EVALUATING LIQUID TO DRIED “CLASS A” BIOSOLIDS (“THE SLURRY WITH THE CAKE ON TOP”)

This paper presents the cost analysis and evaluation of available technologies to produce a “Class A” biosolids at the Upper Montgomery Joint Authority (UMJA) wastewater treatment plant in Pennsburg, PA. It also summarizes the recommendation and selection process that resulted in a final equipment system to be implemented. (As will be seen, an owner's preferred system is not necessarily what appears as most economical and beneficial to the owner's engineer.)The existing 1.2-MGD average capacity plant presently produces a “Class B” aerobically-digested liquid slurry that is applied to nearby farmland (weather permitting), or hauled to a regional plant for dewatering and disposal. The UMJA's treatment system includes primary settling, trickling filters, an aerated contact channel for nitrification, ferric chloride addition for phosphorous removal, chlorine disinfection and post-aeration.The population served by UMJA is projected to grow from the 7,750 served in year 2000, to about 15,000 at buildout. Influent waste loads from industrial sources are negligible in terms of atypical organic and solids concentrations. For comparative analysis, capacity and cost requirements for the various alternatives presented herein were projected for about the “midpoint” of future growth from year 2000 to buildout, or approximately 11,500 persons. All costs were estimated as of late 2001.