Effect Of Different Carbon Sources On Simultaneous Conversion Of Sulfur And Nitrogen In Wastewater Under Micro-Oxygen Condition

The discharge of wastewater containing sulfide and nitrate into the environment will destroy the natural environment and harm human health,so how to effectively treat the wastewater with low energy consumption is one of the research hotspots at present.Biological process has the advantages of green environmental protection,good treatment effect and low cost,mainly including sulfur autotrophic denitrification,sulfur autotrophic and heterotrophic denitrification processes.Adding a certain amount of dissolved oxygen in the anaerobic reaction can promote the conversion of sulfide and nitrate.Adding carbon source into the reactor can effectively improve the desulfurization and denitrification effect,but adding carbon source will increase the operation cost.As the largest output waste of sewage treatment plants,waste activated sludge has great potential for resource utilization.Sludge lysate as a carbon source is one of the hotspots of current research,among which the sludge lysate generated by thermal-alkaline treatment of waste sludge has attracted attention due to its high SCOD yield.In this paper,the sludge lysate was prepared by thermo-alkali method,the feasibility of conversion of sulphide and nitrate as a carbon source was explored under micro-oxygen conditions,and then a continuous flow experiment was carried out to compare the biotransformation effects of sulfur and nitrogen in the reactor when glucose and sludge lysate were used as carbon sources,and the biomes were analyzed to explore the controlling factors of sulfur and nitrogen conversion process.The main findings of the study are as follows:（1）The optimum pH of thermal-alkaline of waste sludge under different pH conditions were investigated.The waste sludge was treated by thermal-alkaline method,and the pyrolysis temperature and pyrolysis time was controled.investigate the dissolution of various indicators under the three conditions of 8,10 and 12.The results showed that the amount of SCOD,polysaccharide,protein and volatile fatty acid in the lysate increased with the increase of p H value.Considering the cost of pyrolysis and the dissolution rate of SOCD,12 was selected as the p H value of the thermal-alkaline treatment of waste sludge in this experiment.（2）The feasibility of sludge lysate as a carbon source for sulfur and nitrogen conversion under micro-oxygen conditions was explored.Under micro-oxygen conditions,the sludge lysate was used as a carbon source to conduct batch experiments on inoculated sludge,and glucose and sludge lysate were used as carbon sources,respectively,of which the sludge lysate and glucose experimental group completely converted the sulfide(S^2-)within 21 h,and the conversion rate of nitrate nitrogen(NO₃^--N)when the sludge lysate was a carbon source within 48 h was about 73%,and the conversion rate of glucose was about 64%when the glucose was the carbon source.At about 30 h,the COD removal rate of both groups reached about 84%,and the conversion rate of S^2-,NO₃^--N and COD was higher than that of glucose when the sludge lysate was used as the carbon source.Sludge lysate as the carbon source can achieve the same sulfur nitrogen conversion effect as glucose.（3）The effect of sulfur and nitrogen conversion in continuous flow experiments at different carbon sources under micro-oxygen conditions was explored.Using sludge lysate and glucose as carbon sources,the hydraulic residence time is first controlled,and the concentration of sulfide and nitrate nitrogen in the inlet water is gradually increased to start the reactor.Subsequently,the concentration of sulphide and nitrate in the inlet water was controlled,the hydraulic residence time of the reactor was gradually reduced to increase the inlet water load of the reactor,and the operation efficiency of the micro-oxygen reactor was examined,and the yield of sulfur element was increased with the increase of the sulfur load of the inlet water.When the inlet water load reached9.95 kg-S·m^-3·d^-1,3.2 kg-N·m^-3·d^-1,12.0 kg-COD·m^-3·d^-1,t the conversion rates of sulfide,nitrate and COD in the two reactors exceed 99%,90%and 80%,respectively.The sulfur production rate of the reactor using sludge lysate as carbon source was more than 80%,and that of the reactor using glucose as carbon source was more than 75%.（4）The microbial community changes of the reactor under different loads under different carbon sources was explored.Through the analysis of the sparse curve,Alpha diversity index and microbial community structure（phylum,genus）,the proportion of functional microorganisms in the reactor with sludge lysate as the carbon source was71.01%,the proportion of functional microorganisms in the reactor with glucose as the carbon source was 76.97%,and the main genus of bacteria in the reactor with the sludge lysate as the carbon source was Tissierella,Acetoanaerobium and Roseomonas.The main strains in the reactor using glucose as the carbon source are Paracoccus,Stappia,Rhodobacter,unclassified＿Rhodocyclaceae,and unclassified＿betaproteobacteria.The main bacteria in the glucose reactor are The proportion of other microorganisms in the sludge lysate reactor is higher than that in the glucose reactor,which may be the reason for the complex organic composition of the sludge lysate.