The potential use of PNP, TCS and THPS AS uncouplers to reduce waste activated sludge

Activated sludge processes are widely used in wastewater treatment plants (WWTPs) but they also generate large quantities of excess sludge, the handling and disposal of which uses large percentage of the annual operation cost. A class of chemicals, referred to as uncouplers, with the ability of generating energy spill inside microbial cells have shown potential in reducing activated sludge production. This study assessed the effectiveness of three uncouplers: 3, 3’, 4’, 5-tetrachlorosalicylanilide (TCS) and para-nitrophenol (PNP) and Tetrakis hydroxymethyl phosphonium sulphate (THPS) in reducing sludge production. <br><br>The results obtained using the sequencing batch reactors for TCS, PNP and THPS at initial concentrations of 0.5, 20 and 0.02 mg/L showed 18%, 28% and 30% reduction in WAS production, respectively. TCS and PNP lead to 5% reduction in COD removal, whereas, THPS reduced COD removal by 13%. For all uncouplers tested, no acclimatisation to the uncoupler was observed during the 30-day SBR tests.<br><br>Spiking the feed with the two uncouplers, TCS and PNP at 0.5 mg/L and 5 mg/L, respectively, showed higher sludge reduction compared to the reduction obtained using each uncoupler individually. The intermittent dosing of the uncouplers into the feed to the SBRs showed that the dosing frequency had no significant effect on activated sludge yield.<br><br>The batch OUR tests showed that TCS and PNP can enhance the activity of sludge, as the activated sludge OUR increased, whereas THPS, on the other hand, inhibited activated sludge activity.<br>