"Several composting research projects were conducted from 1972 to 1978 at the Joint Water Pollution Control Plant (JWPCP) in Carson. California, in response to Federal mandates for sludge treatment. The projects have involved research in both windrow and static pile composting. The research on windrow composting had three distinct phases because of changes in sludge production and the development of improved composting methods. In the first windrow composting phase (1972 through 1976), the sludge used prior to composting was anaerobically digested and dewatered by nine scroll centrifuges without the use of any conditioning chemicals. Approximately one-third of the solids were removed from the sludge by the scroll centrifuges, resulting in 90 dry metric tons/day (100 short tons/day) of cake containing about 35% total solids. In the second phase, which began in December 1976, sludge solids in the centrate from the scroll centrifuges were recovered by a centrifuge system composed of 44 basket centrifuges. The basket centrifuge system was designed to remove 90% of the solids from the centrate of the scroll centrifuges and produce a digested dewatered sludge cake with 15% to 20% total solids. The two types of centrifuged sludge cakes were mixed in some of the compost tests. The third phase began in June 1978 and studied large windrows for their ability to increase compost productivity and produce more consistent temperature elevations and microorganism kills. Alternative bulking agents, odor and dust control techniques. forced air aeration, and covered (sheltered) windrow experiments were also investigated in the third phase of the research program. Static pile composting studies began in November 1977 as a potential replacement for the windrow process. Static pile composting, however, was only marginally successful. Windrow composting was found to be the best method for use at JWPCP. The research projects conducted since 1972 have resulted in the establishment of an effective, full-scale windrow composting operation at this facility."