The phytoremediation potential of water hyacinth: A case study from Hartbeespoort Dam, South Africa

Abstract

Eutrophication has been a prevalent problem in South African water bodies for many decades, resulting in algal blooms and growth of invasive alien aquatic weeds such as water hyacinth. It was brought under control in the 1990′s, but in recent years this problem has been exacerbated by increasing incidences of untreated sewage entering the river systems, along with other anthropogenic nutrient sources. This study investigated the potential for water hyacinth to be used as a phytoremediation tool to reduce the eutrophic state of Hartbeespoort Dam, and to determine if the water quality, aside from the nutrient concentrations, affects the rate of removal of nutrients by water hyacinth. Water hyacinth plants were grown in both water from the Hartbeespoort Dam and Hoagland Solution to test the effect of growth medium ‘purity’ on hyacinth growth. Another set of vessels containing Hartbeespoort Dam water only, without a hyacinth plant, was used to observe the remediation potential of the plant and its effectiveness at suppressing algal growth. The results show that one plant can absorb up to 7,38 mg of Phosphates and 27 mg of Nitrates within 11 days. Water hyacinth can reduce the nutrient concentration of 3 L of Hartbeespoort Dam water from 0,65 mg/L phosphates to 0,04 mg/L phosphate and from 4,1 mg/L nitrates to 0,5 mg/L nitrates in 4 days. These results suggest that water hyacinth can be employed as a phytoremediation tool to mitigate eutrophication in open water bodies and may have the potential to reduce Microcystis blooms.

Keywords

• Eichhornia crassipes, Eutrophication
• Nitrates
• Nutrients
• Phosphates