14 April 1995

Water service for farm

SEVERN Trent Water now believes it offers a service to farmers – rather than merely using land as a convenient means of sewage disposal.

The use of better application machinery combined with treated, almost odourless sewage containing little or no toxic metals, has made the task a more acceptable and sought-after operation.

The company points out that it is, in effect, supplying farmers with a free source of fertiliser and applying it with minimum ground disturbance. The use of boom type, umbilical-fed distributors also means that treated sewage can be applied to cereal crops when they are in their early growth stages – the feed pipe is claimed not to damage the crop at this stage.

With application rates now only limited to the amount of nitrogen which can be applied, usual volumes amount to between 6000 and 7000gal/acre to supply about 125kg/ha of nitrogen (100 units/acre). There is also a significant amount of phosphorus and organic matter supplied.

Each year the Severn Trent Water handles 200,000t of dry solids of sludge – sludge being the natural by-product produced when sewage receives its initial treatment.

Passing the sludge through an anaerobic digestion process produces "liquid digested sludge" which contains 5% solids, 95% water. About 70% of this sludge type is used for field spreading while the remainder is pressed to produce sludge cake and used in landfill sites.

Severn Trent Water is at pains to point out that the treated sewage poses little, if any, risk to health with no pathogen problems being recorded as a result of the use of sewage sludge in its area.

Could this be the ultimate in high hp/low ground pressure, slurry injection? Severn Trent Water has been testing a 205hp Caterpillar Challenger 35 rubber-tracked crawler. coupled up to a three-leg injector unit, on its 2500-acre Stoke Bardolph Estate, near Nottingham. Claimed crawler ground pressure is from 4 to 5psi.