Numerical modeling of clogging of landfill leachate collection systems with co-disposal of municipal solid waste (MSW) and incinerator ash

The influence of co-disposal of municipal solid waste (MSW) and incinerator ash used as daily cover on the clogging of leachate collection systems (LCSs) from landfills is examined. The “BioClog” model is used to simulate the fate and transport of the nine leachate constituents most responsible for clogging the LCSs as they move through the porous media. It then calculates the thicknesses of five films that attach to the porous media and the effect of this clog mass–volume on the porosity and hydraulic conductivity of the granular material. Then it models the consequent growth in the leachate mound with increasing clog mass over time until the service life of the LCS is reached. The modeling shows that the concentrated source of leachable minerals in the incinerator ash accelerates the clogging rate and reduces the service life of the LCSs compared to inert daily cover. If an LCS is not designed to accommodate these higher concentrations of cations in the influent leachate during the landfill operating period, the ash can significantly reduce the LCS service life. Means of extending LCS service life are discussed. A practical technique is also utilized to estimate the service life of LCSs with conservative and reasonable agreement with BioClog.

One-dimensional (1D) immediate compression and creep in large particle sized Tire Derived Aggregate (TDA) for leachate collection and removal systems (LCRS)

Potential cost savings and environmental benefits are two reasons for using Tire Derived Aggregate (TDA) in place of gravel, or drainage geosynthetics, as drainage material in leachate collection and removal systems (LCRS) of waste disposal sites. As a polymeric material, TDA is expected to undergo both immediate and time dependent compression (creep) under sustained compressive loading, and these may influence performance. The response of large particle sized TDA – TDA with individual particle sizes generally greater than 50 mm – to large compressive loads up to 300 kPa was studied to assess void volume reduction from the individual and combined effects of immediate compression and creep. The results showed void volume reduction from creep, but this was considerably less than that from the immediate compression. Isotropic solid volume compression in individual TDA particles was found to be negligible. The final void ratio appeared to be dependent on the initial void ratio, as well as on the applied load, but did not appear to be dependent on the loading rate or to be influenced by elevated temperatures (up to 58 C). Presented here are the details of the study, findings and implications for practice.

Scale Deposition Inhibiting Composites by HDPE/Silicified Acrylate Polymer/Nano-Silica for Landfill Leachate Piping

Scaling commonly occurs at pipe wall during landfill leachate collection and transportation, which may give rise to pipe rupture, thus posing harm to public health and environment. To prevent scaling, this study prepared a low surface energy nanocomposite by incorporating silicone-acrylate polymer and hydrophobically modified nano-SiO2 into the high-density polyethylene (HDPE) substrate. Through the characterization of contact angle, scanning electron microscopy and thermogravimetry, the results showed that the prepared composite has low wettability and surface free energy, excellent thermal stability and acid-base resistance. In addition, the prepared composite was compared with the commercial HDPE pipe material regarding their performance on anti-scaling by using an immersion test that places their samples into a simulated landfill leachate. It was apparent that the prepared composite shows better scaling resistance. The study further expects to provide insight into pipe materials design and manufacture, thus to improve landfill leachate collection and transportation.

Sustainable landfill leachate treatment

Landfilling is one of the most widely used forms of solid waste disposal, yet the management of landfill leachate is challenging because of the complex composition and high contaminant concentration. This study provides an on-site treatment system to treat 500 m3 day-1 of the leachate generated from the Perdido Landfill in Escambia County, Florida. The main concerns of the landfill leachate are ammonium-nitrogen, total dissolved solids (TDS) and biological oxygen demand (BOD) from the long-term monitoring (from September 1999 to May 2015). To target these major contaminants as well as other pollutants, we designed a wetland treatment system by fully utilizing the existing facilities at the Perdido Landfill site. The modified wetland treatment system consists of five components in series: leachate collection/aeration ponds, anaerobic ponds, aerobic ponds, wetlands and limestone filter ponds. The leachate collection/aeration ponds provide functions of nitrification as well as ammonia and CO2 stripping. The following anaerobic ponds focus on nitrogen removal by denitrification. The BOD is removed in the aerobic ponds. The TDS are removed in the wetlands and limestone filter ponds. In the wetlands, 60% of chloride and 40% of other contaminants are absorbed by Parthenium sp. In the limestone filter ponds, bicarbonate, calcium, magnesium and iron are removed.

The BioChemical Clogging of Landfill Leachate Collection System: Based on Laboratory Studies

Leachate collection system (LCS) clogging is a common operational problem in municipal solid waste (MSW) landfills in China, which can result in high leachate levels that threaten the safety of landfill operations and subsequently increase the leachate leakage risk. In our previous research, a filtration test was conducted and the physical clogging effect was evaluated. To fully analyze the LCS failure, in this study, a set of column experiments were carried out to investigate the biochemical clogging development and mechanisms. Results showed that the biofilm and deposited CaCO3 composed the primary clogging materials. During the experimental period, the hydraulic conductivities in simulated gravel and nonwoven geotextile drainage layers were observed (91.7% and five orders of magnitude reduction), and decreased to 10−4 and 10−8 m s−1, respectively. Therefore, the significance of the geotextile layer in LCS designing needs to be reconsidered. The biochemical clogging was positively correlated with volatile fatty acids (VFAs), and Ca2+ loading and the Ca2+ played the dominant role. Meanwhile, an improved method for analyzing biochemical clogging development was proposed.