PUMPED CONVEYANCE OF BIOSOLIDS: THEORETICAL MODELING AND EMPIRICAL DATA TO SUPPORT SYSTEM DESIGN CRITERIA

The City of Los Angeles’ Department of Public Works has recently completed the construction of a replacement conveyance and storage system for handling dewatered sludge at the Hyperion Treatment Plant.This 12 million capital improvement project utilizes an innovative application of hydraulically driven reciprocating piston pumps (HDRPP) and pressure pipe. The new conveyance system, which replaces 20-year old belt and screw conveyors, is fully contained and completely automated.With the increased emphasis on improving the safety and economy of the beneficial reuse of biosolids, publicly owned treatment works (POTWs) are being forced to improve on solids handling methods. The more stringent environmental and regulatory requirements have now made the fully contained pumped biosolids conveyance system a viable and practical option for large and small municipalities.Process designers, operators and equipment mechanics must have a good understanding of how this type of system may work for them and engineers need verifiable criteria for designing biosolids pumping systems.This City's design efforts for the replacement conveyance system included an extensive industry survey, computer modeling and full-scale pilot testing. Theoretical design criteria can now be verified using empirical data collected over the past several years of full scale operation.Specialty equipment and control logic incorporated into the Hyperion design are based on typical process applications and can easily be incorporated into systems at many POWT's. Construction and operating experience on this project can assist POTW owners and designers in evaluating the feasibility of installing similar systems at their facilities. Economic analysis, including capital, operating and maintenance costs based on real data, from an installation that operates under high loading rates, 30% solids content biosolids and near continuous operation provide valuable information and a case study on this relatively unique process improvement.