STUDY ON EFFECT OF PRETREATMENT METHODS ON BIOMETHANATION OF WATER HYACINTH

A comparative study on the effect of different pre-treatment methods on the biogas yield from Water hyacinth (WH) was carried out in 250 ml batch digester for a 60 days retention period. Biomethanation was carried out in mesophilic temperature range of 30 to 37°C. WH was pretreated as: chopped, dried and ground (WH-CDG), treated with NaOH, dried and ground (WH-NaOH), ground WH combined with poultry waste (WH-PW), ground WH combined with primary sludge (WH-PS) while fresh water hyacinth (WH-F) served as control. The results of the study showed the highest cumulative biogas yield was from WH-PW, with yield of 0.38 liters/g VS. This was followed by WH-PS, WH-NaOH, and WH-CDG with cumulative biogas yield of 0.345, 0.31 and 0.281 liters/g VS respectively. The biogas yield of the fresh Water hyacinth (WH-F) was negligible. Gas analysis from WH-P shows Methane (65.0%), CO2 (34.94%). WH- F contained Methane (60.0%), CO2 (39.94%), and WH- NaOH contained Methane (71.0%), CO2 (28.94%). The other gases were found in the same levels and in trace amounts in all the systems. The overall results showed that blending water hyacinth with poultry waste and primary sludge had significant improvement on the biogas yield, and treating water hyacinth with NaOH increased the biogas yield slightly. It also indicated that water hyacinth is a very good biogas producer and the yield can be improved by drying and combining it with poultry waste and primary sludge.