N.C. Division of Waste Management

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Leachate Recirculation as a Liquid Management Tool

The Solid Waste Section has prepared the following guidance for landfill owners and operators desiring to recirculate leachate. Requests to recirculate leachate are considered on a case-by-case basis. The owner/operator must present a proposed plan and the Section may grant a 120- day trial period for leachate recirculation and evaluation of the proposed plan. Upon successful completion of the trial period, leachate recirculation may be approved for continuous use.

To be eligible for a demonstration project to recirculate leachate, the owner/operator must:

1. Be an existing, new or lateral expansion of a MSWLF unit designed and constructed with a composite base liner and leachate collection and removal system (LCRS). Construction quality assurance must be performed. The composite liner must consist of two feet of compacted clay with a maximum permeability of 1 x 10^-7cm/sec, overlain and in intimate contact with a 60- mil HDPE liner. The LCRS must consist of a 6" perforated HDPE pipe, surrounded by a gravel column; two feet of a high (>0.01 cm/sec) permeable sand or equivalent other drainage media such as a geonet. This design and construction must meet the intent and specifications of Rule .1624(b)(1). Liner systems that meet the criteria may be allowed to recirculate leachate, per Rule .1626(9)(a)(ii).

2. Prepare an operation, maintenance and monitoring plan. It is the intent that the plan be flexible, and should include provisions to identify problems and their solutions.

Preoperative conditions

The following shall be met by a facility prior to the leachate recirculation demonstration:

A rain gauge and thermometer shall be placed on site

A base line sampling of the leachate shall be performed (if leachate analysis has been performed within the last thirty days prior to recirculation, the test may suffice, contact the Section for guidance)

An outline of expected operational procedures shall be submitted

A brief description of the equipment and its' associated specifications shall be submitted

A brief description of record-keeping forms shall be submitted including:

Daily/weekly record of leachate generated

Daily/weekly record of leachate recirculated

Weather conditions and other pertinent daily information

A log for reporting operating or other unusual problems, and their subsequent rectification

Any other forms or procedures, etc. that owner/operators will use

An estimation of the height of waste in the cell where leachate is anticipated to be applied.

An analysis of the field capacity of the waste where leachate is to be applied, such that the gallons per unit area does not exceed the field capacity of the waste volume.

Operating conditions

Owners and operators should consider the following operational conditions, and any other that are necessary in their professional opinion

Records shall be kept on a daily/weekly basis as outlined above

No leachate shall be applied on less than one lift (10 feet) of waste

No leachate shall be spray applied or surface circulated when it is raining, or when the waste is too wet

No run-off or side seepage will be allowed

Odors will be controlled

Leachate depth shall be monitored in the manhole to ensure that the head on the liner does not exceed one foot for more than 24 hours
Leachate will be spray applied or surface circulated during daylight hours only

The application system will be properly maintained and documented
Subsurface distribution systems will be outlined

Operation and maintenance of subsurface systems will be proposed

After a minimum period of 60 days, the owner or operator will test the leachate strength again. A progress report will be submitted which contains a further expansion of the operating manual for leachate recirculation, the records of leachate generation and application and copies of record-keeping forms used. The owner/operator shall also submit a report of expected engineering performance of the system. The report shall contain the following evaluation of the system:

An evaluation of the expected maximum head on the liner, under operating conditions, to evaluate the relationship between the base slope, drainage layer permeability and collector pipe spacing (Rule .1624(b)(2)(A).

An evaluation of the hydraulic capacity of the system, including the time to return the head on the liner to less than one foot after loading equal to the 24 hour/25-year storm plus the leachate recirculation.
A demonstration showing that the loading rate of the system due to leachate recirculation is within the design specifications and that the head on the liner does not exceed one foot for a long period of time.

At a minimum, after the 120-day trial, the owner or operator will test the leachate strength again, and submit a final report on the leachate recirculation. The report will contain a final operating manual including equipment specifications and maintenance schedules. A report on the amount of leachate applied, recovered, rainfall and any other pertinent hydraulic loading information, and a summary demonstrating the outcome of the trial.

Should the owner/operator desire to continue the leachate recirculation on a more permanent basis, AND they have demonstrated competence in managing leachate recirculation in a manner that is protective of the public health and the environment, then they must request a modification to the operating permit as required by Rule .1617(c).