Beneficial Use of Dairy, Fountain, and Fruit Beverage Wastes in POTWs
Abstract:Publicly Owned Treatment Works (POTWs) increasingly face more restrictive effluent nutrient limits as Total Maximum Daily Loads (TMDLs) are applied to receiving waters that are impaired due to the presence of excessive nutrients. These limits are causing an increasing number of POTWs to upgrade to provide total nitrogen control (denitrification and nitrification) and total phosphorus control. The cost of iron addition and subsequent excess sludge handling and disposal cause more POTWs to upgrade to biological phosphorus removal. The readily biodegradable chemical oxygen demand (CODrb) naturally present in domestic sewage is inadequate for the denitrification and total phosphorus removal needs of these facilities. Historically, these facilities have added methanol as an additional source of CODrb. The cost of methanol had increased 380 percent through the 5-year period ending in January 2007. Additionally, the safety and security risks of handling methanol have posed concerns. These concerns cause many of these facilities to turn to 56 percent by weight acetic acid as the current low cost source of CODrb. The cost of this material has increased by 35 percent during this same 5-year period. In either case, the cost of this type of supplemental CODrb is only expected to increase for POTWs, making the operating costs of denitrification and biological phosphorus removal escalate with time while continuing to be influenced by market conditions. In addition, POTWs face increasing energy costs (greater than 26 percent increase over the last 5 years). This has caused an increasing number of POTWs to implement energy recovery with anaerobic digestion facilities. This practice will expand as energy costs continue to rise.
Within 200 miles of nearly all POTWs, there are fluid milk plants and carbonated soft drink bottling plants that supply our nation's demand for beverages. These plants dispose of highly concentrated wastes at a considerable expense to the plants. These concentrated wastes offer a source of CODrb.
There is a "win-win" solution for POTWs, the dairy industry, and the carbonated soft drink bottling industry with a combined savings for all three groups projected at greater than $54 million per year. One group needs a low cost source of CODrb; the other two groups provide this source and would benefit from a lower cost disposal option. This paper contains greater details of this synergy and concludes with case histories of those who have benefited from implementing this solution.
Document Type: Research Article
Publication date: October 1, 2007
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