Two-Phase Digestion Improves Digester Performance and Operation at Moreno Valley

Acid-phase (two-phase) anaerobic digestion [APAD]) was installed at Eastern Municipal Water District's (EMWD) Moreno Valley Regional Water Reclamation Facility (MVRWRF). Prior to this expansion, the plant was having issues with the stability of the existing conventional anaerobic digesters. During design, an evaluation of the two-phase digestion was completed that identified potential benefits including reduced disposal costs, increased gas production, and improved process stability.As part of the MVRWRF APAD project, the existing digester process was modified to a two-phase digestion process consisting of acid-phase and methane-phase digesters. Post two-phase performance showed a net improvement of 17-percent Volatile Solids (VS) destruction and 30 percent specific gas production compared to the pre-acid-phase period. From an operational perspective, major improvements were seen in the operation of the digestion process. The pH, volatile acids, and alkalinity of the downstream methane digesters showed very little variability, indicating stable and healthy digestion.