Effect of acid and surfactant treatment on activated sludge dewatering andsettling

The effect of pretreating activated sludge with sulfuric acid and surfactan t on its exocellular polymer(ECP), dewaterability and settleability was inv estigated. It was observed that the centrifugal dewatering efficiency was i ncreased with the decrease of sludge pH value, and which was further improv ed if the surfactant was simultaneously applied. However, to the filtration dewatering, the water content reached the minimum in the case of pH 2.5, a nd the additional use of surfactant was also favorable. The: water content of sludge dewatered with filtration reached 73.99%; when a pH 2.5 and a 0.1 g surfactant were employed, which was reduced by around 2% as compared wit h surfactant unused. Experimental results indicated that the sludge sedimen tation rate was significantly accelerated under pH 2.5 condition. and which was increased once more by the utilization of surfactant. Further studies revealed that treating activated sludge with sulfuric acid at pH 2.5 or com bined with surfactant was an effective method to remove the polymers from s ludge surface and induced the decrease of ECP, which resulted in the improv ement of dewaterability and settleability. This study suggested the potenti ality of improving activated sludge mechanical dewaterability by the use of sulfuric acid to control its pH at 2.5 or together with a surfactant. (C) 2001 Elsevier Science Ltd. Ail rights reserved.