step, when the load of waste water is the highest. The high load of organic matter<br />
would inhibit the presence of algae. A typical anaerobic pond receives more than 3000 kg<br />
BOD/ha/day, whereas facultative ponds should not receive more than 400 kg BOD 5 /ha/day in<br />
order to sustain a healthy algal population (Mara, 2003).<br />
Sedimentation<br />
Large amounts of settleable <strong>and</strong> flocculated colloidal materials that enter the pond will settle to<br />
the bottom of the pond <strong>and</strong> create a sludge layer as the water speed declines. Independent of<br />
whether the particles settle in an anaerobic or facultative pond, the environment, within the<br />
formed sludge layer, will be anaerobic. Even maturation ponds, which are at the last step of the<br />
treatment, may produce a thin anaerobic sludge layer at the bottom. The sludge layer is broken<br />
down anaerobically <strong>and</strong> thickens over time. Gases (methane <strong>and</strong> carbon dioxide) that result from<br />
the degradation arises up though the water <strong>and</strong> escapes into the atmosphere. It is estimated that up<br />
to 30% of the BOD load disappears as gas (Shilton et al., 2005).<br />
Disinfection<br />
There are several factors within a WSP that together contribute to the removal of illness-causing<br />
bacteria, viruses, worms <strong>and</strong> protozoan parasites. It is however difficult to exactly evaluate the<br />
contribution to the disinfection effect from a single factor, since the processes within a WSP are<br />
both complex <strong>and</strong> dynamic. Factors that are known to contribute to disinfection are sunlight (UV)<br />
exposure, pH, temperature, algal toxins, sedimentation <strong>and</strong> hydraulic retention time (Shilton et<br />
al., 2005). The WSP:s are generally considered very good at removal of pathogens (Maynard et<br />
al., 1999). Research about disinfection shows treatment results from 26 WSP:s around the world<br />
(see Table H.1, Appendix H). The reduction performance of pathogens in WSP systems is<br />
<br />
19
generally better than conventional mechanical treatment combined with activated sludge (George<br />
et al., 2002).<br />
Sunlight (UV) is considered to be the most important factor for disinfection (Davies-Colley et al.,<br />
2000). UV disinfection is complex since different wavelengths affects different species in various<br />
ways. Some reactions with certain species required dissolved oxygen dependent photo-oxidations.<br />
In these cases, oxygen is crucial for the performance (Davies-Colley et al., 2000).<br />
<br />
20
3. Pond Hydraulics<br />
3.1 Retention time<br />
When dimensioning a pond, the water flow behavior is crucial. One of the key parameters is the<br />
“retention time”, or “hydraulic retention time” HRT, which occurs as a key parameter in almost<br />
every calculation. The retention time tells us how long the water, on average, stays within the<br />
pond. The formula for retention time is:<br />
θ= pollutant concentration (mg/l)<br />
r is in the form of ammonium (ay be necessary to add. There is also extra sludge produced from<br />
this method.<br />
Sludge treatment<br />
Sludge created from waste water treatment could easily become a public-health hazard if not<br />
h<strong>and</strong>led properly. What to do with the sludge is today considered as one of the main problems in<br />
waste water treatment. Still, there are several methods to choose from when selecting<br />
<br />
21
arrangements which can process sludge. A careful selection of the sludge-treatment method has to<br />
be made, as costs for stabilization, dewatering <strong>and</strong> disposal of sludge may be higher than the<br />
operating cost for the activated-sludge treatment (Hammer, 1986).<br />
In Malaysia facilities for treating sludge are limited <strong>and</strong> today most of the sludge is treated in<br />
sludge lagoons or dried on large sludge-drying beds. Only in semirural areas are these methods<br />
seen as long term solutions. A more long-term solution for urban areas would be to install<br />
digesters <strong>and</strong> mechanical dewatering facilities. Then the gas produced from the digestion<br />
chamber could be captured <strong>and</strong> utilized as fuel.<br />
According to Malaysian st<strong>and</strong>ards presented in Sewerage Services Department (1998) a sludge<br />
strategy consists of three main stages:<br />
Stage 1 – Preliminary treatment <strong>and</strong> digestion<br />
Stage 2 – Conditioning <strong>and</strong> dewatering<br />
Stage 3 – Utilization <strong>and</strong> disposal<br />
In stage 1, the sludge can be thickened in a centrifuge in order to increase the dry-solids content.<br />
After the sludge has been thickened, it is sent to an aerobic or anaerobic digestion chamber.<br />
In stage 2, the stabilized sludge is dewatered in a filter press <strong>and</strong> the dry-solids content in the<br />
sludge is raised to more than 25% (Sewerage Services Department, 1998). Sludge lagoons or<br />
drying beds can also be used in rural areas.<br />
In stage 3, a sludge tank which can h<strong>and</strong>le sludge for more than 30 days must be provided<br />
(Sewerage Services Department, 1998). The final step is composting or disposal of the sludge.<br />
The treated sludge can for example be utilized as fertilizers on fields.<br />
<br />
22
5. Previous studies on WSP systems<br />
5.1 Example of computer simulation of WSP geometry<br />
In a test which was executed at Alex<strong>and</strong>ria University, Egypt by Abbas et al. (2006), different<br />
length/width ratios for a WSP were tested in a computer program in order to determine the<br />
degradation of BOD <strong>and</strong> the amount of dissolved oxygen. In reality, there are always a lot of<br />
parameters affecting the treatment pond which the engineers cannot control, for example<br />
temperature variations, amount of sunlight <strong>and</strong> wind speed. In the computer model these<br />
parameters were set to a constant value. The hydraulic model was assumed to be of dispersed<br />
flow characteristics.<br />
The influent waste water had the following characteristics: BOD concentration 300 mg/l, DO<br />
concentration 0.0 mg/l <strong>and</strong> 150 kg/(ha*day) in surface organic loading rate of BOD. The<br />
retention time was set to 31 days, the inflow was set to 0.18 m 3 /s <strong>and</strong> the pond depth to 1.5 meter.<br />
The water is assumed to move through the pond as completely mixed (Abbas et al., 2006) (see<br />
chapter 3.2). The simulation was executed for the four different length/width ratios which can be<br />
seen in Figure 5.1 below.<br />
<br />
23
Figure 5.1: Different shapes of the waste stabilization pond simulated in the computer program<br />
(Abbas et al., 2006).<br />
For each shape, simulations were also executed with 2 or 4 baffles. The baffles will change<br />
parameters such as the retention time <strong>and</strong> the flow path in the waste stabilization pond. The<br />
retention time is changed because the water velocity is changed through the pond. In Figure 5.2<br />
an example of the 4 ponds with 2 baffles can be seen.<br />
Figure 5.2: A schematic representation of each shape with two baffles (printed with permission from<br />
Abbas et al., 2006).<br />
The effluent amount of BOD 5 was calculated for the different length/width ratios L 1 /L 2 =1, 2, 3<br />
<strong>and</strong> 4. In the first case, simulations were executed for different length/width ratios with no<br />
baffles. The same procedure was then done for each shape with two <strong>and</strong> four baffles respectively.<br />
In Table 5.1 the values of BOD 5 , DO <strong>and</strong> water velocity can be seen from the simulations.<br />
Table 5.1: The amount of BOD <strong>and</strong> DO in effluent water (re-drawn from Abbbas et al.,2006)<br />
<br />
Without<br />
baffles<br />
With two<br />
baffles<br />
With four<br />
baffles<br />
Range of BOD 5 concentration found in effluent water<br />
(mg/l) 235-252 22-233 13-54<br />
Range DO found in effluent water (mg/l) 0.26-0.51 6.24-9.96 9.57-10.03<br />
Range of minimum water velocity (x 10 -3 m/s) 0.002-0.015 0.018-0.91 0.047-0.05<br />
Range of maximum water velocity (x 10 -3 m/s) 2.69-3.01 3.19-169 105-765<br />
The analysis of the results shows that the BOD 5 reduction increases significantly by introducing<br />
two or four baffles. The best removal efficiency of BOD 5 was achieved with four baffles <strong>and</strong> a<br />
<br />
24
value of 4:1 in length/width ratio. Within each case it was reported that increasing the<br />
length/width ratio <strong>and</strong> introducing baffles slightly increases the water velocity <strong>and</strong> DO in the<br />
effluent water (Abbas et al., 2006). The conclusion drawn from these data simulations is that a<br />
pond should have a length/width ratio of 4:1 <strong>and</strong> at least two baffles.<br />
5.2 Facultative <strong>and</strong> maturation ponds in Sri Pulai, Johor Bahru,<br />
Malaysia.<br />
An analysis of the performance of a waste water stabilization pond in Sri Pulai, Johor Bahru was<br />
done in 2002. The treatment system uses a primary facultative pond followed by a maturation<br />
pond (Ujang et al., 2002). This is the same pond arrangement as used at UTM. The system in Sri<br />
Pulai serves a population equivalent (P.E.) of 10 327 from a residential area of approximately 0.7<br />
km 2 . The ponds together cover an area of 17.725 m 2 , with pond volumes of 16.275 m 3 for the<br />
facultative pond <strong>and</strong> 10 115 m 3 for the maturation pond. The volume of the facultative pond<br />
should result in a retention time of about 30 days. Around 40 % of the incoming water is assumed<br />
to origin from infiltrating ground water (Ujang et al., 2002).<br />
Table 5.2: Average waste water characteristics at Sri Pulai WSP. The influent results is based on 24<br />
samples, the results from the effluent facultative pond <strong>and</strong> the effluent maturation pond is based on<br />
14 respectively 7 samples. (re-drawn from Ujang et al., 2002)<br />
COD (mg O 2 / SS (g/l) NH 4 -N (mg/l) NO 3 -N (mg/l)<br />
l)<br />
Influent<br />
Effluent facultative pond<br />
446<br />
139<br />
146<br />
48<br />
23.1<br />
19.7<br />
1.5<br />
1.6<br />
Effluent maturation pond<br />
114<br />
41 16.8<br />
1.2<br />
Removal in entire pond<br />
system<br />
74% 72% 27%<br />
20%<br />
Removal in facultative pond<br />
Removal in maturation pond<br />
69%<br />
18%<br />
67%<br />
15%<br />
15%<br />
15%<br />
- 7%<br />
25%<br />
Compared with the effluent st<strong>and</strong>ard for Malaysia, the treatment process was not sufficient, since<br />
the total COD concentration of the effluent was on average 114 mg O 2 /l (see Table 5.2). The<br />
Malaysian effluent st<strong>and</strong>ard B is set to 100 mg COD/l (Ujang et al., 2002).<br />
The authors´ conclusion of the unexpected low treatment efficiency (the pond should be able to<br />
meet st<strong>and</strong>ard B) could partly be caused by hydraulic short-circuiting. The low treatment<br />
efficiency could also be caused by the specific growth rates of biological degrading bacteria not<br />
being so temperature dependent as expected. The authors recommended aeration <strong>and</strong> installation<br />
of baffles to improve the treatment.<br />
<br />
25
5.3 Previous Study on the studied treatment pond at UTM<br />
In year 1999, an under-graduate report was produced by Zahari <strong>and</strong> Zain (Faculty of Civil<br />
Engineering, UTM) analyzing the same WSP at UTM. The report is written in Malay language,<br />
<strong>and</strong> our focus has been on the waste water composition data found in this report. The<br />
measurements have been conducted without flow measurements, hence, the results only represent<br />
average values, that is the values were not weighted against the influent water flow. When the<br />
waterflow into the treatment pond is high, it is likely that more BOD, COD <strong>and</strong> TSS will end up<br />
in the pond, <strong>and</strong> this is not considered in the report. The results from Zahari <strong>and</strong> Zain can be<br />
found in appendix A.<br />
<br />
26
6. Study Area<br />
<br />
6.1 Climate<br />
Johor Bahru lies in a tropical region very close to the equatorial line with temperatures ranging<br />
between 21 to 32°C all year around. The climate is humid with an average relative humidity<br />
around 90% (Richmond et al., 2007). The precipitation comes in form of short but heavy rain<br />
showers <strong>and</strong> the average rainfall in Johur Bahru is around 2400 mm each year (World<br />
Meteorological organization, n.d.). The rainiest periods are from March to May when Johor<br />
Bahru is influenced by the southwest monsoon <strong>and</strong> November to December when the northeast<br />
monsoon arrives.<br />
As Johor Bahru lies in a region with a typical tropical climate with heavy thunderstorms, the<br />
storm water is usually not connected to the waste water treatment systems. This is also the case at<br />
UTM where the storm water is led through channels <strong>and</strong> ditches directly to the local rivers.<br />
6.2 The waste water treatment facilities at UTM<br />
Within the Universiti Teknologi Malaysia, two waste stabilization pond facilities <strong>and</strong> two<br />
mechanical-biological treatment plants are in operation. The pond system this report will focus on<br />
is located south-west of the UTM campus area (see Figure 6.1) <strong>and</strong> it is treating the waste water<br />
from the western part of the catchment area in UTM (see Appendix D). These WSP’s were built<br />
in 1985. The mechanical-biological treatment plants were built later, as the university exp<strong>and</strong>ed.<br />
<br />
27
Figure 6.1: Map over the UTM campus area with (1) The WSP studied in this report (2) another<br />
WSP within UTM; (3) biological-mechanical treatment plant; (Another campus area <strong>and</strong> treatment<br />
plant is located in the north-east, outside the map) (<strong>Szabo</strong> & <strong>Engle</strong>, 2010)<br />
The treatment system that this report will focus on consists of two parallel lines of facultative<br />
ponds followed by maturation ponds (Figure 6.2). The available documents do not tell for how<br />
many persons the ponds are dimensioned for, but according to the contractor for de-sludging<br />
operation, this pond system was built to serve approximately a P.E. of around 8 000. The pond<br />
system is a simple construction, where the influent waste water is divided in a chamber before it<br />
enters each treatment line through pipes located under the water surface. The ponds have no<br />
screening <strong>and</strong> objects of many different sizes have been seen floating in the pond. These objects<br />
have a tendency to clog the cannels between the ponds. Since the water level of the receiving<br />
river is higher than the effluent level, a pumping station is located between the pond <strong>and</strong> the river.<br />
The pumps are currently working discontinuously, <strong>and</strong> during the time when the pumps are not<br />
pumping, the ponds accumulate waste water beyond the designed water levels. The technical data<br />
of the pond system can be found in Appendix G.<br />
Figure 6.2: Shape of pond system with facultative ponds (1) followed by maturation ponds (2)<br />
(<strong>Szabo</strong> & <strong>Engle</strong>, 2010).<br />
6.3 Recipient<br />
<br />
Introduction<br />
The effluent from the WSP is released into a stream passing through the UTM area (Figure 6.3).<br />
The stream transforms into two small lakes a few hundred meters downstream, where the main<br />
entrance to UTM is located (see Figure 6.4). In these small lakes, canoeing activities take place<br />
which dem<strong>and</strong>s good water quality. The part of water that origin from the WSP is large compared<br />
to the upstream river water. Most of the water in the lakes is therefore considered mainly to be<br />
effluent water from the WSP.<br />
<br />
28
Figure 6.3: The receiving river. Upstream (left) <strong>and</strong> downstream (right) of WSP (<strong>Szabo</strong> & <strong>Engle</strong>,<br />
2010).<br />
Sampling procedure for lake water<br />
Composite samples were collected consisting of 3 samples upstream <strong>and</strong> 3 samples downstream<br />
the WSP on the 14 th of January 2010. The samples were analyzed for COD <strong>and</strong> TSS according to<br />
the procedures described in chapter 7. The points where the three composite samples upstream<br />
<strong>and</strong> downstream were collected can be seen in 6.4.<br />
<br />
29
Figure 6.4: Map over recipient with upstream collection points (1) <strong>and</strong> downstream collection points<br />
(2) (<strong>Szabo</strong> & <strong>Engle</strong>, 2010).<br />
Results <strong>and</strong> discussion<br />
<br />
Figure 6.5: The water quality upstream <strong>and</strong> downstream of WSP on the 14 th of January 2010.<br />
The COD <strong>and</strong> TSS levels are lower downstream of the WSP (Figure 6.5). The stream has not<br />
received any effluent from any kind of treatment facility before passing the WSP. The initial<br />
COD may origin from pollution caused by living organisms such as fishes, birds <strong>and</strong> algae. The<br />
high TSS increase downstream may be the result of the treated waste water, but also from high<br />
concentration of algae <strong>and</strong> bottom sediments stirred up in the stream.<br />
Due to limitations in time <strong>and</strong> the cost for COD reagents, focus has been set on influent <strong>and</strong><br />
effluent water. These values are single analyses of composite samples <strong>and</strong> should only be<br />
considered to give an indication of the changes of pollution levels in the river. To reach a better<br />
<br />
30
accuracy (the accuracy of a single analysis is low) of the COD <strong>and</strong> TSS levels upstream <strong>and</strong><br />
downstream of the pond, more sampling is needed. The COD <strong>and</strong> TSS levels may also fluctuate<br />
over the time, both upstream <strong>and</strong> downstream of the pond.<br />
Another aspect that must be considered is the accuracy of the COD-reagents. The accuracy <strong>and</strong><br />
precision with Hach’s COD tests are around 5-10% <strong>and</strong> can be even higher if the sample contains<br />
suspended solid (Boyles, 2007). It is possible that the sample analyzed from the stream contained<br />
suspended solids (particle size of 1-100 µm).<br />
<br />
<br />
<br />
<br />
7. Sampling <strong>and</strong> analysis methods <br />
Sampling <strong>and</strong> flow measurements<br />
The sampling procedure included filling plastic containers (each about 1 liter of volume) with<br />
sample water from the influent chamber <strong>and</strong> one container with water from the effluent channel.<br />
The samples were immediately transported to the laboratory where they were stored in a cooling<br />
room (temperature between 10-13 °C).The following day the analyses of BOD <strong>and</strong> COD was<br />
started. TSS analyses were usually carried out a few days after the sampling. The procedure for<br />
flow measurements is described in Chapter 8.<br />
COD<br />
COD analyses have been undertaken with Hach st<strong>and</strong>ard procedure for colorimetric<br />
determination. The Hach reagents used were capable of “high range” (0-1500 mg COD/l). The<br />
digestions of the reagents were done in a Hach DRB 200 for 2 hours at 150 °C (see Figure 7.1).<br />
The analysis has been done with single samples.<br />
The reading of the Hach COD reagents was done in a Hach DR/4000 <strong>and</strong> a Hach DR/5000 (see<br />
Figure 7.1). The average values from both machines were calculated.<br />
<br />
31
colorimetric<br />
Figure 7.1: Hach DRB 200 Digestor for reagents (left) <strong>and</strong> Hach DR/5000 for<br />
determination (right) (<strong>Szabo</strong> & <strong>Engle</strong>, 2010).<br />
If the reading showed unexpected low or high values for a specific sample, a new analysis on that<br />
sample was done the following day. If the new analysis gave the same result, the average of these<br />
values was used. If another value, that was in the same range as the other samples from that<br />
measuring event, was measured, that value was used instead.<br />
BOD5<br />
Influent samples from the 5-6 November were successfully analyzed by the incubator method.<br />
The effluent samples from that day were analyzed by the manual method due to lack of available<br />
space in the incubator. Samples from the other testing events failed due to technical problems, or<br />
are not used as they are considered unreliable.<br />
Incubator method<br />
<br />
32
BOD analyzes were carried out using a BOD incubator (Hach, model 205) which is especially<br />
designed for BOD tests. The sampling bottles are connected with a tube (for oxygen<br />
measurements) <strong>and</strong> put in a compartment that keeps the temperature at 20 °C. A computer<br />
records the oxygen consumption over time. The procedure was performed according to the<br />
product manual. One benefit of the BOD incubator is that it allows reading of the oxygen<br />
consumption (BOD) continuously (instead of only a final measurement after 5 days as the<br />
“manual” procedure described above). For calculations of the k-value (Appendix E) readings<br />
were recorded with 0.5 days intervals (Appendix F).<br />
One full testing event with the BOD incubator was successful. Other testing events failed due to<br />
technical problems with the BOD incubator or lack of available storage space in the fridge where<br />
the incubator was.<br />
Manual method<br />
The “manual” measuring of BOD 5 is done with the following procedure:<br />
‐ Filing 300 ml airtight bottles with diluted waste water (The purpose of diluting the<br />
samples was to reach a DO above 7 mg O 2 / liter, which may be necessary for a<br />
successful BOD reading after 5 days, as the DO must be above 2 mg O 2 / liter at final<br />
reading. Dilution 1:1 with distilled water was enough for this purpose).<br />
‐ Measuring the initial DO level in the samples with a DO meter.<br />
‐ Storing the bottles in a refrigerator at 20 °C for 5 days.<br />
‐ Measuring the final DO with a DO meter.<br />
<br />
The BOD 5 was calculated as the decrease of DO per liter of water.<br />
This method was considered as slightly unreliable as the reading of the DO meters was difficult.<br />
The DO measured DO concentration was not stable over time, hence making it difficult to<br />
measure the final DO.<br />
<br />
<br />
33
Total Suspended Solids<br />
TSS analyses were made by filtering 100 ml of sampling through a microfilter (Whatman, GF/C<br />
glasfaser microfilter). In order to force the sampling water through the filter, an air compressor<br />
was used to create low pressure in the bottle receiving the filtered water (see Figure 7.2). The<br />
filters were measured before <strong>and</strong> after filtering. To eliminate the weight contribution of water, the<br />
filters were dried in an oven at around 110°C for one hour after filtering, but before final<br />
measuring.<br />
Figure 7.2: Sample water was filled in the upper glass container. The air compressor (right in the<br />
picture) created a low pressure in the receiving container (containing filtered water in the picture)<br />
(Sxabo & <strong>Engle</strong>, 2010).<br />
<br />
<br />
<br />
34
<br />
35
<br />
36
8. Water flow <strong>and</strong> quality<br />
Sampling procedure for effluent water<br />
Effluent samples were collected every two hours from the pond outlet at the 5-6 November, 18-19<br />
November <strong>and</strong> 9-10 January. From the samples made COD, BOD <strong>and</strong> TSS were analyzed. Since<br />
the ponds have large volumes <strong>and</strong> the retention time is several days, the effluent quality does not<br />
change drastically during a time span of a few hours. Therefore, for 5-6 November <strong>and</strong> 9-10<br />
January, composite samples were created from three effluent samples under approximately a 6<br />
hour period. This was done in order to reduce work <strong>and</strong> costs in the laboratory. The analysis<br />
procedures are described in chapter 7.<br />
De-sludging conditions<br />
The treatment efficiency is dependent on the sludge, since the sludge contains bacteria that<br />
degrade pollutants in the waste water. If the sludge has been removed recently, the system may<br />
operate ineffectively due to the lack of bacteria. If however, the sludge has accumulated for a<br />
long period, the volume of the sludge will reduce the HRT in the pond system, hence making the<br />
treatment less effective. One can assume that the best treatment occurs somewhere in the middle<br />
between the de-sludging operations.<br />
The WSP (north treatment line) was de-sludged after the first measurements were done on the 5-6<br />
November 2009. During de-sludging one treatment line at a time is closed down. The waste water<br />
is pumped out <strong>and</strong> the accumulated sludge from the bottom of the ponds is removed. The desludging<br />
operation takes a few weeks to be completed <strong>and</strong> is done with 10 year intervals. On the<br />
9-10 January 2010, the WSP had been in operation, after de-sludging, for about 2 weeks when the<br />
samples were collected. The average effluent COD was 64 mg/l before <strong>and</strong> 58 mg/l after desludging<br />
(see Figure 8.1 <strong>and</strong> 8.2). The average BOD 5 for 5-6 November was 39 mg/l BOD 5 on<br />
average (Figure 8.1).<br />
Since the samples were collected just before <strong>and</strong> after de-sludging, the results presented above<br />
may be slightly higher than during most of the operation time. Zahari & Zain (1999) showed in<br />
their report an average effluent of 40 mg/l COD (see Appendix A) which is approximately 30%<br />
better than the results in this report. This could be due to the sludge conditions discussed above.<br />
BOD 5 <strong>and</strong> COD in effluent<br />
The quality of the effluent water is relatively stable (see Figure 8.1 <strong>and</strong> 8.2). Variations may<br />
depend on sunlight that changes the concentrations of algae in the surface layer. Another factor to<br />
consider is the effluent pump that is working discontinuously where the treated waste water is<br />
released to the small stream when the waterlevel in the ponds has reached a certain level (more<br />
information about the pumping effect is discussed on page 36).<br />
<br />
37
Figure 8.1: BOD 5 <strong>and</strong> COD in effluent from the northern treatment line on the 5-6 November 2009<br />
(before de-sludging).<br />
Figure 8.2: COD in effluent from the northern treatment line on the 9-10 January 2010 (after desludging).<br />
TSS in effluent<br />
The TSS levels are higher <strong>and</strong> show a different pattern after the de-sludging was carried out. The<br />
average TSS on the 5-6 November was 37 mg/l (Figure 8.3), but 22 mg/l on the 9-10 January<br />
(Figure 8.4). The reason for lower TSS values after de-sludging may be caused by many reasons.<br />
One reason is the fact that if the ponds had high levels of sludge, the volume of water in the<br />
ponds decreased, hence creating less retention time <strong>and</strong> higher water flow, which disturbs the<br />
settling process. If the sludge reaches a high level from the bottom of the pond, the distance<br />
between the top sludge layer <strong>and</strong> outlet channel gets narrower <strong>and</strong> more solid particles may get<br />
<br />
38
stirred up. The algae population may not have developed entirely after the de-sludging, <strong>and</strong> since<br />
algae contribute to the effluent TSS values, it could be another possible explanation.<br />
For the composite value analyzed on the 9-10 January, between 00-04, it can be seen that it is<br />
significantly lower than the other values from this date (Figure 8.4). One possible reason could be<br />
that a pump station is located just after the outlet where the effluent samples were taken. The<br />
pumps are working discontinuously <strong>and</strong> start when the water reaches a specific height in the<br />
treatment pond. When the pumps start operating, the effluent water flow increases drastically.<br />
This causes differences in the water quality <strong>and</strong> the measured changes of effluent quality over<br />
time may therefore have been influenced by the unknown pumping pattern.<br />
Figure 8.3: Total Suspended Solids (TSS) in the effluent on the 5-6 November 2009.<br />
Figure 8.4: Total Suspended Solids (TSS) in the effluent on the 9-10 January 2010.<br />
<br />
39
Average effluent values<br />
The average weighted effluent from 5-6 November, 9-10 January <strong>and</strong> average values from Zahari<br />
& Zain, (1999) give the total average values seen in table 8.1. The values from the report by<br />
Zahari & Zain, (1999) may represent “better” sludge conditions in the pond, hence lowering the<br />
average level of pollutants (data is available in Appendix A).<br />
Table 8.1: Effluent average values.<br />
BOD 5 (mg/l) COD (mg/l) TSS (mg/l)<br />
5-6 November 39 64 37<br />
9-10 January 29 58 22<br />
Zairi & Zain (1999) 16 40 13<br />
Average 28 54 24<br />
Algae in effluent<br />
Algae are present in the effluent <strong>and</strong> are known to contribute to the effluent COD <strong>and</strong> BOD. The<br />
water showed clear signs of microalgae in every effluent sample analyzed. In order to underst<strong>and</strong><br />
the contribution of particles to the effluent COD, one test was carried out with filtered <strong>and</strong><br />
unfiltered composite effluent water from 9-10 January 2010 (see Figure 8.5).<br />
Figure 8.5: Unfiltered <strong>and</strong> filtered composite effluent water (from all 12 samples 9-10 Jan 2010).<br />
<br />
The unfiltered effluent had a COD level of 57 mg/l <strong>and</strong> the same filtered effluent 27 mg/l. The<br />
difference between unfiltered <strong>and</strong> filtered (suspended COD) made therefore up 30 mg/l COD.<br />
Since it has been observed that the quantity of algae in the effluent is prominent, algae are<br />
assumed to contribute to a major part of the 30 mg/l COD difference.<br />
Reduction in pond system<br />
In Tables 8.2 <strong>and</strong> 8.3 below the reduction of average COD <strong>and</strong> average TSS from the samplings<br />
made on the 5-6 November, 2009 <strong>and</strong> on the 9-10 January, 2010 is shown.<br />
<br />
40
Table 8.2: Influent (weighted COD average against the influent water flow, see chapter 10.2) <strong>and</strong><br />
effluent COD values.<br />
Date Influent COD (mg/l) Effluent COD (mg/l) Reduction<br />
5-6 Nov, 2009 122 64 48%<br />
9-10 Jan, 2010 113 58 49%<br />
Table 8.3: Influent (weighted TSS average, see chapter 10.2) <strong>and</strong> Effluent TSS values.<br />
Date Influent TSS (mg/l) Effluent TSS (mg/l) Reduction<br />
5-6 Nov, 2009 63 37 41%<br />
9-10 Jan, 2010 47 22 53%<br />
Survey of waste water producers at UTM campus<br />
Construction drawings over the area were used to identify the sewage pipes connected to the<br />
WSP. The chief engineer at UTM helped to identify the outer borders of the catchment. The<br />
amounts of students <strong>and</strong> staff living <strong>and</strong> studying/working within the catchment were identified<br />
by consulting housing <strong>and</strong> university offices. Some assumptions have been made where no<br />
information could be found about the number of people living <strong>and</strong> working in buildings<br />
connected to the treatment pond (for more information of the estimation of P.E., see Appendix<br />
B).<br />
The number of students <strong>and</strong> staff working within the faculties at UTM were given a P.E. of 0.2<br />
instead of 1 (Sewerage Services Department, 1998) as they do not consume as much water at the<br />
faculties as they would have done at home, thus lowering the P.E. value.<br />
Outside UTM campus there are private family houses where the sewerpipes are connected to the<br />
studied treatment pond. The number of people living in each household is not exactly known so it<br />
was estimated that each household consists of 5 family members.<br />
Other buildings connected to the treatment pond where no information of the number of residents<br />
could be given were the UTM Main Office <strong>and</strong> the Mosque. The number of staff in the UTM<br />
Main Office was assumed to be 500 <strong>and</strong> the number of people visiting the Mosque could be up to<br />
3000 people. The P.E. for the people working <strong>and</strong> visiting the buildings was set to 0.2 in both<br />
cases (Sewerage Services Department, 1998).<br />
The water consumption for UTM’s students is based on a value collected from a report by<br />
Katimon <strong>and</strong> Demun (2004). The report concludes that the average water consumption for UTM<br />
is 260 litres/(person*day). This value is higher than the average value of 208 liter/(person*day)<br />
for the rest of Malaysia (Ithnin, 2007).<br />
The reason for the higher consumption according to our proposition could be:<br />
1. Students <strong>and</strong> staff at UTM have a more water consuming behavior, such as more showering<br />
<strong>and</strong> more use of laundry facilities.<br />
2. Leakage of fresh water from delivery pipes.<br />
A third proposition by Katimon <strong>and</strong> Demun (2004) for the higher water consumption at UTM is:<br />
<br />
41
3. Water intensive faculties at UTM, such as the Environmental Engineering Laboratory <strong>and</strong><br />
Marine Engineering Laboratory, consume large quantities of water.<br />
When estimating the water consumption behavior of UTM the value from Katimon <strong>and</strong> Demun<br />
(2004) of 260 litres/(person*day) is initially used. The water consumption <strong>and</strong> waste water<br />
production is normally of equal amount if no irrigation occurs. At UTM it was observed that<br />
washing machines, cooking facilities <strong>and</strong> students’ laundry in some cases were not connected to<br />
the sewer network so the final waste water production behavior of UTM will be lower than 260<br />
litres/(person*day).<br />
Waste water production in the catchment area<br />
The pond receives waste water from around 10 500 persons according to the survey (see<br />
Appendix B). No factories or other similar activities are present within the catchment. Hence, the<br />
waste water is pure domestic.<br />
If the value of 260 litres/(person*day) from Katimon <strong>and</strong> Demun (2004) is used the waste water<br />
flow into the pond can be calculated:<br />
=10 500 . . 260 /( ∗ )= 2730 t home at campus. The sampling period<br />
started at 17:30 on the 5 th of November but unfortunately there were no flow measurements made<br />
from the first three sample occasions that day due to technical problems. The first flow<br />
measurement started at 23:00 which can be seen in Figure 8.7. The flow decreased at night <strong>and</strong><br />
increased slightly in the morning. From 13:00 to 16:00 a rainstorm started which can be seen in<br />
Figure 8.7 in the precipitation data from UTM’s own rain gauge. In connection to the rainstorm<br />
there was a significant increase of the flow.<br />
<br />
42
Figure 8.8: Above: The water velocity in the inlet chamber for the northern treatment line of the<br />
WSP system during 5-6 November. Below: Precipitation data at site (UTM weather station data)<br />
<br />
Measurements 1819 November 2009 <br />
“Holiday period” <br />
The second measurement period was from the 18 th to the 19 th of November. During this period it<br />
is estimated that approximately two third of the population had left the UTM campus for<br />
vacation. The monsoon had arrived <strong>and</strong> there was rainfall almost every day from the beginning of<br />
November to the beginning of January. The measurements started at 12:30 on the 18 th of<br />
November <strong>and</strong> continued every second hour until 10:00 the next day. A rainstorm started at<br />
around 15:00 on the 18 th of November <strong>and</strong> continued more than one hour. During this period<br />
there is a huge increase in the influent flow. When the rain stops the influent flow is decreasing<br />
rapidly. The flow continues decreasing until late night <strong>and</strong> starts increasing in the morning. The<br />
behavior of the influent flow <strong>and</strong> precipitation data can be seen in Figure 8.8. During this<br />
measurement, only one line of the WSP was in operation, hence the velocity is the double<br />
compared to the flow measurements from 5-6 November.<br />
<br />
43
Figure 8.9 (above): The water velocity in the inlet chamber for the southern treatment line of the<br />
WSP during 18-19 November 2009. Below: Precipitation data at site (UTM weather station data).<br />
<br />
Measurements 910 January 2010 <br />
Weekend <br />
The last flow measurements were made from the 9 th of January to the 10 th of January 2010, during<br />
the weekend from Saturday to Sunday. The first measurements started at 12:00 a.m. on the 9 th of<br />
January <strong>and</strong> continued every second hour to 10:00 a.m. on the 10 th of January. This was the first<br />
flow measurement period with no rain <strong>and</strong> thus no significant flow peak connected to a rain<br />
event. From the afternoon on the 9 th of January the flow decreases gradually <strong>and</strong> in the evening<br />
the flow goes up distinctly. The influent flow reaches a maximum at 20:00 <strong>and</strong> goes thereafter<br />
down during the night. During the morning on the 10 th of January the flow increases slightly<br />
again. The behavior of the flow characteristics from this period can be seen in Figure 8.9.<br />
<br />
44
Figure 8.10: The water velocity in the inlet chamber for northern treatment line of the WSP system<br />
9-10 January 2010. No rainfall occurred during the measurements 9-10 January 2010.<br />
Influent water flow<br />
Figure 8.11: The inlet waste water flow to the WSP system. The designed flow is made to fill the gap<br />
between the measurements during 5-6 Nov.<br />
* On the 5-6 of November <strong>and</strong> 9-10 of January, the total flow is assumed to be twice the flow in<br />
one inlet, since there are two inlets with equal amounts of water.<br />
* On the 18-19 of November, there was only one line <strong>and</strong> one chamber in use. However, some<br />
leakage to the closed line occurred except at the last measurement at 10 a.m., when workers<br />
managed to stop the leakage. The leakage was measured to 9 l/s <strong>and</strong> is considered when<br />
calculating the flow from 18-19 November.<br />
<br />
45
Total influent water flow<br />
The total inflow for 5-6 November has been calculated with Eq. 8.5 where the peak-flow during<br />
the rain is included <strong>and</strong> Eq. 8.6 where the peak-flow during the rain is excluded. The total inflow<br />
for 18-19 November has been calculated with Eq.8.7 where the peak-flow during the rain is<br />
included <strong>and</strong> Eq. 8.8 where the peak-flow during the rain is excluded. The total inflow for 9-10<br />
January has been calculated with Eq. 8.5 <strong>and</strong> since there was no precipitation during this<br />
measuring period no rain peaks has been considered. Average inflow quantity to the pond each<br />
day will be based on Q tot with rain from 5-6 November, 18-19 November <strong>and</strong> Q tot without rain<br />
from 9-10 January. The results can be seen in Table 8.4.<br />
Table 8.4: Calculated total influent waterflow into the pond system for one day. *Partly using<br />
designed values. ** Rainfall peaks excluded (on the 5-6 November designed values are used).<br />
Date<br />
5-6 Nov<br />
Q tot<br />
With rain<br />
(m 3 /day)<br />
6346*<br />
Q tot<br />
Without rain<br />
(m 3 /day)<br />
5428**<br />
Q max<br />
(m 3 /s)<br />
0.190<br />
Q min<br />
(m 3 /s)<br />
0.039<br />
Q Average<br />
With rain<br />
(m 3 /s)<br />
0.073*<br />
Q Average<br />
Without rain<br />
(m 3 /s)<br />
0.058**<br />
18-19 Nov<br />
7527<br />
6617**<br />
0.203<br />
0.059<br />
0.087<br />
0.077**<br />
9-10 Jan<br />
No rainfall<br />
5526<br />
0.085<br />
0.049<br />
No rainfall<br />
0.064<br />
Infiltration<br />
High infiltration of groundwater into the sewer pipes is a common problem. Sewers may leak<br />
waste water out of the pipes or infiltrate groundwater into the sewer pipes, depending on the<br />
water content of the surrounding soil. It has been observed during our measurements that there is<br />
a flow of waste water even in late night or early morning even during vacation periods. The waste<br />
water flow drastically increases during rain events, <strong>and</strong> the waste water strength is weak (diluted).<br />
This is an evidence of infiltration into the pipes. The extra infiltrating water is mostly unwanted<br />
since it dem<strong>and</strong>s bigger tanks, or ponds, <strong>and</strong> to some degree will make the treatment less<br />
effective. However, one benefit is that since the water is already diluted, it may be easier to meet<br />
the requirements for discharging the water.<br />
Three different approaches have been used to find the amounts of infiltrating water.<br />
<br />
46
Method 1: Estimation of domestic water consumption<br />
If one assumes that the average contribution of waste water per capita is 208 l/day, <strong>and</strong> the<br />
number of people is known to be 10 500, the infiltration may be calculated (see Table 8.5).<br />
Table 8.5: Estimation of infiltrating water, taking total water flow <strong>and</strong> assumed domestic water<br />
consumption into consideration. **Assumes all inhabitants present. *Assumes only 1/3 of students<br />
<strong>and</strong> staff present due to holiday.<br />
Date<br />
Measured total<br />
inlet water<br />
during 24h (m 3 )<br />
Assumed<br />
Domestic water<br />
consumption (m 3 )<br />
Infiltration (Total<br />
– Domestic)<br />
(m 3 )<br />
Amount of<br />
infiltration in<br />
pipes<br />
5 – 6 Nov 6346 2184** 4162 66%<br />
18 – 19 Nov 7527 728* 6799 90%<br />
9 – 10 Jan 5526 2184** 3342 60%<br />
Method 2: Calculating base flow <strong>and</strong> rain peaks<br />
The lowest flow measured during night times is considered as base flow. At this time (lowest<br />
flow usually occurred between 04:00 a.m. <strong>and</strong> 06:00 a.m.) the water is considered to be purely<br />
infiltrated water. The contribution from rainfall has been excluded according to Eq. 8.5 <strong>and</strong> Eq.<br />
8.6 respectively.<br />
Table 8.6: Calculations of infiltration by using baseflow <strong>and</strong> peak flow.<br />
Date<br />
Measured total<br />
inlet water during<br />
24h (m 3 )<br />
Total inlet water<br />
without base-flow<br />
<strong>and</strong> rain peak (m 3 )<br />
Infiltration<br />
(Base<br />
flow+Rainpeak)<br />
(m 3 )<br />
5 – 6 Nov 6346 2028 4318 68%<br />
18 – 19 Nov 7527 1559 5968 79%<br />
9 – 10 Jan 5526 1275 4251 77%<br />
Amount of<br />
infiltration in<br />
pipes<br />
Method 3: Calculating the COD dilution in waste water<br />
The load per capita is assumed to be 120 g COD per day (Kemira, 2004). With assumed fresh<br />
water consumption it is possible to estimate the theoretical concentration of COD in the waste<br />
water.<br />
<br />
47
COD concentration, theoretical=er channels contributes with 60-90% of the total incoming<br />
water to the WSP. It can be seen on the velocity measurements that soon after the rainfall occur,<br />
the flow speed increases rapidly. As the rainfall ends, the flow tends to go down quickly. On the<br />
18-19 of November, most students left UTM for holiday. Approximately one half to two thirds of<br />
all students were not at the University during these measurements. Despite this, both Q max <strong>and</strong><br />
Q min (Table 8.4) were higher during the holiday than during the school period. This could be<br />
explained by that the monsoon period started just after the measurements on the 5-6 November,<br />
but before the 18 th of November. More or less every day received heavy rainfalls which could<br />
have raised the groundwater level, thus creating more infiltration into the sewer system. Since the<br />
storm water channels are built to receive all the storm water, no additional water should enter the<br />
sewage network. If the infiltrated water could be reduced, the HRT in the WSP would increase,<br />
hence improving the treatment efficiency. An unavoidable effect of reducing the infiltration is the<br />
increase in concentrations of pollutants in the waste water. It is however preferable to receive<br />
smaller quantities of waste water, even if the concentrations of pollutants are higher, since with<br />
effective reduction the total load of pollutants on the recipient will be lower than with diluted<br />
waste water.<br />
Sampling procedure for influent water<br />
The influent water was collected every two hours during the measurement periods. Samples were<br />
withdrawn from the inlet chamber <strong>and</strong> immediately taken to the laboratory <strong>and</strong> stored in a<br />
refrigerator.<br />
The first sampling started 5 th November at 17:30 <strong>and</strong> continued every second hour until 14:15 the<br />
next day. The second sampling started at 12:30 a.m. on the 18 th of November <strong>and</strong> continued every<br />
second hour until 10:00 a.m. the next day. The third sampling started at 12:00 a.m. on the 9 th of<br />
January <strong>and</strong> continued every second hour to 10:00 a.m. the 10 th of January.<br />
From all these samplings days COD, BOD 5 <strong>and</strong> TSS were analyzed according to the methods<br />
described in chapter 7. From the samples 5-6 November k-values were analyzed. Since the<br />
measurements during 5-6 November lacks flow data between 17:30 <strong>and</strong> 22:00, a designed flow<br />
was created <strong>and</strong> used in order to get complete measuring data <strong>and</strong> to calculate weighted<br />
parameters (see Figure 8.10).<br />
BOD 5 <strong>and</strong> COD in influent water<br />
The inlet COD concentrations show a tendency to rise when people use water consuming<br />
facilities at most, usually in the morning <strong>and</strong> late afternoon. When water flow increases due to<br />
rainfall, the COD values peaks <strong>and</strong> reaches levels much higher than during normal flow. At late<br />
night or early morning (04:00-06:00) all three sampling periods reach their lowest values (12 mg/l<br />
– 33 mg/l) (Figure 8.11). The pattern of COD concentrations is lower during the holiday period,<br />
which is explained by the lower load due to absence of students in combination with infiltration.<br />
According to Mara (2003), a COD concentration of less than 400 mg/l is considered as “weak<br />
strength”. This water is therefore placed into this category.<br />
From the first sampling period 5-6 November, BOD 5 from all 12 measurements were analyzed.<br />
For all 12 measurements that period, COD was also analyzed. This was done in order to get a<br />
<br />
48
atio between BOD 5 <strong>and</strong> COD for the waste water entering the pond. In Figure 8.12 COD- <strong>and</strong><br />
BOD 5 -values have been plotted.<br />
Figure 8.12: The inlet COD concentration during three 24-hours measurements.<br />
Figure 8.13: BOD 5 <strong>and</strong> COD concentration values in inlet to the WSP during 5-6 November 2009.<br />
Ratio BOD 5 /COD in Inlet<br />
By using the samples from the 5-6 November, the average ratio between the BOD 5 <strong>and</strong> COD<br />
values are 0.5 (see Table 8.8 below). This value will be used to estimate BOD 5 when only COD<br />
values are available.<br />
<br />
49
Table 8.8: Measured BOD 5 <strong>and</strong> COD on the 5-6 Nov 2009. Relationship<br />
BOD 5 /COD is calculated from average values. The ratio BOD 5 /COD at 05:00<br />
is not considered because of an invalid value.<br />
Time: COD (mg/l) BOD 5 (mg/l) Ratio BOD 5 /COD<br />
17:00 120 58 0.48<br />
19:00 77 35 0.45<br />
22:00 62 36 0.58<br />
23:00 79 41 0.52<br />
01:00 72 54 0.75<br />
03:00 48 29 0.60<br />
07:00 46 39 0.85<br />
09:00 126 76 0.60<br />
11:00 222 63 0.28<br />
13:00 148 66 0.45<br />
14:15 195 89 0.46<br />
<br />
Average: 102 51 <br />
Ratio = 0.5 <br />
Total Suspended Solids in influent water<br />
<br />
50
Figure 8.14: Above: TSS concentrations from all three measurements periods from influent waste<br />
water to the WSP. Below: Rain data collected from UTMs weather station. It can be observed that<br />
the TSS on the 5-6 November <strong>and</strong> 18-19 November are directly affected by the precipitation.<br />
The TSS trend tends to be highly affected by rainfall (see Figure 8.13). The peak at 08:00 on the<br />
9-10 Jan is not related to any rainfall <strong>and</strong> the cause is unknown. The same sample showed an<br />
unusual high COD-value as well the TSS result is considered as valid.<br />
Dimensioning values<br />
TSS<br />
For all 12 waste water samples collected on 5-6 November 2009, 18-19 November 2009 <strong>and</strong> 9-10<br />
January the maximum <strong>and</strong> minimum TSS-value has been tabulated in Table 8.9 below. From the<br />
flow data collected an average weighted TSS value <strong>and</strong> total load per day has been calculated.<br />
Table 8.9: Measured TSS-values on 5-6 November 2009, 18-19 November 2009 <strong>and</strong> 9-10<br />
January<br />
2010.<br />
* Partly based on designed flow<br />
Maximum Minimum Weighted Total load per<br />
5-6 Nov<br />
18-19 Nov<br />
9-10 Jan<br />
Average value<br />
(mg/l)<br />
150<br />
210<br />
193<br />
(mg/l)<br />
11<br />
1<br />
2<br />
average (mg/l)<br />
63*<br />
52<br />
47<br />
54<br />
day (kg)<br />
401*<br />
389<br />
261<br />
350<br />
COD<br />
For all 12 waste water samples collected on 5-6 November 2009, 18-19 November 2009 <strong>and</strong> 9-10<br />
January the maximum <strong>and</strong> minimum COD-value has been tabulated in Table 8.10 below. From<br />
<br />
51
the flow data collected an average weighted COD-value <strong>and</strong> total load per day has been<br />
calculated.<br />
Table 8.10: Measured COD on 5-6 November 2009, 18-19 November 2009 <strong>and</strong> on 9-10 January 2010.<br />
*Partly based on designed flow<br />
Maximum (mg/l) Minimum (mg/l) Weighted<br />
average<br />
(mg/l)<br />
5-6 Nov<br />
18-19 Nov<br />
9-10 Jan<br />
Average value<br />
222<br />
381<br />
390<br />
23<br />
12<br />
23<br />
122*<br />
112<br />
113<br />
116<br />
Total load per<br />
day (kg)<br />
775*<br />
841<br />
626<br />
747<br />
<br />
BOD5 <br />
For all 12 waste water samples collected on 5-6 November the maximum <strong>and</strong> minimum BOD 5 -<br />
values has been tabulated below. Because there is no data for BOD 5 on 9-10 November 2009 <strong>and</strong><br />
on 9-10 January 2010 the BOD 5 from these measurements are estimated by using the<br />
BOD 5 /COD-ratio from 5-6 November 2009. From the flow data collected an average weighted<br />
BOD 5 value has been calculated in order to calculate the total BOD 5 load per day. The values can<br />
be seen in Table 8.11 on the next page.<br />
<br />
52
Table 8.11: Measured BOD 5 on 5-6 Nov 2009 <strong>and</strong> estimated BOD 5 on 18-19 Nov 2009 <strong>and</strong> 9-10 Jan<br />
2010.<br />
* Partly based on designed flow<br />
** Based on estimated BOD 5 -ratio<br />
Maximum (mg/l) Minimum (mg/l) Weighted<br />
average<br />
(mg/l)<br />
5-6 Nov<br />
18-19 Nov<br />
9-10 Jan<br />
Average<br />
<br />
89<br />
191**<br />
195**<br />
26<br />
6**<br />
12**<br />
59*<br />
56**<br />
57**<br />
57<br />
Total load per<br />
day<br />
(kg)<br />
371*<br />
421**<br />
314**<br />
369<br />
Degradation rate of BOD<br />
K-value used in this report indicates the speed of the BOD degradation. The k-value, in this report<br />
used for degradation of BOD, is calculated by the increase of oxygen consumption over time.<br />
Results of the k-value are listed in Table 8.12 below. The k-value data can be found in Appendix<br />
F. For more information about the k-value see Appendix E.<br />
Table 8.12: k 20 -values calculated with Thomas method (Thomas, 1950);<br />
Influent waste water from 5-6 November 2009.<br />
Time: k-value (d -1 )<br />
17:00<br />
19:00<br />
22:00<br />
23:00<br />
01:00<br />
03:00<br />
05:00<br />
07:00<br />
09:00<br />
11:00<br />
13:00<br />
14:15<br />
Average<br />
k-value<br />
(d -1 )<br />
0.235<br />
0.144<br />
0.254<br />
0.282<br />
0.256<br />
0.294<br />
0.179<br />
0.289<br />
0.274<br />
0.190<br />
0.255<br />
0.222<br />
0.24<br />
<br />
53
<br />
54
<br />
55
9. Proposals for upgrading of the treatment system<br />
<br />
Alternative 1: Upgrading of existing WSP<br />
The existing WSP has advantages since it does not consume any energy <strong>and</strong> the required<br />
maintenance is low. With some, relatively inexpensive adjustments the pond system could<br />
operate more efficiently.<br />
Proposed new design<br />
• Installing screening device<br />
• Rearranging the water flow<br />
• Installing baffles in two ponds<br />
Figure 9.1: Overview over current pond arrangement (left) <strong>and</strong> upgraded alternative 1 (right)<br />
(<strong>Szabo</strong> & <strong>Engle</strong>, 2010).<br />
The purpose of rearranging the water flow to one long train of 4 ponds, instead of two parallel<br />
lines with two ponds in each (Figure 9.1), is both theoretically <strong>and</strong> practically motivated. The<br />
theoretical benefit is due to the enhanced plug-flow behavior of water when more ponds are used<br />
after each other (see Chapter 3.5 <strong>and</strong> 2.3 - Disinfection). The practical evidence was seen in<br />
Christchurch (NZ), where a similar rearrangement was done <strong>and</strong> significant reduction of<br />
pathogens, BOD <strong>and</strong> TSS (Masterton District Council, 2009) took place. The benefits of<br />
installing baffles are discussed in Chapter 5.1.<br />
<br />
<br />
56
<br />
Screening device <br />
The task of the screening device is to separate larger particles from the waste water <strong>and</strong> protect<br />
the following treatment steps. The treatment ponds today have no screening device <strong>and</strong> large<br />
floating objects have been seen in the pond. Except from being an unpleasant sight at the pond<br />
(<strong>and</strong> especially in the receiving river) the larger objects have been observed to clog channels.<br />
According to the Sewerage Services Department (1998) the screening device should have a<br />
maximum clear spacing of 25 mm <strong>and</strong> be automatically raked, since it serves over 10 000 P.E.<br />
Flow through ponds <br />
Design values:<br />
Average temperature for coldest month=26 °C<br />
(TheWeatherChannel)<br />
Qinhe inlet water has a BOD degradation rate (k-value) of 0.24 day -1 at 20 °C (see Table 8.12).<br />
After the first pond the value is<br />
unknown but may be assumed to<br />
be 0.1 day -1 (See Appendix E).<br />
These values must be converted<br />
for actual site conditions of 29<br />
degrees Celsius, using equation 6<br />
from Mara (2003):<br />
<br />
57