CBOD5 treatment using the marshland upwelling system

Five-day carbonaceous biochemical oxygen demand (CBOD5) removal efficiency was evaluated for the marshland upwelling system (MUS) under both intermediate and saltwater conditions. The MUS treated decentralized wastewater from two private camps and a public restroom in the Grand Bay National Estuarine Research Reserve, Moss Point, Mississippi, and one private camp in the Barataria Terrebonne National Estuary, along Bayou Segnette, Louisiana. Raw wastewater was injected into the surrounding subsurface at a depth of 3.8 or 4.3 m. Various injection flow rates and frequencies were tested in addition to a synthetic wastewater trial. All trials followed a first-order background corrected removal equation, resulting in removal constants ranging from 0.49 to 3.32 m−1 and predicted surface concentrations from 5.7 to 33.0 mg L−1. CBOD5 (unfiltered) influent concentrations of 282 ± 173 mg L−1 were reduced to an overall effluent mean of 13 ± 13 mg L−1 by a vector distance of 7 m at Moss Point and from 365 ± 151 mg L−1 to 3.6 ± 7.6 mg L−1 by a vector distance of 6 m for Bayou Segnette. Of seven trials, only one failed to achieve effluent CBOD5 levels below a National Pollutant Discharge Elimination System (NPDES) standard level of 25 mg L−1.