New Advanced Hydrodynamic Seperator

HYDRO International (UK) has launched the next generation of its innovative Downstream Defender® advanced hydrodynamic separator in anticipation of tougher UK legislative requirements for treatment of suspended solids and pollutants in surface water runoff.

The new Downstream Defender® has been developed to offer greater design flexibility with optimum efficiency and minimal maintenance, typically achieving greater than 80% removal of grits, silts and oils in a much smaller footprint than conventional gravity or swirl-type devices.

The expectations of the EU Water Framework Directive for improved water quality standards by 2015, the implementation of the Flood and Water Management Act in England and Wales and the Water Environment and Water Services Act (Scotland) are all likely to place demands on highways authorities and developers for increased treatment of runoff from roads, car parks and developments. Says Hydro Stormwater Director Alex Stephenson:

“Much stronger legislative drivers for stormwater treatment are just around the corner in the UK, with this in mind Hydro has developed Downstream Defender® to be ready for significantly increased demand. New national standards for Sustainable Drainage Systems are also likely to stipulate treatment requirements and we believe it’s important to set the bar high from the outset.

“This next generation device will offer an unrivalled ability to prevent re-entrainment (or washout), even during peak storm conditions, which could be a critical factor in ensuring adherence to discharge limits in future. More conventional alternatives do not provide protection against solids and pollutants stored in the device from being flushed out during intense storm events.”

In response to customer demand, the new Downstream Defender® also incorporates the option to change outlet pipe direction as needed, meeting Building Regulations requirements without the need to construct a second manhole.

The Hydro Downstream Defender® is expected to be used increasingly to treat runoff from impermeable surfaces where there is a build up of sediments, floatables and petroleum products such as highways, car parks and industrial areas. It is particularly effective at removing and retaining sediments that carry with them adsorbed chemical pollutants, metals and hydrocarbons.

Downstream Defender® is also ideal for use as part of a treatment train solution for SUDS schemes, for example as an alternative to a sediment forebay, or to provide protection for a detention basin or pond.

Hydro Downstream Defender® comprises a reinforced concrete chamber with internal polypropylene components and no moving parts. The unit is designed to induce a rotational flow pattern with a low headloss, achieving a long, stable flow path to maximise separation of solids, floatables and oils within a small footprint.

Washout is prevented by retaining captured sediments in an isolated storage area at the bottom of the chamber and a built-in trap stores oils and floatables. Sediments are removed periodically by standard vacuum tanker equipment. Maintenance is significantly easier than for diffuse solutions such as gullies or catch pots, enabling longer maintenance intervals and providing a single point of access.

The new Downstream Defender® has four sizing options with diameters of 1.2 m, 1.8 m, 2.55 m and 3.0 m, as opposed to the previous 7 sizes available, offering simplified design parameters for ensuring greater than 80% removal efficiencies of pollutants at peak flows . Units can also be designed to achieve other defined pollutant removal targets according to site specific conditions and / or performance objectives required.