Journal
WATER RESEARCH
Volume 46, Issue 7, Pages 2057-2066Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.watres.2012.01.020
Keywords
Activated sludge; Biological nutrient removal; Colloidal organic nitrogen; CON; Dissolved organic nitrogen; DON; Nitrogen fractionation; Nitrogen removal
Funding
- Norwegian Financial Mechanism [PL0085-PIP-00151-E-V1]
- Polish Ministry of Science and Higher Education [WERF/45/2007]
- Water Environment Research Foundation [02-CTS-1a]
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The aim of this study was to investigate the occurrence and fate of colloidal and dissolved organic nitrogen (CON and DON) across biological nutrient removal (BNR) activated sludge bioreactors. Primary and secondary effluent total nitrogen (TN) measurements and component fractionation, CON and DON concentration profiles across BNR bioreactors, and laboratory batch experiments with the process mixed liquor were carried out at several full-scale BNR plants in northern Poland. The organic nitrogen (ON) components were divided into high CON, low CON, and DON based on sequential filtration through 1.2, 0.45 and 0.1 mu m pore-size filters. The average influent DON0.1 mu m (<0.1 mu m) concentrations ranged from 1.1 g N/m(3) to 3.9 g N/m(3) and accounted for only 4-13% of total organic nitrogen. In the effluents, however, this contribution increased to 12-45% (the DON0.1 mu m concentrations varied in a narrow range of 0.5-1.3 g N/m(3)). Conversions of ON inside the bioreactors were investigated in more detail in two largest plants, i.e. Gdansk (565,000 PE) and Gdynia (516,000 PE). Inside the two studied bioreactors, the largest reductions of the colloidal fraction were found to occur in the anaerobic and anoxic compartments, whereas an increase of DON0.1 mu m concentrations was observed under aerobic conditions in the last compartment. Batch experiments with the process mixed liquor confirmed that DON0.1 mu m was explicitly produced in the aerobic phase and significant amounts of ON were converted in the anoxic phase of the experiments. (C) 2012 Elsevier Ltd. All rights reserved.
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