Thames Water Utilities
Actiflo® High Rate Clarifiers
Thames Water Utilities is the largest water and wastewater company in the UK. It owns and operates 448 treatment plants located in the south-East of England, covering the area of London and its suburb.
At the Fobney works in Berkshire which supplies over 300,000 people, Thames Water Utilities required an increase in the treatment capacity of the works while reducing the turbidity loading on the primary filtration stream.
Veolia Water Solutions & Technologies provided the process design, construction, installation, testing and commissioning of 2 Actiflo® High Rate Clarifiers. Actiflo® clarification would upgrade the solids removal facility at Fobney WTW. The project included the sand storage, transfer and recovery system, polymer make up and dosing system, coagulation and pH correction system, MCC and software for the process.
In addition, Veolia Water Solutions & Technologies installed and operated a total of 16 weeks of pilot plant trials in 2004 and 2005 at the sites of Fobney and Hornsey WTW, treating up to 100 m3/hr. The pilot plant provided data for Actiflo® performance and subsequent sand filtration. Based on these results Thames Water recognised the ability of Actiflo to cope effectively with the flashy water characteristics of the river Kennet
Both Actiflo® streams are nominally in operation at the same time but one can handle the peak flow to treatment of 57.75 Ml/d.
Actiflo® is a very compact process that utilises microsand as a seed for floc formation. The microsand provides surface area that enhances flocculation and also acts as a ballast or weight. The resulting microsand ballasted floc display unique settling characteristics, which allow for clarifier designs with high overflow rates and short retention times. These designs result in system footprints that are between 5 times smaller than classic lamella clarifier or dissolved air flotation and up to 20 times smaller than conventional clarification systems of similar capacity, with an ability to start up from a “standby” mode of operation to a steady state operating mode within minutes.