| Dairy wasterwater has high ammonia nitrogen and organic matter, after anaerobic treatment, most of oranic matter was able to remove, but also existed high ammonia nitrogen, and the carbon nitrogen was imbalanced. These made subsequent aerobic treatment had poor treatment effect. So it was important to explore efficient and applicative subsequent processing technology. This topic for the status quo of emission of dairy wastewater anaerobic effluent cannot satisfy, a combined ammonia stripping and coagulation method was used to treat the UASB effluents of dairy farm wastewater from Maanshan Mengniu modern ranch. Single factor experiment and response surface test were adopted. The treatment effect of ammonia stripping and coagulation and reciprocal action of technological parameter were analyzed. The best process conditions of ammonia stripping and coagulation were also determined. And the quadratic polynomial regression model which used removal rate of ammonia、CODCr and SS as response value were obtained. This study offered theoretical foundation and essential data for this combined process which used to treat dairy farming wastewater. The main resrarch conlusion are as follows:(1) During stripping experiments for treatment of UASB effluent, ammonia removal rate was gradually increase and verged to slow after 5 hours with the increase of stripping. And there was no significant difference when stripping time was among 5 hours and 6 hours. The experiment confirmed stripping time was 5-6h. Ammonia removal rate increased with the increase of p H value, and slowed down when p H value greater than 11. And there was no significant when the p H value were 11 and 12(P>0.05).The experiment confirmed p H value was 11-12. Ammonia removal rate increased with the increase of air-liquid ratio, and ammonia removal increased outstanding(P<0.01) when the air-liquid ratio was among 1000 and 3000. But ammonia removal rate changed gently when the air-liquid ratio was greater than 3000. The experiment confirmed air-liquid ratio was 3000-4000. Ammonia removal rate increased with the increase of temperature. When the temperature rised from 10℃ to 30℃, ammonia removal rate changed outstanding(P<0.01). Ammonia removal rate varied rarely with the temperature further elevating. The experiment confirmed suitable temperature was 30℃.(2) The ammonia stripping response surface experiment adopted Box-Behnken design, and built quadratic polynomial regression model equation which used ammonia removal rate as response value. Through interactive analysis of ammonia stripping technological parameter, we obtained that the recipeocal action of p H value and stripping time as well as stripping time and temperature were non-significant, the recipeocal action of p H value and temperature was significant. The ammonia stripping optimize parameters at the stripping experiment were p H value of 11.5, stripping time of 5.3 hours, temperature of 32.5℃ through optimized the ammonia stripping craft, and corresponding response value was 92.8%.(3) PFS was confirmed the excellent flocculating agent in the single experiment which used coagulation to treat effluent of stripping. The CODCr and SS removal rate appeared the tendency of after rising first down with the gradually increase of PFS dosage or stirring rate, and all had significant difference(P<0.05). With the increase of stirring time, The CODCr and SS removal rate appeared the tendency of after rising first down and had significant difference(P<0.05). The SS removal rate changed little when the stirring time were 4min and 5min; When the settling time varied between 5 and 20, the CODCr and SS removal rate increased quickly with the prolong of settling time and had significant difference(P<0.05). The growing rate diminished obvious after 20 min and had non-significant difference(P>0.05). The experiment confirmed PFS dosage, stirring rate, stirring time, settling time were 2.85g·L-1, 180r·min-1, 4-5min, 20-25 min.(4) The coagulation response surface experiment adopted Box-Behnken design, and built quadratic polynomial regression model equation which used CODCr and SS removal rate as response values. The experiment evaluated the interaction of CODCr and SS removal rate too. The interaction of PFS dosage, p H value, stirring rate, stirring time, settlement time were non-significant for CODCr removal rate; stirring rate and settlement time had significant, the interaction of others were non-significant for SS removal rate. In optimization experiment, PFS dosage was 2.75 g·L-1, stirring rate was 180 r·min-1, stirring time was 4.4 min, settlement time was 22.8 min, and in this optimize parameters, the CODCr and SS removal rate reached 79.8% and 73.6% respectively.(5) The CODCr、BOD5、SS、NH4+-N concentration met the requirements of “Discharge standard of pollutants for livestock and poultry breeding”(GB18596-2001) when UASB effluent was treated with stripping and coagulation. The engineering application was analyzed according to the test result. The cost of stripping and coagulation was about 5.6 yuan per m3 in total. |
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