Alexander Szabo and Oscar Engle - Svenskt Vatten

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2. Waste Water Treatment Ponds Technology 2.1 Introduction to Waste water treatment ponds Waste water treatment ponds are used around the world for treatment of municipal waste water. They can offer a good alternative where land prices are low and where the climate is beneficial. Since there is a general relationship between growth rate of bacteria and algae that contribute to the treatment of waste water, pond systems in a warmer climate benefit from high temperatures. A pond system can be built easily and does not require much maintenance. Since it can hold large quantities of water, it has a good resistance to shock loads and hazardous substances that may enter the system. A typical arrangement of waste water treatment ponds consists of a primary facultative pond followed by one or multiple maturation ponds. Under some conditions it is also possible to use an anaerobic pond before the facultative pond (see Figure 2.1). Figure 2.1: In this figure three possible arrangements for pond system are illustrated. The first two series illustrates a primary facultative pond (F) followed by one or two maturation ponds (M). The third pond series illustrates an anaerobic pond (A) followed by a facultative pond and finally a maturation pond (Szabo & Engle, 2010).               16 
2.2 Pretreatment   Screening The purpose of a screening device, which is located before the treatment pond, is to remove coarse materials like pieces of plastic and woods etc. The material caught and removed from the screen is often of inorganic characteristics and hard to break down biologically in the treatment pond. The coarse material can also damage pumps and aerators used in the subsequent treatment stages. It is recommended that the water velocity through the screen should be less than 1 m/s so coarse material will be able to stick between the screens (Mara, 2003). The space between the bars should be between 15-25 mm (Mara, 2003). If the flow is above 1000 m 3 /day mechanical screens which automatically remove the captured objects should be used instead of screens that have to be maintained manually. This is because mechanical screens can be cleaned more frequently. It is although wise to have a screen that could be cleaned by hand as a back-up for the mechanical screen in case the mechanical screen would stop working. The waste products collected from the screen can be taken to the nearest landfill or be incinerated. Grit removal Grit is made up of heavier and smaller particles (often of inorganic characteristics) like glass, sand eggshells etc. Grit can damage pumps and aerators in the subsequent treatment steps and should be removed before the treatment pond if the waste water contains large quantities. Before water enters the screen and the treatment pond, the waste water may flow in long grit channels where the water passes through at a desired velocity. The heavier grit particles will settle in the channel as the waste water flows through. The grit channels are made up of two parallel channels so one of the channels can be closed for grit removal. A possible problem with a grit channel is that it is difficult to keep the velocity at a constant level (Mara, 2003).     2.3 Pond Types Anaerobic ponds Anaerobic ponds operate without the presence of algae or oxygen, and have an advantage over the facultative pond since they can deal with higher organic loading. They can reduce the organic load by 40 to 70% with a retention time of only a few days (Shilton et al., 2005). Methane (CH 4 ) and sulphide (H 2 S) are gasses that are produced under anaerobic conditions. Methane gas may be considered as a fuel resource if collected, but if not collected as a greenhouse gas, contributing to the climate change as it escapes into the atmosphere from the pond. If sulphide is produced and released, it is not appreciated since it is releases a bad odor. If the anaerobic pond is not properly design, or when overloaded, the release of sulphide may be problematic for people living in the surroundings (Mara, 2003). This is confirmed by a study at Lee Summit WSP, Missouri, where odor nuisance occurred after the load was increased above the pond capacity (McKinney, 1968).   17 
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Page 5 and 6: List of abbreviations BOD - Biochem
Page 7 and 8: Summary Malaysia is developing fast
Page 9 and 10: Acknowledgements This report is a r
Page 11 and 12: Contents  List of abbreviations..
Page 13 and 14: Waste water production in t
Page 15 and 16: XI   
Page 17 and 18: treatment facilities simple, treatm
Page 19: 1.3 Objective The objective of this
Page 23 and 24: the case of waste water treatment p
Page 25 and 26: 3. Pond Hydraulics 3.1 Retention ti
Page 27 and 28: 5. Previous studies on WSP systems
Page 29 and 30: value of 4:1 in length/width ratio.
Page 31 and 32: 6. Study Area   6.1 Climate Johor
Page 33 and 34: Figure 6.3: The receiving river. Up
Page 35 and 36: accuracy (the accuracy of a single
Page 37 and 38: BOD analyzes were carried out using
Page 39 and 40:   35 
Page 41 and 42: 8. Water flow and quality Sampling
Page 43 and 44: stirred up. The algae population ma
Page 45 and 46: Table 8.2: Influent (weighted COD a
Page 47 and 48: Figure 8.8: Above: The water veloci
Page 49 and 50: Figure 8.10: The water velocity in
Page 51 and 52: Method 1: Estimation of domestic wa
Page 53 and 54: atio between BOD 5 and COD for the
Page 55 and 56: Figure 8.14: Above: TSS concentrati
Page 57 and 58: Table 8.11: Measured BOD 5 on 5-6 N
Page 59 and 60:   55 
Page 61:   Screening device  The task

Alexander Szabo and Oscar Engle - Svenskt Vatten

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