| The specific influence of temperature on SBR system and the technology of sludge dewatering are studied in this paper. The result is used to guide the design and operation of Wastewater treatment plant.The influent quality of Xi'an City Wastewater Treatment Plant fluctuates acutely all of the year. In winter and spring, the COD of the influent changes from 400 to 650 mg/L compared with 275 to 320 mg/L in summer and autumn. All the year round, the concentration of ammonia in it varies from 25 to 42 mg/L, as well as phosphate from 2 to 4.5 mg/L and SS from 264 to 320mg/L.The winter of the northern part is very cold, the ice period lasts 3-6 months. The lowest temperature is below-30℃, the average water temperature in winter is not more than 10℃. The mean annual temperature is 13.3℃ and the lowest temperature is -11.8℃ in Xi'an. Considering that the winter temperature is low and the effluent quality is bad, the specific influence of temperature on SBR system is deeply studied.1. Within 4-31℃ the relation between reaction coefficient K and mixture temperature is:KT=K20θ(T-20)According to the experimental data, removal rate of COD in aerobic phase is:Reaction rate is 1.25mg/gMLSS.h at 15℃Reaction rate is 1.5mg/gMLSS.h at 20℃Reaction rate is 11.8mg/gMLSS.h at 25℃For sanitary Wastewater θ=1.0015 and K is slightly influenced by temperature, but for the industrial Wastewater θ=1.03-1.10 and K is greatly influenced by temperature.In my experiment θ=1.037, this is because the Wastewater of DengJiaCun is consisted of 30% sanitary Wastewater and70 % industrial Wastewater. 2. According to the experimental data, the nitration rate at different temperature is (under the same sludge density):K15=0.87 mg NO3/gMLSS.hK18=1.35 mg NO3/gMLSS.hK20=1.50 mg NO3/gMLSS.hK25=2.2 mg NO3/gMLSS.hK27=2.55 mg NO3/gMLSS.hθ=1.08, nitration rate is higher, the temperature is higher. Compared with COD removal, the influence of temperature on nitrating is greater.Other conditions are the same at 15 ℃,20℃ and 25℃ the rate of conversion of nitrate is 70.5%,87.5% and 98.2% respectively.3. In the 3 phrases no significant correlation is found between both phosphorus release and uptake and temperature. The rates of phosphorus release and uptake is within 2-20 mgP/gMLSS.h. the overall phosphorus removal efficiencies is kept in 30-85%.the phosphorus removal efficiencies is mainly effected by the nitrate. The low temperature decreases the denitrification rate and then the phosphorus release in anaerobic phase.4. The average water ration of residual sludge is 97.4% and the MLVSS is 70.7% ; the average water ration of middle-load sludge is 92.4% and the MLVSS is 34.8%. Since the sludge resistivity is huge, the sludge must be conditioned before they are dewatered by machine.5. The average water ration of residual sludge cake is 84%, the average water ration of middle-load sludge cake is 70%. Medicine dosage of average active sludge is less than the residual sludge, because the water ration of average active sludge is low after nitrifying. The sharp drop of water ration is because the sand is in the sludge.6. The organic substance is more and the sludge is more difficult to dewater vice versa. Water ration is bigger and the sludge is more difficult to dewater. For Wastewater plant the thickened sludge is more difficult to dewater than the digestion sludge.
|
PDF Full Text Request