Phytoremediation potential of Echinochloa crus galli and Hibiscus cannabinus in the stabilization of municipal wastewater sludge

Abstract

In this study, the phytoremediation potential of municipal sewage sludge was studied by Echinochloa crus galli and Hibiscus cannabinus plants with special reference to total organic carbon, total Kjeldahl nitrogen, total phosphorus, sodium uptake ratio, pH, electrical conductivity and lead and cadmium heavy metals. Design and construction of E. crus galli beds in Kermanshah and E. crus galli and H. cannabinus in Sarpol Zahab wastewater treatment plant was carried out at the outdoor. In Kermanshah wastewater treatment plant, the removal efficiency of total organic carbon in phytoremediation by E. crus galli increased with maturity and reached 62 ± 1.3% (P < 0.05). At the end of 75 days, total phosphorus and total Kjeldahl nitrogen concentrations were 1.8 ± 0.24 and 1.49 ± 0.18%, respectively. Lead removal efficiency was significantly high, and cadmium concentration which in crude sludge was 0.08 mg/kg decreased to zero (P < 0.05). In Sarpol Zahab wastewater treatment plant, the efficiency of total organic carbon, lead and cadmium phytoremediation by E. crus galli was high. The removal efficiency of total organic carbon in H. cannabinus treatment increased with time (P < 0.05). Though, the nutrient removal efficiency was moderate. The removal efficiency of lead and cadmium significantly increased during the experiments. It can be concluded that the studied plants can be used to remove heavy metals such as lead and cadmium and total organic carbon and to some extent nutritious from municipal sewage sludge. However, the yield of plants varied according to the culture medium. It also increased with increasing ripening time and electrical conductivity and decreasing pH.