Landfill leachate collection system

Case 2 - The Hyde Park Landfill site, located in an industrial complex in the extreme northwest corner of Niagara, New York, was used from 1953 to 1975 as a disposal site for an estimated 80,000 tons of chemical waste, including chlorinated hydrocarbons. A compacted clay cover was installed in 1978 over the landfill and a tile leachate collection system was installed in 1979. Hazardous compounds such as ortho-, meta- and para-chlorobenzoic acid toluene ortho- and meta-chlorotoluene 3,4-dichlorotoluene and 2,6-dichlorotoluene were detected in the leachate (Irvine et al., 1984). Since 1979, the existing leachate treatment system has used activated carbon as the technology for removing organic carbon. Although... 

FIGURE 26.1 Schematic of a double-liner and leachate collection system for a hazardous landfill. (Adapted from U.S. EPA, Training Module Introduction to Land Disposal Units, EPA530-K-05-014, U.S. Environmental Protection Agency, Washington, DC, September 2005.)... 

Other disposal options for the sewage sludge are landfill, dumping at sea (forbidden in the EU since 1998) [30], and incineration. The most popular for solid waste disposal is landfill. However, many of the disposal sites are open dumps without protective barriers or leachate-collection systems, which represent a potential risk to the quality of the nearby groundwater. 

Double Liners and Leachate Collection Systems for Hazardous Waste Disposal Units Subparts M, N, and O Land Treatment, Landfills, and Incinerators... 

The United States Environmental Protection Agency (EPA) requires all new landfills to include a leachate collection system. Recirculation of leachate accelerates the decomposition of solid waste. Another alternative use of landfills is to capture the methane gas produced during decomposition to generate electricity. For example, in Yolo County, California, a landfill releases 1.4 million cubic feet of gas a day used to generate electricity. 

Construction and Demolition (C D) waste typically consists of concrete, bricks, asphalt, wood, glass, masonry, roofing, siding and plaster, alone or in combinations. Intermediate C D landfills must have a 3-foot-thick clay liner and a leachate collection system. The diameter of leachate collection pipes must be at least six inches. Engineered landfills for municipal and industrial waste are constructed with a base liner and a leachate collection system. The primary purpose of the liner is to prevent grormdwater pollution. The liner may consist of clay only or be a combination of geomembrane and clay (known as a composite liner). The liner is constructed with at least a 2% slope towards perforated leachate collection piping to direct leachate to a collection system. 

The minimum thickness of a clay liner is five feet except in intermediate C D landfills where three feet is allowed. In a composite liner, a 60-mil or thicker geomembrane is placed directly over a 4-foot-thick clay liner. Composite liners are required for all new mimicipal waste landfills. The maximum allowable slope of inside walls of a landfill is three horizontal to one vertical. In clay-lined landfills, leachate transfer lines may penetrate die liner horizontally at the perimeter berm. An antiseep collar is placed around the transfer line penetrating the liner to minimize the escape of leachate. In composite-lined landfills, on the other hand, leachate is pumped from the landfill s leachate collection system inside a sideslope riser - a large-diameter pipe that extends from a sump at the base of the landfill to the top of the berm. 

Modem hazardous-waste landfills typically have dual leachate collection systems, one located between the two impermeable liners required for the bottom and sides of the landfill, and another just above the top liner of the double-liner system. The upper leachate collection system is called the primary leachate collection system, and the bottom is called the secondary leachate collection system. Leachate is collected in perforated pipes that are embedded in granular drain material. 

Shredded tyres can be used in the construction of landfill sites as a replacement for other construction materials. The areas that they are used in include lightweight backfill in gas-venting systems, leachate collection systems and operational liners. Shredded waste tyres can also be used to cap, close or daily cover landfill sites [75]. Their use as a backfill material and cover material can be more cost-effective than the use of other fill materials, as they can be shredded on site rather than being transported in for that particular purpose. 

Gas and Leachate Movement and Control Under ideal conditions, the gases generated from a landfill should be either vented to the atmosphere or, in larger landfills, collected for the production of energy. Landfills with >2.5 miUion cubic meters of waste or >50 Mg/y NMOC (nonmethane organic compounds) emissions may require landfill-gas collection and flare systems, per EPA support WWW, CFR 60 Regulations. The leachate should be either contained within the landfill or removed for treatment. 

Control of ga.s movement by recovery. The movement of gases in landfills can also be controlled by instadhng gas-recovery wells in completed landfills (see Fig. 25-74b). This is considered an active venting system. Clay and other hners are used when landfill gas is to be recovered. In some gas-recovery systems, leachate is collected and recycled to the top of the landfill and reinjected through perforated lines located in drainage trenches. Typically, the rate of gas production is greater in leachate-recirculation systems. 

National capacity variance When developing a treatment standard, U.S. EPA examines the available treatment capacity to determine whether it is sufficient to handle current and future waste management needs. If U.S. EPA determines that nationally there is not enough capacity to treat a waste, it can automatically extend the effective date of the waste s treatment standard. Such an extension to the effective date is intended to give the waste treatment industry more time to develop the capacity to handle the waste. Wastes under a national capacity variance can be disposed of, without meeting the treatment standards, in landfills and surface impoundments that meet minimum technical requirements (e.g., liners, leachate collection and removal systems, and leak detection systems). 

The site conditions for an on-site landfill, such as location, geology, hydrogeology, physiography, climate, and so on, should also be suitable. Landfill should meet the minimum technology requirements and regulations for hazardous waste landfills such as double liners and leachate collection and removal systems, leak detection systems, closure procedures and final cover, and construction quality assurance.59... 

Percolation monitoring can also be evaluated indirectly by using leachate collection and removal systems. For landfills underlain with these systems, the amount and composition of leachate generated can be used as an indicator of the performance of a cover system (the higher the percolation, the more leachate that will be generated).22... 

As described earlier, concerns around water and air pollution have transformed landfill technology. Figure 17.4 is an illustration of a modem lined landfill with a gas recovery system, leachate collection and treatment, a cap to prevent rain water entry, and ground water monitoring to confirm the integrity of the liner. The composition of landfills have been characterized by various garbologists and... 

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