Alexander Szabo and Oscar Engle - Svenskt Vatten

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COD concentration, theoretical=er channels contributes with 60-90% of the total incoming water to the WSP. It can be seen on the velocity measurements that soon after the rainfall occur, the flow speed increases rapidly. As the rainfall ends, the flow tends to go down quickly. On the 18-19 of November, most students left UTM for holiday. Approximately one half to two thirds of all students were not at the University during these measurements. Despite this, both Q max and Q min (Table 8.4) were higher during the holiday than during the school period. This could be explained by that the monsoon period started just after the measurements on the 5-6 November, but before the 18 th of November. More or less every day received heavy rainfalls which could have raised the groundwater level, thus creating more infiltration into the sewer system. Since the storm water channels are built to receive all the storm water, no additional water should enter the sewage network. If the infiltrated water could be reduced, the HRT in the WSP would increase, hence improving the treatment efficiency. An unavoidable effect of reducing the infiltration is the increase in concentrations of pollutants in the waste water. It is however preferable to receive smaller quantities of waste water, even if the concentrations of pollutants are higher, since with effective reduction the total load of pollutants on the recipient will be lower than with diluted waste water. Sampling procedure for influent water The influent water was collected every two hours during the measurement periods. Samples were withdrawn from the inlet chamber and immediately taken to the laboratory and stored in a refrigerator. The first sampling started 5 th November at 17:30 and continued every second hour until 14:15 the next day. The second sampling started at 12:30 a.m. on the 18 th of November and continued every second hour until 10:00 a.m. the next day. The third sampling started at 12:00 a.m. on the 9 th of January and continued every second hour to 10:00 a.m. the 10 th of January. From all these samplings days COD, BOD 5 and TSS were analyzed according to the methods described in chapter 7. From the samples 5-6 November k-values were analyzed. Since the measurements during 5-6 November lacks flow data between 17:30 and 22:00, a designed flow was created and used in order to get complete measuring data and to calculate weighted parameters (see Figure 8.10). BOD 5 and COD in influent water The inlet COD concentrations show a tendency to rise when people use water consuming facilities at most, usually in the morning and late afternoon. When water flow increases due to rainfall, the COD values peaks and reaches levels much higher than during normal flow. At late night or early morning (04:00-06:00) all three sampling periods reach their lowest values (12 mg/l – 33 mg/l) (Figure 8.11). The pattern of COD concentrations is lower during the holiday period, which is explained by the lower load due to absence of students in combination with infiltration. According to Mara (2003), a COD concentration of less than 400 mg/l is considered as “weak strength”. This water is therefore placed into this category. From the first sampling period 5-6 November, BOD 5 from all 12 measurements were analyzed. For all 12 measurements that period, COD was also analyzed. This was done in order to get a   48 
atio between BOD 5 and COD for the waste water entering the pond. In Figure 8.12 COD- and BOD 5 -values have been plotted. Figure 8.12: The inlet COD concentration during three 24-hours measurements. Figure 8.13: BOD 5 and COD concentration values in inlet to the WSP during 5-6 November 2009. Ratio BOD 5 /COD in Inlet By using the samples from the 5-6 November, the average ratio between the BOD 5 and COD values are 0.5 (see Table 8.8 below). This value will be used to estimate BOD 5 when only COD values are available.   49 
Page 1 and 2: ___________________________________
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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 and 20: 1.3 Objective The objective of this
Page 21 and 22: 2.2 Pretreatment   Screening The
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: Method 1: Estimation of domestic wa
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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