Modeling Depth Filtration of Activated Sludge Effluent Using a Compressible Medium Filter
Abstract:A new filter, using a compressible-filter medium, has been evaluated for the filtration of secondary effluent. The ability to adjust the properties of the filter medium by altering the degree of the medium compression is a significant departure from conventional depth-filtration technology. Unlike conventional filters, it is possible to optimize the performance of the compressible-medium filter (CMF) by adjusting the medium properties (i.e., collector size, porosity, and depth) to respond to the variations in influent quality.
Because existing filter models cannot be used to predict the performance of the CMF, a new predictive model has been developed to describe the filtration performance of the CMF and the effect of medium-compression ratio. The model accounts for the fact that the properties of the filter medium change with time and depth. The model, developed for heterodisperse suspensions and variable influent total suspended solids concentrations, can be used to predict all possible phases of filtration (i.e., ripening, constant removal, and breakthrough). A hyperbolic-type, second-order, nonlinear, partial-differential equation was derived to model the CMF. The equation was solved using the finite-difference numerical method. The accuracy of the numerical method was tested by a sensitivity analysis and a convergence test. The model is first-order accurate with respect to medium depth and time.
Field data were obtained for the filtration of settled secondary effluent using a CMF with a capacity of 1200 m3/d. Model predictions were compared with observed performance from filter runs conducted at medium-compression ratios between 15 and 40% and filtration rates from 410 to 820 L/m2·min. The difference between the observed and the predicted values was found to be within 0 to 15%.
Document Type: Research Article
Publication date: 2005-11-01
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Water Environment Research� (WER�) publishes peer-reviewed research papers, research notes, state-of-the-art and critical reviews on original, fundamental and applied research in all scientific and technical areas related to water quality, pollution control, and management. An annual Literature Review provides a review of published books and articles on water quality topics from the previous year. Published as: Sewage Works Journal, 1928 - 1949; Sewage and Industrial Wastes, 1950 - 1959; Journal Water Pollution Control Federation, 1959 - Oct 1989; Research Journal Water Pollution Control Federation, Nov 1989 - 1991; Water Environment Research, 1992 - present.
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