(See ‘Pesticide Handling Area and Biobed Manual’ (Version 5 9 February 2015) for the full details as summarised here.)
It goes without saying that pesticides getting into water of any kind (ditches, ponds, streams, rivers, aquifers for water supplies etc.) can cause serious pollution. In turn, kills of wildlife within the water environment will seriously damage your pocket with fines running into eye-watering sums. To safeguard the environment and your farm from prosecution there are practical ways to handle pesticides safely. Quite simply, all that is required is a concrete area to catch and contain contaminated water. Next the pesticide has to be made safe by natural biological degradation. This is a guide which describes good design of handling areas where the sprayer is filled and often used for sprayer washing, nozzle calibration, sprayer testing, maintenance and storage. The use of a bio-bed or bio-filter (containing a mixture by volume of 50% straw (wheat or barley), 25% soil and 25% peat-free compost) is described. The approach here helps you avoid the risk of spillages in the field, costs of disposal by a third party and the need for a Groundwater Permit.
Planning and permissions are not discussed as this is intended to simply describe the sort of infrastructure to be considered. However, bear in mind the need to check groundwater protection zones as mapped below via Magic Map Application (defra.gov.uk) and shown under ‘Non-statutory’ layers. Also consider the location of springs and boreholes.
Construction of a concrete sprayer filling area is shown below which means any pesticide is contained within the area.
Under gravity the contaminated water drains into temporary storage (seamless polythene or similar with pump) via a silt trap. The storage capacity must be no more than 1,500 l as set by the pump’s switch level. Next, the liquid must be made safe by one of three options.
Option 1 – Indirect (offset) Lined Biobed
From temporary storage the liquid is passed to an Indirect (offset) Lined Biobed. The transfer is regulated, (1-2 litres/hour) and gently dripped evenly in lines 0.25-0.4m apart across the bed. The biomix in the biobed allows any pesticides within the waste liquid to cling or lock onto organic matter, particularly onto the straw. Some chemicals do this very rapidly. The bacteria within the soil and within the biomix then slowly work to break down the pesticide residues, with the compost helping stabilise the moisture content within the mix.
The final stage is where the ‘treated’ liquid is pumped from the biobed over a vegetated area.
Option 2 Direct (Drive over) Biobed
An alternative to that above is to construct a Direct (Drive over) Biobed as shown below. The biobed is bunded and covered by a grid to support the sprayer with contaminated liquid falling directly onto the bed. The treated liquid can be transferred to an area of vegetation or to a storage tank before final disposal.
Option 3 – Biofilter
As an alternative to an excavated biobed, contaminated liquid that has been held in temporary storage, such as from the bunded sprayer filler area, can be treated within a biofilter. This uses intermediate bulk containers to hold the biomix as shown below.
The sprayer washings are pumped to the highest container which filter slowly through the plumbed IBCs. As before, the final uncontaminated liquid is collected and transferred to the vegetated area.
A free external consultant can be arranged to advise on ‘Pesticide Filling – washdown Facilities and Bio-bed / biofilter design’ at your farm. Contact firstname.lastname@example.org for details.
NB All illustrations taken from ‘Pesticide Handling Area and Biobed Manual’