Assessing the physicochemical parameters of leachate from biowaste fractions in a laboratory setting, using the elusion method

Abstract

Leachate emissions, which are regarded as one of the primary polluters of groundwater and the environment, are unavoidable side effect of landfill operation. The leachate includes hazardous chemicals, heavy metals, suspended particles, and soluble organic molecules. The objective of this study was to simulate the leachate quality from the biowaste and assess its impact on groundwater pollution in a laboratory setting. For laboratory analysis, a variety of waste fractions that make up the waste composition of household bins in Windhoek were collected and mimicked in the laboratory for analysis. The aim of modeling these scenarios in the laboratory was to examine the quality of the leachate in the eluate when substantial volumes of biowaste were added to the residual samples. The analysis was carried out in accordance with the German Institute for Standardization's (DIN 12457) with respect to the process for sampling strategy and sample preparation. From the laboratory analyses, the values of pH decreased from 6.9 to 4.4 as the biowaste was increasing from 0 to 100 %, while EC was increasing with the increase in biowaste input from 0.6 to 4.99 mS/cm; equally, the concentrations of COD were increasing with the increase of biowaste input from 643 to 24,616 mg/l. These parameters had the strongest influence on the properties of leachate, as the high level of COD indicates the presence of high level of organic strength and a sign of organic pollution. The low or acidic pH values were also as a result of the production of volatile organic acids, which can cause the landfill leachate of such a nature to enhance pH of drinking water and contribute in trihalomethane formation which is a toxic substance for human health. High values of EC on the other hand indicate the discharge or other sources of pollution that has lowered the water body’s relative quality. From the findings, it can be concluded that leachate in this study is biodegradable and un-stabilized, as shown by the low pH levels and high COD concentrations. It also alluded that a change in physicochemical parameters, regardless of how little the concentration is, has the ability to change the quality of groundwater. According to this study, leachate was highly contaminated with organic matters. This has proven that the more biowaste inputs, the higher the concentrations of the physicochemical metrics, which can then alter the quality of groundwater. Hence, a recommendation for organic waste to be diverted from landfill sites or treated before landfilled. The findings from the leachate and groundwater samples of the Kupferberg showed that the landfill is mature methanogenic and stabilized stage, when compared to the pH of the laboratory results. COD values in the leachate samples are way higher than the permissible limit of the Namibian standard guidelines for drinking water, as well as the WHO guidelines. As alluded to by many researchers, high COD concentrations indicate high organic strength and pollution. Just as observed in the laboratory, conductivity is equally high in the leachate samples of the Kupferberg landfill, indicating high salts or dissolved inorganic components. This study can conclusively say that there is a relationship between the observed laboratory results and the actual field results, because of the similar trends they portray, noting that the filed values are always higher than the laboratory values. Hence, a proper correlation method is recommended.