污泥热水解处理过程重金属的迁移转化与风险评价

通过分析污泥热水解处理过程中重金属含量与形态的变化，考察不同温度（120~200℃）和不同处理时间（15~90min）对污泥中重金属（Cr、Mn、Ni、Cu、Cd、Pb）迁移转化和环境风险的影响，并对污泥热水解过程中理化参数挥发性固体（VS）、溶解性蛋白质、多糖、溶解性化学需氧量（SCOD）、碱度、NH₄⁺-N和pH]与重金属生物可利用性变化的相关性进行了分析。结果表明，热水解处理后污泥得到有效破解，部分重金属释放进入液相，但大部分重金属仍残留在固相中。固相中Cr和Mn含量在处理温度较高时（≥180℃）较原泥升高，其他重金属含量均低于原泥。热水解处理后大部分重金属（除Pb外）弱酸提取态占比随处理温度升高和处理时间延长呈下降趋势，且处理后污泥中Cr、Ni、Cu、Cd和Pb残渣态占比明显上升。具有生物有效性重金属含量与污泥NH{}_{\mathrm{4}}^{+}-N、SCOD、溶解性蛋白质、VS等指标变化有较强相关性。单个重金属生态风险变化与重金属迁移转化密切相关，污泥重金属总潜在生态风险RI在热水解处理后显著降低。

Migration,transformation and risk assessment of heavy metals in municipal sludge treated by thermal hydrolysis

The effects of different temperatures (120—200℃) and treatment times (15—90min) on the migration transformation and environmental risks of heavy metals (Cr, Mn, Ni, Cu, Cd and Pb) in sludge were investigated by analyzing the changes of heavy metal content and morphology during sludge thermal hydrolysis treatment, and the correlation between physicochemical parameters (VS, soluble protein, polysaccharide, SCOD, alkalinity, ammonia-N, and pH) and changes of heavy metal bioavailability was analyzed. The results showed that the sludge was effectively cracked by thermal hydrolysis, and some of the heavy metals were released into liquid phase, but most of them remained in solid phase. The contents of Cr and Mn in the solid phase increased at higher treatment temperatures (≥180℃) compared to those in the original sludge, while the contents of other heavy metals decreased. Most of the heavy metals (except Pb) in weak acid extracted fraction in sludge showed a decreasing trend with increasing temperature and prolonged time after thermal hydrolysis treatment, while Cr, Ni, Cu, Cd and Pb in residue fraction increased significantly after treatment. The contents of bioavailable heavy metals were strongly correlated to indicators such as ammonia-N, SCOD, soluble protein, and VS. The ecological risk of individual heavy metal was closely related to its migration and transformation, and the risk index of total potential ecological risk of heavy metals in sludge was significantly reduced after thermal hydrolysis treatment.