Water Hyacinth: A Sustainable Resource for Water Phytoremediation, Ethanol Production, Soil Nutrient Improvement, and the Dynamics of Microbial C and N in Vermicompost

The water hyacinth Eichhornia crassipes is a rapidly growing weed that grows in shallow fresh water. It can be used for the removal of nutrients and heavy metals from water, as feedstock for biofuels, and as a bulking agent for the vermicompost process. The present study focused on the use of water hyacinth plants for nutrient and heavy metal removal from water. Water hyacinth removed >95% of ammonium nitrogen, nitrite, and nitrate from the water. The bioaccumulation potentials of water hyacinth for Cu, Cd, Cr, As, Li, and Zn after 30 days of treatment were 80 ± 2.3%, 78.6 ± 3.2%, 73.2 ± 1.2%, 69.6 ± 2.1%, 65.5 ± 1.9%, and 44.2 ± 2.2%, respectively. The heavy metal accumulation in water hyacinth was in the following order: Cu>Cd>Cr>As>Li>Zn. Water hyacinth was pretreated with acid and base. It was further digested with cellulolytic enzymes, and Saccharomyces cerevisiae was further inoculated to produce ethanol in a liquid culture. The ethanol yield was 0.09 mL/mL culture. Water hyacinth was cut into small pieces, mixed with goat manure and used for vermicomposting. The microbial C content of the vermicompost ranged between 398 ± 12.8 and 537 ± 11.2 µg/g, and the microbial N content ranged from 104.4 ± 2.2 to 254.9 ± 2.2 µg/g. The vermicompost had an 84.3 ± 2.2% germination index after 48 h in the pots treated with 20% vermicompost.