Testimonials
“We have found the performance of the system to be quite satisfying and user friendly. We are currently running low level O2 uptake experiments and are impressed with the sensitivity of the instrument.”
“I have found the performance of the Challenge AER-200 to be unmatched. The precise measurement of oxygen consumption, homogenous mass transfer of test materials, and constant and consistent operating temperature have enabled me to obtain extremely accurate test results, particularly as compared to other respirometer systems. I find the Challenge system to be extremely user friendly.”
OUR Set-Point Control of Activated Sludge Processes
The OUR Set-Point method is useful for controlling the activity and loading–rate capacity of an activated sludge mixed liquor. In this case, sufficient amounts of stock substrate are added to a mixed liquor suspension to provide kinetic saturation with subsequent measure of OUR. Once an acceptable substrate is found for a specific wastewater treatment plant, an OUR can be identified that provides acceptable performance. This OUR is identified as the "Set-Point OUR". The operator then maintains a constant OUR by adjusting mixed liquor volatile suspended solids concentrations to maintain the desired OURmax.
MLVSSoperation = MLVSSmeasured * (OURset–point/OURmeasured)
Figure A below shows oxygen uptake rates for three mixed liquor concentrations in which acetate was used as a standard substrate – as measured using a Challenge AER–200 respirometer system. The three tests show a consistent OUR fingerprint but with changes in OURmax that reflect changes in active biomass. Figure B shows a repeat test after adjusting the biomass concentration to give the desired Set–Point OUR. The relationship allows plant operators to maintain a constant loading rate capacity under all operating conditions. In this case, adjustment of the OUR for the 830 mg/L MLVSS sample and the 2,290 mg/L MLVSSsample to 1,685 mg/L brought all mixed liquors to the same OUR. Once a Set–Point OUR has been identified, the changes in MLVSS concentrations are relative so that the substrate type should not be a major concern as long as it is constant.