奶牛养殖废水厌氧出水的吹脱混凝处理试验研究

Treatment of Anaerobic Effluent of Dairy Wastewater by Ammonia Stripping-Coagulation Combination

为探索高效、可行的养殖废水处理方法,以马鞍山蒙牛现代牧场废水处理中的UASB出水为研究对象,进行吹脱和混凝试验处理。通过UASB出水吹脱处理试验,对比不同p H值、吹脱时间、气液比(体积比)、温度等参数对氨氮的去除效果,再对吹脱出水进行混凝处理试验,选择PFS(聚合硫酸铁)、PAC(聚合氯化铝)为混凝剂,分别研究混凝剂投加量、p H值、搅拌速率、搅拌时间、沉淀时间对混凝效果的影响。结果表明:吹脱试验中,当p H值为11、吹脱时间为5 h、气液比为3000、温度为30℃时,氨氮去除效果最好,去除率达85.5%,UASB出水氨氮浓度由468.1 mg·L-1降到67.9 mg·L-1。混凝试验中,确定PFS为较佳混凝剂,当PFS投加量为2.85 g·L-1、搅拌速率为180 r·min-1、搅拌时间为4 min、沉淀时间为20 min时,处理效果最好,处理水CODCr和SS分别由713.4、458.0 mg·L-1降到154.1、123.2 mg·L-1,去除率分别达到78.4%和73.1%。出水氨氮略有降低,降至50.9 mg·L-1,最终出水达到《畜禽养殖业污染物排放标准》(GB 18596—2001)。

The UASB effluents often contain relatively high ammonia, which affects their secondary treatment. In this experiment, a combined ammonia stripping and coagulation method was used to treat the UASB effluents of dairy farm wastewater from Maanshan Mengniu modern ranch. In the stripping experiment, influences of p H values, stripping time, air-liquid ratios(volume ratio), and temperature on ammonia removal rate were investigated. In the coagulation experiment, PFS(Polymeric Ferric Sulfate) and PAC(Polyaluminium Chloride)were selected as coagulants to treat the ammonia stripping effluent. Influences of coagulant rates, p H values, stirring rates, stirring time, and settlement time on coagulation effectiveness were studied. The results showed that the highest ammonia removal rate was 85.5% at p H value of 11, stripping time of 5 hours,air-liquid ratio of 3000 and temperature of 30 °C, reducing ammonia concentration from 468.1 mg·L-1to67.9 mg·L-1. PFS was a better coagulant, and decreased CODCrand SS concentrations to 154.1 mg·L-1and 123.2 mg·L-1from 713.4 mg·L-1and 458.0 mg·L-1, respectively. The CODCrand SS removal rates were up to 78.4% and 73.1%, respectively, at PFS rate of 2.85 g·L-1, stirring rate of 180 r·min-1, stirring time of 4 min and settlement time of 20 min. After coagulation, ammonia nitrogen further dropped to 50.9 mg·L-1. The final effluent met the requirements of'Pollutant discharge standards of livestock and poultry breeding'(GB 18596—2001).