Land and Water Link

Issue No. 11, December 2001

CSIRO's land-based wastewater treatment system, FILTER (PDF, 386 kB), has been shown to reduce pesticide levels in drainage water in trials conducted in southern NSW.

The FILTER (Filtration and Irrigated cropping for Land Treatment and Effluent Reuse) system was originally developed by CSIRO research scientists, Dr Nihal Jayawardane, Mr John Blackwell and Dr Tapas Biswas to deal with the treatment and reuse of sewage effluent.

But it now appears that this system could also have potential in helping to deal with high pesticide levels in drainage water from irrigation farms.

Pesticide build-up can become an issue for irrigators through the summer irrigation months, as pesticide residue in the drainage water leaving farms must not exceed strict residue limits.

Prior to FILTER, the only management strategy available to farmers to meet Environment Protection Authority (EPA) limits was to hold water in on-farm storages for up to 60 days, or until pesticide levels dropped below the required limits.

However, CSIRO Land and Water experiments at Griffith have shown that FILTER's active soil barrier system is effective at removing the major rice and soybean crop production chemicals from drainage water before discharge.

The FILTER system can offer an alternative in some situations and soil types, says CSIRO Land and Water scientist Dr Tapas Biswas.

Dr Biswas says the trials show that the FILTER system, which is based on a close-spaced subsurface drainage system about one metre below the soil surface, is capable of successfully removing pesticides from drainage water.

'The pesticide contaminated water is initially applied to the FILTER plots with the drainage system closed. Later, the drainage system is opened to allow de-contaminated water to flow to the drains, "explains Dr Biswas".

'As the contaminated waterÿpercolates through the soil to the subsurface drains, the pesticides are absorbed and attached to the soil. This process removes the pesticide residues from the drainage water - literally "cleaning" the water.'

Natural processes occurring in the soil gradually break down the pesticides retained in the soil.

According to Dr Biswas, the FILTER system reduces pesticide residue loads in drainage water by 98 to 100 per cent for a range of chemicals including chlorpyrifos, endosulfan, molinate, atrazine, malathion and diuron. The end result is a concentration below current EPA discharge limits.

For farmers considering this system, there is the added benefit that the land used to install FILTER can be used for growing crops, rather than sacrificed, as is the case with withholding ponds.

Results of this research, which has been supported by funding from the Australian Centre for International Agricultural Research (ACIAR), Griffith City Council, Coleambally Irrigation Cooperative Limited and Murrumbidgee Irrigation Limited, have been presented internationally.

Having won an award at the Indian Chemical Engineering Congress in Calcutta in December last year and sparked widespread interest, including collaboration with the China Institute of Water Resources and Hydropower Research, the CSIRO team looks forward to further developing this novel solution to cleaning up pesticide contamination.