Low‐Cost On‐Site Treatment of Landfill Leachate Using Infiltration Beds: Preliminary Field Trial

Abstract

A small‐scale field experiment was carried out to demonstrate the effectiveness of using septic system ‐type infiltration beds for on‐site treatment of landfill leachate. Using an infiltration bed with a 3‐m‐thick vadose zone of medium sand, and loaded at a rate 01 18 cm/day, a treatment efficiency of >99 percent was obtained for Fe, 94 percent for NH4+, and 54 percent for dissolved organic carbon (DOC). Attenuation occurred during one‐ to two‐day residency in the aerobic vadose zone (pore gas O2 > 12 percent by volume) as a result of oxidation reactions that caused nitrification of NH4+, convened Fe2+ to Fe3+ allowing subsequent precipitation of sparingly soluble Fe oxyhydroxide minerals, and biodegraded DOC. Attenuation of an aerobically degradable trace volatile organic compound (dichlorobenzene) was also noted, although other less degradable compounds (trichloroethylene and tetrachloroethylene) persisted. Fe mineral precipitation caused a discontinuous hardpan layer to occur in the zone immediately below the infiltration pipes. However, this layer did not become impermeable or continuous enough to significantly impede infiltration during the 82‐day experiment. Advantages of this technology for leachate treatment are that it is low cost, it is simple to construct and operate. and treatment occurs on‐site, avoiding the cost of transporting leachate off‐site for treatment.

Landfill Cover Soil, Soil Solution, and Vegetation Responses to Municipal Landfill Leachate Applications

“…Although average concentrations of NO 3 –N remained above drinking water criteria on irrigated plots, soil solution concentrations of NH 4 –N were below 0.3 mg L −1 on irrigated plots in all years (Table 6). Low NH 4 –N soil solution concentrations accompanied by increases in NO 3 –N as a result of nitrification also were observed by Robertson et al (1995), Bowman et al (2002), and Godley et al (2004b, 2005) in studies of land‐applied leachate. After application, NH 4 –N also can be lost from leachate via volatilization or through adsorption in the soil (Tyrrel et al, 2002).…”

“…Disposal of municipal solid waste landfill leachate is carefully regulated in Europe (Duggan, 2005) and in the United States must comply with the Resource Conservation and Recovery Act and Clean Water Act administered through the U.S. Environmental Protection Agency and authorized state agencies. After collection, landfill leachate typically is transported to sewage treatment plants, treated in on‐site facilities, or recirculated through the landfill (e.g., Lema et al, 1988; Robertson et al, 1995; Townsend et al, 1996; Wiszniowski et al, 2006). Although these treatment methods are effective, they are expensive and may be unnecessary if landfill leachate can be spray irrigated on the vegetated landfill cover (Shrive et al, 1994; Adarve et al, 1998; Jones et al, 2006).…”

On the Incorporation of Drains into Three‐Dimensional Variably Saturated Groundwater Flow Models

“…For example, a very common method to dispose of and treat domestic sewage is to release septic tank effluent into the vadose zone using parallel arrangements of tile drains. A similar method for treating landfill leachate has recently been investigated [Robertson et al, 1995]. Because drains are usually located within several meters of the ground surface, the flow field often involves a portion of the unsaturated zone.…”