Capacity of Wastewater Treatment Plants

With the following data it is possible to calculate the short-term capacity of a municipal wastewater treatment plant according to the german design rule 'ATV A 131 (1991)'. Both the capacity of the biological treatment and for secondary clarification will be computed. The result will give an indication for the potential of optimization of existing plants.

Data-Input Unit Value Remarks
wastewater quantity
daily flow m3/d
actual flow m3/h flow for which capacity will be computed
volume of excess-sludge m3/d weekly average
solid content excess sludge g/l
influent quality to activated sludge tank
BOD5 mg/l 2-hour or daily average
total solids mg/l
total nitrogen mg/l
total phosphorous mg/l
effluent quality
total nitrogen mg/l
total solids mg/l
mixed liquor suspenden solids MLSS g/l in activated sludge tank
temperature wastewater °C
sludge volume index SVI ml/g
phosphorous precipitation -
max. flow rate secondary clarifier l/m2/h for horizontal-flow: 450 for vertical flow 600
plant / tanks
total volume activated sludge tank m3 combined aerobic and anoxic zones
total surface secondary clarifiers m2
depth of secondary clarifiers m water depth at 2/3 of radius

Results Units Value Remarks
activated sludge tank
max. capacity of biological treatment m3/h for current wastewater quality and process
percentage used of treatment capacity %
secondary clarifiers
max. capacity for given surface m3/h
percentage used of treatment capacity %
max. capacity for given tank depth m3/h
percentage used of treatment capacity %


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