3. Test Procedure
The tests have been conducted in compliance with the procedures described in the ASCE Standard ANSI/ASCE 2-91 'A Standard for the Measurement of Oxygen transfer in Clean Water'.
Public supply drinking water from the area (Les Fonts, Mina Pública de Terrasa) was used to fill the test tank to the water depth specified for the tests. Multiple tests were conducted in the same water checking the conductivity did not exceed 3000 mS.
Before reaching this limit, the test tank was emptied and refilled with fresh water from the same source before any further tests were conducted.
3.1 Deoxygenation
Deoxygenation of the test water volumes was achieved by addition of technical grade (98%) anhydrous Sodium Sulphite in excess of the stoichiometricamounts required for the removal of all DO present in the test water using Cobalt II Chloride · 6H20 as a catalyst.
To allow good catalyzation, a minimum free cobalt concentration of 0.30 mg/l is maintained in the test volume.
Cobalt catalyst was added to each batch of fresh water as a solution with the aeration system turned on at least one hour before the first addition of Sodium Sulphite to allow adequate mixing.
Sodium Sulphite in excess of stoichiometric amountsrequired for DO depletion is added as a solution prepared beforehand in a separate mixing tank by pumping over the tank surface with a flexible hose.
The aeration system was kept in operation at the desired test flow at all times, even during sulfite addition procedures.
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