A Study On The Mechanism Of Anaerobic Strengthening Of High Salt Organic Wastewater By Sludge Lysate

Many processes in industrial production will generate a large number of high salt organic wastewater.Anaerobic biological treatment technology is widely used in the treatment of high salt wastewater because of its advantages of high efficiency in removing organic matter and low operating cost.However,high salt will cause a sharp increase in the osmotic pressure of microbial cells,which will lead to the separation and death of the cell and the treatment effect are also not well.For this problem,the way to sustain cell viability is to add osmoprotectant to balance osmotic pressure on both sides of the cell membrane.Osmoprotectant extracted from the living is the first choice because of its simple operation and good effect.However,the high cost of extraction and complex production process limit its application.Sludge lysate was used as osmoprotectant and added to anaerobic reactor to explore the effect and mechanism.Firstly,the effects of different salinity conditions on methanogenesis and dehydrogenase activity during anaerobic treatment were studied.The domestication cycles were all shorter than one week when applying the sludge lysate into the system compared with the results with NaCl concentration of 35 g/L,40 g/L and 45 g/L respectively.Dehydrogenase activity was also 53%,40%and 56%higher than the control.Among them,the CH₄ yield was enhanced about 5 times higher than the control group when the salinity was 40 g/L on day 19 of the reaction.The results present that the activity of sludge lysate on microorganism and the metabolic ability of organic substance were significantly enhanced.The protein content in the control was 2⁷ mg/g·Vss more than that in the enhanced group with NaCl concentration of35 g/L to 50 g/L.The cells in the controlwere tightly packed with EPS but the EPS on the cell surface of the enhanced group was loose.This indicates that the protection of sludge lysate to microorganisms is not caused by stimulating the secretion of EPS in cells.Further analysis of the cellular structure and intracellular substances showed that cell permeability changes of activated sludge was reduced 9.2%and sludge size of the enhanced group was enhanced 3.92?m than the control group.Therefore,sludge lysate acted as an osmotic protector could effectively maintain cell morphology and enhance microbial tolerance.The changes of K⁺concentration in the cells of the enhanced group were small,indicating that the osmotic protection of sludge lysate is not an intracellular salt mechanism.The concentration of Mg²⁺was enhanced 0.44 mg/L and the concentration of Ca²⁺was enhanced 0.53 mg/L.It could be concluded that the sludge lysate maintains the original metabolic pathway in cells mainly by increasing the concentration of Mg²⁺and Ca²⁺.In general,sludge lysate mainly resisted the osmotic pressure from the outside environment by increasing the content of betaine and free amino acids in the cell.The concentration in the enhancement group of intracellular polysaccharide was 63.9 mg/g·Vss higher than that in the control group.It can be concluded that the intracellular pathway of the enhanced group changes less than that in the control group and it is helpful for the maintenance of normal physiological metabolism of microorganisms.From what has been discussed above,the protective effect of sludge cracking fluid is mainly to maintain the osmotic pressure balance on both sides of the cell membrane by changing the concentration of intracellular substances through small molecular osmosis.