In activated sludge wastewater treatment process, the demand of carbonsource affects the biological nutrient removal, and that a large number ofsludge needed desposed confines the development of wastewater treatmentplant (WWTP). However, organic matter, main component of waste activatedsludge (WAS), could be used as carbon source for biological nutrient removal,simultanenously comprehensive utilize of sludge is accomplished. This paperinvestigated the disintegration performances of ultrasound, alkaline,combination of ultrasonic and alkaline on WAS. During disintegrated sludgehydrolysis and acidification process, the effects of soluble organic matter andsludge average particle size on volatile fatty acids (VFAs) accumulation andmicrobial community structure were studied. In order to inhibit VFAsconsumption, initial and process alkaline regulations were applied to sludgehydrolysis and acidification, and the optimal conditions for VFAsaccumulation were analyzed. Moreover, the combined process of ultrasonicdisintegration and alkaline process regulation was used for VFAs accumulation,which was supplemented into A/A/O process as carbon resource. In thisprocess, the effects of acidification product on biological nutrient removal andmicrobial community structure were analyzed.The comparison of extracelluar polymeric substance (EPS) and solubleCOD by ultrasound, alkaline, and combination of ultrasound and alkaline wereanalyzed. The results show that SCOD concentration reached to4287mg/Lafter1d by pH12, equal to EPS. Alkaline pretreatment could destroy EPSstructure effectively. Ultrasonic pretreatment (3.0W/mL) and the combinationof ultrasound (3.0W/mL) and alkaline (pH=10) pretreatment decreased sludgeaverge particle size from200-300to10μm within30min, and soluble CODwere7520and7890mg/L more than the EPSCODconcentration. This resultsshowed that ultrasound can destroy the the structure of EPS and cell wall. Inaddition, oxygen uptake rate analysis of disintegrated sludge supernatantdemonstrated that the proportion of readily biodegradable substance andbiodegradable substances were up to50%and76%. In order to gain small organic matter such as VFAs for biological nutrientremoval, different disintegrated sludge were used to hydrolyze and acidificateat pH7and25℃within15days. The change of VFAs showed that theoptimal time for VFAs accumulation was5days and VFAs concentration were1380,1180and1480mg/L, respectively. Through comparing SCOD andparticle size with VFAs production, higher initial SCOD and smaller particlesize were beneficial for VFAs production. The study of microbial communitystructure by PCR-DGGE in sludge hydrolysis and acidification processeshowed that different sludge pretreatment resulted in different substrates andmicrobial community. The main microbes involved in hydrolysis andacidification of disintegrated sludge were Proteobacteria, Firmicutes,Bacteroidetes, TM7, Actinobacteria and Chloroflexi. Of interest,Actinobacteria mainly hydrolyzed proteins to amino acids, Bacteroidetes andChloroflexi converted polysaccharides and amino acids to pyruvic acid.Firmicutes could degrade amino acid and pyruvate to acetic acid, propionicand butyric acid, but β-Proteobacteria could use and decrease acetic acid.To improve the VFAs accumulation of sludge hydrolysis and acidification,alkaline regulation was applied to inhibit VFAs consumption. Therefore,disintegrated sludge and inoculated sludge (1:1) were mixed, and then pH wasadjusted to7-12for hydrolysis and acidification, respectively. The resultsshowed that initial alkaline regulation could inhibit methanogenesis andenhanced VFAs accumulation in initial time, and the VFAs concentrationreached2620mg/L at initial pH11and7d. By maintaining pH (7,8,9and10)in sludge hydrolysis and acidification process for VFAs accumulation, pH9not only promoted VFAs accumulation, but also inhibited acetic acidconsumption. The maximum of VFAs was3111mg/L within15d. Theacidification product by initial pH11and processed pH9were used fordenitrification and phosphorus release, and the result showed that VFAsproduced by alkaline processed regulation was better than initial alkalineregulation and sodium acetate for denitrification and phosphorus release.The acidification product, by ultrasonic disintegration and pH9regulations, was added into A/A/O reactor as carbon resource to observe thenutrient removal performance. The effluent of TN and TP decreased to4.1and 0.5mg/L from13.5and6.2mg/L, and corresponding removal rate werereached85.4%and94.7%, respectively. Microbial community was detected byPCR-DGGE technology, and the results demonstrated that microbialcommunity changed enormously with acidification product addition.Proteobacteria increased gradually and played important role in nutrientremoval, Bacteroidetes were significant denitrification phosphorus-removingbacteria, Actinobacteria and Firmutes had close relationship with CODremoval, while Chloroflexi and TM7discovered. At the same time,simultaneous nitrification the denitrifying bacteria Alphaproteobacteria anddenitrifying phosphorus removal bacteria Sphingobacteriaceae were enrichedby acidification product application. |