Design, Testing and Operation of Grit Chambers with Hydraulic Roll

Abstract

The Soreq biological treatment plant has been recently brought into operation, after a comprehensive start-up and testing program. The plant's preliminary treatment facilities include four grit chambers 40 m long, equipped for both grit removal and scum skimming. The variable energy input required to control the deposition of the grit and the floating of the scum, is provided by a hydraulic jet system, using pumped recycled wastewater to generate the necessary motive power. The basic concept in designing grit chambers equipped with a hydraulic jet system, instead of a bubble aeration system, is to avoid the release of noxious odours and corrosive gases which are often associated with the conventional aerated grit chambers. Experiments were conducted on a hydraulic model of the grit chamber to develop the necessary design criteria for the full scale jet system. During the initial start-up program of the Soreq plant, the grit chambers and the related equipment were tested with clear water, and the actual transversal velocities were measured through a range of simulated operating conditions. This paper summarizes the hydraulic model test results, the upscaling approach used for design of the prototype system, and the on-site full-scale tests with clear water. A follow-up program under actual operating conditions is now in progress to establish the variable parameters for optimal operation of the hydraulically powered grit chambers with wastewater.