The Effects Of Bio-stimulant On Extracellular Polymeric Substances Performance Of Activated Sludge

As reported currently,the waste water from pulp and papermaking in China is about 2755 million ton,accounting 14.7% of the whole industrial waste water.How to dispose this waste water is a bottleneck problem in papermaking mill.It is difficult to processing the waster water because water discharge is large,the pollutant type is complex.Bio-stimulant can promote the microbial self-metabolism and biosynthesis.It can also accelerate the decomposition of microorganisms for the decomposition of organic matter.Hence,extensive attention has been paid in the application of the Bio-stimulant.EPS is a microbial metabolite,its content and composition can affect the properties of the sludge as well as the water quality.A Bio-stimulant?BS?has been developed for refractory organic industrial waste water by our research group three years.It has found that adding BS in papermaking waste water,the removal rate of CODCr increased by about 6%,the inhibition ration of biological toxicity is reduced by 98.84%.However,the research on promoting the mechanism of BS for microbes is needed.In this paper,we study that EPS in aerobic flocculent sludge is how to effected by BS additive amount under the different water CODCr,we also analyze the absorption and secretion of nutrients in water and the structural changes of EPS in the sludge as well as effect the performance of sludge.Using a single factor experiment,we got a result that when the influent concentrations was 813 mg · L^-1,1100 mg · L^-1 and 1300 mg · L^-1,the BS optimum removal rate of CODCr was 4.8%,4.3% and 4.2%,respectively,which higher than that of BS0 group,and the optimum removal rate was 300?L·L^-1,400 ?L·L^-1 and 500 ?L·L^-1.The orthogonal experiment results also showed that CODCr was 1100 mg · L^-1 and the optimum amount of BS was 400?L·L^-1,and the optimum treatment was 30 h.By analyzing the composition of EPS,the addition of BS has a significant influence on the composition and structure of EPS.It was found that the influence of BS additive amount to EPS and TB-EPS content was less than 800 mg · L^-1 under low influent CODCr concentration,and the influence of CODCr concentration was significant and TB-EPS was the largest when CODCr concentration was 1100 1300 mg · L^-1.BS was significantly promoted by LB-EPS polysaccharide and TB-EPS protein and humus under different influent CODCr concentrations.BS optimal group was associated with the maximum content of protein,polysaccharide and DNA in LB-EPS and the maximum content of humus in TB-EPS,and the minimum DNA content.When the influent CODCr concentration was at 1100 mg · L^-1,the ability of BS2 group to absorb and secrete protein and absorb and secrete polysaccharide was significantly increased by 33% and 23.9%.The surface morphology of sludge was observed by environmental scanning electron microscopy.The results show that the sludge of BS2 had good water retention performance,the sludge skeleton was full and had strong continuity.After extracting TB-EPS,the cavity layer and structure cavity was appeared.Using XRD instrument,it was found that the crystallization was CaSO4 · 2H2 O and the sludge of the BS2 group was more smoother.The new characteristic peaks of carboxyl group,hydroxyl group and lipid were observed in the BS2 group by IR analysis.The primary amides and aliphatic amines from TB-EPS sludge was affected.The results showed that the main components of LB-EPS in BS0 and BS2 groups were protein,and the aggregation effect of BS2 group was stronger.The amino functional groups in TB-EPS was increased in the BS2 group,the protoplast of the main chain was changed.The peptide chain was changed and flocculation activity was increased because of chemical bond effect.BS0 group contains glucuronic acid,N-acetyl amino carbohydrates and amides which contained in TB-EPS of BS2 have a significant flocculation characteristics.Using ICP-AES analysis method to analyze the conversion process of the metal ions in the activated sludge system,we found that the amount of metal ions in the sludge of BS2 was decreased.the content of Fe3+ increased significantly in BS group.The ion content of TB-EPS in BS group was about twice as large asBS0 group.LB-EPS and TB-EPS were the main part of the adsorption of Ca²⁺ in BS2 group.the TB-EPS adsorbed more Ca²⁺ and Mg²⁺ than that of BS0.Finally,it is concluded that the adsorption order of metal ions in LB-EPS and TB-EPS as follow: Ca²⁺>Mg²⁺>Fe3+>Zn²⁺>Mn²⁺.The deposition order of metal ions in activated sludge as follow: Fe3+>Mg²⁺>Mn²⁺>Zn²⁺>Ca²⁺.The flocculation effect was analyzed by ESS and Zeta method.The priority order was BS2 group> BS1 group> BS0 group> BS3 group.LB-EPS was reverse correlation to flocculation performance.TB-EPS was positive correlation to flocculation performance.The results showed that the settling performance of sludge was positively correlated with the ratio of the amount of protein in LB-EPS and with the amount of protein in EPS.DSC found that the dehydration performance of sludge was enhanced with the TB-EPS?protein and polysaccharide?and the bound water content?WB?decreased,and the LB-EPS?protein and polysaccharide?increased.Excessive addition of BS will cause a certain degree with deterioration on sludge dewatering performance.In this paper,we study the relationship between BS addition under different influent CODCr and composition of EPS in aerobic flocculent sludge.According to variation of EPS,microbial absorption and secretion of nutrients in water were studied.We study the effect of BS on the properties of EPS and activated sludge which provided a theoretical basis for the application of BS in industrial wastewater treatment.The results showed that microbial absorption and secretion were promoted by BS.It can be exposured carboxyl,hydroxyl,acetyl and amino by regulating the amount of protein and polysaccharide.And the sludge performance of flocculation,sedimentation,and tolerance can be improved.