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Shutdown of BAC filters: effects on water quality
Author(s) -
Niquette Patrick,
Prévost Michèle,
Servais Pierre,
Beaudet JeanFrançois,
Coallier Josée,
Lafrance Pierre
Publication year - 1998
Publication title -
journal ‐ american water works association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.466
H-Index - 74
eISSN - 1551-8833
pISSN - 0003-150X
DOI - 10.1002/j.1551-8833.1998.tb08551.x
Subject(s) - backwashing , shutdown , nitrite , filtration (mathematics) , effluent , water quality , nitrate , pulp and paper industry , filter (signal processing) , nitrification , ammonia , dissolved organic carbon , biodegradation , chemistry , environmental science , water treatment , environmental engineering , environmental chemistry , nitrogen , nuclear chemistry , ecology , biology , inlet , mechanical engineering , statistics , mathematics , organic chemistry , computer science , computer vision , engineering
Adding a filter backwash after shutdown restored the quality of filtered water to its preshutdown standard. Biological activated carbon (BAC) filtration is used in drinking water treatment to biodegrade dissolved organic carbon (DOC) and to nitrify ammonia. This study evaluated BAC filters before, during, and after shutdown. Concentrations of five substrates were measured: ammonia, nitrite, nitrate, DOC, and dissolved oxygen. Media samples were taken simultaneously at similar depths to evaluate the effect of a shutdown on the densities of fixed bacteria. Dissolved oxygen concentrations quickly dropped below 2 mg/L within the BAC filters during the first 2 h of filter shutdown. At the same time, nitrite and bromide concentrations increased rapidly. Fixed bacterial biomass densities, measured at several depths in the filter after a 24‐h shutdown, declined. Concentrations of DOC and ammonia, measured in the effluent after the filter was restarted, were higher than those measured before shutdown. Backwashing after shutdown, before the filter was returned to normal operation, eliminated these negative effects and restored the biodegradation performance of the BAC filters.