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Modeling External Carbon Addition in Biological Nutrient Removal Processes with an Extension of the International Water Association Activated Sludge Model
Author(s) -
Swinarski M.,
Makinia J.,
Stensel H.D.,
Czerwionka K.,
Drewnowski J.
Publication year - 2012
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143012x13373550426670
Subject(s) - anoxic waters , activated sludge , volatile suspended solids , activated sludge model , wastewater , phosphorus , chemistry , pulp and paper industry , nitrification , enhanced biological phosphorus removal , nutrient , nitrate , sewage treatment , environmental science , environmental engineering , environmental chemistry , nitrogen , organic chemistry , engineering
The aim of this study was to expand the International Water Association Activated Sludge Model No. 2d (ASM2d) to account for a newly defined readily biodegradable substrate that can be consumed by polyphosphate‐accumulating organisms (PAOs) under anoxic and aerobic conditions, but not under anaerobic conditions. The model change was to add a new substrate component and process terms for its use by PAOs and other heterotrophic bacteria under anoxic and aerobic conditions. The Gdansk (Poland) wastewater treatment plant (WWTP), which has a modified University of Cape Town (MUCT) process for nutrient removal, provided field data and mixed liquor for batch tests for model evaluation. The original ASM2d was first calibrated under dynamic conditions with the results of batch tests with settled wastewater and mixed liquor, in which nitrate‐uptake rates, phosphorus‐release rates, and anoxic phosphorus uptake rates were followed. Model validation was conducted with data from a 96‐hour measurement campaign in the full‐scale WWTP. The results of similar batch tests with ethanol and fusel oil as the external carbon sources were used to adjust kinetic and stoichiometric coefficients in the expanded ASM2d. Both models were compared based on their predictions of the effect of adding supplemental carbon to the anoxic zone of an MUCT process. In comparison with the ASM2d, the new model better predicted the anoxic behaviors of carbonaceous oxygen demand, nitrate‐nitrogen (NO 3 ‐N), and phosphorous (PO 4 ‐P) in batch experiments with ethanol and fusel oil. However, when simulating ethanol addition to the anoxic zone of a full‐scale biological nutrient removal facility, both models predicted similar effluent NO 3 ‐N concentrations (6.6 to 6.9 g N/m 3 ). For the particular application, effective enhanced biological phosphorus removal was predicted by both models with external carbon addition but, for the new model, the effluent PO 4 ‐P concentration was approximately one‐half of that found from ASM2d. On a PO 4 ‐P removal percentage basis, the difference was small, that is, 94.1 vs 97.1%, respectively, for the ASM2d and expanded ASM2d.