| 7-ACA pharmaceutical wastewater is characterized by high COD,high sulfate,and high ammonia nitrogen.The high sulfate content may result in a significant reduction in anaerobic biological treatment efficiency and severe pollution threat to the environment.For the nitrogen removal,conventional biological processes remain complicated and high energy consumption.At present,it is difficult to realize the efficient treatment of such wastewater.In order to solve these problems,in the present study,a novel technique for carbon nitrogen sulfur co-removal was established,and a pilot scale study was carried out.This research was based on a wastewater treatment project of 7-ACA production enterprise located in Shijiazhuang,Hebei.A pilot scale of SR-CR reactor(UASB)and DSR reactor(EGSB)were established.The process of removing carbon,nitrogen and sulfur and the optimal operation parameters of each section were studied.In addition,the effluent of the final settling tank of the sewage treatment plant was treated by the method of coagulation sedimentation and Fenton oxidation.Influence factors and treatment effect of each process unit were investigated by the evaluation index of COD and color,the optimum process parameters were determined.The results were listed as below:1)SR-CR reactor is a UASB.When COD of the wastewater maintained in the range of 11000~12000 mg/L,sulfate remained in 3500~4000 mg/L,and the sulfate influent load was less than 1.0 kg/(m3·d),methane producing bacteria(MPB)and sulfate reducing bacteria(SRB)could coexist in the anaerobic environment.The removal rates of COD and sulfate were both more than 80%;when the sulfate influent load was 2.5 kg/(m3·d),MPB was severely inhibited,the effluent sulfide reached 300 mg/L,the removal rate of COD eventually reduced to about 20%,and the sulfate removal rate remained at about 90%.2)DSR reactor is an EGSB.In the design of reactor,the effect of mass transfer was improved by the inner loop,and the content of sludge was increased by adding suspended filler in the middle and upper of the reactor.In this study,the optimal molar ratio of wastewater influent pollutants was n(TOC): n(N):(n):(S),(3.5:1.1:1).The influent COD volume load could reach 2.36 kgCOD/(m3·d)under the condition of 3.5:1.1:1 of the influent n(TOC): n(N): n(S),the removal rate of COD was 55%.30 of temperature,8 ?of Ph and 1.3m/h of flow rate.While,when the NO3-N volume loading reached 0.337 kgN/(m3·d),the removal rate of NO3-N was more than 95%.When the S2--S volume loading reached 0.7 kgS/(m3·d),sulfide biotransformation rate was 74%,and the effluent sulfide concentration remained less than 200 mg/L.After the system operating 90 d,the sulfide conversion efficiency of DSR reactor was promoted by the method of micro oxygen enhancement.When the content of DO was 0.15 mg/L,the removal rate of COD increased to 70%,the conversion rate of sulfur was increased to 90%,and the removal rate of nitrate nitrogen was about 95%.3)Advanced treatment of final settling tank effluent was conducted by coagulation sedimentation and Fenton oxidation.The coagulation conditions were: initial pH 7,PAC 80 mg/L,PAM 8 mg/L,mixing 15 min with 45 rpm;Fenton oxidation conditions were: initial pH 3,H2O2(30%)4.0 ml/L,dosage(H2O2:Fe2+ molar ratio)is 4:1,the reaction time is 75 min.Wastewater COD decreased from 420 mg/L to 75 mg/L,and the chroma was decreased from 200 times to 50 times,the removal rate of COD and chroma were 82.14% and 75%,respectively,which could meet the discharge requirements. |
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