WATER RESOURCES RESEARCH GRANT PROPOSAL
Project ID: 2002TN3B
Title: Acid Catalyzed Hydrolysis of Wastewater Activated Sludge for Removal and Possible Conversion to Products
Project Type: Research
Focus Categories: Treatment, Waste Water, Models
Keywords: activated sludge, data analysis, economics, energy use and conservation, mathematical models, optimization, pollution control, waste disposal
Start Date: 03/01/2002
End Date: 02/29/2004
Federal Funds: $25000.00
Matching Funds: $79222.00
Congressional District: TN2
Principal Investigators: Bienkowski, Paul R.; Counce, Robert M.
Abstract: Both municipal and industrial treatment of wastewater using an activated sludge process generates large quantities of biosolids referred to as sludge. Currently the Knoxville Utility Board (KUB) generates 65 tons/day of these solids (dry basis) from their activated sludge wastewater treatment facilities. This material is concentrated from 4.2 wt % up to 35 - 40 wt % via filtration and disposed off-site by trucking it over 70 miles for disposal through land farming. Every year the distance becomes greater due to KUB?s inability to find acceptable sites for land farming. At least several industries (DuPont and Tennessee Eastman) have similar problems with sludge disposal. On site destruction of the excess biosolids is preferred from both an economic and environmental standpoint. Currently both Dupont and Tennessee Eastman use on site incineration and would prefer a more environmentally benign process which uses less energy. A nitric acid catalyzed hydrolysis process can convert most of the sludge into a biodegradable material suitable for recycle. There is also a possibility that the sludge could be converted into acetic acid for commercial sale. The major products from this hydrolysis are organic acids. It may be possible to optimize production of these acids to the point were it is economically feasible to convert the waste activated sludge stream into a commercial product or convert it to hydrogen in a gasifier. If it is not economically feasible to recover the organic content of the stream it can be recycled back to the waste treatment unit where the organic?s will biodegrade. This proposal will consist of a batch scale kinetic study and continuous pilot scale experiments using activated sludge from KUB?s Kuwahee treatment facility and Tennessee Eastman, employing a factorial experimental design. The variables consist of residence time, reaction temperature, solids concentration, and acid concentration; with percent conversion and acetic acid concentration as the dependent variables. The concentration of the sludge can have a significant impact on the economics of any potential process and must be investigated. The sludge stream from KUB?s activated sludge treatment process is 4.2 wt % and is concentrated to 35 - 40 % by filtration prior to land farming. A feed sludge concentration in the range of 4.2 - 40 wt % will be investigated. The data will be analyzed and a mathematical model will be developed for the reaction kinetics over the range of the input variables. The model will be utilized to evaluate the economics of the process and to develop a preliminary process design. A continuous pilot scale unit was designed and built during the first year of this project. This unit will be used at KUB's Kuwahee treatment facility and at Tennessee Eastman's Kingsport facility in the second year of the project (2003).