Experiment On Solidification/stabilization Of Textile Dyeing Sludge

The problem on how to dispose sludge appropriately and economically in order to avoid secondary pollution has become one of the central issues in environmental protection. The sludge from the biochemical treatment of textile dyeing wastewater and the subsequent physico-chemical treatment process is categorized to waste that should be under serve control in Guangdong province (HY02). Potential negative effects might be posed on environment with sludge production, storage, disposal and recycle process. In China, the current dominant disposal methods are sanitary landfill and incineration. Incineration was limited due to the vast capital cost and operating cost. Besides, high technology is required in operating the incineration processes. Hence, sanitary landfill is preferred and employed in most cases. Pre-treatment, such as solidification and stabilization, is required prior to the textile dyeing sludge enter into landfill site.With the assistant of YangJiang Industrial Solid Waste Disposal Center, we selected cement, fly ash and cinder as the curing agent in the solidification/stabilization process of textile dyeing sludge. The moisture content of sludge was 75-85%, and the volatile organic matter content was about 65.8%. COD concentration in leaching solution of sludge was approximately 1590mg/L. Through the heavy metal concentrations in sludge were below the minimum limit value requirement of relevant standards, the mechanical properties and moisture content of the sludge did not reach the standards for sludge enter into landfill sites. The L9(34) orthogonal test was established in the research. The cement, fly ash, cinder and curing days were selected as influencing factors, while the mechanical properties of solidification block was chosen as the evaluation standards. The study aims to obtain the test-prioritizing influence factors. Moreover, extended experiments was conducted for analysis of different auxiliaries and curing days based on the test-prioritizing influence factors, and discussion was hold to evaluate the impacts on sludge solidification/stabilization. To our satisfaction, the optimium formula was obtained in the end.The orthogonal test demonstrated the effectiveness prioritize, which is cement>curing days>cinders>PFA. By applying the optimization tests, the optimium formula for solidification/stabilization processes obtained is comprised of cement(0.15kg/kg),6 curing days,cinders(0.08kg/kg),PFA(0.02kg/kg). Results have shown that the addition of cement, cinder and curing days extension contribute positive effects on the compressed strength of the sludge block; curing agents helps to stabilize organic matters and heavy metals in textile dyeing sludge. The cinders plays a role as aggregate additive and adsorbent in improving the mechanical properties of sludge block. Furthermore, the strength of solidified sludge mainly based on the gelatin of cement clinker slurry and the interface cementation between fly ash, cinder and granular sludge particle.Under the optimum formula, after a curing time of 6 days, with 44.6% moisture content and 360kPa compressive strength, the sludge met with the landfill standards. At the same time, the cost of the pre-treatment of textile dyeing sludge by above formula is 59.9 yuan/ton, only 12.8% of the total cost. In summary, the optimum formula which obtained in this research is technically and economically feasible.