Abstract
Abstract : The aim of this research was to test the effectiveness of three small-scale constructed wetlands (CW) on the treatment of residential household greywater of different sources. The main objective was to analyse and compare pre- and post-treatment greywater for parameters such as pH, pathogens, total dissolved solids (TDS), nitrates (NO3), sulphates (SO4), total phosphorous (TP), sodium (Na), boron (B), calcium (Ca), magnesium (Mg), oil and grease, total organic carbon (TOC), and other parameters for treatment efficiency. The design and construction of the wetlands was written up in a manual for use by residential home owners for the treatment of greywater to standards suitable for use in irrigating the garden and for other activities that require non-potable water. Three sub-surface flow (SSF) horizontal CW were designed and constructed on site at Rand Water’s Environmental Management Services Nursery. Each system was planted with a variety of indigenous wetland plants. The systems were constructed adjacent to greywater sources, namely office kitchens and bathrooms. Only basin water, kitchen sink water, and shower water was used for treatment. Samples of pre- and post-treatment greywater were taken over a period of 9 months in 2017/2018. Samples were analysed at Rand Water's laboratory (SANAS-accredited). Results of the research showed that CW were efficient at removing organics and nutrients from the greywater influent, showing a significant decrease in TOC for the main office artificial wetland (MO-AW), nursery artificial wetland (N-AW) and Zwartkopjes artificial wetland (Z-AW), oil and grease for the MO-AW and N-AW, TP for the MO-AW and N-AW, and SO4 for the MO-AW. There was also a significant decrease in B post-treatment for the N-AW, in E. coli counts for the MO-AW, turbidity for the MO-AW and N-AW, and TDS for the MO-AW. Overall, concentrations of most pollutants post-treatment fell within the accepted range for long-term and sustainable use of treated greywater for drip irrigation of small-scale crops and household gardens, according to the Target Water Quality Range (TWQR) for the Water Quality Guidelines for Irrigation (WQG/I). The results of this research show that easily implementable, sustainable, and aesthetically-pleasing greywater treatment solutions are available to the homeowner that they will be able to implement and maintain themselves.
M.Sc. (Aquatic Health)