调理剂对堆肥产品重金属生物有效性的影响

Effect of conditioners on bioavailability of heavy metals in sludge compost

城市污泥中重金属含量及其生物有效性是限制污泥农用的主要因素,因此,研究污泥堆肥化处理过程中重金属生物有效性,对污泥的农用具有重要意义。实验以城市污泥为原料,以菌菇渣和秸秆为调理剂,设置4个处理:A(污泥∶菌菇渣∶秸秆=1∶0.4∶0.025)、B(污泥∶菌菇渣∶秸秆=1∶0.3∶0.025)、C(污泥∶秸秆=1∶0.12)和D(污泥∶秸秆=1∶0.09),进行好氧堆肥实验,采用BCR顺序提取法测定各种形态的重金属,研究堆肥前后重金属形态的变化规律。结果表明,城市污泥中Cu、Ni、Pb和Cr主要以可氧化态及残渣态存在,生物有效性较低,而Zn和Cd主要以酸溶态和可还原态存在,生物有效性较高;堆肥过程显著降低了Cu、Zn、Ni和Pb的生物有效性,并改变了Cu、Zn、Ni、Pb、Cr和Cd的形态分布,使污泥中的Cu、Zn、Ni、Pb和Cd向着更稳定的可氧化态或残渣态转变;污泥经过堆肥处理后,Cu、Zn和Ni 3种重金属生物有效性关系为:A<B<C<D,与其他处理相比,处理A残渣态的Pb和Cr增加比例较多,综合来看,处理A对重金属生物有效性的降低最为明显,重金属钝化效果最佳。

The heavy metals contents in the sewage sludge and their biological effectiveness are the main factors which limit the agricultural use of sewage sludge. It was very important to study the bioavailability of heavy metals during the prosess of sludge composting. With the sewage sludge as a raw material,the mushroom residue and straw as conditioners,four treatments of aerobic composting were designed which were A( sludge ∶ mushroom residue ∶ straw = 1 ∶ 0. 4 ∶ 0. 025),B( sludge∶ mushroom residue∶ straw = 1∶ 0. 3∶ 0. 025),C( sludge∶ straw = 1∶ 0. 12)and D( sludge ∶ straw = 1 ∶ 0. 09). Various forms of heavy metals of the compost product were determined according to BCR sequential extraction method. The results showed that the Cu,Zn,Ni,Pb in sewage sludge were mainly in the oxidisable state and residual state,with lower biodegradable utilization. But the Zn and Cd were mainly in acid-soluble state and reducible state,with higher biodegrable utilization. Composting process significantly reduced the biological effectiveness of heavy metals content of Cu,Zn,Ni,Pb,and changed the formation distribution of Cr and Cd. The compost also changed the biodegradable utilization of heavy metals of Cu,Zn,Ni,Pb,Cd in the sludge to oxidation state or residual state which are more stable. After the composting,the relationship among the treatments of Cu,Ni,Zn biological effectiveness was A < B < C < D,and the treatment of A with more residual Pb and residual Cr increased compared to other treatments. It means that A treatment reduced heavy metals biological effectiveness most significantly,and had remarkable passivation effect to heavy metals.