Formulation of a landfill pollution potential index to compare pollution potential of uncontrolled landfills

Progress and prospects in mitigation of landfill leachate pollution: Risk, pollution potential, treatment and challenges

The escalating loads of municipal solid waste (MSW) end up in open dumps and landfills, producing continuous flows of landfill leachate. The risk of incorporating highly toxic landfill leachate into environment is important to be evaluated and measured in order to facilitate decision making for landfill leachate management and treatment. Leachate pollution index (LPI) provides quantitative measures of the potential environmental pollution by landfill leachate and information about the environmental quality adjacent to a particular landfill. According to LPI values, most developing countries show high pollution potentials from leachate, mainly due to high organic waste composition and low level of waste management techniques. A special focus on leachate characterization studies with LPI and its integration to treatment, which has not been focused in previous reviews on landfill leachate, is given here. Further, the current review provides a summary related to leachate generation, composition, characterization, risk assessment and treatment together with challenges and perspectives in the sector with its focus to developing nations. Potential commercial and industrial applications of landfill leachate is discussed in the study to provide insights into its sustainable management which is original for the study.

Temporal variation of leachate pollution index of Indian landfill sites and associated human health risk

The present study investigated the variation in leachate pollution index (LPI) of four municipal solid waste (MSW) dumping sites: non-engineered (Okhla, Ghazipur, Bhalswa) and engineered (Narela-Bawana) of Delhi, India. A review of 142 screened studies from Google Scholar database was done for synthesis of information on LPI parameters. Further, the rate constant determination and human health risk assessment for various leachate parameters was done. Results showed the following LPI trends: Okhla landfill: irregular with exceedance to threshold value; Bhalswa landfill: exponential increase; and Narela-Bawana landfill: linear increase. Parameters such as pH, dissolved solids, copper, nickel, zinc, and chromium of Bhalswa landfill, exhibited an exponential decay with LPI variation. Whereas, for Narela-Bawana's leachate BOD and COD parameters, an exponential decay in LPI vs zinc and linear increase for LPI vs lead was observed. For all dumping sites, a positive correlation was observed between heavy metals and LPI. In case of human health risk assessment, order of oral risk posed by Okhla's metals was cadmium > chromium > nickel > lead, with maximum hazard quotient (HQ) of 1.61 for cadmium. For Ghazipur and Bhalswa landfills, cancer risk values for both adult and child sub-populations were observed to be maximum for cadmium followed by nickel, chromium, and minimum for lead. For Narela-Bawana landfill, the order of cancer risk was as follows: chromium > nickel > lead. HQ for Pb-contaminated groundwater exceeded the threshold limit in Ghazipur and Bhalswa landfills. For dermal groundwater exposure, cadmium for Okhla (adult 2.3 × 10^-4 and child 1.4 × 10^-4), Ghazipur (adult 9 × 10^-5 and child 5.2 × 10^-5), and Bhalswa (adult 1.5 × 10^-4 and child 8.6 × 10^-5) was observed to have maximum cancer risk. The analyzed year-wise LPI trend, calculated rate constants, and human health risk values from present study provide a basis to waste managers and regulators for understanding various waste sources.

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.

An analyses of the status of landfill classification systems in developing countries: Sub Saharan Africa landfill experiences

Municipal solid waste (MSW) management remains a challenge in developing countries due to increasing waste generation, high costs associated with waste management and the structure of the containment systems implemented. This study analyses the classification of landfilling systems by using documented cases reported mainly in publications in waste management in relation to non-engineered landfilling systems/approved dumpsites in Sub Saharan African (SSA) countries from 2000 to 2018. The work identifies an existing system for the classification of landfill sites and utilises this system to determine the situation of landfill sites in SSA countries. Each article was categorised according to the main landfilling management practice reported: Uncontrolled dumping, semi controlled facility, medium controlled facility, medium/high-engineered facility or high state-of the-art facility. Findings suggested that 80% of the documented cases of landfill sites assessed in SSA countries were classified as level 0 or 1. The structure of the containment and controlled regime were identified by the focus group discussion participants as important predictors of possible strengths, weaknesses, opportunities and threats for the landfill sites considered. The study represents the first identifiable and comprehensive academic evaluation of landfill site classification based on site operations reported in the available peer reviewed literature. The information provides insight on the status of landfill sites in SSA countries with respect to the landfilling management practice and a baseline for alternative corrective measures.

Leachate pollution index as an effective tool in determining the phytotoxicity of municipal solid waste leachate

Phytoremediation is a promising option for the treatment of municipal solid waste leachate. Combining the leachate pollution index with the phytotoxicity data will be useful in predicting the suitable concentration of leachate for the phytoremediation applications. Understanding the tolerant mechanisms of plants to leachate stress will further help to select the appropriate dose. The aim of the study was to investigate the effect of different concentrations of leachate on germination, growth, chlorophyll content and antioxidant enzyme activities in the plant Vigna unguiculata. The crude leachate has an LPI value of 31.99 with high concentration of organic matter, ammonia and dissolved solids. The results of the phytotoxicity study suggest that at lower concentrations the leachate enhanced the germination and promoted plant growth. Up to 5% concentration (v/v) of the leachate which had a LPI value of 11.84 the growth promotion was observed in V. unguiculata. This was made possible by the controlled modulation of reactive oxygen species through the enhanced antioxidant enzyme activities. However at higher concentration, the pollutants in leachate disrupt the enzyme activities and leads to the peroxidation of membrane lipids and significantly affected the plant growth. The study suggest that phytotoxic effects in plants are directly related to the LPI value and leachate with LPI values less than 10 are likely to promote plant growth and LPI values greater than 10 are likely to exert detrimental effect on the plant.

Development of model for prediction of Leachate Pollution Index (LPI) in absence of leachate parameters

Leachate pollution index (LPI) is an environmental index which quantifies the pollution potential of leachate generated in landfill site. Calculation of Leachate pollution index (LPI) is based on concentration of 18 parameters present in leachate. However, in case of non-availability of all 18 parameters evaluation of actual values of LPI becomes difficult. In this study, a model has been developed to predict the actual values of LPI in case of partial availability of parameters. This model generates eleven equations that helps in determination of upper and lower limit of LPI. The geometric mean of these two values results in LPI value. Application of this model to three landfill site results in LPI value with an error of ±20% for ∑_iⁿw_i⩾0.6.

Review of groundwater contamination hazard rating systems for old landfills

A large number of old uncontrolled landfills exist in developing countries. These are potentially harmful to the environment, especially with respect to groundwater contamination, and therefore, are in need of appropriate control and remedial measures. However, due to resource constraints, such measures are to be undertaken in a phased manner. An appropriate landfill hazard rating system that can evaluate relative groundwater contamination hazard of different sites is a useful tool for site ranking in order to set priorities. This paper reviews 18 existing hazard rating systems that follow the index function approach. Nine systems that are best representative of the existing systems, have been applied to six hazardous waste landfills as well as six municipal solid waste landfills. When used for ranking hazardous waste landfills, some systems such as HRS-1990, ERPHRS, WARM and RSS respond well whereas others like DRASTIC, NCS, NPC system and JENV system show a clustering effect. However, these rating systems do not perform well when applied to old municipal solid waste landfills. Even the HRS-1990, which is observed to be the most sensitive among all rating systems, exhibits some shortcomings. Improvements have been suggested in the waste quantity factor values of HRS-1990 to make it suitable for old municipal solid waste landfills. The improved system is observed to provide superior results in comparison with the existing systems, making it appropriate for use as a tool for ranking of old landfills in need of remediation and control measures.