The A~2/O+SNAD Combined Process For Treating Slaughtering And Meat Processing Industrial Wastewater

The industrial wastewater of slaughter and meat process exists high COD and ammonia nitrogen.The type of wastewater can be biodegradable and suitable by using biological treatment,which contains a large number of high-concentration organic compounds,suspended solids,proteins,fats,bacteria and other carbohydrates,and the components are complex.The effect of N,P in wastewater on eutrophication of water bodies has become the most serious water pollution problems in the river basin in China.In recent years,with the strengthening of pollution control by the state,the discharged requirements for industrial waste water have become more and more stringent.Facing new standards,some sewage treatment plants are urgent to upgrade in the early 21st century or earlier.In view of this situation,the development of a new biological treatment process for slaughter and meat processing industry becomes particularly critical.This project uses a couple of short-cut nitrification and denitrifying phosphorus and SNAD(short-cut nitrification,anaerobic ammonia oxidation,and denitrification)technology to deal with slaughter and meat processing industrial wastewater.The experimental device uses self-designed and developed A~2/O reactor in combination with the SNAD reactor.The short-cut nitrification and denitrification phosphorus removal process is run in the A~2/O reactor,and the AOB screening and aggregation are completed by controlling the dissolved oxygen and the sludge age that acquire a stable operation of short-cut nitrification,and then extend the sludge age to enrich the denitrifying phosphorus accumulating bacteria.When the denitrifying phosphorus removal process is opened,most of the ammonia nitrogen,COD,and TP can be removed in the A~2/O reactor.In the SNAD reactor,short-cut nitrification,anaerobic ammonia oxidation,and denitrification processes are run to increase the removal of ammonia nitrogen,total nitrogen and partial COD by controlling dissolved oxygen and temperature.The experimental reactor operation includes three stages.The first phase A~2/O short-cut nitrification and denitrification phosphorus removal start-up and commissioning test:(1)In the condition of influent ammonia nitrogen is 160mg/L and COD is 600mg/L,the reactor of short-cut nitrification can be achieved and stable operation by controlling the dissolved oxygen in the aerobic zone at 1.0mg/L,sludge age 5d,and temperature 23°C.The final effluent nitrite nitrogen concentration can be reached 30.2mg/L,nitrosation ratecan be stabilized at 90%.(2)When the influent water quality makes a difference,COD concentration is 1000mg/L, and ammonia nitrogen is 190mg/L,denitrification occurs in the sedimentation tank,and the dissolved oxygen in the aerobic tank is adjusted to 2mg/L timely,and 8.0L of activated sludge is added.After two weeks of acclimation,the final effluent ammonia nitrogen and COD can be reached 40 mg/L and198 mg/L,respectively.(3)In the case of COD concentration at 1000mg/L,ammonia nitrogen at 190mg/L,and short-cut nitrification in normal operation,the sludge age can be extended to 15d by reducing sludge discharge to 1.5L/d.In days of cultivation,denitrifying phosphorus removal process is successfully started.The amount of phosphorus adsorbed by the anoxic tank is as high as 20.5 mg/L,the absorption rate of phosphorus absorption can be reached 64%,and the data of total effluent phosphorus is 8.9mg/L.The start and stable operation test of second phase of SNAD:(1)When the water temperature is(30±1)°C,p H is 8.0 and the influent ammonia nitrogen concentration is maintained at 50 mg/L,the anaerobic ammonia oxidation sludge biofilm method is used to inoculate the baffled reactor.The aeration volume in the individual compartments can be activated by the 92d acclimation and can start the baffle CANON reactor and stabilize the operation phase.The concentrations of the effluent NH4+and TN in the reactor reach 1.9mg/L and 12.0mg/L,respectively.The rates reached 94.5%and 75%,respectively.(2)The simulated effluent of A~2/O is used as the feedwater to the SNAD reactor.The influent ammonia nitrogen concentration is kept at 50mg/L and the COD concentration is kept at 50mg/L.After130 days,the SNAD reactor is successfully started and operated stably.And the reactor was operated stably,the removal rates of NH4~+-N,TN and COD were 95%,85%,and 70%,respectively.(3)When the concentration of ammonia nitrogen is 50mg/L,COD concentration is 100mg/L,the SNAD reactor has the best removal abilities.When the COD concentration was 125 mg/L,the SNAD reactor is slightly inhibited.When the COD is increased to 150 mg/L,the COD shows a great inhibition of the SNAD reactor.The third phase of the experiment on the treatment of slaughter and meat processing industrial wastewater by the combination of short-cut nitrification and denitrification phosphorus removal and SNAD(short-cut nitrification,anaerobic ammonia oxidation and denitrification)technologies:(1)When the influent COD concentration is 1000 mg/L,the ammonia nitrogen concentration is 190 mg/L,and the total phosphorus is 28 mg/L,the dissolved oxygen in the aerobic zone of the A~2/O reactor is controlled at 2.0 mg/L.The residence time is 8.6h,the sludge discharge is 1.0L/d;the dissolved oxygen in the SNAD reaction is controlled at 1.0 L/min,the operating temperature is controlled at about 30°C,the hydraulic retention time is 4 h,and the A~2/O reaction is used.The effluent of the SNAD reactor is the effluent of the sedimentation tank of the unit.The effluent COD concentration of the combined process can reach 35 mg/L,the ammonia nitrogen concentration can reach 8.9 mg/L,the average removal rate of COD can reach 96%,and the average removal rate of ammonia nitrogen can reach 95%,the average removal rate of total phosphorus can reach 65.7%.The removal efficiency of ammonia nitrogen and COD have reached the industry-level standard for the“Emission Standard of Water Pollutants for Meat Processing Industry”(GB13457-92).(2)The contribution rate of A~2/O reactor in treating sewage is much larger than that of SNAD.The contribution rate of COD and ammonia nitrogen removal are more than 75%,and the contribution rate of SNAD reactor in total nitrogen removal is 40%.The A~2/O short-cut nitrification and denitrification phosphorus removal reactor play major roles in the treatment of denitrification and COD removal of sewage.The SNAD plays an important role in strengthening the removal of total nitrogen and ammonia nitrogen,ensuring that the effluent reaches the standard.