缩短厌氧消化时间改善猪场废水厌氧消化液好氧后处理性能的可行性

采用批式厌氧消化以及间歇曝气的摇瓶试验进行猪场废水厌氧-好氧处理,研究了猪场废水厌氧消化对好氧后处理的影响,以及控制厌氧消化进程改善猪场废水厌氧消化液好氧后处理性能的可行性.对猪场废水原水(厌氧消化0d)直接进行好氧处理,COD和NH4 -N去除率分别可达到95%和98%以上,出水COD低于300mg·L-1,NH4 -N低于10mg·L-1.对厌氧消化液进行好氧后处理,出水COD和NH4 -N浓度随好氧处理时间的增长逐渐升高,厌氧消化前处理时间越长,升高时间越早,幅度越大.实验结束时,出水COD基本在500-600 mg·L-1之间;厌氧消化3、6、9、12d的消化液好氧后处理出水的NH4 -N分别达到22.2、105.4、147.6、171.4 mg·L-1.尽管厌氧消化3d时,COD去除率只有47.5%,但消化液好氧后处理的效能仍然没有提高,只是系统恶化的时间略迟于厌氧消化6、9、12d的消化液.厌氧消化液好氧后处理效果差的原因主要是:在厌氧消化过程中,各污染物降解的差异导致了厌氧消化液可生化性降低以及碳、氮、磷比例失调,影响了好氧后处理过程微生物的生长;厌氧消化液中缺乏易降解有机物,导致反硝化效果差,产生的碱度不能弥补硝化过程消耗的碱度,引起pH下降,进而影响了微生物活性.因此,通过缩短厌氧消化时间的方式来改善消化液好氧后处理的性能是不可行的.

Feasibility of improving the post-treatment performance of digested swine wastewater by means of shortening anaerobic digestion time

Anaerobic-aerobic treatment of swine wastewater was carried out in a batch anaerobic reactor and shaker bottles based on SBR (Sequence Batch Reactor) to investigate the influence of anaerobic digestion on aerobic post-treatment, and the feasibility of improving the post-treatment performance of digested effluent by means of shortening the anaerobic digestion time. When raw, undigested, swine wastewater was directly treated through the aerobic process, more than 95% and 98% of COD and NH+4-N were removed, and the effluent COD and NH+4-N concentrations were less than 300 mg·L-1 and 10 mg·L-1, respectively. During the aerobic treatment of digested effluent, the effluent COD and NH+4-N concentrations increased gradually. As the duration of anaerobic digestion increased, the effluent COD and NH+4-N concentrations increased. Towards the end of the experiment, the effluent COD after aerobic post-treatment of the digested effluent was in range of 500 mg·L-1 to 650 mg·L-1, and the effluent NH+4-N concentrations of aerobic post-treatment for effluent after 3d, 6d, 9d, and 12d anaerobic digestion were 22.2, 105.4, 147.6 mg·L-1 and 171.4 mg·L-1, respectively. After 3d digestion, the digested effluent had a COD removal rate of only 47.5%. The post-treatment performance of the digested effluent was poor in spite of the fact that the deterioration time was later than that of digested effluent with 6, 9 or 12d digestion. The poor post-treatment of the digested effluent may be ascribed to the following facts. On the one hand, the difference of pollutant degradation during the anaerobic digestion results in bad biodegradability and unsuitable ratio among carbon, nitrogen and phosphorus in the digested effluent, which influenced the growth of microbes during aerobic post-treatment of digested effluent. On the other hand, the shortage of biodegradable organic substrate in the digested effluent led to poor denitrification that in turn resulted in deficiency of alkalinity and pH drop. The low pH value was the main cause of lost microbial activity . Therefore, it was not feasible to improve the post-treatment performance of digested effluent by means of shortening the time of anaerobic digestion.