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Low chlorine residual in reservoirs

Last Post 23/04/2019 3:43:44 PM by Riverina Water County Council. 2 replies.
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Low chlorine residual in reservoirs

18-04-2019 01:20 PM
 
richard.spain@nambucca.nsw.gov.au
by richard.spain@nambucca.nsw.gov.au
Joined 16-04-2013 01:03 PM
Posts 12
Has anyone used chlorine tablets (as used in swimming pools) as a means of maintaining chlorine residuals in reservoirs in the water sipply system. Was the method effective?What number of tablets were required per Ml of water stored?

Re: Low chlorine residual in reservoirs

23-04-2019 03:40 PM
 
Tamworth Regional Council
by Tamworth Regional Council
Joined 01-01-0001 12:00 AM
Posts 2
Richard, Tamworth Regional Council doses tablets to most of our reservoirs. We use the brand “hth Duration” and we generally dose using the following rule: For a 5 ML Res, dosing 5 tablets will give a chlorine residual of 0.2 mg/L. For example, to raise the residual in a 5 ML Res from zero to 1.0 mg/L you would need to dose 25 tablets. Our guys check the residual chlorine in the res. before they calculate and dose the required no. of tablets. We dose the tablets using a canister suspended from the hatch of the Res. In summer, the residual disappears very quickly, and we often dose a bit higher. We have to be more careful in winter & keep to the formula to risk overdosing. I can put you in contact with appropriate staff if you wnat further information. Thanks Bruce Logan

Re: Low chlorine residual in reservoirs

23-04-2019 03:43 PM
 
Riverina Water County Council
by Riverina Water County Council
Joined 01-01-0001 12:00 AM
Posts 17
Hi Richard,We have at Riverina Water County Council. The method is effective if no other means are available such as transferring hypo via portable dosing pumps and hoses into reservoirs. Literature suggests that the available chlorine for trichloroisocyanuric acid based tablets is 90% and granular calcium hypochlorite based tablets is 65%. A good resource that best explains the quantities I found was https://nt.gov.au/__data/assets/pdf_file/0010/208846/disinfection-of-water-tanks.pdfBasically is says you need 8g of Calcium Hypochlorite tablets (ie 5.2g available Cl @ 65%) for every 1,000L of water to get 5% solution strength of chlorine, or similar, 5.6g of trichloroisocyanuric acid tablets (ie. 5g available Cl @ 90%) for every 1,000L water.Make sure the tablet dispencer is suited and regular checks on chlorine residuals are done. I hope this helps.Jason - Riverina Water County Council
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