Electrode potential monitoring and electrolytic control in anaerobic digestion.

Abstract

INCREASED BIOLOGICAL SLUDGE PRODUCTION that results from higher treatment re quirements and new ocean and land dis posal restrictions has created sludge han dling and disposal problems in many areas. Anaerobic digestion is one of the most ex tensively used sludge stabilization methods, and the digestion units account for a sub stantial portion of the existing wastewater treatment plant investment. In addition to the sludge stabilization, the digestion process produces a methane rich gas that can be used as a fuel. Present methods of anaerobic digestion monitoring and control have resulted in conservative operation at lower rates and loadings than the maximum possible. The present increased activity toward tighter restrictions on the level of toxic metals in sewers is a favorable indication for in creased use of this process. It is therefore necessary to find better process monitoring and control methods so that the advantages of the process can be realized. This paper deals with electrode potential measurement as a digestion monitoring parameter and reports on the relationship of electrode potential measurements to the methane-forming phase of the digestion process. It also reports on research that demonstrates that the pH of a digesting sludge can be controlled by direct current electrolysis with a resulting stability in the electrode potential and an increase in al kalinity.