If leachates have a distinguishing characteristic, it is that they are variable.  Flows change based on the weather  – increasing during rainy periods, decreasing during dry and waste concentrations can change dramatically over the life of the landfill.   As a result, no landfill leachate is constant over time, and no two leachates are the same.

Leachate can consist of many different organic and inorganic compounds that are typically either dissolved or suspended in the wastewater.  High concentrations of chemical oxygen demand (COD)associated, BOD, nitrogen, phenols, pesticides, solvents and heavy metals are common in these systems.

Leachate treatment technologies fall into two basic types, biological and physical/chemical. In larger systems and depending on the treatment goals, integrated systems which combine the two are often used.

The most common biological treatment is activated sludge, which is a suspended-growth process that uses aerobic microorganisms to biodegrade organic contaminants in leachate. With conventional activated sludge treatment, the leachate is aerated in an open tank with diffusers or mechanical aerators.

Siemens Water Technologies' PACT® systems combine biological treatment (activated sludge) with adsorption (powdered activated carbon) so that physical and biological treatment occur simultaneously. The system removes biodegradable and non-biodegradable pollutants in a single process. The single-step treatment process results in significant cost and performance advantages over individual systems such as activated sludge and granular carbon.  We can also provide inclined plate separators or ion exchange systems for metals removal, if necessary, as well as rapid sand filters for suspended solids control and bulk chemical handling equipment.

Landfill leachate has also been effectively treated by the rotating biological contactor (RBC) process.  The RBC is a biological process consisting of a large disc with radial and concentric passages slowly rotating in a concrete tank. During the rotation, about 40 percent of the media surface area is in the wastewater. The rotation and subsequent exposure to oxygen allows organisms to multiply and form a thin layer of biomass. This large, active population causes the biological degradation of organic pollutants. Excess biomass shears off at a steady rate and is then carried through the RBC system for removal in a clarifier.

Activated carbon adsorption systems have also been used in the treatment of landfill leachates for removal of dissolved organics, however, they are generally considered one of the more expensive treatment options and often, must be combined with other treatment techologies to achieve desired results.

Landfill Leachate Treatment Technologies:

Biological Treatment - Integrated/Advanced WW Treatment
Biological Treatment - Mechanical Aeration WW Treatment
Activated Carbon Adsorption