CALCULATION OF SLUDGE PRODUCTION FROM AEROBIC ASP BASED ON COD AND BOD5 – COMPARISON OF METHODS AND MODEL VALIDATION
Tomasz Janus
Water Software Systems, De Montfort University
(free)
A 5-day Biological Oxygen Demand (BOD5) is one of the parameters which are used to
determine the amount of biodegradable organic substances in water environments. In
dimensioning wastewater treatment plants, BOD5 is used for determining organic loading
rates which enter the wastewater treatment plant and affect such parameters as surplus
sludge production and oxygen demand. Conventional “static” design methods are based on
using BOD5 as a representation of the amount of organic substrates in wastewater and then
use empirically obtained coefficients for such parameters as biomass yield per BOD5 removed
or amount of oxygen required per BOD5 oxidised to calculate surplus sludge production and
oxygen demand. In contrast, new design methods taking advantage of dynamic activated
sludge models (ASM) are based on COD (Chemical Oxygen Demand) fractions for
determination of organic loading, oxygen demand and surplus sludge production. It has been
found out during the course of work on wastewater treatment plant design and dynamic
simulation that the results obtained from both approaches can vary significantly. Theoretical
explanation of such behaviour is presented here and a design method on COD fractions is
validated on two bench-scale SBR reactors operating on two different wastewater streams.
KEY WORDS
Activated Sludge, Design, Simulation, Sludge Production, Sludge Yield
