Enhancement of biogas generation during anaerobic digestion of excess activated sludge (a review)

Summary

In the process of biological wastewater treatment vast amounts of sludge are generated. Among the methods of sludge handling anaerobic digestion holds a prominent place combining both possible biogas production and prevention of secondary environmental pollution. The rate-limiting stage of anaerobic digestion is hydrolysis. Sludge pretreatment is a common way to increase the rate of hydrolysis and enhance biogas production; developing pretreatment options has been an area of noticeable exploratory activity. Methods of chemical pretreatment (acidic, alkaline, electrochemical oxidation, ozonation, Fenton process, persulfate process, treatment with calcium peroxide), biological pretreatment (two-stage thermophilic/mesophilic process) and physical pretreatment (thermal hydrolysis, microwave treatment, electrokinetic disintegration, ultrasonic treatment, high pressure homogenization) are considered. The patented technologies for pretreatment of wastewater sludge and the main manufacturers of the relative equipment are presented. As an alternative to the traditional anaerobic digestion a microbial electrolysis cell is considered where methane generation during electromethanogenesis occurs in the presence of exoelectrogenic bacteria. A number of wastewater sludge pretreatment technologies are currently available for the implementation on an industrial scale. In this regard, an urgent need in the development of a standardized methodology for analyzing the technical and economic indicators of various anaerobic digestion systems is evident in order to select an optimal option for specific conditions.

Key words

surplus active silt , anaerobic fermentation , thermal hydrolysis , pretreatment , acidic treatment , alkaline treatment , electrochemical treatment , Fenton process , persulfate process , microbial electrolysis cell , electrokinetic disintegration , ultrasonic treatment , homogenization , microwave treatment

Tackling the problem of energy saving in the Saint-Petersburg wastewater system

Summary

The technologies of primary and secondary sludge treatment at the Saint-Petersburg wastewater treatment facilities are considered. The technologies of thermal hydrolysis and thermophilic and mesophilic digestion were suggested by European companies PWT (Germany), Veolia (OTV, France) and Cambi (Norway). Implementing the project of using the energy potential of wastewater sludge will allow Saint-Petersburg Vodokanal PUE to gain unique experience of systematic approach to the solution of sludge utilization problem.

Key words

sludge , fermentation , biogas , methane tank , mesophilic process , thermophilic process , thermal hydrolysis