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Zinc in Relation to Activated Sludge and Anaerobic Digestion Processes GERALD N. McDERMOTT, Senior Sanitary Engineer EDWIN F. BARTH, Chemist VINCENT SALOTTO, Chemist M. B. ETTINGER, Chief, Chemistry and Physics Robert A. Taft Sanitary Engineering Center Cincinnati 26, Ohio The efficiency of treatment of sewage containing zinc was studied by operation of pilot activated-sludge plants. Sewage from a common source was fed to three replicate plants. Zinc solutions were introduced continuously to the feed of two of the plants to produce selected constant concentrations; one plant was operated with no metal addition to the feed. Differences in effluent quality, as measured by BOD, COD, suspended solids, and turbidity, between the zinc fed units and the unit receiving the unaltered sewage were attributed to the presence of zinc in the feed. The digestion of the zinc-bearing sludges was studied by operation of bench-scale digesters on sludge feeds obtained from the activated sludge plants. Differences in gas production between the digesters receiving control sludge and those receiving the zinc-bearing sludges were attributed to the zinc in the sludge. The objectives of the research were to determine the level of zinc that can be tolerated in waste waters without reducing the efficiency of biological processes in removing the organic matter or in stabilizing the sludges, and to determine the efficiency of the process in removing zinc. PLANT DESCRIPTION AND OPERATION The pilot activated-sludge plants were designed to simulate standard activated-sludge plants of the spiral flow type. The activated-sludge plant included: primary settling, aeration with continuous sludge return, and secondary settling. Thus opportunity existed for precipitation, reduction, and complexing such as might occur during primary settling in an actual situation before a biological process is reached. Effects were related to metals added to the incoming sewage rather than to metals added to some specific plant component. The units are illustrated in a previous article concerning heavy metals and se>vage treatment (1). Capacity and loading factors for the plant are given in Table I. Sewage was fed to the units at a constant rate. Sludge from the final settler was pumped continuously to the head of the aerator at a rate of about 35 per cent of the sewage feed flow. An automatic device, activated once per minute, diverted the return sludge about 5 per cent of each minute to a collecting vessel. This procedure wasted about 25 per cent of the suspended matter in the aeration tank each day. The sewage available in the area where the pilot plant was located, while of essentially domestic origin, had an average BOD of about 75 mg/1 because of high ground water infiltration. Fortification of this sewage with dog food produced a sewage showing characteristic behavior and adequate strength. Dry granular dog food was ground, soaked in water overnight, - 461 -
Object Description
Purdue Identification Number | ETRIWC196239 |
Title | Zinc in relation to activated sludge and anaerobic digestion processes |
Author |
McDermott, G. N. (Gerald N.) Barth, Edwin F. Salotto, Vincent Ettinger, M. B. |
Date of Original | 1962 |
Conference Title | Proceedings of the seventeenth Industrial Waste Conference |
Conference Front Matter (copy and paste) | http://earchives.lib.purdue.edu/cdm4/document.php?CISOROOT=/engext&CISOPTR=9369&REC=10 |
Extent of Original | p. 461-475 |
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 | 2009-05-18 |
Capture Device | Fujitsu fi-5650C |
Capture Details | ScandAll 21 |
Resolution | 300 ppi |
Color Depth | 8 bit |
Description
Title | page 461 |
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 | Zinc in Relation to Activated Sludge and Anaerobic Digestion Processes GERALD N. McDERMOTT, Senior Sanitary Engineer EDWIN F. BARTH, Chemist VINCENT SALOTTO, Chemist M. B. ETTINGER, Chief, Chemistry and Physics Robert A. Taft Sanitary Engineering Center Cincinnati 26, Ohio The efficiency of treatment of sewage containing zinc was studied by operation of pilot activated-sludge plants. Sewage from a common source was fed to three replicate plants. Zinc solutions were introduced continuously to the feed of two of the plants to produce selected constant concentrations; one plant was operated with no metal addition to the feed. Differences in effluent quality, as measured by BOD, COD, suspended solids, and turbidity, between the zinc fed units and the unit receiving the unaltered sewage were attributed to the presence of zinc in the feed. The digestion of the zinc-bearing sludges was studied by operation of bench-scale digesters on sludge feeds obtained from the activated sludge plants. Differences in gas production between the digesters receiving control sludge and those receiving the zinc-bearing sludges were attributed to the zinc in the sludge. The objectives of the research were to determine the level of zinc that can be tolerated in waste waters without reducing the efficiency of biological processes in removing the organic matter or in stabilizing the sludges, and to determine the efficiency of the process in removing zinc. PLANT DESCRIPTION AND OPERATION The pilot activated-sludge plants were designed to simulate standard activated-sludge plants of the spiral flow type. The activated-sludge plant included: primary settling, aeration with continuous sludge return, and secondary settling. Thus opportunity existed for precipitation, reduction, and complexing such as might occur during primary settling in an actual situation before a biological process is reached. Effects were related to metals added to the incoming sewage rather than to metals added to some specific plant component. The units are illustrated in a previous article concerning heavy metals and se>vage treatment (1). Capacity and loading factors for the plant are given in Table I. Sewage was fed to the units at a constant rate. Sludge from the final settler was pumped continuously to the head of the aerator at a rate of about 35 per cent of the sewage feed flow. An automatic device, activated once per minute, diverted the return sludge about 5 per cent of each minute to a collecting vessel. This procedure wasted about 25 per cent of the suspended matter in the aeration tank each day. The sewage available in the area where the pilot plant was located, while of essentially domestic origin, had an average BOD of about 75 mg/1 because of high ground water infiltration. Fortification of this sewage with dog food produced a sewage showing characteristic behavior and adequate strength. Dry granular dog food was ground, soaked in water overnight, - 461 - |
Resolution | 300 ppi |
Color Depth | 8 bit |
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