Development of promising methods of wastewater treatment with energy recuperation in China and India (a review)

Summary

In China, active research is underway for developing a technology for excess activated sludge fermentation to obtain hydrogen. The process of anaerobic fermentation includes three main stages: hydrolysis, formation of hydrogen and acids, and methane generation. At the hydrolysis stage, the formation of low-molecular substances from high-molecular starch, fibers and proteins. At the stage of the hydrogen and acids formation hydrogenogenic and acetogenic bacteria ensure the fermentation of low-molecular substances with the formation of a number of organic acids, hydrogen and carbon dioxide. At the stage of methane generation, methanogenic bacteria metabolize the products formed in the previous stages with the release of methane and carbon dioxide. As a result, hydrogen can be obtained only by inhibiting the activity of methanogenic bacteria eliminating the impact on the activity of hydrogenogenic bacteria. Considering these circumstances methods are being developed to enhance the production of biohydrogen. The main efforts in this area aim at finding strains with high efficiency of anaerobic fermentation. Another direction is choosing a method of activated sludge pre-treatment from among thermal, acid, alkaline, microwave treatment, sterilization and ultrasonic treatment. Significant prospects are associated with the use of a consortium of microorganisms and mixed substrate containing, along with wastewater sludge, food waste, straw or manure. In India, the technologies of processing various types of industrial wastewater with the production of biomass enriched with lipids for the subsequent production of biodiesel have been on the march. The studies have been performed using Rhodococcus opacus bacteria, Rhodosporidium kratochvilovae yeast and Desmodesmus sp microalgae.

Key words

wastewater , surplus active silt , biodiesel fuel , biohydrogen , anaerobic fermentation , hydrogeonogenic bacteria , Rhodococcus opacus bacteria , Rhodosporidium kratochvilovae yeast , Desmodesmus sp. microalgae , intracellular lipid accumulation