LANDFILLS: Should You Keep Your Landfill Wet?

John Rohr and Helen May

Is recirculation a cost-efficient option for handling leachate? Under the appropriate circumstances and at the right site, this management practice could produce significant savings.

Leachate recirculation can be used in one of the two types of landfilling.

The bioreactor method (a vessel-contained or in-ground, biologically managed system for encouraging rapid waste degradation) can stabilize waste more quickly.

Operating a landfill as a bioreactor hinges on the ability to distribute moisture and micro-organisms to all of the waste.

The other method is dry tomb (insufficient moisture in the landfill).

To determine if recirculation is an effective leachate management option for a particular landfill, site personnel can compare their operation and maintenance (O&M) costs to that of other leachate management practices and determine the amount of leachate requiring disposal.

A site is a good candidate for recirculating leachate if:

* the site's characteristics are optimal (i.e., waste type, waste permeability, regional weather conditions, stage of cell operation);

* the method is permitted in the landfill's state;

* O&M costs currently exceed 5 cents per gallon or $100,000 annually; and

* leachate volumes currently exceed one million gallons per year.

Before establishing a leachate recirculation program, develop a comprehensive plan that includes determining leachate generation, storage capacity, distribution method design and recirculation operations.

The five primary methods of implementing a leachate recirculation program are: horizontal wells/trenches, surface application, vertical wells, spray irrigation and injection needles. A combination of these methods provides the most flexibility for adapting to regional weather conditions, accommodating various operating requirements and managing different stages of landfill cell operation (from active through post-closure).

The leachate re-circulation system that has proven to be the most effective for post-closure is a dedicated horizontal distribution system that incorporates a high permeability blanket of material and leachate pipes within for even distribution.

For an active landfill, the working face spray method (a water truck with a rear-mounted spray bar with nozzles sprays leachate onto the working face) appears to be the most economical and efficient. The procedure is simpler and faster (30-45 minutes to fill a 5,000-gallon water truck, and 10 minutes to spray), and provides excellent distribution (covers a 30'x30' area). No pipes need to be inserted in the waste, and landfill operations can continue around the water truck.

In addition, leachate evaporates in the summer months, helping to reduce the landfill's liquid volume. Re-circulation can be performed year-round and with any waste type.

Leachate recirculation, in addition to simplifying operations and improving a site's "green" image:

* Reduces amounts of leachate to manage, which eliminates the need to haul and process leachate off-site at an average cost of 10 cents per gallon.

* Increases waste degradation/stabilization and improves refuse compaction, which can lead to lower risks and lessened long-term closure costs. Refuse decomposition typically takes more than 30 years in a non-recirculated landfill, but recirculation can reduce this period by 10 years to 15 years.

* Improves waste degradation and compaction densities, which help increase air space (by 10 percent to 50 percent), while gas production increases proportionally with the waste increase.

As with all new practices, there are potential disadvantages and challenges to leachate recirculation. For example:

* Ponding, seepage, increased leachate and localized accumulation;

* Excess leachate production and disposal;

* Insufficient liquid levels in arid climates;

* Equalization/storage capacity during wet weather;

* Additional demands on site operation and leachate extraction systems; and

* Regulatory implications for air emissions and odor control.

Most of these potential problems can be minimized through planning, design and operational procedures.

New Facility Northern California's first tire recycling and crumb rubber factory has opened at the Davis Street Transfer Station in San Leandro, Calif. Bay Area Tire Recycling will operate the tire factory under contract with Waste Management of Alameda County, a subsidiary of Waste Management Inc., Oak Brook, Ill.

New Offices JPS Elastometrics Corp., Holyoke, Mass., has opened a European sales office in Motherwell, Scotland.

Superior Services Inc., Milwaukee, has moved its corporate office to One Honey Creek Corporate Center; 125 South 84th Street Suite 200,; Milwaukee, WI 53214. (414) 479-7800. Fax: (414) 479-7400.

New Landfill Eastern Environmental Services Inc., Mt. Laurel, N.J., has opened the Lawrence County Regional Landfill, Bridgeport, Ill., a 85-acre site designed to accept municipal solid waste and industrial and non-hazardous special waste.

Permit Keystone Environmental Services Inc., Shoemakersville, Pa., has received a permit from the Pennsylvania Department of Environmental Protection to handle and store non-hazardous, residual waste.

Websites Institute of Scrap Recycling Industries Inc., Washington, D.C.: www.sri.org, and Scrap magazine: www.scrap.org

Ametek Inc., Paoli, Pa.: www.ametek.com

Rehrig Pacific Co., Los Angeles: www.rehrigpacific.com

Infiltrator Systems Inc.: www.infiltratorsystems.com