POTENTIAL OF AQUATIC WEED SALVINIA-MOLESTA (MITCHELL) FOR WATER-TREATMENT AND ENERGY RECOVERY

Salvinia molesta (Mitchell), has been studied as a bioagent for treating wastewaters containing 1-100 ppm of nickel(II), copper(II), chromium(VI), molybdenum(VI), cadmium(II), and mercury(II). Subsequently, conversion of Salvinia harvested from these metal-spiked waters into energy (biogas) has been explored. The results indicate that Salvinia can survive and grow (multiply) for atleast a week on waters containing 10 ppm of chromium, nickel or cadmium; and < 100 ppm of zinc or molybdenum. The weed can also grow upto 4-5 days in 100 ppm of nickel and cadmium. Anaerobic digestion of the weed spiked with low concentrations (1.18 mg L-1) of each of the metals revealed that all metals studied, except chromium, enhance biogas yield. The stimulatory effect followed the trend Cu (51%) > Mo (45%) > Zn (30%) > Hg (24.4%) = Cd (23.8%) > Ni (14%). Chromium retarted biogas production by 44%.