The role of dispersed nocardioform filaments in activated sludge foaming.
Activated sludge foaming caused by filamentous microorganisms is a major wastewater treatment plant operating problem. This paper presents the results of an investigation of the role of dispersed nocardioforms in activated sludge foaming. Dispersed nocardioforms had a greater propensity for foaming than floc-bound nocardioforms. The mode of effluent withdrawal from an aeration basin plays a major role in determining the relative proportion of dispersed and floc-bound nocardioforms in the activated sludge. Reactors with "trapping" features (sub-surface mixed liquor withdrawal) had significantly higher dispersed nocardioform populations than reactors with "non-trapping" features (surface mixed liquor withdrawal). High dispersed nocardioform filament concentrations were correlated with a high propensity for foaming. Cationic polymer and polyaluminum chloride reduced foaming by flocculating dispersed nocardioforms, thereby converting them to floc-bound nocardioforms. Low non-ionic surfactant concentrations changed the relative proportions of dispersed and floc-bound nocardioforms by deflocculating floc-bound filaments and converting them to the dispersed growth form. This could act as a trigger for initiating the rapid-onset nocardioform foaming events observed at activated sludge plants.
Narayanan
B
B
Carollo Engineers, Walnut Creek, California, USA. flodoc@pacbell.net
de Leon
C
C
Radke
C J
CJ
Jenkins
D
D
D000077410:Aluminum Chloride; D017607:Aluminum Compounds / Q000494:pharmacology; D001420:Bacteria, Aerobic / Q000187:drug effects / Q000502:physiology*; D019149:Bioreactors; D002412:Cations / Q000737:chemistry / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D011108:Polymers / Q000737:chemistry / Q000494:pharmacology; D012722:Sewage / Q000737:chemistry* / Q000382:microbiology*; D013997:Time Factors; D014865:Waste Disposal, Fluid; D014871:Water Microbiology
D017607:Aluminum Compounds; D002412:Cations; D002712:Chlorides; D011108:Polymers; D012722:Sewage; D000077410:Aluminum Chloride