Study On The Treatment Of Garlic Wastewater By Activated Sludge System

For the past many years, industrial wastewater pollution is increasingly seriously due to acceleration of the process of industrialization in China, and food wastewater occupies a large ratio of this pollution. The garlic processing wastewater is quite special kind of food wastewater, it has the common feature of food wastewater such as high organic load, rich in nitrogen and phosphorus. Moreover, because garlic's own characteristics, the wastewater contains a number of bactericidal diallyl ether and other organic sulfur. In this background, this thesis presents the activated sludge method and the pretreatment-activated sludge method to curb the garlic processing water. Besides, optimal parameters and the final treatment effect of two methods were studied depth.Firstly, the baffle was installed in every reactor to isolate the precipitation zone and extend residence time. Then, the pulse method was used to determine the resident time distribution of the reactor. Results of experiment showed that under the flow of 12L/h, the system's average residence time respectively was 28.74min and 26.83min whether use the baffle or not. So it can explain that the set of baffle achieve the desired goals.At the same time, under three different flow of 12L/h,7.2L/h and 4.8L/h, the system's average residence time respectively was 34.15min,41.26min and 54.27min. Furthermore, the dimensionless variance respectively was 0.552,0.319 and 0.276. Research showed the backmixing degree of the system reduced as the flow decreased, it also indicated that flow pattern of the material in reactors approach to the plug-flow state as the flow decreased.The best technological conditions of active sludge system that processed garlic wastewater was determined by the COD removing rate.The experiment showed that when accidental activated sludge was culture in the conditions of temperature for 25℃, feeding speed of flow 0.8L/h and influent COD concentration for 2000mg/L, treatment effect was best.In this experiment, to disposed garlic wastewater by activated sludge process directly caused series of problems. The condition of activated sludge was not too stable, the sludge even occurred to die. The COD removal rate could only achieve to 73%, the COD of effluent water was over 600mg/L. Generally, these results cannot discharge to reach standard.GC-MS was applied to carry out qualitative analysis on the principal components of the garlic wastewater before and after pretreatment, results showed that after the pretreatment, the amount of diallyl sulfide in garlic wastewater which can disinfect reduced obviously. It proved that the pretreatment method was feasible. Based on the COD removal rate, taken the pretreatment optimum temperature as 70℃from three pretreatment temperatures of 60℃,70℃and 80℃.The activated sludge in garlic wastewater was stable in pretreatment-activated sludge craft. Effluent water was clear and COD removal rate reached as high as 93%, moreover, COD of effluent water approximately was 110mg/L, so it can discharge to reach standard. By contrast of the two processes, the pretreatment effect was an ideal application to achieve the desired objectives.