Green Water System aids green project

By Joseph Sanchez

The Delaware Solid Waste Authority (DWSA) is near completion of an environmentally green project of constructing a landfill phyto-cap (vegetative covering) over a landfill for the purpose of treating leachate generated by rainwater and decomposition of materials at the Solid Waste Management Center in Sandtown, Del.
 The landfill location, known as Area A/B, generates an average of 8,000 gallons of leachate each day. Before the project, leachate was collected in storage tanks and taken periodically by tanker to a treatment facility in Wilmington. Considered wastewater due to its acidity and chemical makeup, authorities cannot dump Leachate into streams because it is not of drinking water quality.
   When landfills near capacity, they are covered with either a geo synthetic cap, or a natural earth cap depending on the age of the landfill as mandated by the Environmental Protection Agency. Given the age of this particular landfill, a natural cap, technically known as a “phyto cap” was the answer utilizing an environmentally friendly leachate treatment system that avoids having to transport and store the waste.
   The process treating the leachate consists first of a 3-cell vertical Wetland Biofilter System that sits atop the phyto cap that filters the leachate. The phyto cap is 25-acres in size and consists of man-made wetlands and over 10,000 planted trees that play a crucial role in the water recycling process. The treated fluid from the Biofilter System will drain into an existing storage pond, which is covered. From there the water is pumped to irrigate the phyto cap’s trees and plant life. The plants absorb this water and release uncontaminated water below the roots.
   Working together with Engineer GeoSyntec of Portland, Contractor Tetra tech EC, Inc., of Cranston, R.I., Metropolitan Industries, Inc. of Romeoville, Ill., supplied a prefabricated housed irrigation pump station that takes the treated leachate from the storage pond and pumps it through an irrigation system that waters the phyto cap’s trees and plant life.
   The irrigation pump station was completely factory built at Metropolitan’s Romeoville plant requiring only water and power connections once the station was delivered to the site. Prefabricating the system in-house provided the added benefit of having a controlled environment during manufacturing which saved time and cut costs.
   “A prefabricated system benefits the customer by eliminating the headaches during scheduling, logistics and varying site conditions. The result is a system delivered on-time because we eliminate these problems up front,” says Metropolitan National Sales Manager Mike Tierney who oversaw the sale of the equipment.
   The station includes a modular building; all pumps, motors, valves, internal piping, electrical distribution equipment and a variable speed pump control system.
   The station was delivered with the intent that the irrigation system supplier would provide an interface control panel to coordinate the operation of the main pumps with the field installed irrigation spray nozzles.
   Metropolitan Industries installed a vacuum prime system on the two vertical multi-stage pumps used in this system for their easy accessibility for service and maintenance.
   “Using the vacuum prime system put all equipment in one room on the floor so, it is accessible. This benefit will be realized during maintenance and repair work,” says Tierney.
   The primer system used is a .6 hp vacuum pump, with a 30 gallon vacuum storage tank, simplex control panel, (2) automatic air release valves and a water level control switch.    
   The two vertical multi-stage pumps each rated 350 gallons per minute (GPM), total system flow of 700 GPM @245’ total dynamic head, pump the water from the storage pond through the irrigation system and finally to the plants and vegetation.
   A Metropolitan custom-designed variable-speed control panel controls the entire system. It came complete with a touch screen interface, logic controller and two variable speed drives each rated 30HP.
   Variable speed systems are fast becoming the first choice for both operating and design engineers due to the advantage of reduced equipment maintenance costs, reduced energy costs, and variable speed’s ability to maintain accurate pressure settings.
   Variable speed water pressure systems use a transducer to sense pressure and automatically adjust the speed of the pump in order to maintain a constant discharge pressure regardless of demand or flow. During off-peak usage, the pump system will sit idle reducing energy consumption and pump wear and tear.
   The prefabricated building was constructed of steel using a Sandex finish and measured 18’ ½ long x 10’ W x 8’ 2’’ D. All equipment was installed inside the building and was tested on Metropolitan’s test lab and operational before delivery.
   Another unique aspect of the green water system was the installation of a filtration system. This system removes any small solids that remain in the water after treatment by the Wetland Biofilter System. Using a unique backwash process, the filter removes small solids that could clog the irrigation sprinkler heads and prevent water from reaching areas of the phyto cap’s plant life.
   Other accessories inside the building included HVAC with thermostatic control, indoor and outdoor lighting, a drain kit, smoke alarm and a portable crane for moving the pumps.
   Metropolitan Industries manufactures a variety of factory pre-fabricated water and wastewater pump systems such as booster systems, self-priming pump stations, submersible pumping systems, above and below-grade sewage valve vaults, custom control panels and more for the municipal, commercial and industrial markets.
   For information about green water systems you may log onto their website at http://www.metropolitanind.com.