BIOGEOCHEMICAL PROCESSES IN A TIDAL WETLANDS WASTEWATER TREATMENT FACILITY

Most municipal wastewater treatment facilities are expensive and require large inputs of energy. Therefore, rural areas and third world countries do not always have access to these large municipal facilities so alternative forms of treating wastewater must be developed. A tidal wetlands wastewater treatment facility is an example of a low-energy system appropriate for these areas and their budgets. The purpose of this study is to assess the effectiveness of Furman University’s Tidal Wetland Wastewater Treatment System at transforming and removing nutrients such as carbon, nitrogen and phosphorous from the wastewater using microbial processes. This project studied the impact of biofilms alone for a full year before adding plants into the system. Four different tanks within the wastewater treatment system were sampled periodically and analyzed for chemical composition in order to ascertain biogeochemical transformations as wastewater progressed through the system. Wells were installed in four treatment cells and were sampled during fill-drain cycles. During the treatment process, the average amount of ammonium dropped from about 760 umol/L to under 30 umol/L from the influent to the effluent chambers while the amount of nitrate increased from just over 4 umol/L to over 500 umol/L in the last cell. Only 76 umol/L of ammonium was present after the first treatment cell, indicating a nearly 90% reduction in ammonium in the first treatment cellAmmonium concentrations are reduced about 96% through the treatment process. Well samples showed a varying weak to strong inverse relationship between ammonium and nitrate concentrations during individual fill-drain cycles. In contrast to nitrogen, the average amount of phosphorous stayed constant at around 83umol/L throughout the entire treatment process. The data suggest that nitrification by biofilms effectively converted ammonium to nitrate and denitrification removed about half the dissolved nitrogen, but the treatment process does not effectively remove the phosphorous. Nitrogen cycling is enhanced by sorption/desorption processes of ammonium and nitrate on the biofilms. Preliminary data suggests that plants do not have a major impact on biogeochemical transformations.