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Title:Dewatering biosolids from a milk processing plant: Agricultural fibers as flocculant aids and ultrafiltration membrane concentration
Author(s):le Roux, Louis D. DJ
Doctoral Committee Chair(s):Litchfield, J. Bruce
Department / Program:Agricultural and Biological Engineering
Discipline:Agricultural and Biological Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Agriculture, Animal Culture and Nutrition
Engineering, Agricultural
Engineering, Sanitary and Municipal
Abstract:Biosolids constitute a large portion of the total organic wastes produced by food plants each year. Disposal of these solids is a significant environmental problem. Biosolids contain between 30 and 45% protein; therefore, they can be recycled as animal food.
To prevent microbial spoilage and decrease transportation costs, biosolids need to be dewatered and dried to 90% total solids (TS). Commercial dewatering equipment requires polymer to effectively separate biosolids from water. Most polymers contain acrylamide, which has been shown to cause cancer in laboratory animals. In this study, ferric chloride (FeCl$\sb 3$) was tested as a coagulant aid for biosolids coagulation and agricultural fibrous materials were evaluated for their ability to flocculate biosolids. Also, ultrafiltration (UF) membrane biosolids dewatering, without polymer, was investigated.
Biosolids coagulation with FeCl$\sb 3$ showed that specific resistance to filtration (SRF) decreased from 3.32 Tm/kg at no FeCl$\sb 3$, addition to 0.35 Tm/kg at 3,000 mg FeCl$\sb 3$/L of biosolids; SRF values below 1 Tm/kg is indicative of good coagulation. A concentration of 200 mg FeCl$\sb 3$/L of biosolids was recommended to be acceptable from the standpoint of using the material as an animal food supplement.
From all the agricultural fibers tested, wood fiber, oat fiber and corn pericarp resulted in better biosolids flocculation compared to corn gluten and corn germ. Highest filter yield was obtained at 40 g corn pericarp/L of biosolids; whereas, filter yield continued to increase with increasing oat fiber concentration above 60 g fiber/L of biosolids.
Ceramic MF membranes, with 2 mm x 2 mm flow channel dimension, could not be used for biosolids dewatering, since blockage of the membrane flow channel occurred at biosolids concentration above 3% TS. However, biosolids were successfully dewatered from 1.5 to 6% TS with tubular, PVDF, UF membranes. Highest permeate flux was obtained at 103 kPa transmembrane pressure and 3.89 m/s cross flow velocity at constant biosolids temperature (27$\sp\circ$C). UF membranes produced permeate of superior quality since they retained all suspended solids and permeate chemical oxygen demand was low enough (below 100 mg/L) to be discharged directly into municipal sewer system.
Biosolids total nitrogen (TN) increased with increasing biosolids concentration during UF membrane biosolids dewatering. TN increased from 6.95 g N/100 g biosolids (db) at 2% TS to 7.1 g N/100 g biosolids (db) at 5.5% TS when biosolids were dried at 50$\sp\circ$C. Available nitrogen (AN) of raw and concentrated biosolids were similar; AN was 2.3 g N/100 g biosolids (db) at 50$\sp\circ$C drying temperature. AN of both raw and concentrated biosolids increased from 2.3 to 3.2 g N/100 g biosolids (db) with an increase in drying temperature from 50 to 150$\sp\circ$C.
Issue Date:1996
Rights Information:Copyright 1996 le Roux, Louis D. DJ
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9712348
OCLC Identifier:(UMI)AAI9712348

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