不同来源家庭户用沼气池沼液成分分析及风险评价

Abstract

采集了中国8个省市的43个不同原料家庭户用沼气池的沼液,进行化学需氧量(COd)、氨氮(nH+4-n)、磷酸盐(PO43？)和重金属等指标分析,阐述不同原料导致沼液成分的差异,评价了不同来源沼液存在的生态风险,旨在为不同来源沼液的资源化利用提供理论依据。研究结果表明,以牛粪和秸秆为原料的沼液COd浓度较高,分别达到6800 Mg·l？1和5800 Mg·l？1;以猪粪和混合粪便为原料的沼液氨氮浓度较高,都超过1800 Mg·l？1,而牛粪原料沼液氨氮浓度明显低于其他原料,平均值仅有450 Mg·l？1,因此以牛粪为原料的沼液COd/nH+4-n显著高于其他三种原料,COd/nH+4-n达到15,而其他三种原料的沼液COd/nH+4-n均低于5;所有原料沼液磷酸盐浓度的平均值均低于80 Mg·l？1;沼液中汞的污染较严重,且在不同原料和不同地区的沼液中具有普遍性;潜在生态风险指数rI分析结果表明,云南、河南和湖北的沼液rI介于130~260之间,属于中等生态危害,存在一定的生态风险。

Forty-three biogas slurries from household biogas plants using different substrates were collected from different parts of China.The contents of chemical oxygen demand(COD), ammonium nitrogen(NH+ 4-N), phosphate(PO4 3?) and heavy metals were determined.The concentrations of COD in cow dung and straw as raw materials were higher than other treatments, reaching 6800 mg·L?1 and 5800 mg·L?1 respectively.The concentrations of NH+ 4-N in pig manure and mix manure were higher than other treatments, reaching more than 1800 mg·L?1..The concentration of NH+ 4-N in cow dung was significantly lower than that in other materials, with the average being 450 mg·L?1.Therefore, COD/ NH+ 4 ratio of 15 in the slurry with cow dung as raw material was significantly higher than those in other three materials(less than 5).The average PO4 3? concentrations of all raw biogas were lower than 80 mg·L?1.Mercury pollution was serious and universal in different materials and different provinces.Environment risk evaluation showed that the pollution in biogas slurries from Yunnan, Henan and Hubei was medium and could not be ignored.