Study Of Desulfurization Under Different Conditons And Sulfur Metabolism In Light UASB

Sulfate-containing wastewater is characterized by wide sources,various types and great harm.At present,anaerobic reactors are mostly used to treat organic wastewater with high concentration of sulfate,and certain results have been achieved.In this paper,the anaerobic reactor with light was used and the non-light reactor was set as the control.The reactor was started up in the way of gradually increasing the load and operated under different conditions.pH,COD,SO4^2-,S^2-of the effluent and gas production were detected continuously.The sludge index and biological phases were analyzed regularly.The experiment included four phases:start-up,adding sulfate,increasing sulfate load and exchanging operation conditions.In phase-?,COD in influent was increased to 4000mg/L and the pH as well as COD removal rate got stable after 65 days.There was little difference between the light and non-light reactors.In phase-?,sulfate was added to the water as the COD concentration was simultaneously increased to 8000 mg/L,and the reactor remained stable after 67 days.It showed that SO4^2-removal rate of the light reactor was about 10%higher than that in the non-light reactor as SO4^2-concentration surpass 1500mg/L.In addition,adding a little sulfate into influent was beneficial to maintain gas components stable though might inhibit gas production.In phase-?,the SO4^2-concentration was continuously increased to made reactors operate under different COD/SO4^2-ratios?4:1².5:1?.The results showed that as COD/SO4^2-ratio decreased,the effluent quality deteriorated and the gas production reduced.At the same time,when the ratio was less than 4:1,the light effect on the removal of COD and SO4^2-as well as gas production was significantly improved.It was also found that light was beneficial to sulfate reduction and the further transformation of S^2-.In phase-?,circulation was added to the reactor and the optimal circulation ratio was0.75.In the meanwhile,four small reactors were used with different wavelengths of light.It showed that reactors with white and yellow light operated better than others.The sludge got worse in high organic load and sulfate concentration.And light was beneficial to sludge proliferation in low COD/SO4^2-ratio.After a period of operating time,some faint yellow solid appeared in the outlet and it was almost concluded as sulfur with elemental analysis.The sludge at different phases was analyzed with SEM and high-throughput sequencing.It showed that there were mainly spherical and rod-shaped microorganisms in sludge as the COD/SO4^2-ratio decreased.And the majority in the light reactor was short rod-shaped.The microbial diversity and abundance in sludge were also affected when the COD/SO4^2-ratio decreased.Moreover,light was beneficial to the growth of desulfurization bacteria in low COD/SO4^2-ratio.