9 / 2023-04-24 14:17:04

The detoxification and resourcation of tannery sewage sludge

tannery sewage sludge,,Soilless culture,,Cr pollution,,Co-composting

Tannery sludge is a common pollutant generated during leather production. The management of tannery sludge is usually a concern due to the large content of Cr, which has high toxicity and bioavailability, poses threat to the ecosystem. On the other side, rich of organic matter and other nutrients gives it strong potential to support the plants growth. Aerobic composting is an effective treatment to inhibit the harm of heavy metals through transforming the valences and forms, as well as decomposing the organic matter to stable humus. Therefore, the composting products can be used for cultivating the plants to achieve the resource utilization. To explore the efficiency and feasibility of these managing strategies, the tannery sludge was mixed with inorganic bulking agents: coal fly ash, bentonite, or organic bulking agents: straw, chicken feces respectively and composted. Subsequently, the soiless culture substrates made from the composts were used to plant four kinds of garden plants: Orychophragmus violaceus, marigold, Salvia japonica and ryegrass. During the composting process, the long-lasting thermophilic stage made the organic matter content decreased, which also contributed to the increase in the total Cr content and the reduction in the concentration of Cr(Ⅵ). The addition of bentonite showed the great improvement on easing the poisonousness of the sludge by reducing the Cr(Ⅵ) content as much as the largest decrease by 54.3%. The phytotoxicity test result further proved the control in the toxicity since GI raised from 0.41±0.05 to 2.33±0.02. The plants in the soiless culture substrates all grew well, despite the oxidative damage emerged particularly. Throughout the cultivation process, with more Cr contained in the substrates and longer growth time, some plants got the higher SOD and CAT activites, showed a resistance to Cr. These results indicated that co-composting with proper bulking agents and making soilless culture substrates was an appropriate disposal way for tannery sludge recycle.