Comparison of a modified and traditional rapid infiltration basin for treatment and control of nutrients in wastewater effluent

Rapid infiltration basins (RIB) have been historically used in Florida for groundwater recharge, effluent disposal, or a combination of both. However, this technique has proven ineffective in providing nitrogen control unless the RIB is modified in some manner. In this study, a traditional RIB was compared to a modified RIB constructed with manufactured biosorption activated media (BAM) to evaluate nitrate removal from reclaimed water. The RIBs are used for reclaimed and excess storm water disposal. Few, if any, studies have been published where BAM-modified RIBs have been used for this purpose. In this work, a mixture of clay, tire crumb, and sand (CTS) was selected to serve as the BAM material (Bold and Gold™ CTS media). Each RIB was constructed with two feet of either sand or BAM, covering more than 43,600 square feet of surface area. The BAM-modified RIB had an initial 90 pounds per cubic-foot in-place density, and the density of the control RIB approximated about 94 pounds per cubic-foot. Over an eight-month period, loadings to the BAM RIB and control RIB approximated 5.4 million gallons (MG) per acre each. Water samples, collected from lysimeters installed below the 2-foot of sand or BAM materials, were gathered monthly during 2017 (except for September and October due to the impacts of hurricane Irma); these samples were analyzed for water quality to determine nitrate removal. Soil moisture and weather data were also collected over the study period. This study demonstrated the nitrate removal effectiveness of a field-scale BAM-modified RIB as compared to a traditional field-scale sand-based RIB. Results suggest that BAM removed 30 percent more nitrates than the Control (78% and 47%, respectively) under the conditions of the study. Furthermore, BAM removed higher percentages of TN (31%) and TP (62%) than the Control (12% and 28%, respectively)