Effective use of iron-aluminum rich laterite based soil mixture for treatment of landfill leachate

Leaching behavior of copper tailings solidified/stabilized using hydantoin epoxy resin and red clay

Tailings produced by mining engineering and metal smelting industries have become a major challenge to the ecological environment and human health. Environmental compatibility, mechanical stability, and economic feasibility have restricted the treatment and reuse of tailings. A novel solidification/stabilization technology using hydantoin epoxy resin (HER) and red clay for copper tailing treatment was developed, and the leaching behaviors of solidified/stabilized copper tailings were investigated in this paper. The leaching characteristics were analyzed by toxicity characteristic leaching procedure (TCLP) leaching tests. Besides, the influence of red clay content and acid rain on the permeability characteristics and leaching characteristics were investigated based on flexible-wall column tests and microstructure tests. The results showed that the copper tailings solidification/stabilization technology with HER and red clay had excellent performances in toxicity stabilization. The leaching concentration of Cu in TCLP tests and flexible wall column tests remained within the limit specified by the Chinese national standard, and the concentration of Cu decreased significantly with the increase of the red clay content. Moreover, acid rain leaching changed the mineral composition and microstructure of solidified tailings, and the porosity of the samples increased with the dissolution of soluble minerals. Additionally, the hydraulic conductivities decreased slightly with the increase in the pH value of acid rain, and the solidified sample with 5% red clay had the lowest hydraulic conductivity.

Global Situation of Bioremediation of Leachate-Contaminated Soils by Treatment with Microorganisms: A Systematic Review

This systematic review presents the current state of research in the last five years on contaminants in soils, especially in leachates from solid waste landfills, with emphasis on biological remediation. In this work, the pollutants that can be treated by microorganisms and the results obtained worldwide were studied. All the data obtained were compiled, integrated, and analyzed by soil type, pollutant type, bacterial type, and the countries where these studies were carried out. This review provides reliable data on the contamination of soils worldwide, especially soils contaminated by leachate from municipal landfills. The extent of contamination, treatment objectives, site characteristics, cost, type of microorganisms to be used, and time must be considered when selecting a viable remediation strategy. The results of this study can help develop innovative and applicable methods for evaluating the overall contamination of soil with different contaminants and soil types. These findings can help develop innovative, applicable, and economically feasible methods for the sustainable management of contaminated soils, whether from landfill leachate or other soil types, to reduce or eliminate risk to the environment and human health, and to achieve greater greenery and functionality on the planet.

Contaminant migration and the retention behavior of a laterite-bentonite mixture engineered barrier in a landfill

Groundwater pollution has become increasingly severe in recent years, particularly owing to leachate leakage in landfills. In this study, the migration of Cu²⁺ in a landfill and the retention behavior of a compacted laterite-bentonite engineered barrier system toward the contaminant were analyzed by a numerical simulation based on laboratory and field test results. The results show that the hydraulic conductivity of the laterite-bentonite mixture decreased with an increase in the bentonite ratio: The hydraulic conductivities of the laterite-bentonite mixture were 4.718 × 10^-7, 2.103 × 10^-7, 7.899 × 10^-8, 3.918 × 10^-8, and 1.614 × 10^-8 cm/s when the bentonite ratios were 0, 2%, 5%, 10%, and 20%, respectively. The hydraulic conductivity of laterite and of the mixture with a bentonite ratio of 2% decreased gradually under infiltration of deionized water and CuSO₄ solutions with concentrations of 0.01 and 0.1 mol/L. This could be attributed to the increased degree of flocculation of laterite with the increase in the solution concentration. The results of the numerical simulation indicate that the migration range of Cu²⁺ after 3650 days was approximately 1500 m. The retention efficiency of a 0.5 m engineered barrier for Cu²⁺ was 67%. However, the retention efficiency exceeded 83% when the engineered barrier thickness was increased to 1.0 m. The results of the laboratory tests and numerical simulation demonstrate that a compacted laterite-bentonite engineered barrier system has a good retention effect on Cu²⁺. These observations may provide effective concepts for the prevention and control of groundwater pollution in landfills.

Dilution rate of compost leachate from different biowaste for the fertigation of vegetables

Compost leachate (CL) is often treated as sewage. Limited studies have characterised the use of CL for agriculture application due to the variation of nutrient range, potential pollutants and need for pretreatment before use. This paper reviewed the characteristics of CL in terms of its nutrients and physical characteristics from three types of biowastes, i.e. the organic portion of municipal solid waste (OP-MSW), animal manure and green waste. The nutrient range characterised are used to develop the dilution rate of the CL as fertigation water for three types of vegetables. The dilution rate of CL developed is based on the fertigation standards set by the Food and Agriculture Organization of the United Nations and Malaysia Standards. The results show that all CL contain high organic content and micronutrients, which exceeded the upper limits. For the fertigation of vegetables using the CL, based on the requirement of COD and micronutrients (Fe, Mn, Zn, Cu, Pb, Ni, Cd, Cr) of the vegetables, the CL from green waste required the lowest dilution rate (8-45 fold), followed by animal waste (33-65 fold) and the OP-MSW (193-1770 fold). The novel dilution range developed is vital to balance the essential nutrients in the CL while avoiding phototoxicity on plant and soil pollution. The dilution strategy developed is essential to support the conversion of CL as an organic liquid fertiliser for agricultural application.

Anammox, biochar column and subsurface constructed wetland as an integrated system for treating municipal solid waste derived landfill leachate from an open dumpsite

This study aims to treat nitrogen-rich landfill leachate from Karadiyana open dumpsite, Sri Lanka, through an integrated treatment train consists of an anammox process, Municipal Solid Waste derived biochar column followed by a biochar embedded subsurface constructed wetland. Characterization of leachate was done and the leachate pollution index (LPI) was estimated. Meanwhile, leachate was treated through a treatment system comprising an anammox reactor having 140 mm diameter and 250 mm height, a biochar reactor having the same dimensions with 1.3 kg of MSW biochar, and a laboratory-scale constructed wetland of 1 × 0.3 × 0.45 m. The influent and effluent quality was assessed for the samples taken in 24 h intervals. The analysis indicated that the leachate was high in COD (4000-14,000 mg/L), ammonia (760-900 mg/L), nitrate (60-126 mg/L), and phosphorus (33-66 mg/L). Ammonia and nitrite were removed 94 and 99% by anammox unit, respectively. Nitrate, phosphate, COD and conductivity were significantly removed by the constructed wetland system in 78, 70, 65 and 61%, respectively, whereas biochar barricades extended support for removal of the contaminants and color. The combined treatment system demonstrated treatment efficiencies as 100% of ammonia, 98.7% of nitrite, 98.2% of nitrate, 80.9% of phosphate, 79.7% of COD, and 69.9% of conductivity. Thus, it can be concluded that the anammox, combined with biochar embedded treatment train is promising to treat landfill leachate, having a high pollutant index.