Performance evaluation of three different grasses for use as willows in greywater treatment in semi-arid Ghana

Abstract

The focus of this experimental study was to identify appropriate grass for use as willows for greywater treatment in constructed wetlands. Cymbopogon flexuosus (lemon grass), Pennisetum purpureum (elephant grass) and Andropogon gerardi (giant bluestem) were planted separately and watered with greywater for a period of fifteen weeks. Growth measurements were recorded weekly and the quality of the effluents from each of these grasses assessed using standard methods to determine their treatment efficiency. Elephant grass recorded the highest plant height of 88.9mm and the highest number of new leaves of 49, while lemon grass recorded the largest surface area of 5502mm². With regards to treatment performance, lemon grass recorded the highest efficiency with reductions of 80% in TDS, 81% in NO₃-N, 30% in PO₄-P and 82% in BOD. Except for BOD that was missed by elephant grass and giant bluestem, all the other effluent parameters met the WHO guidelines. A scaling up of the experiment for continuous greywater feed and over a longer period is recommended in order to ascertain the performance over time.

Keywords: Greywater treatment, willows efficiency, growth measurements