| The purpose of this study was to develop and evaluate a portable, recycled vertical flow constructed wetland (RVFCW) built with recyclable polyethylene terephthalate (PET) plastic, and to compare this wetland's treatment efficiencies to constructed wetlands built with traditional gravels. The ability of the RVFCWs to effect contaminant levels would be evaluated during the treatment of domestic greywater (GW) and dairy wastewater (DWW), to fully understand the capacities and limitations of the RVFCW across an entire wastewater spectrum.;A total of four 1 m2, portable, recycled vertical flow constructed wetlands (RVFCW) were built for this study. Two RVFCWs were built with recycled PET plastic as the primary wetland bed media, and two units were constructed with traditional volcanic tuff. Two sedimentation basins were built to provide wastewater flow to one of each type of RVFCW unit. The RVFCW units were dosed with 350 l d-1, six times during a two month period for both greywater and dairy wastewater. Each RVFCW was equipped with a reservoir which received the effluent from the wetland. The wetland effluent was recirculated back to the wetland with a submersible pump for a period of 16 hr. Water samples were taken at four different locations within the treatment stream: at the wastewater source, sedimentation basin outflow, RVFCW unit outflow, and recirculation outflow. Each water sample was analyzed for the following parameters: total phosphate (TP), ammonia-nitrogen, nitrate-nitrogen, sulfate (for the GW stage only), total suspended solids (TSS), total dissolved solids (TDS), total organic carbon (TOC), total nitrogen (TN) (for DWW stage only), biochemical oxygen demand (BOD) (for DWW stage only), pH, total plate count (TPC), fecal coliforms (FC), and Escherichia coli (for DWW stage only).;There was no statistical difference between the RVFCW unit types for all parameters except ammonia, nitrate and pH. The RVFCW units constructed with PET showed a 72.8+/-33% (p = 0.0266) and 65+/-11.7% (p = 0.0411) decrease in ammonia-nitrogen concentrations during GW and DWW treatment, respectively. Whereas, the RVFCW units constructed with volcanic tuff achieved an 84.5+/-20% (p = 0.0266) and 75+/-9.8% (p = 0.0411) reduction in ammonia-nitrogen concentrations during GW and DWW treatment, respectively. Also, the RVFCW PET units demonstrated a 4742+/-2526% (p = 0.0155) and 1449+/-1069% (p < 0.0001) increase in nitrate-nitrogen concentrations during GW and DWW treatment, respectively. The RVFCW VT units demonstrated significantly a higher increase in nitrate-nitrogen concentrations, with a 7032+/-3207% (p = 0.0155) increase during GW treatment, and a 2607+/-1605% (p < 0.0001) increase during DWW treatment. The final pH values for the RVFCW PET units were 8.23 (p = 0.0132) during GW treatment, and 8.2 (p = 0.0099) during DWW treatment. Whereas the final pH value for the RVFCW VT units was 8.32 during GW treatment (p = 0.0132) and 8.38 during DWW treatment (p = 0.0099).;The results of this study indicate that, under current design parameters, the RVFCW units are suitable for remediation of bacterial contamination in greywater, and that plastic PET can be successfully used as a construction medium without compromising treatment efficacy. The results also indicate that, under current design parameters, the RVFCWs are not entirely suitable as a holistic treatment system for greywater if nutrient and solids reduction is a priority. However, the RVFCW units would perform well as a primary or secondary treatment system for high strength agricultural wastewaters, if nutrients and solids reduction is a priority. The RVFCW design would be an unsuitable stand alone treatment system for wastewaters characterized by elevated concentrations of nitrate-nitrogen. However, the RVFCW PET unit outflow nitrate-nitrogen concentrations suggest that, with some design modifications, these units could be effectively used as stand-alone treatment systems for agricultural wastewaters. (Abstract shortened by UMI.)... |
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