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Fit-for-purpose solution

A custom-modified Hydro Up-Flo filtration unit has made a difference at a development in Kent.

One of the first UK stormwater treatment solutions using Hydro’s innovative Up-Flo filtration technology has enabled developer Fairview New Homes to incorporate SuDS with two levels of treatment into the surface water drainage for a new access road.

Environment Agency (EA) planning requirements sought two levels of treatment for the new commercial access road in Faversham, Kent, but a SuDS solution using completely natural features was not possible.

Developer Fairview New Homes (FNH) and consultant Infrastructure Design worked with Hydro International to develop a solution for the site that combined a custom-modified Up-Flo filtration unit with Hydro StormBloc modular storage and infiltration blocks.

Jim Brand, FNH maintenance manager, explains: “Working with our engineering consultants and Hydro, we put together a fit-for-purpose solution which met the maintenance requirements of Kent Highways, while satisfying SuDS principles.”

The access road is needed to service retail and light commercial units as part of the mixed-use redevelopment of the Eurocentre wholesale distribution centre on the site which is bounded by the London to Dover main railway line. While much of the access road offers natural flow to a swale for treatment, around 100m of the road was below surrounding land.

“We needed to provide polishing treatment to remove finely dispersed pollutants, as it was adjacent to a source protection area,” says Phil Tomes, of engineering consultant Infrastructure Design. “To create sufficient fall for a swale, we would have had to try and install it 3m below ground level, which wasn’t possible. We looked at engineered solutions and the Hydro Up-Flo solution was ideal. The unit could be located in a chamber at sufficient depth to provide effective settlement, screening and filtration treatment for the water.”

Rainwater from the road passes initially through a bypass separator before entering the concrete chamber containing the Up-Flo Filter. The Up-Flo Filter acts as a sump where sediments are allowed to settle. Any floatables are controlled by baffles on the Up-Flo Filter module inlet.

The water flows up through the fine sand filter medium in the six filter modules until it discharges through the outlet. The Up-Flo Filter unit provides the essential second level of treatment, removing coarser sediments and fine suspended solids.

Marcus Mumford, of Hydro’s design team, says: “To accommodate this requirement, the consultants asked us for input. We responded to the need by innovating a design modification, which demonstrates the versatility of the Up-Flo Filter unit.”

To meet the surface water discharge constraints for the site, the final discharge from the filtration unit has to be infiltrated into the ground. Without room for a separate soakaway, a Hydro modular construction StormBloc storage infiltration tank was used. Because it is load bearing, it could be easily sited under public space in a shallow excavation and landscaped over. This provides around 180m3 of storage attenuation and infiltration, without occupying valuable surface area.

Already used in the US, The Hydro Up-Flo Filter is a relatively new technology to the UK. It has a gentle action to facilitate sediment settlement, due to the rising water flow through the filter unit system. The drain down system eliminates virtually all possibility of blinding and clogging.

Topic: Sewer Networks
Tags: filtration , environment agency , rainwater harvesting


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