低温厌氧发酵对奶牛养殖废水沉降特征的影响

Influence of low-temperature anaerobic fermentation on sedimentation characteristics of dairy wastewater

为了降低养殖废水处理成本,增加有机肥水在喷滴灌系统中的透过性能,该研究以不同低温(10~25℃)条件对奶牛养殖废水进行厌氧发酵处理,并与传统厌氧发酵进行比较分析研究。结果表明:低温(15℃)条件下驻留时间4 d进行厌氧发酵能够改变养殖废水的沉降特征,养殖废水出现分层沉降现象,上清液浊度为1.4,上清液沉降情况可以达到稳定状态,干物质含量在2.3%左右,75μm筛滤渣含量接近0%,可以通过喷灌滴灌系统;处理后的上清液CODCr降低至(2627.8±548.1)mg/L,总氮降低至(565.2±79.5)mg/L,粪大肠菌群降至360个/L,无害化程度达到国标要求。16S全长r RNA高通量测序结果显示,与传统颗粒状厌氧污泥207个otu相比,低温厌氧污泥中检测到199个otu,其中96个属于共有菌株,低温厌氧污泥菌群主要由厚壁菌门(Firmicutes)19.2%、拟杆菌门(Bacteroidota)18.9%、Caloacimonadota 21.2%、Verrucomicrobiota 10.6%和变形菌门(Proteobacteria)6.3%组成,种水平以Candidatus Cloacimonas为优势菌属;在颗粒状厌氧污泥中门水平以Campilobacterota为特有菌门,种水平以Sulfurovum为优势菌属。因此在寒冷地区低温(15℃)厌氧处理能够减少废水处理能耗,实现废水无害化、总养分循环、水肥一体化、水资源回收利用,为循环农业和可持续发展提供研究基础。

Large volume of dairy wastewater has caused a great threat to the ecological environment,due to the difficulty to treat it.Traditional treatment requires more heating energy at the least temperature of 36℃.Alternatively,non-hazardous fertilizers are widely expected to treat wastewater,particularly easy soluble in water to transfer through dripping or spraying irrigation.However,the chemical fertilizers derived from wastewater contain many organic matters and nutrients,resulting in the blockage of spray nozzles.In this study,a feasible bio-treatment of dairy wastewater was proposed using the low-temperature anaerobic fermentation,thereby lowering energy consumption,while increasing the fluid permeability through dripping or spraying irrigation.The treated dairy wastewater was observed in the anaerobic fermentation at low temperatures(10-25℃)through an array of time points by no inoculants,as well as at a normal temperature of 36℃by inoculants of granular anaerobic sludges.A full-length 16 S rRNA gene sequencing was used to detect microbiological compositions.Response surface analysis was performed on fermentation parameters.The results showed that there was a significant influence of anaerobic fermentation under low temperature on the sediment characteristics of dairy wastewater.The sedimentation and layering performance of wastewater were significant under the condition of 9 days at 10℃,where the turbidity of supernatant was about 5.The most energy-efficient and economical condition was at 15℃in the 4 d for the low-temperature anaerobic treatment.There was an average energy saving of 2865 kW·h/d by l5℃anaerobic fermentation with ambient temperature around 7.8℃,compared with fermentation at 36℃.Low-temperature anaerobic fermentation changed the sedimentation characteristics of wastewater over a longer time but with equal quality,where supernatant CODCr was reduced to(2627.8±548.1)mg/L,nitrogen to(565.2±79.5)mg/L,fecal coliforms to around 360 g/L,the residue ratio of the dry filter by mesh diameter 75μm filters approximately to 0%.The dry matter ratio of supernatant dropped from 18.9%to 2.3%after treatment,while a part of of wastewater was recycled as irrigation water,where the total nutrients(N+P2 O5+K2 O)content of supernatants were 1.7449 g/L.The number of fecal coliforms reduced down to 360 g/L,while,the mortality ratio of ascarid egg was above 95%.Both granular and low-temperature sludges showed the treating functions of wastewater(methanogenesis and wastewater turbidity change),but with different efficiency,where 199 otu were detected in the anaerobic sludges via the full-length 16 S rRNA gene sequencing,while 207 otu in the acclimatized granular anaerobic sludges,and 96 otu were common in both sludges.Candidatus Cloacimonas was a dominant species in the long-term(over 6 mon)low-temperature conditioned anaerobic sludges,while genus Sulfurovum dominated in inoculated granular anaerobic sludges.In the study site with the mean annual temperature of 4.1℃,low-temperature(15℃)anaerobic fermentation saved much more energy consumption than the thermal anaerobic fermentation(36℃).The supernatant could transmit through to the nuzzle irrigation,the environmental non-hazardous proxies met with the discharge requirements of the national standard.The finding can provide a potential application for future recycling in agriculture and sustainable development.