贮存过程中猪粪沼液重金属量及大肠杆菌数量变化研究

Effects of Storage on Contents of Heavy Metals and E. coli in Digested Pig Slurry

【目的】研究沼液在不同贮存过程中其重金属量和大肠杆菌数量的变化,总结更安全的沼液管理方法,使沼液更安全、高效地用于农田灌溉。【方法】以规模化养猪场沼气工程产生的新鲜沼液为材料,在冬春季(WS)和夏秋季(SA)对其进行有盖(C)和无盖(O)贮存试验,贮存90 d中定期采样分析沼液中大肠杆菌数量、Cu^(2+)、Zn^(2+)和总As[As(III)和As(V)]及固体悬浮物量、色度和浊度变化。【结果】贮存中,沼液中固体悬浮物、浊度均呈下降趋势,贮存90 d后沼液成透明、清亮的液体;沼液中重金属Cu^(2+)、Zn^(2+)和总As量随贮存时间延长而下降,夏秋季敞口贮存可加快沼液中Cu^(2+)、Zn^(2+)量的降低,加盖贮存则不利于总As去除;贮存90 d后,静置条件下,Cu^(2+)、Zn^(2+)和总As量分别下降51.27%～87.31%、70.46%～80.10%和64.26%～82.71%;扰动后,沼液中3种重金属量有所提高,但相对于初始沼液,Cu^(2+)、Zn^(2+)、总As总量依然分别下降26.45%～58.10%、21.80%～63.89%、30.33%～49.20%。沼液中大肠杆菌数量在贮存的初期会有所增加,但随后会随着贮存时间延长而下降,温度较高时大肠杆菌存活时间更长,沼液敞口贮存更有利于大肠杆菌去除。【结论】沼液贮存90 d后可大幅度降低安全风险,沼液敞口贮存更有利于抑制沼液中大肠杆菌的繁殖和重金属的钝化;夏季对于重金属的钝化效果大于冬季。

【Objective】Study the changes of heavy metal content and E.coli quantity in different storage processes of biogas slurry,and to obtain a safer management of biogas slurry,so that the biogas slurry can be applied more safely and efficiently.【Method】In this paper,anaerobically digested pig slurry from a intensive pig farm were stored in covered and open ponds during the periods of winter and spring(WS),summer and autumn(SA),respectively.Samples were collected regularly to measure the numbers of E.coli,contents of Cu2+,Zn2+and total As[As(III)and As(V)],solid suspended matter,chroma and turbidity during 90-d storage.【Result】The contents of solid suspended matter and turbidity in digested pig slurry decreased during 90 days.The digested pig slurry turned into transparent and clear liquid at the end of storage.The contents of Cu2+,Zn2+and total As in digested pig slurry decreased with the storage time.The contents of Cu2+and Zn2+were removed more effectively under open condition in SW;while it was not benefit for As decrease.The contents of three heavy metals reduced by51.27%~87.31%,70.46%~80.10%and 64.26%~82.71%in the standing condition,respectively,for Cu2+,Zn2+and total As contents in digested pig slurry after storage.After disturbing,the contents of three heavy metals were improved than standing,but the total amount of Cu2+,Zn2+and total As were decreased by 26.45%~58.10%,21.80%~63.89%and 30.33%~49.20%respectively than initial.The number of E.coli increased slightly in the early period,but decreased with the storage.High temperature was propitious to the survivorship of E.coli.However,open storage was benefit to the purification of E.coli in digested pig slurry.【Conclusion】The safety risk can be greatly reduced after 90 days storage of biogas slurry.The open storage of biogas slurry is more conducive to inhibiting the reproduction of E.coli and the passivation of heavy metals in biogas slurry.The passivation effect of heavy metals in summer is greater than that in winter.