Operation of carbon removal activated sludge plants using online measurement of the oxygen uptake rate (OUR)
High-loaded activated sludge (HLAS) plants for carbon removal at municipal wastewater treatment plants (WWTPs) operates at low aerobic solids retention times (SRTs) (1-3 days) without nitrification. Controlling and maximising removal of colloidal and particulate COD while minimising mineralisation and hydrolysis of the slowly biodegradable COD is pivotal for carbon redirection in HLAS plants (Jimenez et al., 2015). Recently, automatic SRT-controlled excess sludge withdrawal was implemented for the HLAS at Sjölunda WWTP in Malmö, Sweden, since drifting SRT to low levels deteriorates the effluent quality. This Master´s thesis study is a part of the evaluation of this strategy as well as to further refine and optimise this operation. Online oxygen uptake rate (OUR) measurements can potentially determine the SRT and dissolved oxygen (DO) concentrations in the activated sludge tanks needed for optimised treatment. In the beginning of the next decade, Sjölunda WWTP has to increase its treatment capacity to fulfil new treatment standards. Optimising the HLAS operation will help to increase the plant´s carbon removal capacity without deteriorating the effluent quality and affecting other important treatment processes at Sjölunda WWTP.
The aim of this Master’s thesis is to experimentally determine how online OUR measurements can be used for optimising the operation of the HLAS at Sjölunda regarding excess sludge removal (SRT control) and aeration control.
OURs (both momentary and endogenous respiration rates) of the sludge from different activated sludge lines and zones at different operation conditions at Sjölunda WWTP will be performed with a lab method similar to the one described in Hagman & la Cour Jansen et al. (2007). The OUR measurements should be compared to different parameters, such as effluent quality, SRT and aeration strategy.
Oskar Modin, associate professor at Chalmers University of Technology, and David Gustavsson, R&D engineer at VA SYD/Sweden Water Research
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