Initial Stage in Designing Household Constructed Wetlands: Selection of a Suitable Aquatic Plant

Constructing centralized wastewater treatment plant systems to serve and control city sanitation requirements is vastly expensive in developing countries. Consequently, employing decentralized wastewater treatment systems through utilizing constructed wetlands (CWs) for individual households should be promoted. In this study, the most appropriate aquatic species planted in constructed wetlands were examined for treating greywater at the household level in humid tropical regions. Three different decorative aquatic plants (i.e., Echinodorus palaefolius, Typha latifolia, and Cyperus alternifolius) were compared based on their performances. Also, three similar wetlands having a total working volume of 158.42 liters with a gravel sand filter were used in this study. One day, a period was allocated for the hydraulic retention time (HRT), which corresponds to the applied hydraulic loading rate of 115.5- and 150.5-mm d-1 for the first and second experiments, respectively. The high percentage removal of 5-day biological oxygen demand (BOD5), along with an aesthetic green view and minimum maintenance of decorative plants, was employed as the selection criteria. In- situ measurements were also undertaken for pH, temperature, and total dissolved solids. The findings indicate that the most significant BOD5 removal was with the Cyperus alternifolius plants, which showed a very high BOD5 removal rate (91.18%). The Cyperus alternifolus species were more resistant in full direct sunlight conditions and adaptable to grow in temporarily or fully submerged conditions. These results, therefore, suggest that Cyperus alternifolius is the most suitable plant species for the treatment of greywater in household CWs in the tropics