Cold weather dechlorination

• Published in: Water engineering & management Vol. 137; no. 12; pp. 21 - 24
• Main Author: Sloan, D W
• Format: Journal Article
• Language: English
• Published: Des Plaines Scranton Gillette Communications, Incorporated 01.12.1990
• Subjects: Case studies; Chemicals; Effects; Hazardous substances; Pressure; Sulfur; Water treatment; Water utilities; Weather conditions; United States > US
• ISSN: 0273-2238

U.S. regulations severely limiting the concentration of chlorine permissible in the effluent from a wastewater treatment works serve as background to a review of methods for dechlorination and in particular to the use of sulphur dioxide for this purpose. The paper is principally devoted to alternative means of ensuring that a system using it could remain effective at temperatures below 18C, at which its vapour pressure of 35 p.s.i.g. was inadequate. Alternative means of raising the vapour pressure in the sulphur dioxide storage vessels above that determined by the ambient temperature are considered, the most favoured being reinforcement of pressure in the vessel by the addition of an externally-supplied gas. The options considered for the gas are nitrogen, dry air and sulphur dioxide. The commerically-available volume supplies of these in the U.S.A. are considered and technical difficulties associated with their use are outlined, much depending on the size, siting and warmth of the storage available and in some instances on what was legally permissible. The solution adopted at 1 works in Texas, where access for railway containers of bulk sulphur dioxide and heating for subsidiary storage tanks were available, is described and illustrated in a flow diagram.