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Nocardia control in activated sludge by classifying selectors
Author(s) -
Pagilla Krishna R.,
Jenkins David,
Kido Wendell H.
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 - 10.2175/106143096x127677
Subject(s) - activated sludge , nocardia , chemistry , chromatography , pulmonary surfactant , pulp and paper industry , waste management , sewage treatment , bacteria , biology , engineering , biochemistry , genetics
Laboratory‐ and full‐scale experiments investigated the use of a classifying selector for Nocardia control in activated sludge. A classifying selector is a device that produces surface foam from the bulk mixed liquor and then removes it. The laboratory‐scale classifying selector activated sludge system operating at a 10‐day mean cell residence time (MCRT), pH = 6.6, dissolved oxygen (DO) = 8.0 mg/L, and temperature = 24°C produced mixed liquor Nocardia levels lower than an unfoamed control activated sludge plant. Addition of low doses (0.5 mg/L) of a readily biodegradable nonionic surfactant (NEODOL 25–7) to the classifying selector system just before foaming reduced the mixed liquor Nocardia levels to below those achieved in a classifying selector system without surfactant addition. A classifying selector installed in the RAS channel combined with selective foam wasting from the mixed liquor channels and secondary clarifiers in a full‐scale activated sludge plant reduced Nocardia levels below those achieved during operation without a classifying selector.