Research On A New Process For Removing COD From Sewage Through The Process Of Sulfate Reduction

Conventional sewage treatment processes generate a large amount of sludge and require relatively large operating costs.This article attempts to use the sulfate reduction process to remove COD in wastewater,and then combine the A/O process to remove nitrogen in the wastewater,so as to achieve the purpose of reducing the amount of sludge and operating costs.The main research contents are as follows:(1)Under the condition of COD of 2000mg/L and COD/SO42-of 2,a system for removing COD by sulfate reduction was constructed.After 20 days of operation,the COD removed by the sulfate reduction process accounted for about 83% of the total COD removal.(2)The sulfate reduction process has a high removal effect on different concentrations of COD.When the COD concentration is 500 mg/L and the hydraulic retention time is 24 h,the COD removal rate under the conditions of COD/SO42-equal to 2,0.83 and 0.5 are 52%,54% and 46%,respectively.When the COD concentration is 1000 mg/L and 2000 mg/L,and the hydraulic retention time is more than 16 h,the COD removal rate of different COD/SO42-ratio can reach about 80%.Among them,COD/SO42-of 2 has the best effect,and the removal rate can reach more than 90%.When the COD concentration is 2000 mg/L and the hydraulic retention time is reduced to 10 h,the COD removal rate of different COD/SO42-ratio is similar,close to 66%.(3)The removal of COD in the sulfate-reducing anaerobic system has two effects,namely the removal of sulfate-reducing bacteria and the removal of microorganisms other than sulfate-reducing bacteria.The former is the main contributor.The ratio of COD removed by sulfate reducing bacteria to the total COD removed increased with the decrease of COD/SO42-,decreased with the increase of organic matter concentration,and increased with the decrease of hydraulic retention time.(4)When calcium sulfate is used as the source of sulfate,the removal effect of COD is lower than that of sodium sulfate.When the COD concentration is 500 mg/L,1000 mg/L,and 2000 mg/L,and the hydraulic retention time is 24,the COD removal rate with calcium sulfate as sulfate is 45%,68%,and 68%,respectively.And the removal rate showed a slow downward trend with the extension of running time.(5)The effluent quality of the combined process reaches the city’s first-level A discharge standard.The COD removal rate of sewage is over 97%,the COD concentration of effluent is below 45 mg/L;the removal rate of ammonia nitrogen is about 98%,and the concentration of effluent ammonia nitrogen is below 1 mg/L,the total nitrogen removal rate is about 87%,and the total nitrogen concentration in the effluent is about 12 mg/L.(6)High-throughput sequencing analysis showed that the diversity of bacterial communities under the conditions of COD/SO42-of 0.83 and 0.5 was higher than that of COD/SO42-of 2.The main functional bacteria of the anaerobic system are Desulfomicrobium and Desulfococcus,the abundance of both is higher under the conditions of COD/SO42-of 0.83 and 0.5 than COD/SO42-of 2.And with the increase of organic matter concentration,the abundance of SRB genus under the conditions of COD/SO42-of 0.83 and 0.5 is increased,which is related to the increase of COD removal rate.The reduction of HRT promotes the enrichment of SRB genus,changes the distribution of SRB genus,and increases the proportion of incompletely oxidized SRB.During MBBR carrier filming,the main bacterial phyla are Proteobacteria,Bacteroidetes and Nitrospirae.The change trend of Nitrospirae abundance is related to the treatment effect of ammonia nitrogen.The main functional bacteria are Nitrosomonas and Nitrospira,and their abundance reaches 21.53% and 8.34% respectively by the end of the filming.After the reactors are connected in series,the bacterial community of MBBR biofilm has changed greatly.Saccharimonadaceae bacteria and Thiotrix related to sulfur metabolism appeared in the bacterial community.The abundance of Nitrosomonas decreased slightly,which was related to the decrease of the ammonia nitrogen concentration in the influent.The abundance of Nitrospira first increased,then decreased,and finally stabilized at 10.4%.In DNUASB,Rhodanobacter is mainly involved in denitrification,and its abundance is about 2.08%.