| The fermentation biogas used in this experiment was a kind of inteactable manure fermentation wastewater. Due to the large production, it was not all used in agriculture and must be treated. To achieve dischargement standard, a combined process of struvite-anaerobic-MBR-Fenton was used to treat the fermentation biogas.Struvite was used to pretreatment the fermentation biogas. To determent the optimal experiment conditions by single factor test, orthogonal experiment and response surface experiment. The experiment investigated the effect of pH, n(Mg2+):n(NH4+),n(PO43-): n(NH4+), reaction time and strring speed on removal ratio of ammonia nitrogen. The single factor results showed that when pH=10-10.5, n(Mg2+): n(PO43-):n(NH4+)=1.3:1.1:1, reaction time= 20 min and strring speed= 300 r/min, the removal ratio of ammonia nitrogen reached 75.79%. The removal rate of TP is 97.95% and phosphorus content was 1.8 mg/L under the same conditions. The response surface experiments results showed that when pH= 10.57,n(Mg2+):n(PO43-):n(NH4+)= 1.27:1.12:1, the removal ratio of nitrogen reached 75.81%. The best response surface experiments refined and validated the reaction conditions. The struvite precipitate under optimal conditions were characterized with SEM and XRD. The results showed that it was struvite and laid the foundation for further processing.During anaerobic pretreatment of fermentation biogas, the effect of hydraulic retention time, initial pH and reaction temperature on effluent quality were investigated. The results showed that the optimum parameters of the reaction temperature was 30℃-35℃, MLSS was 4000 mg/L-5000 mg/L, initial pH was 7-8, hydraulic retention time was 48 h. After 30 days continuous running, the average COD, ammonia were 718.8 mg/L and 341.11 mg/L. And average removal efficiency of COD, ammonia were 60.11% and 54.11%. The water B/C was increased from 0.17 to 0.35.The operation conditions of MBR were following when treating the fermentation biogas:MLSS was 5000mg/L, HRT was 24 hours, SRT was 30 days, air-water ratio was 30:1. the average COD, ammonia were 279.35 mg/L and 6.98 mg/L. And average removal efficiency of COD, ammonia were 61.07% and 97.99%.In this study, Fenton advanced oxidation and ozone oxidation were compared as pretreatment process. The results showed that Fenton advanced oxidation was better than the ozone oxidation. The optimum conditions of Fenton advanced oxidation were determined. The results showed that the process parameters were optimized as [Fe2+]: [H2O2]= 1:10, reaction time was 2 h, initial pH was 3.0, the dosage of FeSO4 was 6 mmol/L and the dosage of H2O2 was 60 mmol/L. The average COD was decreased from 300 mg/L to 58.99 mg/L, the removal efficiency of COD was 78%. Ozone oxidation was uesd to treat the fermentation biogas. The results showed that the process parameters were optimized as the reaction time was 120 min, initial pH was 7-8, the catalyet dosage was 30 g/L, the average COD was decreased 70.5 mg/L and the removal efficiency of COD was 77.96%.Continuous operation was uesed to treat the wastewater. The average COD was decreased from 2311.34 mg/L to 315.1 mg/L and The average ammonia was decreased from 3228.13 mg/L to 59.8 mg/L. The small pilot plant was stable and well.The ammonia, COD and TP were lower than 60 mg/L,8 mg/L and 1mg/L respectively after the treatment of struvite-anaerobic-MBR-Fenton combined process. The effluent met the requirements of the first B standard of the urban sewage treatment plant pollutant discharge(GB 18918-2002). |
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