Upcoming trends of processing waste activated sludge.
Preparation of volatile fatty acids (a review)

Summary

Among the methods of obtaining products with higher added value from waste activated sludge, produced avoiding the emission of greenhouse gases, anaerobic digestion is considered as a viable alternative to biogas production to obtain volatile fatty acids as the final product, that are an intermediate product of methane production in the traditional process. The main factors affecting the production of volatile fatty acids are considered, including pH value, temperature, C/N ratio, process duration, organic matter load of the fermenter, and the presence of microelements. An effective way of increasing the yield of volatile fatty acids is the combined digestion of waste activated sludge and substrates with a high organic carbon concentration (food waste, corn stover, manure, wastewater from dairy and pulp-and-paper production, filtrate from solid waste landfills), as well as pretreatment methods: physical (ultrasonic, microwave, thermal), chemical (alkaline treatment, free nitrous acid, metallic iron, peroxomonosulfate, etc.) and biological (biological surfactants, hydrolytic enzymes, hydrolytic bacteria) ones. The main fields of application of volatile fatty acids are presented including the preparation of medium-chain fatty acids, the production of polyhydroxyalkanoates, protein of single-cell organisms, electricity, hydrogen, as well as the use as a carbon source in the process of biological nitrogen removal.

Key words

surplus active silt , anaerobic fermentation , electric power , volatile fatty acids , polyhydroxyalkanoates , protein of unicellular organisms , medium-chain fatty acids , hydrogen , additional carbon source