Hazardous Landfill Sites Research Articles

Solidification and Stabilization of Spent Pine-cone Biochar using Chemically Bonded Phosphate Cement

Spent biochar is produced after adsorption of heavy metal which is hazardous by nature. A suitable disposal technique is required to prevent the leaching of heavy metals from spent biochar into the environment. This study highlights the solidification and stabilization (S/S) of copper loaded spent pine-cone biochar by chemically bonded phosphate cement (CBPC). The response surface methodology (RSM) was used to conduct S/S experiments in order to evaluate the compressive strength of CBPC products. The CBPC samples were prepared by varying biochar content (5-50 wt. %); W:S (0.15-0.3) and curing time(3-28d). Results illustrated that CBPC products containing biochar had higher compressive strength upto 12.8 MPa in comparison to CBPC without biochar i.e., upto 10.8 MPa. XRD and SEM analysis confirmed the presence of K-struvite (MgKPO4.6H2O), copper containing phases (Ca-Cu-Si), copper phosphate precipitates (Cu3(PO4)2) and filling of pore spaces by spent biochar. Highest compressive strength of 12.8 MPa was obtained at an optimized biochar content of 25%, W:S of 0.18 and curing time of 28 d. The evaluation of leaching potential by TCLP illustrated that stabilization of Cu (II) upto 99.9% was achieved in CBPC product. The risk assessment study revealed that there is no significant danger due to leaching of heavy metals from final CBPC product indicating that it can be readily disposed in the hazardous landfill sites.

An assessment of surficial aquifer vulnerability and groundwater pollution from a hazardous landfill site, Torbali/Turkey

The Torbali River Basin is an important part of the Kucuk Menderes Basin in western Turkey, containing a highly productive alluvium aquifer. Hazardous waste from urbanization and industrialization has been stored above the main unconfined alluvial aquifer for the last five years. This study is intended to determine the surficial aquifer vulnerability characteristics and to assess the groundwater pollution mechanism from the hazardous landfill site that is located above the surficial aquifer. Two main vulnerable zones of the aquifer were determined using a GOD vulnerability model. The hazardous solid waste was dumped on a moderately vulnerable zone without any precautionary measure. Leachate seepage from the landfill is a main contaminant for NaCl water types with electrical conductivity (EC) values of 4,275 to 4,575 μS/cm. The pH values of the leachate are between 6.3 and 6.6. Concentration of As, Al, Fe, Mn, Ni, Sb, Se and Cd in the leachate are above and Pb, Zn and Cu concentrations are below the drinking water standards. As a result, the waste leachate has a high contaminant content that is causing groundwater pollution in a highly productive vulnerable zone. In this case, this vulnerable zone is not suitable for waste disposal activities, and some improvement studies should be done immediately to protect the main aquifer from the hazardous landfill site.

Leaching characteristics of residual lateritic soils stabilised with fly ash and lime for geotechnical applications

The effective use of residual lateritic soils as fill material for various construction activities is often limited by the difficulty in handling them. Attempt to improve their workability with fly ash and lime has shown promising results, although accompanied by risk of release of heavy metal leachates to the groundwater. In the present work, the leaching properties from residual lateritic soils from a part of Northeast India stabilised with fly ash and lime (CaO) was investigated with the help of single batch leaching test and column leaching test for different soil–fly ash–lime mixes. Test results show that the high pH induced by lime treatment of the mixes helps in keeping most of the metals within the stabilised soil matrix. Although the heavy metal concentrations in the leachates were generally within permissible limits, the release response for different metals was different suggesting implications for permeate solutions having metal pre-concentrations, such as those emanating from hazardous landfill sites. The observed characteristics provide insights towards the potential and realistic estimates of leaching of metals and its variation due to change in fly ash and lime content in the stabilised mix. Many of these constituents found in the stabilised soil had a first-flush phenomenon. But, as they occur only for short duration (about 5 pore volumes over 5 days) and at low concentration, dilution effect may eliminate them. The effect of continuous permeation on the flow parameters and the leaching pattern of the mixes have also been highlighted.

Toxicity and biodegradability of high strength/toxic organic liquid industrial effluents and hazardous landfill leachates

Industrial effluents and leachates from hazardous landfill sites were tested for toxicity using the anaerobic toxicity assay. This test was done on several industrial effluents (brewery spent grain effluent, a chemical industry effluent, size effluent), and several hazardous landfill leachates giving vastly different toxicity results. The brewery effluent, spent grain effluent and size effluent were found to be less toxic than the chemical effluent and hazardous landfill leachate samples. The chemical industry effluent was found to be most toxic. Leachate samples from the H:h classified hazardous landfill site were found to be less toxic at high concentrations (40% (v/v)) while the H:H hazardous landfill leachate samples were found to be more toxic even at low concentrations of 4% (v/v). The 30 d biochemical methane potential tests revealed that the brewery effluent, organic spent grain effluent and size effluent were 89%, 63%, and 68% biodegradable, respectively. The leachate from Holfontein hazardous landfill site was least biodegradable (19%) while the chemical effluent and Aloes leachate were 29% and 32% biodegradable under anaerobic conditions.