花生壳炭对污泥堆肥营养元素和重金属动态变化的影响

Effects of peanut shell biochar on dynamic changes of nutrient elements and heavy metals during sewage sludge composting

为探索城市污泥无害化利用,于60℃恒温条件下利用花生壳炭和城市污泥、秸秆进行好氧高温堆肥试验。试验设置4个处理,即:CK(不添加花生壳炭)、3个花生壳炭不同添加量处理,分别为CK堆体干基质量的10%(H1)、20%(H2)、30%(H3),监测了堆肥过程中pH值、电导率(EC)、全氮(TN)、铵态氮(NH+4-N)、硝态氮(NO-3-N)、全磷(TP)、速效磷(AP)、全钾(TK)、速效钾(AK)、以及重金属Cu、Zn全量及其分级形态分配率等相关数据的变化。结果表明,与初始值相比,堆肥结束后CK、H1、H2和H3堆体EC值增长率分别为113.20%、98.98%、89.62%和79.82%;pH值增长率分别为1.13%、4.63%、5.06%和6.51%。试验结束时TN含量损失率分别为18.96%、16.25%、12.51%和12.44%;NH+4-N损失率分别为89.20%、87.11%、84.11%和82.43%;NO-3-N损失率分别为45.51%、44.10%、30.01%和19.08%;TP增长率分别为19.72%、42.03%、62.26%和89.99%,AP损失率分别为11.04%、10.69%、9.67%和1.76%。由于花生壳炭中富含大量钾素,堆肥结束后,TK增长率分别为63.59%、81.21%、91.14%和94.05%,AK含量增长率分别为23.21%、11.58%、2.11%和3.21%。30%花生壳炭添加的堆体,Cu的生物可利用态减少比例最大值为9.72%,但对Zn只能降低其活化程度,且只有H3可降低2.03%的生物可利用态锌。说明花生壳炭具有降低堆肥EC值和提高pH值的作用,其凭借自身多孔的特点能够改善堆肥环境,促进堆体养分的吸附固持。同时,花生壳炭的碱性和大量的羧基、羟基等官能团,对降低生物可利用态重金属具有积极作用。

In order to explore the harmless utilization of urban sludge,the aerobic composting at high temperature was conducted using peanut shell biochar(PB),urban sludge and straw.Sludge with straw was treated with three different contents of peanut shell charcoal(10%,20%,30%)under constant temperature of 60℃for 30 d.Sludge plus straw without peanut shell carbon served as control.The pH,electrical conductivity(EC),total nitrogen(TN),ammonium nitrogen(NH+4-N),nitrate(NO-3-N),total phosphorus(TP),available phosphorus(AP),total potassium(TK),available potassium(AK),total Cu,total Zn and the different fractions value of heavy metals(HMs)were detected.Compared with initial values,the growth rates of EC in four treatments were 113.20%,98.98%,89.62%and 79.82%,respectively.The increases of pH values were 1.13%,4.63%,5.06%,and 6.51%,respectively.At the end of the experiment,the loss rates of TN in four treatments were 18.96%,16.25%,12.51%and 12.44%respectively,the lost rates of NH+4-N were 89.20%,87.11%,84.11%,and 82.43%,respectively;45.51%,44.10%,30.01%,19.08%for NO3-N loss rates,respectively;11.04%,10.69%,9.67%,1.76%for AP loss rates,respectively;while TP growth rates were 19.72%,42.03%,62.26%,and 89.99%,respectively.Since potassium content was rich in the peanut shell biochar,the growth rates of TK after composting were 63.59%,81.21%,91.14%,94.05%,respectively and the growth rates of AK content were 23.21%,11.58%,2.11%,and 3.21%,respectively.The maximum passivation rate of Cu was 9.72%when 30%PB was added.As for Zn,only 30%PB addition could reduce the activation of Zn.The results indicated that the piles with PB exhibited a lower value of EC and a higher value of pH than those of CK.It could also improve the composting environment and promote the adsorption of the nutrients in the compost because of its porous characteristics.Moreover,the basicity and a large number of functional groups such as carboxyl groups and hydroxyl groups positively affected the reduction of the bioavailable heavy metals.