Pilot Study On Municipal Wastewater Treatment With Integrative Biofilm Reactor

Integrative biofilm reactor was designed according to the characteristics of small town sewage, which combined the A/O process and the biofilm process in one single treatment facility. The pilot experiment was designed to study municipal sewage treatment with integrative biofilm reactor based on the laboratory experiment study. In addition, the model for integrative biofilm system was developed to simulate the operation state of the pilot experiment.The experiment was performed under continuous inflow condition. In the experiment, the water quality of influent was described as follows: COD 56-1188 mg/L, ammonia nitrogen 9-54 mg/L, TN 14-59 mg/L, TP 2-30 mg/L, SS 30-1266 mg/L, pH 6.5-8.0. The operating parameters were optimized on HRT, reflux ratio, temperature and DO.The contrasting experiment was performed to optimize the parameter with other parameters fixed. The optimal HRT, reflux ratio, temperature was 7h, 100%, 28-30 oC respectively. The optimal DO for nitrogen removal was 3-4 mg/L, and the optimal DO for phosphorus removal was 4-5 mg/L. The optimal organic volume loading and organic sludge loading was 2.50 kgCOD/(m3·d), 0.55-0.81 kgCOD/(kgMLSS·d) respectively.The steady running experiment was operated under the optimal condition. In the whole stage, the organic pollutants removal efficiency was well and steady. Average removal rate of total COD and BOD5 was 89.5 % and 92.4 % respectively, and the water quality of effluent could reach the national discharge standard of pollutants for municipal WWTP(Class 1st B standard). When DO of aerobic zone was 4-5 mg/L, average removal rate of ammonia nitrogen, TN and TP was 79.7 %, 48.0 %, 91.8 % respectively. When DO of aerobic zone was 3-4 mg/L, average removal rate of ammounia nitrogen, TN and TP was 84.6 %, 64.4 % and 66.5 % respectively. When DO was 4-5 mg/L and 3-4 mg/L, there was 11.4 % and 31.3 % of TN removed in aerobic zone respectively, which showed that the phenomenon of simultaneous nitrification and denitrification happened in the aerobic zone.The model for integrative biofilm system was developed based on the simplified model of ASM2. The practical measurement value of total COD was simulated exactly, but there was a certain gap between the modeling value and the paractical measurement value for nitrogen and phosphorus. According to the sensitivity analysis of model parameters, the parameter with the big influence was adjusted to calibrate the model. After the parameter was adjusted, the relative error was basically below 5 %. During the dynamic simulation process, the average relative error of total COD, ammonia nitrogen, TN and TP was 12 %, 27 %, 16 % and 11 % respectively. The result indicated that the model could simulate the integrative biofilm system properly.