H2O2 / O3, H2O2 / UV And H2O2 / Fe2+ Processes For The Oxidation Of Hazardous Wastes

Activated hydrogen peroxide produces very reactive OH-radicals which destroy hazardous contaminants in water. The principles and different methods of activation are described. Results from laboratory studies show the numerous applications of this new technology. A successful scaleup of laboratory tests to an industrial level is discussed. Finally, a cost estimate for treating different types of water with hydrogen peroxide is presented.     

Mature landfill leachate treatment from an abandoned municipal waste disposal site

We investigated treatment techniques for the leachates derived from an abandoned waste disposal landfill facility known as Nan Ji Do in Seoul, Korea. To this end, the general characteristics of those leachates were carefully examined. The feasibility of leachate handling techniques was then examined through an application of both offand on-site processes as a combination of direct treatment methods and/or pretreatment options. They include operation of such systems or methods as: (1) activated sludge process, (2) adsorption-flocculation methods, and (3) anaerobic digestion. When the fundamental factors associated with the operation of an activated sludge process were tested by a simulated system in the laboratory, those applications were found to be efficient at leachate addition of up to 1%. Application of adsorption/precipitation method was also tested as the pretreatment option for leachates by using both powdered activated carbon (PAC) as adsorbent and aluminum sulfate (alum) as flocculant. Results of this test indicated that the removal of chemical oxygen demand (COD) was optimized at PAC and alum contents of 100 to 300 mg/L, respectively. In addition, an anaerobic digester also examined the effect of leachate components on the rate of anaerobic digestion. According to our study, treatment and pretreatment options investigated were, in general, effective enough to reduce the rate of organic loading and the occurrences of hazardous incidents.     

Evaluating the applicability of regulatory leaching tests for assessing the hazards of Pb-contaminated soils

Soil contamination is a major environmental problem due to the ecological threat it poses. In this work, electron probe microanalysis (EPMA), X-ray diffraction (XRD), and leaching studies were employed to explain the different leaching behaviors of non-stabilized and stabilized soils. The applicability of the leaching fluids used in the toxicity characteristic leaching procedure (TCLP) and Australian Standards, AS 4439.1-1997 for assessing the hazards of contaminated soils was investigated as was the leaching of lead from soil stabilized by cement and buffered phosphate techniques. The results showed Pb speciation in the soil highly influenced metal leaching. The synthetic leaching fluids were unable to provide a reliable estimation of Pb concentration in the municipal landfill leachate (ML) due to the absence of organic ligands capable of forming stable complexes with the lead. Water provided the closest representation of lead leaching from the non-stabilized and phosphate stabilized soils while sodium tetraborate buffer was found to be suitable for cement-stabilized soil in a non-putrescible landfill leachate system. A comparison of stabilization methods revealed that the buffered phosphate technique was more suitable for stabilizing the lead in the soil relative to cement stabilization.     

Stabilized leachates: ozone-activated carbon treatment and kinetics

Ozone has been used as a pre-oxidation step for the treatment of stabilized leachates. Given the refractory nature of this type of effluents, the conversion of some wastewater quality parameters has been moderate after 1 h of ozonation (i.e. 30% chemical oxygen demand (COD) depletion). Ozone uptake was calculated in the interval 1.3–1.5 g of ozone per gram of COD degraded. An optimum dose of ozone has been experienced in terms of biodegradability of the processed effluent (60 min of treatment, 1×10⁻³ molL⁻¹ ozone inlet feeding concentration and 50 Lh⁻¹ gas flow-rate). pH and other typical hydroxyl radical generator systems exerted no influence on the efficiency of the process, suggesting the negligible role played by the indirect route of oxidation (generation of hydroxyl radicals). The ozonated effluent was thereafter treated in a second adsorption stage by using a commercial activated carbon. Removal levels up to 90% of COD in approximately 120 h were experienced for adsorbent dosages of 30 gL⁻¹. Both steps, the single ozonation and the adsorption stage have been modelled by using different pseudoempirical models.     

Ammonium removal from landfill leachate by anodic oxidation

The feasibility of removing ammonium from landfill leachates by electrochemical oxidation was studied. Raw leachates and biologically/physico-chemically pretreated leachates from a municipal landfill site were treated. Boron doped diamond was used as anode and stainless steel as cathode, both electrodes with an area of 70 cm(2). The effects of the applied current density (15-90 mA cm(-2)), the initial ammonium concentration (480-2000 mg L(-1)), and the initial chloride concentration were experimentally studied. Total ammonium removal was obtained after 360 min of processing and almost half of the initial ammonium nitrogen was oxidized to nitrate. On the other hand, the concentration of chloride enhanced the rate of ammonium oxidation. In addition, the amount of N-NH(4)(+) transformed into N-NO(3)(-) decreased when additional chloride was provided.     

沉淀法回收氧化酸浸—络合法浸出液中的锑和铜

广西河池某冶炼厂氧化酸浸—络合法浸出获得的含锑、铜浸出液中锑、铜含量分别为538.51 mg/L、395.91 mg/L。对该浸出液进行水解沉淀法回收锑,沉锑残液Na2S沉淀法回收铜的试验研究,结果表明:在搅拌强度为150 r/min、反应温度为56℃、反应时间为20 min、反应终了pH=3.15条件下水解沉锑,可获得锑品位、沉淀率分别为10.35%、98.23%的沉锑产品;沉锑残液在Na2S添加量为2.5 g/L、搅拌强度为150 r/min、反应温度为50℃条件下反应10 min,反应完全后静置20 min进行过滤,可获得铜品位、沉淀率分别为36.92%、98.38%的沉铜产品。试验结果证明分步沉淀法是回收该浸出液中锑、铜的有效方法。