Degradation and leaching potential of pesticides in biobed systems

Abstract

Biobeds provide a potential solution to pesticide contamination of surface waters arising from the farmyard. Previous work has shown that biobeds can effectively treat spills and splashes of pesticide. This study investigated the potential for biobeds to treat much larger volumes and amounts of pesticide waste not only arising from spills but also from washing processes. Two systems were assessed using a range of pesticides at the semi-field scale, ie a lined biobed system and an unlined system. Studies using the lined biobeds demonstrated that water management was crucial, with biobeds needing to be covered to exclude rain-water. Once covered, the top of the biobed became hydrophobic, restricting moisture loss and resulting in saturated conditions at depth. The drying out of the top layer coincided with a measured decrease in microbial biomass in the treated biobeds. Applied pesticides were effectively retained within the 0-5 cm layer. Whilst all pesticides tested degraded, low moisture content and microbial activity meant degradation rates were low. Studies using unlined biobeds showed that only the most mobile pesticides leached, and for these > 99% was removed by the system, with a significant proportion degraded within 9 months. Peak concentrations of the two most mobile pesticides did however exceeded the limits that are likely to be required by regulatory bodies. However, it is thought that these limits could be reached by optimisation of the system.

Biobeds for Environmental Protection from Pesticide Use—A Review

“…In the UK study, two sets of lysimeters were prepared using PVC piping (19 cm internal diameter × 75 cm length) with one end of the pipe sealed using a socket fitted with a drain outlet (35). Cores were filled with 2-3 cm of gravel followed by 15 cm of washed sand.…”

Assessing the effectiveness of a three-stage on-farm biobed in treating pesticide contaminated wastewater

“…Lastly, compost is 77 added to increase sorption capacity, improve moisture content and decrease the pH to make 78 conditions favourable for fungi growth. The surface grass layer aids water regulation and prevents 79 surface crusting, thus limiting the formation of cracks that would open up preferential pathways for 80 pesticides to escape the biobed prior to degradation (Fogg et al, 2004;Castillo and Torstensson, 81 2007; Castillo et al, 2008). In lined biobed systems, common in the United Kingdom (UK), the 82 leachate is typically collected from the bottom of the biobed and re-used for either irrigation, 83 sprayer washing or as a carrier for further herbicide applications.…”

Advances in Chile for the Treatment of Pesticide Residues: Biobeds Technology

“…Several studies have demonstrated that biobeds can effectively retain and degrade a wide range of pesticides, either alone or in mixtures (Torstensson and Castillo 1997 ;Castillo et al 2007;Fogg et al 2003Fogg et al , 2004Vischetti et al 2004 ;Castillo and Tortensson 2007 ;Vischetti et al 2008 ). For example, studies with mecoprop and isoproturon have shown that these pesticides can be degraded in biobeds (Henriksen et al 2003 ).…”

“…In terms of the biomix composition, laboratory-based studies showed that mixtures of soil-organic waste may be able to degrade high concentrations and complex mixtures of pesticides (Fogg et al 2004 ). Castillo and Tortensson ( 2007 ) observed that a straw, peat, and soil ratio of 50:25:25 % v/v (respectively) is recommended for the organic mixture composition, because such a mixture favors a low pH, convenient for lignin-degrading fungi and phenoloxidase production and activity.…”