制革污泥堆场中含Cr污泥胶体在不同pH和离子强度条件下稳定性及迁移行为研究

Stability and migration behavior of Cr-containing sludge colloids in tannery sludge landfill under different pH and ionic strength conditions

制革污泥中含有大量的重金属Cr,毒性大,易迁移,会威胁人类健康.本研究以某停用制革污泥露天堆场作为研究对象,在揭示制革污泥污染特征的基础上,提取污泥中的胶体颗粒,研究不同pH、离子强度下含Cr污泥胶体稳定性及迁移情况.结果表明,堆场污泥中Cr含量为5170~25000 mg·kg^(-1),Cr赋存形态以铁锰氧化物结合态为主,总Cr含量表深层污泥之间无明显分异.表层污泥pH=4.35,处于有氧环境,好氧菌与嗜酸菌为优势菌群;深层污泥pH=7.30,处于无氧环境,厌氧菌为优势菌群.深层污泥中含有大量含Cr污泥胶体(含Cr量为7.851 mg·g^(-1)),在中性和碱性条件下较为稳定,迁移性强;在酸性条件下快速聚沉,迁移性弱.离子强度越高,污泥胶体越容易聚沉、移动性显著降低,且Ca^(2+)比Na^(+)更容易引起污泥胶体的聚沉和弱移动性,因此,向污泥胶体中引入Ca^(2+)可作为降低Cr迁移风险的有效途径.本研究成果可为全面认识同类型制革污泥堆场的污染风险评估和修复方案设计提供重要的理论支撑.

Tannery sludge contains a large amount of Cr,which is high toxicity and easy to migrate,therefore threatening human health.This paper takes a decommissioned tannery sludge landfill site as a research subject,and the pollution characteristics of sludge landfill sites are investigated.On top of that,Cr-containing sludge colloids were collected from the sludge yard to analyze their stability and migration under various pH and ionic strength conditions.The results demonstrated that the Cr concentration in the sludge ranged from 5170 to 25000 mg·kg^(-1),and the majority of Cr fraction was in the form of Fe-Mn oxide bound state.There was no significant difference in Cr concentration between the surface and deep sludge.The pH value of the surface sludge was 4.35,which was in an aerobic environment.The aerobic bacteria and acidophilus were the dominant bacteria species in surface sludge.The pH value of the deep sludge was 7.30,which was in an anaerobic environment.The anaerobic bacteria species were the dominant bacteria in deep sludge.The deep sludge contains a large amount of Cr-containing sludge colloids(7.851 mg of Cr per gram of sludge).Sludge colloids are more stable and migratable under neutral and alkaline conditions compared to that under acidic conditions.With the ionic strength rising,the aggregation of sludge colloids became heavier and the mobility of sludge colloids decreased.Compared to Na^(+),Ca^(2+) can more easily lead to aggregation and decline in mobility of the sludge colloid.Thus,adding Ca^(2+) into tannery sludge can be an effective way to reduce the migration risk of Cr.The results of this research can provide significant theoretical support for the systematic and comprehensive understanding of pollution risk assessment and remediation plan design for the similar decommissioned tannery sludge yard.