FREDERICK COUNTY LANDFILD LEACHATE

We are pleased to announce that Frederick County has completed the upgrade of its landfill leachate lagoons with a full AquaMats® Treatment Process. With it, they will be able to meet Virginia’s stringent permit conditions for stream discharge from the landfill facility. This is an important installation that marks the continued acceptance of the AquaMats® Process as a cost effective solution to high strength and municipal wastewater across the U.S.

Upgrade Highlights:

Meridian engineers determined that for optimal performance an upgrade of the entire process was necessary. The design of our upgrade proposal focused on removal of ammonia nitrogen (NH3) at the requested flow volumes. Frederick County Landfill’s permit requirements were achieved with an AquaMats® Process upgrade that converted the current primary and polishing treatment lagoons into high performance bioreactors.

Primary Cell

The principal challenge of the Primary Cell is to enhance treatment and removal of approximately 75% of the BOD5 and TSS along with initial nitrification. Additionally, this must be achieved under conditions where the water level may vary from 6 to 10 feet in water depth and the hydraulic residence time may vary from 31-62 days. Oxygen and circulation for the Primary Cell as upgraded consists of two zones, the mixing zone and the treatment zone, respectively. The mixing zone consists of approximately the first 200 ft of the Primary Cell (commencing from the side with the inlet). Aeration for the mixing zone is accomplished with LTC disc diffusers supplied by Air Diffusion Systems.

Immediately following the mixing zone is a permeable submerged and surface baffle across the width of the Primary Cell to increase biological performance of the Primary Cell and to provide uniform flow distribution into the secondary treatment cell area. The baffles consist of 90 units of AquaMats® for Flow Control Model 16000 that rest on the bottom surface of the lagoon and extend upward 1.8 meters and a cable connected row of 60 AquaMats® for Biofiltration at the surface. Treatment areas following the Primary Cell consists of a sequence of AquaMats® bio-arrays separated by linear rows of diffusion aeration. In total, the SDF AquaMats® will provide the Primary Cell with approximately 12,616,000 sq. ft. of additional effective surface area for water treatment.

In order to provide for varying water levels, the AquaMats® for Biofiltration bio-arrays are outfitted with a counter compression spring system to adjust to the changing water depths. (This system of counter compression is ideal in maintaining line tension despite water level changes without the problems associated with conventional spring systems in an effort to alleviate the need for repair or replacement. These units are sized in the 5 foot range to compensate for the fluctuation in ballast area and the corresponding water level fluctuation).

Dissolved oxygen (“DO”) and circulation for the treatment area of the Primary Cell are provided by two positive displacement, rotary lobe air blowers, one in operation and one on standby for peak loads and in the event of outage of a main unit. The wire drawn horsepower operating load is 50 HP which will provide 612 SCFM @ 6 psi. Air is distributed from the main blower building through 8” and 6” diameter feeder pipes to weighted fine bubble aeration tubing. The tubing requirement to meet the O2 demand of the aerated segments of the Primary Lagoon is 5,900 linear feet of LTC piping consisting of 3,900 feet in the mixing zone and 2,000 feet in the treatment zone. The primary cell provides approximately 75% of the required BOD5 and TSS removal and nitrification of approximately 20-25% of the influent loading.

Secondary cell

The principal challenge of the Secondary Cell is nitrification of the remaining NH3 loading to the system to achieve the 5 mg/l NH3 treatment goal.

The upgrade for the polishing cell includes approximately 1,596 units of AquaMats® for Biofiltration Model 15000 to enhance effective surface area for nitrification/denitrification processes of approximately 6,384,000 sq. ft. and additional aeration tubing. The estimated tubing requirement to meet the DO demand of the aerated segments of the Secondary Lagoon is 1,198 linear feet of LTC piping. The aeration grid deployment will provide not less than 3 mg/l DO at the inlet to the Polishing Lagoon and we project not less than 5 mg/l DO at the discharge.


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