Heavy Metals in Digesters: Failure and Cure

Both primary and secondary digesters at the Lexington, Ky., wastewater treatment plant experienced process failure because of a slug of toxic heavy metal wastes. Gas production ceased followed by a decrease in pH and an increase in volatile acids. To reinstate normal operation, which required 211 da...

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Bibliographic Details
Published in:Journal - Water Pollution Control Federation 1970-10, Vol.42 (10), p.1832-1839
Main Authors: Regan, Terry M., Peters, Mercer M.
Format: Article
Language:English
Subjects:
Activated sludge
Aeration
Industrial plants
Septic tanks
Sludge
Sludge digestion
Sodium
Storage tanks
Sulfides
Wastewater treatment
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Summary:Both primary and secondary digesters at the Lexington, Ky., wastewater treatment plant experienced process failure because of a slug of toxic heavy metal wastes. Gas production ceased followed by a decrease in pH and an increase in volatile acids. To reinstate normal operation, which required 211 days, the Kraus-system plant was operated as a conventional activated sludge plant. Lime, sodium sulfide, and aqueous ammonia were added to the digesters to restore them. Total direct costs and estimated indirect costs amounted to about $35,000 or 23 percent of the plant's annual operating budget. For local laboratory work, sampling, and labor only, over 1,400 man-hours were expended. A new, more extensive industrial waste sampling program is underway, plant laboratory expansion is planned, revision of the city's sewer use ordinance is under study, an on-site supply of sodium sulfide is stocked, and a program of education and development of increased awareness among local industries is planned.
ISSN:0043-1303