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Historical data routinely collected by the staff of the plant were obtained from HCWW, Egypt. The data include a detailed description of the processes, plant components, and historical daily measurements from raw sewage, settled sewage, and biologically treated effluent. Data for one treatment train (out of three treatment trains) were selected over 10 months (from April 2014 to February 2015) for model validation. The selected treatment train operated continuously without interruption or major maintenance over these 10 months. Fortunately, the operator was operating this treatment train with semi-constant flow, which is not common in municipal WWTPs. The incoming flow was pumped to the studied treatment train with a constant flow of 50,000 m3/day, and any overflow was sent to the rest of the treatment trains in the WWTP. Historical data lacked certain measurements, such as filtered COD, alkalinity, phosphorus, and nitrogen compounds (nitrates, nitrites and total Kjeldahl nitrogen (TKN)). SRT was estimated based on Equation (1) (Tchobanoglous et al. 2003). Tables 1 and 2 show the average historical daily routine measurement and operating conditions.
formula
1
where SRT, sludge retention time (days); V, reactor volume (m3); MLVSS, mixed liquor volatile suspended solids (g/m3); Qex, excess sludge quantity (m3/d); Qeff, effluent flow rate (m3/d); VSSex, volatile suspended solids in excess sludge (m3/d), and VSSeff, volatile suspended solids in effluent (m3/d).
Table 1

WWTP average of historical daily routine measurements over 10 months

TestRaw sewageSettled effluentBiologically treated effluent
Flow (m3/d) 49,106 ± 633   
BOD5 (mg/l) 506 ± 91 263 ± 47 36 ± 5 
CODtot (mg/l) 1,459 ± 279 462 ± 82 95 ± 17 
TSS (mg/l) 452 ± 94 182 ± 36 36 ± 5 
VSS (mg/l) 401 ± 75 128 ± 33 30 ± 6 
Temp. (°C) 25 ± 5.3 – – 
pH 8.3 ± 0.6 8.2 ± 0.6 8.2 ± 0.45 
TestRaw sewageSettled effluentBiologically treated effluent
Flow (m3/d) 49,106 ± 633   
BOD5 (mg/l) 506 ± 91 263 ± 47 36 ± 5 
CODtot (mg/l) 1,459 ± 279 462 ± 82 95 ± 17 
TSS (mg/l) 452 ± 94 182 ± 36 36 ± 5 
VSS (mg/l) 401 ± 75 128 ± 33 30 ± 6 
Temp. (°C) 25 ± 5.3 – – 
pH 8.3 ± 0.6 8.2 ± 0.6 8.2 ± 0.45 
Table 2

Average of historical operational data of activated sludge process over 10 months

TestBiological treatment
MLSS (mg/l) 4,010 ± 697 
MLVSS (mg/l) 2,730 ± 687 
F/M ratio 0.16 ± 0.15 
SRT 11.5 ± 4 
DO (mg/l) 1.6 ± 0.44 
RAS flow (m3/d) 50,112 ± 0 
WAS flow (m3/d) 864 ± 0 
RAS TSS (mg/l) 7,264 ± 1,244 
RAS VSS (mg/l) 5,610 ± 1,785 
TestBiological treatment
MLSS (mg/l) 4,010 ± 697 
MLVSS (mg/l) 2,730 ± 687 
F/M ratio 0.16 ± 0.15 
SRT 11.5 ± 4 
DO (mg/l) 1.6 ± 0.44 
RAS flow (m3/d) 50,112 ± 0 
WAS flow (m3/d) 864 ± 0 
RAS TSS (mg/l) 7,264 ± 1,244 
RAS VSS (mg/l) 5,610 ± 1,785 
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