Study On Effect Of Complex Organic Conditioners On Sewage Sludge Dewatering

With the widely-building of wastewater treatment plants (WWTP) and theincreasing treatment rate of municipal sewage, sludge yield is lager and larger. Sewagesludge has a large amount of organic matters and pathogenic bacteria, if not properlytreated and let it go into the open air, it may cause serious second-pollution to thesurrounding environment. Skeleton builders can reduce the compressibility of sludgecontaining high content of organic matters; surfactants are able to reduce capillarytension and enhance the hydrophobicity of sludge flocs and then change the states ofwater besieged. Thus, in this study, skeleton builders and surfactants were used tocondition sewage sludge, trying to improve the dewaterability of sewage sludge andachieve deep water-removal.Biomass powder was used as the skeleton builder, the graded design experimentcame to a conclusion that using the evaluation index i.e., specific resistance to filtration(SRF), its optimum proportion is （0.3-0.5）mm：6.25%、（0.15-0.3）mm：6.25%、（0.075-0.15）mm：37.5%、（<0.075）mm：50%, SRF reduced to59%of SRF of rawsludge.During the process of surfactants screening, micro images associated with image proplus showed that, both non-ionic surfactants and amphoteric surfactants could decreasethe floc sizes, and generate more homogenous and regular shape, hence they couldimprove the dewaterability, and among the studied surfactants, APG and BS were ofgreat significance to sludge dewaterability. SRF of conditioned sludge with APG dosageof0.05%DS decreased to42%of SRF of raw sludge, and its dewatering efficiencyreached93%. SRF of conditioned sludge with BS dosage of0.4%DS decreased to30%of SRF of raw sludge, and its dewatering efficiency was as high as95%.The co-conditioning experiment using biomass powder and surfactants indicated, themode of first the surfactant and then biomass powder was more advantageous thanswitching sequence to sludge dewatering. And the co-conditioning experiment also showed the best APG dosage was invariant when associating with biomass powder, butthe best BS dosage increased to0.5%DS with biomass powder dosage of40%DS. Theplate and frame filter press experiment showed either APG(0.05%DS)+biomass powder(40%DS) or BS(0.5%DS)+biomass powder(40%DS), the moisture contents of filteredcakes were both about55%, and their organic contents were above83%of raw sludge.This research provides some technical supports for the application of APG and BScombined with biomass powder in sludge dewatering.