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

The use of coarse coalescent materials in the units
for oil field water treatment

Summary

The Republic of Tatarstan is a federal subject of Russia with high technology and economic level including petrochemical, oil extraction and oil refining industries. At the oil extraction facilities big amounts of oily water are generated. Reuse of this water for oil reservoir flooding to improve the production rate is an efficient method of utilization. Before the injection oil and mechanical admixtures must be removed from wastewater. This is provided by sedimentation method. To enhance the process wastewater pretreatment is used. Coalescence process with the use of granulated coalescent porous media is one of the most efficient methods. To enhance the treatment process granulated coalescent materials based on polymers and expanded clay were developed. As a result of experimental studies it was concluded that coarse hydrophobic media with increased filtration rate that work in self-regeneration mode is the best material for coalescence. Herewith the purification level is improved and the duration of sedimentation process is cut by half and more.

Key words

filtration , oil field water , coalescent media , coalescent nozzle , pretreatment , grain particle size , self-regeneration