Hydroponic Vetiver Treatment of Post Septic Tank Effluent

A series of trials have been conducted to evaluate the efficacy of Vetiver growing under hydroponic conditions to treat motel effluent, which has been primary treated in septic tanks. Water quality results and management issues are of interest. The aim is to surface irrigate the motel gardens with the treated effluent in a sustainable way. This can be accomplished if excessive nitrogen does not seep through and contaminate groundwater, and if pathogen concentrations are almost minimal so as not to cause sickness for humans working or playing in the gardens sprayed with treated effluent. Results indicate that the best method trialled is effluent flow at 20 L/min through Vetiver roots, a method that is highly successful in reducing nitrogen concentrations. At an effluent flow rate of 20 L/min, one square metre of long rooted hydroponic Vetiver can treat 30,000 mg total nitrogen in eight days, and with light excluded in the recirculation tank can treat 3575 mg total phosphorus in eight days. Phosphorus reduction was not as successful but is often not an environmental issue if irrigated with no run-off. Pathogen content needs further testing to ascertain if sand filtering is necessary post hydroponic Vetiver treatment.