Surgoinsville, Tenn.’s STEP System is installed around existing buildings and landscaping.
Plastic tanks used for STEP systems allow for easy retrofit applications and cost- effective solutions for new or existing developments.
Collection: STEP systems Septic Tank Effluent Pump (STEP) collection systems can be a cost- saving alternative for many communities. In these cases, septic tanks, like the versatile yet tough plastic tanks mentioned above, are placed at each home or every couple of homes to retain solids onsite. The tanks have pumps that pressurize a small-diameter collection line that can be buried at a shallow depth, making them perfect for rocky or rolling terrain. These lines deliver settled wastewater to either an existing cen- tralized facility or to single or multiple satellite treatment and disposal facility locations throughout the development. This eliminates the need for additional primary settling at the treatment locations. Treatment: Secondary and tertiary Many packaged treatment systems have proven performance in not only obtaining exceptional secondary effluent quality but also accom- plishing nutrient removal and disinfection. Just about any treatment system technology available for large-scale plants is now available to develop small “plug and play” systems to meet even the most strin- gent effluent requirements. Activated sludge systems, trickling/media filters, Integrated Fixed Activated Sludge (IFAS), Moving Bed Biore- actors (MBBRs), and even Membrane Bioreactors (MBRs) have been scaled down for use in some of the toughest applications. A range of applications from schools with high incoming total nitrogen, to restau- rants with very high biological oxygen demand (BOD), to even direct- discharge applications can be addressed with decentralized packaged systems. Dispersal: Using the soil One diminishing resource is groundwater. In some areas, sinkholes are swallowing up land and homes, but even worse, the elevation of large areas of land such as the San Joaquin River Valley in California fell in recent years due to groundwater depletion. Using soil dispersal as part of the overall design of a decentralized wastewater collection/treat- ment/distribution plan, groundwater is extracted, consumed, treated onsite, and returned close to its point of origin to recharge the aquifer. This is in sharp contrast to the centralized model, where treated waste- water is discharged to a river where it gets taken miles away from the origination point and is essentially a wasted resource.
STEP system example Surgoinsville is a low-income community in northeastern Tennes- see with a population of 1,800, no public sewer system, and limited economic development opportunities. Existing homes had failing or compromised subsurface sewage disposal systems and the current package plant was at the end of its useful life. With no previous waste- water infrastructure experience, Surgoinsville faced big challenges, including project funding. Grants or loans from the Rural Development Community Program, the Appalachian Regional Commission, the U.S. Environmental Protection Agency, and USDA Rural Development made the $4.5 million project possible. Designed to serve 700 properties and installed on lots with existing homes, outbuildings, and landscaping, the low-pressure STEP sewer system currently serves 247 residences, two schools, and nine busi- nesses. It delivers wastewater to the neighboring city’s wastewater plant via nine miles of low-pressure sanitary sewer collection lines, two pump stations, and individual STEP services utilizing Infiltrator IM-1060 plastic tanks. An excellent example of successfully incorpo- rating decentralized design concepts into centralized infrastructure, Surgoinsville benefited from the best possible solution to its waste- water treatment challenges at a cost it could manage with the help of funding sources. AOWTS example In Suffolk County, N.Y., nitrogen from residential septic systems is a significant factor in the degradation of Long Island estuaries. When New York State listed portions of the Long Island Sound, Peconic Estuary, and South Shore Estuary as impaired water bodies, Suffolk County officials began a review to understand the source of the water supply pollution. Seventy-four percent of Suffolk County utilizes onsite sewage disposal systems. Currently, the drainfield systems in Suffolk County consist of deep leaching pits, concrete rings, or leaching pools that can be in- stalled as deep as 25 feet. A study revealed numerous pollution sources; however, nitrogen pollution from cesspools and septic systems was identified as the primary cause of water quality issues. Impacts include beach closures, toxic algae blooms, and shell fishing restrictions — all detrimental to resident health and tourism revenues.
45
january 2018
csengineermag.com
Made with FlippingBook Annual report