Project: Hart Lane, Contact Tank Performance Improvement

Client: Water Corporation, UK

Completed: 2012

Project Description:


Contact tanks installed at Hart Lane Water works facilities are found to be under performing; as a result quality of water is compromised. Access Petrotec was appointed to carry out the computational fluid dynamics (CFD) analysis to calculate actual residence time under the current design and to suggest remedial measures to meet the requisite performance criterion identified in section 2 of this report.
Design of an existing contact tanks internals was carried out by Access Petrotec to achieve requisite retention time performance.

CFD modelling of the Hart Lane contact tank computed the retention time performance as 3.42 min. It was found that a strong water jet emanating from the inlet nozzle was short-circuiting to outlet, leaving significant dead volume in the contact tank. It was also found that a single baffle in the existing contact tank was insufficient to provide enough resistance to break the water jet.

Finally, nine perforations were made to the redirected inlet nozzle pipe to break the jet effect. Together with perforations in the inlet pipe and two rows of circular baffles has been sufficient to meet the performance criteria specified:

  • The overall nature of RTD curve for Design Option 3 is very close to the ideal reactor
  • T5 (24.12 min) is greater than half of the mean time (17.26 min)
  • T9 (49.83 min) is less than twice the mean time (69.02 min)
  • Retention time is greater than 20 minutes.