Water grants 2015: biofilter (RP26)

Eligibility and requirements for the biofilter.

This guidance was withdrawn on

Capital items for improving water quality are now available through the Mid Tier of Countryside Stewardship.

Farmers and other land managers can apply for water grants.

Read the accompanying guidance to find out more about Countryside Stewardship water grants 2015.

How much will be paid

£990 per unit.

Where the item is available

This item is available in Catchment Sensitive Farming (CSF) target areas.

When this item can’t be used

It can’t be used:

  • within 10m of a watercourse;
  • within 50m of a spring, borehole or well;
  • within 250m of a borehole used for food production; or
  • on historic or archaeological features or areas of wildlife value.

How this item will benefit the environment

This item reduces the risk of water pollution by degrading the pesticide residues that arise from pesticide handling activities.


Applicants must send the following with their application for this item:

If the site is in a Groundwater Source Protection Zone 1 area, applicants must consult the Environment Agency about using this item.

Applicants must send any advice and consent they receive with their application.

With permission from Natural England, advice and consent can be received up until 29 May 2015; applicants can discuss this with their local Catchment Sensitive Farming officer

On the land

Successful applicants will need to construct a biofilter that meets the requirements of the T32 waste exemption. All the capital works must also meet the relevant British Standards - check the most up-to-date standards.

Purpose-made biofilters can be bought that meet the requirements, or can be constructed. To construct one, successful applicants will need to:

  • use 3 new, chemical-resistant impermeable containers - these will typically be 1000 litre intermediate bulk containers (IBCs) stacked vertically;
  • store pesticide washings in additional containers next to the IBCs, either before or after treatment;
  • alternatively, pump the washings directly from an underground storage tank that collects washings from a pesticide handling area;
  • cut the tops off the IBCs, leaving the corners intact;
  • insert wire mesh lining in the base of each one;
  • cover the lining with a permeable membrane;
  • install a layer (at least 10cm) of pea gravel over the membrane so that the drainage outlet to the container below isn’t blocked;
  • make a biomix by mixing one part peat-free compost, one part topsoil and 2 parts straw (wheat or barley) by volume;
  • allow the biomix to compost for 30 to 90 days before filling the IBCs;
  • fill the IBCs with biomix, leaving a 10cm gap at the top for piping;
  • allow the biomix to settle, then top up to a volume of at least 0.5 cubic metres of biomix in each one;
  • stack the 3 IBCs vertically into a tower on a flat concrete base;
  • if the biofilter isn’t covered, replace the top of the uppermost container to prevent rainfall from getting in;
  • install pumps, pipes and a hose to pump washings from the initial storage tank to the top biofilter container and on to the biomix through a piped ring distribution system;
  • allow the washings to flow by gravity through the pipes to the containers below;
  • pump discharge from the bottom container to a storage tank, or for direct irrigation through a perforated hose on a vegetated area; and
  • build a concrete bund at least 100mm high around the biofilter.

Keeping records

Successful applicants will need to keep:

  • dated photographs taken before, during and after the construction of the biofilter (submit these with any claim and show them on request);
  • the documents relating to waste exemption T32 (sent with the application);
  • any consents received in connection with the work (show these on request); and
  • receipted invoices and bank statements relating to this work.

What must not be done

Don’t treat more than 15,000 litres of pesticide washings (excluding rainfall) in any 12-month period.

How to carry out this item

The following section gives advice on carrying out this item successfully.

How to choose a location

Successful applicants should choose a site where the biofilter safely can be operated safely, for example:

  • away from thoroughfares;
  • on a flat concrete base; and
  • against a wall or other surface where it will be well-supported.

The biofilter can be placed in a farm yard or building or under a roof. It can also be placed on areas of land, or farm buildings that are not used for production. For best results, place it close to the pesticide handling and washdown area.

How to maintain the biofilter

A fresh, pre-composted biomix should be added to the biofilter to maintain its depth. Make sure that the biomix remains moist, using irrigation if necessary. Be careful not to allow the container to overflow. The biomix should be replaced every 5 years. Waste will be needed to spread the biomix.

Hazardous waste should not be treated in the biofilter.

The following items can be used on the same area as the biofilter:

Further information

See the Voluntary Initiative website for further information about pesticide handling areas and Biofilters, including sizing and volume calculations.

Published 2 March 2015