Innovative Material Handling System at Biosolids Cake Storage Facility

Abstract

This paper describes the design and recent startup of an innovative bulk biosolids cake storage facility for the City of Albany, Oregon Wastewater Treatment Plant. With the City facing a need to develop biosolids storage facilities, the City's consultants first completed a predesign analysis that compared options for providing storage, including a lagoon storage system and a system incorporating dewatering and cake storage. It turned out that the dewatering/cake storage system was most advantageous for the City.The dewatering system includes two, 2.0 meter belt filter presses with a dry polymer preparation system. From there, the cake is transferred to the bulk cake storage facility. Storage is provided in two concrete bunkers, each 40 feet by 80 feet by 16 feet deep, for a total of 3,600 cubic yards of storage. This provides about six months' storage capacity.The facility includes two innovative systems: (1) the use of progressing cavity pumps to transfer the cake 250 feet to the cake storage bunkers, and (2) automated unloading from the bunkers using shaftless screws installed in the floor. Those screws convey the material through the wall to inclined conveyors that lift the cake to truck loading stations.This unloading system is a significant improvement over previous designs that are based on unloading similar bays by use of stop logs or large gates and front-end loaders. It saves operator time, avoids a messy operation, minimizes the potential for odor generation, and removes material on a "first in-first out" basis. The use of the progressing cavity cake pumps saved about $400,000 relative to the original design concept, which used screw conveyors. It is also a much cleaner and quieter operation with lower maintenance requirements.The paper provides information about the system design, startup, and costs, including observations about the material handling aspects and hydraulic behavior of belt filter press cake.16th Annual Residuals and Biosolids Management Conference