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Evaluation of substrate and pH effects in a nitrifying biofilm
Author(s) -
Zhang Tian C.,
Bishop Paul L.
Publication year - 1996
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 - 10.2175/106143096x128504
Subject(s) - nitrification , biofilm , heterotroph , ammonium , substrate (aquarium) , chemistry , nitrifying bacteria , population , microbiology and biotechnology , environmental chemistry , bioreactor , extracellular polymeric substance , biology , bacteria , ecology , nitrogen , organic chemistry , demography , sociology , genetics
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 /O 2 . 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 O 2 ) and space greatly affects the degree of pH decreases within nitrifying biofilms.