Evaluation of substrate and pH effects in a nitrifying biofilm
The effects of substrate and pH on biofilm nitrification were studied using a microelectrode technique and a microslicing technique. Three different kinds of biofilms were cultured using lab-scale, rotating drum biofilm reactors fed with synthetic wastewaters. The measured concentration profiles provide direct experimental evidence of the substrate and pH effects on biofilm nitrification. It was found that pH decreases within the nitrifying biofilm depended on the mole ratio of HCO− 3/O2. When this mole ratio was >5, the maximum pH decrease within the nitrifying biofilm was <0.4–0.6 pH units. When this ratio was <3, the maximum pH decrease could be 1.4–1.6 pH units. A pH decrease of 1.4–1.6 pH units resulted in an inhibition of the biofilm nitrification process, and therefore stopped a further decrease in pH. No dramatic pH decrease (>2–2.5) was observed during the study. It was found that increases in glucose loading or ammonium loading caused more consumption of oxygen, which resulted in inhibition of the biofilm nitrification. The bacterial trophic population measurement revealed that even in a pure nitrification system, heterotrophs could exist in the nitrifying biofilm. In biofilms cultured with an influent COD of 170 mg/L or higher, the numbers of nitrifiers were always four to five orders lower than those of heterotrophs. This study demonstrates that competition between heterotrophs and nitrifiers for substrate (including O2) and space greatly affects the degree of pH decreases within nitrifying biofilms.
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Document Type: Research Article
Publication date: 1996-11-01
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Water Environment Research (WER) publishes peer-reviewed research papers, research notes, state-of-the-art and critical reviews on original, fundamental and applied research in all scientific and technical areas related to water quality, pollution control, and management. An annual Literature Review provides a review of published books and articles on water quality topics from the previous year. Published as: Sewage Works Journal, 1928 - 1949; Sewage and Industrial Wastes, 1950 - 1959; Journal Water Pollution Control Federation, 1959 - Oct 1989; Research Journal Water Pollution Control Federation, Nov 1989 - 1991; Water Environment Research, 1992 - present.
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