Grey Water System Reduces Water Consumption

...is one such initiative that is driving down mains water consumption and thus costs.

A first in this type of application, the grey water system begins with the rain water dripping from trains and then in the wash down process used in train sheds and external bays for cleaning the West Coast Virgin Rail fleet. The Underframe cleaning system uses high pressure jet wash units that, on start up, automatically trigger a series of Wilo submersible pumps arranged in a sequence of increasingly large drainage sumps, with the smallest sumps being located within the train sheds. The dirty water, suspended solids and sludge drains into the smallest sumps and is subsequently pumped from sump to sump until it eventually reaches a large grey water holding tank.

The huge grey water tank is emptied on a timed basis, after allowing debris to settle and be removed at regular intervals. The grey water is used for secondary cleaning, for the removal of dirt and debris that collects in the Underframe cleaning gullies in the train sheds. The run-off from these processes is also collected in the drainage sumps and is again returned to the holding tank.

This simple yet effective process was a means of ensuring Bombardier Transport's water consumption and metered water costs were kept to a minimum, while ensuring that essential cleaning duties can easily be maintained.

The system was designed and constructed by Flowmech, in conjunction with Wilo and the main contractors, Hilton Building Services. Ian Craft, Managing Director at Flowmech explains that; "We have an established relationship with Wilo and trust the high standards to which its pumps are manufactured. In this application their submersible pumps were ideal, as they can be mounted vertically or horizontally and incorporate built-in macerators that reduce debris to small particles; these easily pass through the pumps and associated drainage channels, thereby minimising maintenance, and easily settle out in the holding tank.

In addition, the pumps have lightweight yet robust composite bodies, so they are much simpler to handle and install than traditional cast iron units. This is particularly useful as the site is on reclaimed marsh land with a relatively high water table and the grey water tank is positioned above ground; so maintenance engineers therefore have to lift pumps to the top of the tank with the use of chains. A lighter pump makes this quicker, simpler and significantly reduces the safety risks".