For this study, small and middle scale laboratory lysimeters, and a large scale field lysimeter in situ in Shanghai Refuse Landfill, with refuse weights of 187, 600 and 10,800,000 kg, respectively, were created. These lysimeters are compared in terms of leachate quality (pH, concentrations of COD, BOD and NH3-N), refuse composition (biodegradable matter and volatile solid) and surface settlement for a monitoring period of 0-300 days. The objectives of this study were to explore both the similarities and disparities between laboratory and field scale lysimeters, and to compare degradation behaviors of refuse at the intensive reaction phase in the different scale lysimeters. Quantitative relationships of leachate quality and refuse composition with placement time show that degradation behaviors of refuse seem to depend heavily on the scales of the lysimeters and the parameters of concern, especially in the starting period of 0-6 months. However, some similarities exist between laboratory and field lysimeters after 4-6 months of placement because COD and BOD concentrations in leachate in the field lysimeter decrease regularly in a parallel pattern with those in the laboratory lysimeters. NH3-N, volatile solid (VS) and biodegradable matter (BDM) also gradually decrease in parallel in this intensive reaction phase for all scale lysimeters as refuse ages. Though the concrete data are different among the different scale lysimeters, it may be considered that laboratory lysimeters with sufficient scale are basically applicable for a rough simulation of a real landfill, especially for illustrating the degradation pattern and mechanism. Settlement of refuse surface is roughly proportional to the initial refuse height.

Refuse in landfills becomes stabilized or aged, as organic matter in the refuse gradually degrades and as the soluble inorganic substances dissolve during its long-term stabilization process. Within this paper, this process is referred to as mineralization and the resultant stabilized or essentially stabilized refuse is referred to as "aged refuse."The aged refuse contains a wide spectrum and large quantity of microorganisms, which have a strong decomposition capability for refractory organic matter present in some wastewaters, such as leachate. In this study, aged refuse excavated from two to ten year old closed landfill compartments in Shanghai Refuse Landfill (SRL) was characterized in terms of particulate distribution by screening, and a biofilter consisting of ten year old aged refuse was then used for biofiltration of leachate sampled from the landfill. Typically, 400 kg of screened aged refuse with limiting diameter less than 15 mm was used as biofiltration materials in a round shaped biofilter with 80 cm inner diameter and 80 cm height. Leachate with initial chemical oxygen demand (COD), biological oxygen demand (BOD), and NH3-N concentrations of 3,000-7,000, 540-1,500, and 500-800 mg/L, respectively, was passed through the biofilter. As a result, the corresponding concentrations in the effluent were reduced to lower than 100-350, 10-200, and 10-25 mg/L, respectively, 90-99% removal for these parameters at a hydraulic load of 80-200 L/m3 refuse/day. The color of the effluent became slightly gray, in comparison with the heavy brownish color of the influent. The treatment efficiencies heavily depend on hydraulic load, BOD/COD ratios in the leachate, and preliminary treatment of the aged refuse. A variety of leachates with various BOD/COD ratios was tested. It was found that the effluent deteriorated when BOD/COD ratios were lower than 0.1-0.2. Increase of hydraulic load resulted in a decrease of removal efficiencies. Removal of stone, plastics, and glass, etc., from the aged refuse improved the treatment. A pilot test was conducted at SRL and the experimental results obtained at laboratory scale were verified.

Zinc and lead are usually concomitantly present in Zn-Pb ores and solid wastes, such as electric arc furnace (EAF) dusts. One of the treatment methods is to extract zinc and lead from the ores and wastes by an alkaline leaching process if applicable. The selective and quantitative separation of lead from zinc is an important step in these processes. In this work, the separation of lead from zinc in alkaline zinc solution, in leaching solutions of EAF dusts, and in oxidized zinc ores by sodium sulfide precipitation was studied. When the weight ratio of sodium sulfide (average molecular weight 222) added to the lead present in alkaline solution was over 1.8-2.0 (molar ratio approximately 1.5-1.7), lead could be separated selectively and quantitatively, while the zinc remained in the solution without concomitant loss. The residues from the precipitation step were identified as mixtures of PbS and Na2Pb (OH)2S, with PbS being the predominant compound.

In this study, a novel and integrated hydrometallurgical process for the production of zinc powder from electric arc furnace (EAF) dust in alkaline medium is reported. The dust is firstly hydrolysed in water, and then fused in caustic soda at 350 C for 1 h, followed by leaching in alkaline solution in which both zinc and lead are effectively extracted. Zinc powder is then produced by electrowinning from the leach solution after the lead is selectively removed by precipitation using sodium sulphide as precipitant. The EAF dust tested contained 25% Zn, 1.8% Pb and 33% Fe. It was found that 38% of zinc and 68% of lead could be extracted from the dust when leached directly in caustic soda solution. Leaching of zinc increased to 80% when dust was directly fused with caustic soda followed by alkaline leaching. However, the leaching further increased to 95% when the dust was hydrolysed first with water before fusion. Zinc powder with a purity of 99.95% was then produced by electrowinning from the lead depleted solution. Stainless electrodes were used as both anode and cathode.

In this work, the impact of moisture on the volatility of heavy metals present in municipal solid wastes (MSW) in a laboratory scale simulated incinerator was studied, using synthetic waste consisting of 5.4 g of wood powder, 2.6 g lava, 1.9 polythene, 0.19g polyvinyl chloride, and a given quantity of water and heavy metals represented by lead, zinc and copper in forms of metallic, chlorides and oxides. It is found that the presence of high moisture in MSW will greatly reduce the volatilization of heavy metals in MSW in the incineration process. The volatilization behavior of chlorides, oxides and the metallic species with respect to the effect of moistures is quite dierent. For copper, the presence of moisture in MSW depresses the volatilization of oxides, and increases that of chloride and the metallic species, while in contrast, the volatilization of both lead and zinc is always depressed by the presence of moisture in MSW, regardless of the chemical forms used. The chemical mechanisms, which govern the volatilization behaviors of dierent chemical forms in the incineration process, are proposed. Hydrolysis, dewatering of hydrolyzed species, sublimation, chemical transformation of less volatiles to more volatiles or reverse, may participate in and aect the volatilization of heavy metals in MSW.