Vexamus Water has completed a successful pilot trial for United Utilities to investigate the treatment of UIDs (Unsatisfactory Intermittent Discharges, or storm flows) from sewage treatment works.

Vexamus Water has completed a successful pilot trial for United Utilities to investigate the treatment of UIDs (Unsatisfactory Intermittent Discharges, or storm flows) from sewage treatment works. This award-winning process can be considered as an alternative option to that of constructing storm tanks. The 10-month trial, which took place at Millom WWTW in Cumbria was the first time in the UK that a continuous process had been applied to resolve a UID problem.

Its ability to meet the quality parameters and provide an operator-friendly plant now provides an alternative solution to the building of storm tanks.

The development of the StormEasy process also provides inherent benefits, namely that of saving up to 90% of the area of a conventional settlement tank and therefore conserving the existing valuable land for other processes.

The bacteriological standards worked to during the trial were an overall bacteriological log kill, between crude sewage and receiving water, of 5.4 for bathing water discharges and 5.25 for shellfish waters.

To achieve this, United Utilities required the StormEasy process to produce an effluent with a suspended solids concentration of less than 15mg/l and a % transmissivity greater than 50%.

This would then allow a UV system to provide the additional treatment to ensure that the log kill figures could be met.