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A New Process for Enriching Nitrifiers in Activated Sludge Through Separate Heterotrophic Wasting from Biofilm Carriers
Author(s) -
Parker Denny S.,
Rusten Bjørn,
Wien Asgeir,
Siljudalen Jon G.
Publication year - 2002
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 - 10.2175/106143002x139758
Subject(s) - activated sludge , nitrification , moving bed biofilm reactor , heterotroph , aerated lagoon , aeration , mixed liquor suspended solids , environmental engineering , bioreactor , environmental science , biomass (ecology) , chemistry , waste management , pulp and paper industry , sewage treatment , biofilm , ecology , nitrogen , biology , engineering , organic chemistry , bacteria , genetics
A new process, the biofilm–activated sludge innovative nitrification (BASIN) process, consisting of a moving‐bed biofilm reactor (MBBR) with separate heterotrophic wasting, followed by an activated‐sludge process, has been proposed to reduce the volumetric requirements of the activated‐sludge process for nitrification. The basic principle is to remove chemical oxygen demand on the biofilm carriers by heterotrophic organisms and then to waste a portion of the heterotrophic biomass before it can be released into the activated‐sludge reactor. By this means, the amount of heterotrophic organisms grown in the activated‐sludge reactor is reduced, thereby reducing the volume of that tank needed for nitrification. For nitrification applications, the simplest method for stripping biomass was to use an in‐tank technique using high shearing rates with aeration. Bench‐scale testing showed sludge yields in the BASIN process were one‐half of that in a control activated‐sludge process and twice that of a process line with intermediate settling between the MBBR and activated‐sludge stage. Critical washout solids retention times for nitrifiers were the same for all three lines, so activated‐sludge volumes for the BASIN process could be reduced by 50% compared with the control. Originally conceived process concepts for the BASIN process were confirmed by the experimental work.