The Adams Field Wastewater Treatment Facility has been in operation since 1961 and was Little Rock's first wastewater treatment facility. From 1961 until 1972, the facility was equipped with only primary treatment. Secondary treatment facilities were added in 1972 and the facility is now rated as a 36 million gallons per day complete-mix activated sludge facility, serving approximately 70% of the City of Little Rock.
The facility is a two-stage "secondary" treatment facility, designed to reduce the pollutant load by approximately 90%. A combination of physical and biological processes are utilized to reduce this pollutant load in wastewater. Wastewater from Little Rock enters the facility via three 60-inch diameter gravity sewer lines at an average depth of 30 feet below ground and requires the pumping or lifting of the sewage to the surface.
Wastewater is then sampled, flow measured, and is then screened to remove large particles. The flow then passes through three parallel primary clarifiers where solid materials settle to the bottom or float to the top to be skimmed off. Solids and floatables are then sent to a Preliminary building where grit, gravel, and scum are removed. Each circular clarifier is 11 feet deep and 115 feet in diameter. Wastewater is held in these basins for about two hours.
Following primary treatment, the flow enters the activated sludge secondary process. Each of the six rectangular activated sludge aeration tanks are 15 feet deep, 40 feet wide, and 160 feet long. A biological microorganism population, which utilizes the incoming dissolved organic material in the wastewater as food, is maintained in the tanks.
Following the aeration tanks, the wastewater passes through a final clarifier section to capture the biological organisms that settle in the final clarifiers. These biological organisms that settle are returned to the activated sludge aeration tanks. These circular clarifiers are 15 feet deep and 145 feet in diameter. The overflow then passes to the Disinfection Building where four channels of ultraviolet lights are utilized to sterilize the bacteria remaining after treatment.
Treated wastewater, which meets or exceeds all State and Federal requirements, is then piped to the Arkansas River through a six-foot diameter pipeline and discharged, causing no adverse effect on the river or public health. Solids captured during the treatment process are re-circulated in the aeration tanks to maintain a viable microorganism population, while some solids are wasted from the facility process daily via pumping through a five-mile, 12-inch force main to the Fourche Creek Treatment Facility for further processing.