Leachate indicators of an elevated temperature landfill

Abstract

Elevated temperature landfills (ETLFs) are municipal solid waste (MSW) landfills that have been impacted by subsurface exothermic reactions (SERs) and display unusual gas and leachate composition. Leachate quantity and quality data were analyzed to identify indicators of a SER at an ETLF in Ohio, USA. ETLF leachate generation increased from 2.04 to 14.4 m³/hectare-day (218 to 1,539 gallons/acre-day), peaking 16 months after the reaction was first noticed. The leachate generation rate for this ETLF remains about two times greater than the average Ohio MSW landfill. Several general parameters such as pH, electrical conductivity (EC), and total dissolved solids (TDS) remain impacted 5 years later. Similarly, metals such as arsenic, iron, calcium, potassium, and magnesium have increased in concentration. Volatile organic compounds (VOCs) behavior was less consistent as a group of chemicals. Increases of VOCs such as acetone, benzene, and methyl ethyl ketone (MEK) also increased. Importantly, in one year, benzene exceeded its toxicity characteristic threshold meaning the leachate was a hazardous waste, substantially increasing treatment and disposal costs. It is not clear if the VOCs are produced directly by the SER or if they are an indicator that microbial processes -which would otherwise consume them- have been disrupted. ETLFs likely do not all undergo the same exothermic reaction(s) and, unlike the analysis of landfill gas composition, temporal changes in leachate constituents' concentrations may be more important than comparing to absolute values.

Keywords: Elevated temperature landfill; Leachate; Organic compounds; Subsurface exothermic reaction.

Fig. 1.

Landfill waste composition by year of disposal from 1997 to 2020. Notes: Five categories are reported to Ohio EPA. “Asbestos” is asbestos-containing wastes. “C&D” is construction and demolition debris. “Exempt” is material that is excluded from the definition of solid waste. “Other” is for material that does not fall into any of the existing categories.

Fig. 2.

Leachate generation for this ETLF (red) and the average Ohio MSW landfill (green). Surface area (black) indicate ETLF leachate generation increases and remains sustained for years. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 3.

A selection of general chemical parameters (left), inorganic constituents (center), and VOCs (right) in leachate samples over time at the case study ETLF.