The 2011 ASHS Annual Conference

The reuse of waste water in produce production will continue to gain traction as sources of fresh water become increasingly scarce.  Grey water (wastewater arising from activities such as bathing, washing clothes and washing dishes) is one potential source of waste water that could be used during irrigation of produce.  However, this water may contain foodborne-pathogenic organisms, and must first be treated to remove bacteria prior to reuse.  There is a need to develop cost effective methods to remove pathogenic bacteria from grey water prior to its reuse. The objective of this study was to construct and evaluate portable, vertical flow constructed wetland units for its ability to remove bacteria from grey water.  A total of four 1 m², portable, recycled vertical flow constructed wetlands (RVFCW) were built for this study. Two RVFCWs were built with recycled, polyethylene terephthalate (PET) plastic as the primary wetland bed media, and the other two were constructed using volcanic tuff. The wetlands were dosed with 350 l d^-1 of greywater six times during a three month period. Water samples were taken at four different locations within the treatment stream, and analyzed for total plate count (TPC), Fecal Coliforms (FC), and total organic carbon (TOC), as indicators of the presence of fecally associated bacteria.  Bacterial counts were analyzed by plating 1 ml of sample on Petrifilm plates, followed by incubation overnight at 37 (TPC) or 45 (FC) degrees Celsius.  Total Organic Carbon was measured using a commercial test kit.  The RVFCWs achieved 2 log reduction for TPC (p <  0.0001), and 3 log reduction for FC (p < 0.0001) (no statistical difference found between the RVFCWs constructed with recycled PET and volcanic tuff). In addition, the RVFCWs achieved 51.5% removal of TOC (p < 0.0001) (no statistical difference found between RVFCW types).  The results of this study indicate that RVFCWs can achieve appreciable removal efficiencies for TPC, FC, and TOC. Therefore, RVFCWs may be a viable, low cost technology for treating greywater prior to reuse as irrigation water. In addition, RVFCW construction cost can be drastically reduced by utilizing recycled PET plastic as a primary wetland bed media without compromising treatment efficacy.