Treatment of water hyacinth anaerobic fermentation wastewater by combining Fe-C micro-electrolysis with Fenton reaction

The anaerobic fermentation of water hyacinth is an effective way to turn waste-water hyacinth (a noxious plant of malignant growth) into treasure (methane). However, the technology also brings much water hyacinth anaerobic fermentation wastewater with high COD value, high ammonia nitrogen value and deep color, and thus specific treatment of wastewater is required before its drainage. In this study, iron-carbon micro-electrolysis combined with Fenton reaction was used to treat the water hyacinth anaerobic fermentation wastewater. Removal rate of COD after iron-carbon treatment and Fenton reaction were around 85 % and 80 %, and removal rate of ammonia nitrogen and color were 95 % and nearly 100 % after adjusting pH to alkaline following Fenton reaction in the optimal processing conditions: pH before micro-electrolysis and before Fenton reaction was adjusted to 2.0 and 3.0, 0.15 % (v/v) hydrogen peroxide was the most economical and efficient concentration for Fenton reaction. After iron-carbon micro-electrolysis and Fenton reaction, COD, ammonia nitrogen and absorbance of wastewater were reduced to less than 50 mg/L, 25 mg/L, and almost 0 from the initial value 720 mg/L, 275 mg/L and 0.155, respectively, and all of these satisfy the national emission standards. In the scale up and continuous treatment, good results were also obtained under the optimal conditions. Overall, iron-carbon microelectrolysis combined with Fenton reaction can effectively treat water hyacinth fermentation wastewater and this technology will make the utilization of water hyacinth resources to be much more environmentally friendly.