title: Sequential polymer dosing for effective dewatering of ATAD sludges.
abstract: Dewatering problems associated with the sludge from autothermal thermophilic aerobic digestion (ATAD) of sludge, result in large chemical conditioning costs for effective dewatering. A variety of chemical conditioners were used to improve dewatering, but none of them were able to dewater the sludge as desired at acceptable conditioning doses. It was found that during the digestion process, chemical precipitation of divalent cations occurred. Some of the ATAD sludge colloids were found to have a positive zeta potential and these were thought to be the precipitated divalent cations. Sequential polymer dosing using either iron or cationic polymer, followed by anionic polymer, was found to improve dewatering. The use of anionic polymer is essential and allows the use of smaller amounts of iron or cationic polymer for effective dewatering. The use of the less expensive anionic polymer along with cationic polymers has the potential to make the use of the ATAD process more economical.
authors.affiliation: Department of Civil Engineering, College of Engineering, Virginia Polytechnic Institute and State University, 419 Durham Hall, Blacksburg, VA 24061-0105, USA.
authors.forename: Saurabh
authors.initials: S
authors.lastname: Agarwal
authors.forename: Mohammad
authors.initials: M
authors.lastname: Abu-Orf
authors.forename: John T
authors.initials: JT
authors.lastname: Novak
mesh_terms: D000534:Alum Compounds / Q000737:chemistry; D001420:Bacteria, Aerobic / Q000378:metabolism; D019149:Bioreactors; D002118:Calcium / Q000032:analysis; D011232:Chemical Precipitation; D002712:Chlorides; D003890:Desiccation; D005290:Ferric Compounds / Q000737:chemistry*; D006358:Hot Temperature; D008274:Magnesium / Q000032:analysis; D011108:Polymers / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000032:analysis; D012722:Sewage / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D000534:Alum Compounds; D002712:Chlorides; D005290:Ferric Compounds; D011108:Polymers; D000644:Quaternary Ammonium Compounds; D012722:Sewage; C041524:aluminum sulfate; D008274:Magnesium; D002118:Calcium; C024555:ferric chloride