猪粪及奶牛粪中温厌氧发酵对Cu和Zn的影响

以猪粪和奶牛粪为发酵原料,在中温〔(37±2)℃〕条件下采用完全混合式厌氧反应器进行了158 d的室内试验研究,分析厌氧发酵过程中Cu和Zn在沼液中质量浓度的变化及其在沼渣中的赋存形态. 结果表明:①猪粪沼液中ρ(TCu)和ρ(TZn)(TCu和TZn分别为总Cu和总Zn)随发酵时间的增加逐渐升高,而奶牛粪沼液中二者变幅不明显. ②整个发酵过程中,猪粪沼液中ρ(TCu)和ρ(TZn)的平均值极显著低于进料(P<0.001),降幅分别为80%和43%；而奶牛粪沼液中二者降幅分别仅为11%和13%. ③猪粪和奶牛粪沼液中ρ(溶解性Cu)占ρ(TCu)的53%和43%,与进料相比有小幅降低；而猪粪和奶牛粪沼液中ρ(溶解性Zn)占ρ(TZn)的35%和19%,极显著高于进料(P≤0.01),增幅分别为109%和37%. ④猪粪和奶牛粪沼渣中Cu主要以可氧化态存在,Zn主要以残渣态和酸溶态/可交换态存在. 中温厌氧发酵对猪粪和奶牛粪中溶解性Cu和Zn的削减效果有限,并且沼渣中残渣态Cu和Zn的减少可能增加二者的生物有效性,因此不利于农田的直接利用. 

Effects of Mesophilic Anaerobic Digestion of Pig and Dairy Manures on Cu and Zn

Identification of the variations of Cu and Zn during the anaerobic digestion of manures is important to evaluate their input and environmental safety after application of digested residues. In order to study the concentration variations and chemical form changes of Cu and Zn during the anaerobic digestion of pig and dairy manures, two bench-scale complete stirred tank reactors were carried out under mesophilic ((37±2)℃) condition. The results showed that:1) Cu and Zn concentrations in the digested pig slurry (DPS) distinctly increased with the anaerobic reaction time, whereas the variation trends in digested dairy slurry (DDS) were not obvious. 2) During a 158 d period of anaerobic digestion, the concentrations of Cu and Zn in DPS were significantly (P<0.001) lower than those in the raw pig slurry (RPS), with decrease rates of 80% and 43%, while those in DDS were slightly lower than those in raw dairy slurry (RDS), with decrease rates of 11% and 13%, respectively. 3) The percentages of dissolved Cu (filtered through 0.45 μm membrane) in DPS and DDS were 53% and 43% of the total Cu, respectively, while those of dissolved Zn were 35% and 19% respectively in DPS and DDS, with increase rates of 109% (P≤0.01) and 37%. 4) Cu and Zn in digested residues of pig manure and dairy manure were mainly oxidizable forms and residual and extractable/exchangeable forms, respectively. Mesophilic anaerobic digestion did not affect the removal of dissolved Cu and Zn in pig and dairy manures. In addition, the bioavailability of Cu and Zn would be enhanced due to the transformation of residual fractions of Cu and Zn in pig and dairy manures during the anaerobic digestion. This is not favorable for land application.