CONVERSION OF A FORESTED LAND APPLICATION SYSTEM TO CONSTRUCTED TREATMENT WETLANDS
Abstract:Land treatment of wastewater in the southeast has been exemplified by the E. L. Huie Water Reclamation Facility forested land application system operated by the Clayton County Water Authority (CCWA) in Clayton County, Georgia. Since 1982, this land application site (LAS) has received secondary treated effluent that is applied with a slow-rate spray irrigation system. The site covers approximately 4,000 acres with about 2,500 acres being irrigated through approximately 18,000 sprinkler heads. The current Huie LAS site capacity is approximately 19 million gallons per day (mgd).
Secondary effluent applied to the site undergoes further treatment within the soil medium as it travels to the Blalock Reservoir, located further downstream. The natural recharge of this reservoir from the existing CCWA facilities is critical, as the Blalock is a major source for drinking water within the county. This facility was included as one of the field tours conducted by WEFTEC at the 2001 Atlanta Conference.
The Huie LAS is reaching its permitted capacity and recent CH2M HILL studies commissioned by CCWA have indicated that the site and soils may not adequately sustain the current loading rates for the long term. Additionally, increasing flows from continued metropolitan Atlanta area growth require that the site treatment capacity be expanded.. Expansion of spray irrigation into additional land areas is not an economically viable solution even though this natural treatment system technology has a 20 year history of serving the needs of CCWA and Clayton County residents. A Master Plan 2000 document that was implemented by CCWA in January 2000 recommends the construction of treatment wetlands to provide for increased flows generated at their new wastewater reclamation facilities. Due to the lack of available land, the most cost effective solution is to remove existing forested land application areas from the Huie LAS and replace it with constructed wetlands.
The ability of wetland ecosystems to improve water quality naturally has been historically recognized. Constructed treatment wetlands are an effective option for providing advanced polishing of municipal effluents and for protecting downstream surface water resources. CCWA's use of natural effluent management technologies will work well in combination with land application. The use of engineered wetlands has evolved from a research concept to an accepted pollution control technology, effective at decreasing the concentrations of BOD, TSS, nutrients, metals, pathogens, and trace organics To construct treatment wetlands for additional effluent management capacity, CCWA is developing a phased wetland plan to be implemented on the Huie site in conjunction with the existing LAS.
Ultimately, CCWA chose constructed treatment wetlands for their ability to treat large volumes of effluent while minimizing land area requirements. For example, the permitted hydraulic loading rate for the Huie sprayfields is 2.52 inches/week which equates to approximately 1 mgd of treatment capacity per 100 acres. Based on projected effluent water quality data from the newly constructed W.B. Casey Water Reclamation Facility, treatment wetlands will be able to treat in excess of 1 mgd per 15 acres based on regulatory permitting requirements. A NPDES permit application has been submitted for approval of the wetland treatment discharge.
Document Type: Research Article
Publication date: 2002-01-01
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