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dc.contributor.authorAgarwal, Saurabhen
dc.date.accessioned2014-03-14T20:32:40Zen
dc.date.available2014-03-14T20:32:40Zen
dc.date.issued2004-03-04en
dc.identifier.otheretd-03152004-104708en
dc.identifier.urihttp://hdl.handle.net/10919/31480en
dc.description.abstractAutothermal thermophilic aerobic digestion (ATAD) of sludge has been used to produce class A biosolids. With stringent EPA guidelines, more and more municipalities are looking to use this process for digestion of sludge. However the large polymer costs associated with dewatering these sludges has made the use of this technology unfavorable. Several studies have been conducted in the past which have looked into the mechanism leading to such a poor dewatering of sludge. Some of these studies have attributed the release of protein and polysaccharide during the high temperature digestion to be responsible for the poor dewatering. However the exact mechanism leading to the poor dewatering is still not totally clear. Laboratory scale studies were conducted to evaluate the mechanism leading to the poor dewatering of these sludges and also to be able to economically condition these sludges. ATAD sludge samples were collected from ATAD processing facilities in Ephrata, PA, Cranberry, PA, Titusville, FL and College Station, TX. The research included experiments evaluating the protein and polysaccharide concentrations in solution, cations and anions, iron and aluminum, zeta potential and capillary suction time. It was found that during digestion large amounts of protein and polysaccharide were released which were in the colloidal range, and the dewatering of each of these sludges became poorer as the amount of protein and polysaccharide in the solution increased. The release of protein and polysaccharide was related to the monovalent to divalent cation ratio and the iron and aluminum concentration in the sludge. Also during the digestion process, the pH of the sludge increased appreciably and the divalent cations precipitated out. The zeta potential of the ATAD digested sludge was also found to be positive. Different chemical coagulants were used to condition the sludge, but even with high polymer doses the dewatering of the sludge was not satisfactory. A combination of iron (or cationic polymer) followed by anionic polymer was found to improve the dewatering to a desired level. The use of this combination of sludge conditioning also provides an economical solution to the problem of dewatering. The role of iron in improving the dewatering of the sludges was found to be important, with the sludge dewatering being better for sludges with a high iron content. The combination of high pH, divalent cation precipitation, iron deficiency and biopolymer release all contribute to the poor dewatering of ATAD sludge.en
dc.publisherVirginia Techen
dc.relation.haspartthesis.pdfen
dc.relation.haspartIndex.pdfen
dc.relation.haspartTitle.pdfen
dc.relation.haspartAbstract.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectdewateringen
dc.subjectaerobic digestionen
dc.subjectanionic polymeren
dc.subjectbiopolymeren
dc.subjectM/D ratioen
dc.subjecthigh ironen
dc.subjectthermophilicen
dc.titleConditioning and Dewatering Behavior of ATAD Sludgesen
dc.typeThesisen
dc.contributor.departmentEnvironmental Engineeringen
dc.description.degreeMaster of Scienceen
thesis.degree.nameMaster of Scienceen
thesis.degree.levelmastersen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.disciplineEnvironmental Planningen
dc.contributor.committeechairNovak, John T.en
dc.contributor.committeememberRandall, Clifford W.en
dc.contributor.committeememberBoardman, Gregory D.en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-03152004-104708en
dc.date.sdate2004-03-15en
dc.date.rdate2005-03-16en
dc.date.adate2004-03-16en


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