Use of the Chemical Uncoupling Effect to Reduce Sludge Production in Activated Sludge

Chilro, N.1, Edmunds, S.2, Richmond, H.2, Ballinger, D.1, Stephenson, T.3, 1Southern Water, 2Rhodia Novecare, 3Cranfield University


A readily biodegradable chemical uncoupler, tetrakishydroxymethylphosphonium sulphate
(THPS), was applied to a full-scale activated sludge plant to achieve a reduction in excess
sludge production without affecting the operational process. The plant was situated in the south
of the UK and consisted of two parallel oxidation ditches operated as a sequential batch reactor
with an 8 h cycle including a 3 h aeration period. Performance was monitored during control and
test periods corresponding to summer and winter. The THPS was dosed during the aeration
cycle of the activated sludge plant to achieve a concentration of 3 mg THPS/l MLSS/d.

Results have shown a 42% biomass yield reduction. There was no adverse effect on the
process operation i.e. suspended solids, biochemical and chemical oxygen demands (BOD and
COD) and ammonia removal efficiencies and final effluent concentrations. There were no
detectable increases in final effluent concentrations of THPS breakdown products.

Activated sludge, sludge reduction, chemical uncoupler, tetrakishydroxymethylphosphonium
sulphate (THPS)

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