H1-HH-7-A n eupex coupling type h Helical gear unit H1

Flender/Flender Gear Units/Helical gear unit H1

. 4-9 Table 4-4: Zeekoegat WWTP Average Wastewater Characteristics (based on data collected during the 2 and 2 special sampling programs) Parameter Symbol Value Raw Settled Organics/COD BO (SB)/ Total ( ) fSbi 0.8 0.8 BPO (Sbp)/Total (St) fSbpi 0.6 0.4 FBSO (` bs)/Total ( ) fSbsi 0.2 0.3 VFA (Sa/Total (St) fSai 0.0 0.0 USO ( us)/Total ( ) fSusi 0.0 0.0 UPO ( up)/Total ( ) fSupi 0.1 0.0 Nitrogen Fractions FSA/TKN fnai 0.6 0.7 Phosphorus Fractions Ortho / Total fpai 0.4 0.6 Other Fractions TKN/COD 0.0 0.1 Total /COD 0.0 0.1 FSA/TKN 0.6 0.7 Ortho / Total 0.5 0.6 VSS/TSS 0.9 0.9 The wastewater characteristics and fractions fall within the generally expected ranges for South African Municipal wastewater. It should be noted that the average values in Table 4-4 were deduced from rigorous data reconciliation process combining both statistical analysis of measured data and steady state activated sludge modelling. 4.4.2 Baseline Plant Operation and Performance Operating Parameters Prior to commissioning the new sludge treatment facili ty in 2, the plant was in essence treating raw wastewater since primary sludge was discharged to the bioreactors. The existing DAF units, which were designed to thicken WAS generated from treating settled wastewater at the recommended design sludge age range of 2-2 days, do not have sufficient capacity to treat the additional WAS generated from treating raw wastewater. Thus to reduce the quantity of WAS, in 2 the plant was operated at very long sludge ages averaging 2-3 days in summer and 4-6 days in winter. The MLSS concentrations were consequently high ranging from 4,0-7,0 mg/. Figure 4-5 shows the variation of MLSS and sludge age for the four reactors in 2. The -recycle was abstracted from the outlet of the th ird aerobic cell for all the reactors where only two out of the six installed pumps are accessible for each reactor. This limited the - recycle to maximum of about