Performance of methane fermentation pits in advanced integrated wastewater pond systems

Abstract

Advanced Integrated Wastewater Pond Systems (AIWPSs) involve a series consisting of Advanced Facultative Ponds with internally located fermentation pits; secondary ponds with either photosynthetic oxygenation or mechanical aeration; tertiary ponds for sedimentation of either algae or aeration solids; and, quaternary ponds for controlled discharge, irrigation storage, aquaculture, or other beneficial uses of reclaimed wastewater. This paper deals mainly with design and performance of Advanced Facultative Ponds containing internally located fermentation pits. Experiences with a 1,894 m3 day−1 (0.5 MGD) AIWPS and a 7,576 m3 day−1 (2.0 MGD) AIWPS indicate that primary facultative ponds with internal fermentation pits require less land than do conventional anaerobic ponds and that sludge removal is postponed for many years. New, more detailed, and controlled scientific studies on a 133 m3 day−1 (0.035 MGD) demonstration AIWPS at the University of California, Berkeley, Environmental Engineering and Health Sciences Laboratory in Richmond, California provide evidence that these simple pits remove suspended solids and biochemical oxygen demand more effectively than do comparably loaded conventional anaerobic ponds and produce much less odor. In addition they improve removal of parasites, bacteria, viruses, heavy metals, and halogenated hydrocarbons. The reliability and cost effectiveness of AIWPS is compared with more conventional ponds and with mechanical wastewater treatment systems.