| Ultrafine silver powder is widely used in various industrial fields due to its special quantum size effect and surface effect,as well as its excellent electrical conductivity,thermal conductivity and chemical stability.In industry,silver powder is mostly produced by liquid phase reduction method.Due to the wide application in industry,the liquid phase reduction method is also known as one of the research hotspots in the production of silver powder,but the wastewater treatment technology generated in the production process is rarely reported.This paper takes waste water from two series of silver powder production in a silver powder production enterprise as the research object,the detection results of main pollutants in raw water are analyzed by combining the information of water quantity and main pollutant composition provided by enterprises,it was found that the reaction mother liquor s3-1 and s5-1 in the two series of wastewater contained more than 90% of the pollutants in the total wastewater,and the water amount was 40% of the total water amount.Therefore,according to the water quality characteristics of the two reaction mother liquor,stripping/evaporation and evaporation processes were adopted to pretreat the wastewater of s3-1 and s5-1 respectively to remove most of the pollutants and toxic substances in the wastewater and improve the biodegradability of the wastewater,then mixed with low concentration cleaning water for further anaerobic and aerobic combined biological treatment.Finally,advanced oxidation method was used to further treat the remaining refractory organic matter in the biological water to reduce the difficulty of advanced treatment at later period.The whole process was studied through the laboratory tests,the feasibility of treating silver powder wastewater by this process was discussed,On the other hand,the optimized operation parameters can not only ensure the treatment effect,but also control the consumption of energy and drugs,providing reference for the later engineering application.The laboratory tests results showed as follows.(1)The pH of inflow water at S3-1 ammonia nitrogen blowoff segment is set as12,temperature is 20 ?,gas liquid ratio is 3000,and the ammonia nitrogen concentration of inflow water is 16800 mg/L,after this process,effluent can drop to600-850 mg/L,and the removal rate can be up to 94.9% or more.After s3-1 is blown off,the effluent is evaporated directly without pH adjustment,and the removal rate of COD,total nitrogen and sulfate can reach 99.01%,95% and 99.65%.The removal rates of ammonia nitrogen and COD in the S5-1 evaporation section were 93.03% and96.4% respectively after the pH was adjusted to 4,both effectively removed most of the contaminants from the mother liquor.The concentration of sulfate in s3-2 was reduced by ion exchange method,and the final concentration of COD,ammonia nitrogen,sulfate and total nitrogen in the mixed water were 2580.8mg/L,243.82mg/L,103.5mg/L and 579mg/L,respectively.(2)The mixed water is treated in an integrated ABR+A/O reactor.The overall effluent COD,ammonia nitrogen and total nitrogen concentrations of the reactor were1170mg/L,43mg/L and 245mg/L respectively.Mainly due to the high concentration of nitrogen-containing organics that were difficult to be biodegraded in the mixed water,The removal rates of COD and total nitrogen in the reactor were about 50% and60% respectively.(3)Fenton oxidation method was used to further remove the refractory organic compounds in the effluent of the biological section.COD,total nitrogen and ammonia nitrogen in the effluent were reduced to 141mg/L,170mg/L and 37mg/L,respectively.Finally,the removal target(COD<300mg/L,total nitrogen <200mg/L,ammonia nitrogen <50mg/L)before the deep treatment was achieved. |
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