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PRESSURE FILTRATION OF WASTE INDUSTRIAL SLUDGES- MODELING, DESIGN AND OPERATIONAL PARAMETERS James L. Martin, Sanitary Engineer Phillip L. Hayden, President Pollution Control Science, Inc. Miamisburg, Ohio 45342 INTRODUCTION One of the most expensive unit operations of biological and certain other water and wastewater treatment processes is handling and dewatering the large quantities of sludges produced. If the ultimate disposal method is landfill or incineration, economic considerations as related to transportation costs or fuel costs necessitate a high level of solids concentration. More stringent landfill requirements may also dictate higher sludge solids concentrations. Several dewatering techniques have been employed with varying degrees of success, such as horizontal-belt vacuum or pressure filters, rotary vacuum filters, centrifuges and vertical plate and frame or recessed-plate filter presses. Overall economics as related to capital, transportation, chemical, manpower and maintenance costs or perhaps specific solids level requirements will determine what type of system is employed. Pressure filtration dewatering produces well-formed compact sludge cakes which are easily handled. The cakes have a density of approximately 65 to 80 lb/ft3 with a solids concentration of between 20 to 50%, depending upon sludge characteristics and operational parameters. Sludge at concentrations of between 2 to 11% solids is pumped into the filter at pressures which may ultimately be in excess of 100 psig. The recessed-plate filter press consists of several separable plates, each side of which forms one half of a cake chamber. Each face of the plate is corrugated in some fashion to provide support for the filter cloth and channels for the filtrate to drain to outlet ports. Sludge is pumped into the cavity between the filter cloths, where the solids are retained. The effluent, which is essentially free of suspended particles, passes through. The filter media actually becomes the initial layer of sludge solids deposited on the cloth, thus the rate of filtration decreases as the sludge layer thickens. Upon completion of a filter run, dictated by the cake solids concentration desired or the rate of filtrate discharge, the plates are separated sequentially to permit the sludge cakes to fall to a conveyor or hopper for removal from the filter room. A filter precoat of fly ash, diatomaceous earth, or paper fiber is often used to prevent cloth blinding and to provide a shear plane to permit the cakes to readily separate from the filter cloth. Overall dewatering rates may be enhanced considerably by using chemical coagulants such as lime, alum, and ferric chloride and/or sludge admixtures (also termed body feed or filter aid) such as fly ash, diatomaceous earth and paper fiber. The design parameters, i.e., cycle length, cake solids, cake density, or mass loading per unit area as a function of time, may be obtained by the following methods: 1. Pilot-Scale Tests. Several vendors supply pilot-scale filter units consisting of three chambers, 4 in.,6 in. or 12 in. in size. The filter unit is equipped with an air operated feed pump and is rented on a monthly basis plus shipping charges. Approximately 2 to 20 gal of sludge are required per test. 2. Bench-Scale Tests. Bench-scale equipment which may be quite simple or elaborate and expensive is also available from some vendors. Although some vendors offer to conduct tests in their laboratories, dewatering tests performed onsite with fresh sludges will provide more realistic and reliable results. 792
Object Description
Purdue Identification Number | ETRIWC197671 |
Title | Pressure filtration of waste industrial sludges : modeling, design and operational parameters |
Author |
Martin, James L. Hayden, Phillip L. |
Date of Original | 1976 |
Conference Title | Proceedings of the 31st Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://e-archives.lib.purdue.edu/u?/engext,27048 |
Extent of Original | p. 792-806 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Date Digitized | 2009-07-08 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 792 |
Collection Title | Engineering Technical Reports Collection, Purdue University |
Repository | Purdue University Libraries |
Rights Statement | Digital object copyright Purdue University. All rights reserved. |
Language | eng |
Type (DCMI) | text |
Format | JP2 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Transcript | PRESSURE FILTRATION OF WASTE INDUSTRIAL SLUDGES- MODELING, DESIGN AND OPERATIONAL PARAMETERS James L. Martin, Sanitary Engineer Phillip L. Hayden, President Pollution Control Science, Inc. Miamisburg, Ohio 45342 INTRODUCTION One of the most expensive unit operations of biological and certain other water and wastewater treatment processes is handling and dewatering the large quantities of sludges produced. If the ultimate disposal method is landfill or incineration, economic considerations as related to transportation costs or fuel costs necessitate a high level of solids concentration. More stringent landfill requirements may also dictate higher sludge solids concentrations. Several dewatering techniques have been employed with varying degrees of success, such as horizontal-belt vacuum or pressure filters, rotary vacuum filters, centrifuges and vertical plate and frame or recessed-plate filter presses. Overall economics as related to capital, transportation, chemical, manpower and maintenance costs or perhaps specific solids level requirements will determine what type of system is employed. Pressure filtration dewatering produces well-formed compact sludge cakes which are easily handled. The cakes have a density of approximately 65 to 80 lb/ft3 with a solids concentration of between 20 to 50%, depending upon sludge characteristics and operational parameters. Sludge at concentrations of between 2 to 11% solids is pumped into the filter at pressures which may ultimately be in excess of 100 psig. The recessed-plate filter press consists of several separable plates, each side of which forms one half of a cake chamber. Each face of the plate is corrugated in some fashion to provide support for the filter cloth and channels for the filtrate to drain to outlet ports. Sludge is pumped into the cavity between the filter cloths, where the solids are retained. The effluent, which is essentially free of suspended particles, passes through. The filter media actually becomes the initial layer of sludge solids deposited on the cloth, thus the rate of filtration decreases as the sludge layer thickens. Upon completion of a filter run, dictated by the cake solids concentration desired or the rate of filtrate discharge, the plates are separated sequentially to permit the sludge cakes to fall to a conveyor or hopper for removal from the filter room. A filter precoat of fly ash, diatomaceous earth, or paper fiber is often used to prevent cloth blinding and to provide a shear plane to permit the cakes to readily separate from the filter cloth. Overall dewatering rates may be enhanced considerably by using chemical coagulants such as lime, alum, and ferric chloride and/or sludge admixtures (also termed body feed or filter aid) such as fly ash, diatomaceous earth and paper fiber. The design parameters, i.e., cycle length, cake solids, cake density, or mass loading per unit area as a function of time, may be obtained by the following methods: 1. Pilot-Scale Tests. Several vendors supply pilot-scale filter units consisting of three chambers, 4 in.,6 in. or 12 in. in size. The filter unit is equipped with an air operated feed pump and is rented on a monthly basis plus shipping charges. Approximately 2 to 20 gal of sludge are required per test. 2. Bench-Scale Tests. Bench-scale equipment which may be quite simple or elaborate and expensive is also available from some vendors. Although some vendors offer to conduct tests in their laboratories, dewatering tests performed onsite with fresh sludges will provide more realistic and reliable results. 792 |
Resolution | 300 ppi |
Color Depth | 8 bit |
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