The Pilot Scale Study And Operation Of Malt Wastewater Treatment By Hydrolytic Acidification IFAS Process

Malt production wastewater is produced in the course of processing barley into malt.In 2016,the total discharge of waste water in our country is 20.47 million tons.The treatment process of malt wastewater at home and abroad includes SBR process,CASS process,hydrolysis acidification-biological contact oxidation process,hydrolysis acidification-activated sludge-air flotation process,etc.The hydrolytic acidification process can degrade the refractory organics in wheat husks in the treatment of malt wastewater.It can also improve the biodegradability of wastewater and provide a buffer for the change of water quality.Integrated fixed-film and activated sludge technology combines the advantages of biofilm process and activated sludge method.IFAS process has high efficiency,stable effluent effect and less occupied area in malt production wastewater treatment.A malt factory in Dalian,producing 6,000 tons of wastewater per day,is in need of upgrading.In this paper,the wastewater discharge condition of the malt factory and its original process effect were investigated and a pilot scale experiment was carried out.Under the guidance of the pilot experiment,the system of wastewater treatment in the malt factory was reformed,and the water quality of the effluent was investigated.According to the characteristics of the wastewater and the existing problems in the wastewater treatment system,a new design is presented based on the hydrolytic acidification-IFAS process,and a pilot plant is designed.The pilot design used elastic fine filtration device to remove suspended solid,using cross flow filler in anaerobic tank,using suspended filler in the aerobic tank forming activated sludge-biofilm structure,and increased the second pond and sludge return system.The tanks are reduced in proportion to the existing tanks,and had the same hydraulic retention time as the original ones.The pilot plant successfully started up in the environment with air temperature at-17~3? and water temperature at 3 ~ 8 ?.The pH in hydrolytic acidification tank was reduced from 6.7 to 6,and the B/C increased from 6.0 to 6.8,which improved the biodegradability of wastewater.Concentration of active sludge in aerobic tanks reached MLSS of 4000 ~ 5000 mg/L,and the biofilm biomass on the fillers reached 12 g/L.The best operation condition was discussed and the conclusion is that the sludge return ratio(R)is 75%,and the best gas/water ratio(G)is 20:1.Under the condition above,the removal rate of COD of the pilot plant reached more than 90% with COD below 150 mg/L in effluent,and the concentration of ammonia nitrogen in effluent was lower than 2 mg/L.The pilot plant was run at the optimum operating condition,which can meet the standards of discharging into the municipal network.In experiments of further removal to pollutant in the biochemical effluent,Fenton method could well remove the organic matter in the water,which steadily controlled the COD of effluent under 80 mg/L,achieving the standard of discharging into natural water.The cost of using Fenton method to treat the wastewater is 3.1 yuan per ton.Based on the results of the pilot-scale test,the modification scheme of the malt production wastewater treatment system was designed,and the modification and successfully started up.During the stable operation,COD of the effluent remained in the 220 mg/L,and the ammonia nitrogen was less than 5 mg/L,which met the design standard.After the renovation project is completed,the factory's effect on the environment will be greatly reduced,and the cost of treating each cubic meter of wastewater under normal operation will be 2.28 yuan,which is 15.6% cheaper than the original system.