Project: OTE Testing
Site: Monkmoor STW, Shropshire
Client: Biwater
When: June 2006

WEBS undertook OTE testing on the new 4 lane FBDA ASP built at Monkmoor STW. 

Testing was conducted on both aerated zones of one lane utilising 6 dissolved oxygen probes per zone to meet Severn Trent Water’s ME18F testing specification.  Static air balancing of the whole ASP was conducted prior to OTE testing to ensure that the design airflow split was achieved to all zones in all lanes. 

Nitrogen gas was used to ensure a well mixed deoxygenation process prior to each test without affecting water quality, and three replicate tests were conducted at each of maximum and average airflow conditions.  Temporary certified power monitors measured power consumption of the blowers during testing for determination of energy efficiency of the aeration system. 

Due to the high cost and impracticalities of using large volumes of potable water, final effluent from the existing biological filter works was used to fill the ASP for testing.  WEBS used an at depth pilot tank to determine the alpha factor to account for the use of final effluent as test water.

Project: OTE Testing
Site: Huthwaite STW, Nottinghamshire
Client: Nomenca
When: August 2006

WEBS undertook OTE testing on one of two new oxidation ditches built at Huthwaite STW. 

Eight dissolved oxygen probes were used to meet Severn Trent Water’s ME18F specification, in addition to the standards detailed in the ASCE document ‘Measurement of Oxygen Transfer in Clean Water’. 

Three surface aerators provide aeration to each ditch, and therefore the chemical deoxygenation procedure was required.  Cobalt II Chloride was added to the ditch prior to testing to act as a catalyst to the sodium sulphite deoxygenation procedure.  An excess of sodium sulphite was added to the ditch to deoxygenate the test water prior to each test, and the flow inducers were used to aid mixing of the chemicals. 

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