Geological Survey USGS details how landfill leachate, disposed from landfills to environmental pathways, is host to numerous contaminants of emerging concern CECs. Photo Credit: Dana W. Kolpin, USGS. Landfills are the final repository for a heterogeneous mixture of liquid and solid waste from residential, industrial, and commercial sources, and thus, have the potential to produce leachate—a liquid waste product that consists of a diverse mixture of chemicals as precipitation or applied water moves through the waste.
Landfills are often not the final repository for leachate which can be discharged to surface waters following onsite or offsite wastewater treatment. In this national-scale study, scientists provide an assessment of CECs in landfill leachate disposed offsite that has undergone treatment or storage processes final leachate at landfills across the United States to gain a greater understanding of this potential contaminant source to the environment.
This study follows and advances previous USGS research of leachate prior to onsite treatment, storage processes, and offsite disposal fresh leachate. The sampling network included municipal and private landfills with varying landfill waste compositions; geographic and climatic settings; ages of waste, waste loads, and leachate production; and leachate management strategies.
In some cases USGS scientists collected leachate samples from manhole access points like this one. The most frequently detected CECs were lidocaine local anesthetic, found in 91 percent of samples , cotinine nicotine breakdown product, 86 percent , carisoprodol muscle relaxant, 82 percent , bisphenol A component for plastics and thermal paper, 77 percent , carbamazepine anticonvulsant, 77 percent , and N,N-diethyltoluamide DEET, insect repellent, 68 percent.
A detailed comparison of CEC concentrations between final leachate in landfills included in this study and the previous study of fresh leachate indicated that levels of CECs were significantly less in final leachate compared to those observed in fresh leachate samples. Nevertheless, final leachate still contained a complex mixture of CECs at concentrations that may be potential cause for concern if released to the environment. This research is part of continuing USGS efforts to quantify the contribution of contaminants in leachate released from landfills to various pathways that ultimately lead to the environment.
Use of landfills as a means of waste disposal will likely increase as the global population continues to increase. Despite advancements in recycling, source reduction, and composting, the amount of municipal solid waste discarded in U. The study is intended to inform landfill managers, stakeholders, and regulators about chemicals present in landfill leachate disposed offsite to environmental pathways.
Geological Survey USGS scientists processing leachate samples collected for a national-scale study on the occurrence of contaminants of emerging concern CECs in landfill leachate disposed offsite. Photo Credit: Jason R. Masoner, USGS. Landfills are the final depository for much of the solid waste we generate.
While it is known that such landfill waste can contain a wide variety of contaminants, little research to date has been conducted regarding contaminants of emerging concern CECs in final landfill leachate. Final leachate is leachate that is collected after all storage and treatment processes that are in place within a given landfill. This sample type is in contrast to the sampling of "fresh" leachate i.
This study was comprised of a mix of public 16 and private 6 landfills to properly capture the range operating conditions that exist for the landfills present within the United States.
The landfills were selected to provide a range of hydrogeologic setting, climate, size, and leachate treatment and disposal practices. Ultimately, however, we could only collect samples at landfills that were willing to participate in this research. Samples were collected via a combination of U.
Humic acids and fulvic acids are also commonly present in old landfills and leachate plumes. Other toxic pollutants which are present in landfill leachates are the aromatic hydrocarbons Benzene, Toluene, Ethylbenzene, and Xylene , phenols, pesticides, polyethylene, plasticizers, and halogenated organic compounds like PCBs and dioxins.
Landfills are also a shelter for pathogenic microorganisms, mostly coliform bacteria and a few viruses. The pH and temperature changes may, however, inactivate these microorganisms. A variety of microorganisms degrades the various components present in the landfill waste and produces their metabolic products and other decaying organic matters.
Through decomposition of organic constituents by microorganisms dwelling in the landfill site and also through chemical reactions between the components of waste, landfill gases are released in the form of methane and carbon dioxide which are greenhouse gases. The gases release increases gradually over time and poses environmental threat and security issues to the people residing near the landfill sites.
Table 1 shows a comparision of some important pollution parameters of landfill sites at various places. It is observed that the pHs of these landfill sites are mostly in the alkaline range, there is increased level of electrical conductivity, COD, chloride and nitrate concentrations, and the common heavy metals which are present are Fe, Ni, Cu and Cr. Landfill leachates cause serious environmental issues mostly in developing countries polluting the groundwater, soil and air.
Even in an engineered landfill site with landfill liners, the barriers tend to get damaged or deteriorate with time, therefore, leachate may get leaked and pass through the soil. The consequence is harmful effects to human health and also causes hindrance to economic health and development. Heavy metals such as Pb, As, Cd, Cr and Hg leach out from uncontrolled landfill sites and cause a major threat to human health.
Due to rapid urbanization, areas near the landfill sites in many cases are gradually transformed into residential areas and also covered by agricultural fields. Inorganic cations and anions like sodium, calcium, chloride, sulphate etc. These inorganic substances are not altered by the soil type and remain a pollutant of the water and soil [ 7 ].
This ultimately gives rise to changes in soil composition and fertility. Studies have shown that iron and zinc are the major pollutants of the soil samples in the vicinity of landfill sites. Zinc is present mostly in the upper soil layer and iron has highest dispersion rate [ 2 ].
Leachate percolation in soil reduces the hydraulic conductivity resulting in clogging of the soil and these changes the properties of the soil such as water retention, field capacity etc. The soil microbial community gets changed and formation of biofilms with metal precipitation may arise. Remediation of landfill leachate using microorganisms is a cost effective approach as compared to conventional treatment processes.
However, a lot need to be explored and studied regarding this area. However, in many cases, cost of the whole process and also production of non-degradable sludge remains a disadvantage. Use of microorganisms does not have these disadvantages and are also effective in the treatment process as there are a number of microorganisms which produce various extracellular enzymes through which they can degrade toxic compounds to less toxic or non-toxic products.
Landfill leachate samples have been studied to investigate the microorganisms dwelling in them and which have the capability of degrading the main pollutants of leachate such as nitrate, phosphate and ammonia. It has been found that certain fungi, actinomycetes, and bacteria belonging to Firmicutes and Proteobacteria have efficient degrading potential.
Many of these microorganisms are also tolerant to heavy metals like Arsenic, iron, nickel, cadmium and copper. Table 2 shows the removal efficiency of some microorganisms as well as microalgae isolated from landfill leachates. Bioremediation using microorganisms is a method of choice due to its low cost and simplicity in operation mechanism.
The various types of biological treatment processes are upflow anaerobic sludge blanket UASB , activated sludge reactor, membrane bioreactor, rotating biological contactor, batch reactor and moving bed biofilm reactor.
All of them are efficient in treatment of young leachates. The UASB and batch reactor processes are also efficient in treatment of middle aged and mature leachates. Phytoremediation is one efficient and inexpensive process for remediation of mature leachates. However, phytoremediation has many limitations like remediation only limited to the surface and depth where the roots can reach, slow growth, and inadequacy in preventing the contaminant from leaching into the groundwater.
Various bioremediation processes have been experimented and their efficiency studied so far, but it has been observed that bioremediation when combined with physical and chemical processes in a monitored manner shows much promise and efficacy in removal of pollutants of leachate plumes. Landfill is the preferred method for solid waste disposal all over the world due to its ease and low-cost operations.
Rate of global adoption of MABR continues to increase MABR technology is now clearly considered an established and proven biological treatment technology within the wastewater industry.
With almost a decade of in-the-field trials and testing, the technology has matured over recent years. As a result, it now offers end-users and operators considerable benefits when they consider upgrading legacy treatment plants or planning their future sustainable wastewater treatment or resource recovery plants.
Faq s. Upgrade Type. WWTP Type. MABR Benefits. How it Works. All Posts. What is the composition of leachate? Wayne Byrne. Overcoming the Challenges of Wastewater Treatment Upgrades. Leachate is one of the more common contaminants capable of seeping into our water supply. Fortunately, steps can be taken to minimize the negative impact of leachate.
Leachate is the liquid that drains to the bottom of a landfill. The liquid that produces leachate typically comes from a combination of rainfall, snowmelt, and the waste itself. The composition of leachate varies depending on the age of the landfill and the type of waste it contains. Leachate usually consists of both dissolved and suspended materials.
0コメント