Optimization of Pressure Filter Performance on Mud Solids in a Potato Processing Plant

A major Canadian, east-coast based, potato producer and processor required the mud solids captured from its potato fluming and washing operations to be dewatered into a sludge cake prior to being hauled to a company-owned landfill some distance from the processing site. To this end, the firm contracted the building of a sludge dewatering system that centered around a 5 cubic meter recessed plate pressure filter and its auxiliary equipment, enclosed in a new structure adjacent to the firm's potato receiving area. The site's activated sludge wastewater treatment plant personnel were initially given the responsibility for operating this system. The operation captured mud solids across a mud thickener (clarifier), by settling solids and concentrating them at the bottom of the unit. An operator estimated when there were sufficient solids present to complete a press cycle. He then initiated an automated program that controlled an air-diaphragm pump which pulled the sludge from the bottom of the clarifier and pumped it directly to the pressure filter, in a "stepped" phase format, governed by the program. Characteristics of this "continuous feed" operational approach was: 1. Clarified effluent was of poor quality, 2. Filter press cycle times were frequently overly long, from 8 to 18 hours, 3. Cake quality was poor and 4. Cleaning the press often required two men for the better part of a full shift to clear the cake and scrape the filter cloths in preparation for the next press. This paper addresses the four phases used to transform the existing "continuous feed" model for operating the filter press to a "batch feed" model: 1. An initial evaluation and documentation of the press operation including modifying this "continuous approach" to optimize cake quality. 2. Introduction of the batch feed approach using temporary tankage and routing of sludge feed lines plus operator training. 3. Acquisition and installation of appropriately-sized tankage with associated mixers to establish a permanent "batch feed" operation and 4. A final review of the new batch treatment approach and development of an experienced-based operations manual. In the end, the filter press operation reflected a much improved mud thickener operation, press cycle times of 2 to 3 hours, cake quality of 60% Total Solids plus, a trained operator group, considerable unused press capacity, an operations manual and standardized record keeping. Also, the press center provided an ideal location to inventory mud solids acquired from the potatoes and to develop a mass balance which changed historical estimates of their quantities.