The Correlation Between The Characteristics Of Activated Sludge And Polyhydroxyalkanoates(PHAs) Accumulation

The biodegradable plastic,PHAs,is a kind of high value-added products synthesized by activated sludge,attracting more and more attention as a promising products.In this study,the sludge properties such as particle size,COD,Zeta,MLSS,EPS in the process of PHAs accumulation were investigated,so as to establish the correlation between the characteristics of activated sludge and the PHAs accumulation.The results were concluded as follow:(1)The polymer produced from the sludge acclimated was PHB,PHV and PHBV by using sodium acetate,sodium propionate and mixed substrates as the carbon substrate,respectively.(2)MLSS concentration increased in SBRPHB?SBRPHV and SBRPHBV(fed with sodium acetate,sodium propionate and the two-mixture,respectively).There was a significant positive linear correlation between PHAs and MLSS.The correlation coefficients of PHB,PHV,PHBV and MLSS were 0.782,0.480 and 0.489,respectively.The combined correlation coefficient was 0.455 between PHAs and MLSS.(3)The Zeta potential of SBRPHB remained at the range of-2 mV?0 mV,while that of SBRPHV changed smoothly with dropping trend at the range of-20 mV?-3 mV.For SBRPHBV,the Zeta potential was-20 mV?-10 mV.(4)The content of protein and polysaccharide in TB-EPS(Tightly bound EPS)was higher than that of LB-EPS(Loosely bound EPS).For SBRPHB,the content of protein and polysaccharide in TB-EPS were 100?140 mg/L and 20?50 mg/L respectively,while TB-EPS were 150?220 mg/L and 60?120 mg/L.In the process of PHAs accumulation,the PHAs held no obvious correlation with content of protein in EPS,however,a significant positive linear correlation with content of polysaccharide in SBRPPHB and SBRPHBV(R=0.726;R=0.557)was obtained.In addition,the ratio of protein/polysaccharide in EPS and accumulation time also had obvious linear positive correlation in SBRPHV and SBRPHBV(R=-0.583;R=-0.551).(5)The particle size of sludge was in the range of 20?110 ?m.The mean particle size of sludge floc showed a decreasing trend in the process of PHAs accumulation.The mean particle size was negatively correlated with the content of PHAs and MLSS.The correlation coefficients of PHAs and mean particle size were-0.580,-0.666 and-0.921 in SBRPHB,SBRPHV and SBRPHBv,respectively.The correlation coefficients of mean particle size and MLSS were-0.434,-0.499,-0.707,respectively.In a word,the floc size tended to be smaller and the MLSS tended to be higher while the PHAs content was high.