Behaviour and fate of heavy metals at Air Hitam Sanitary Landfill, Puchong, Selangor

In this modern age, pollutants can come in many forms, but one of the most devastating type of pollutants are heavy metals. Heavy metals pose a major environmental problem as they are not biodegradable and will persist for extended periods of time. One of the biggest sources of heavy metal pollution is from the disposal of solid waste, which is usually by storing them at landfills. There is the possibility of heavy metal accumulation in the soils and also the leachate contaminating other ecosystems, and for flora and fauna to uptake these heavy metals. Besides landfills, atmospheric deposition is also a common source of heavy metal pollution. Thus, there is a need to evaluate the impact of heavy metals from both these sources. This study was undertaken with the following objectives; To compare the soil heavy metal concentrations according to the various phases of Air Hitam Sanitary Landfill, to determine the heavy metal concentrations in plants, invertebrates, landfill leachates and river at Air Hitam Sanitary Landfill, to compare atmospheric deposition and top soil heavy metal concentrations at Air Hitam Sanitary Landfill and Seri Kembangan, to compare the heavy metal speciation between Air Hitam Sanitary Landfill leachate sediments with Rasau River sediments and to evaluate the potential of heavy metal pollution at Air Hitam Sanitary Landfill. The study was conducted at Air Hitam Sanitary Landfill (AHSL), located near the Air Hitam Forest Reserve in Mukim Petaling, Daerah Petaling, Puchong, Selangor ( longitude 101° 39’ 55’’ E and latitude 03° 0’ 10’’ N). Samples were collected from various aspects related to the landfill sites. Acid digestion was used to determine the concentration of heavy metal in all the samples collected. After digestion, the total concentrations of Cd, Fe, Zn, Cu, Pb, As and Cr was determined using the Atomic Absorption Spectrometer (AAS). Soil, plant, invertebrate and atmospheric deposition sampling was conducted at Phase 1-5 of Air Hitam Sanitary Landfill. Soil sampling was conducted in all three phases. These phases ceased operating at different periods, with Phase 1-5 ceasing operation the earliest while Phase 7 being the last to stop operating. Leachate sampling was conducted at the leachate collection ponds, which are Pond 1, Pond 2 and Pond 3. The leachate from all landfill phases is collected in Pond 1 and then undergoes aeration treatment at Pond 2 and Pond 3. River sampling was also conducted at the nearby river where treated leachate is disposed into. Appropriate statistical analyses was conducted using SPSS to analyze the research data. The heavy metal concentrations were lower in phases that ceased operating earlier, meaning Phase 7 had the highest concentration of heavy metals. This could be attributed to heavy metals being leached out from the later phases. The aeration treatment of the landfill leachate was successful in reducing Cu and Pb concentrations, however Zn and Cr concentrations remained unchanged. Fe concentrations decreased in Pond 2 but then increased in Pond 3. As and Cd concentrations were found to increase in the final stages of leachate treatment. This could be because the leachate pool’s sludge wasn’t removed from the three leachate collection pools, and the concentration for most of the heavy metals in these leachate sediments were significantly high. Hence, aeration treatment solely is not sufficient in removing heavy metals from AHSL leachate, and a sludge removal system needs to be in place. Besides that, atmospheric deposition could also be contributing to the heavy metal concentrations within these leachate pools, as evident by the high heavy metal concentrations in the road dusts of Seri Kembangan. Another notable but worrying finding when comparing the speciation of landfill sediments with river sediments, was that the speciation composition of Cd, Cu and Pb for Station 7 onwards was similar to that of the leachate sediment, but this trend wasn’t exhibited for Station 1 to Station 6. This is a sign that there is a possibility that landfill leachate is infiltrating the stream at this point, most likely due to damaged landfill liners not being able to contain the leachate efficiently. Besides that, it is also possible that atmospheric deposition was influencing the spike in heavy metal concentrations from Station 7 onwards. This finding was further substantiated when determining the pollution potential of the heavy metal concentrations in the river. Rasau River’s heavy metal concentrations exceeded several international guidelines, indicating that the river heavy metal concentration was a serious pollution potential. This is especially true for Cd and Cu; the concentrations were categorized under Class V according to the National Water Quality Standards for Malaysia, meaning that the river water couldn’t be used for anything. This research concluded that releasing the treated leachate into a nearby river is compromising long-term environmental quality. There also needs to be improvements to the leachate treatment system. Primarily, the leachate sludge needs to be removed. The treated leachate should also be channeled through a constructed wetland to allow phytoremediation to further treat the leachate. Atmospheric deposition was also a cause for concern at this area, thus the exact source of this pollution needs to be determined so that the harms can be mitigated.

Text FS 2018 78 IR.pdf Download (930kB)

Actions (login required)

View Item