A methodology to determine pesticides pollution sources in water catchments: study case (Belgium).

In the Walloon Region (Belgium), a Committee of Investigation was created in 2007 to investigate and determine the potential pesticides pollution sources in drinkable water catchments. This Committee, constituted by a multidisciplinary team of experts i.e agronomists, soil scientists, phyto-chemists, hydrogeologists, is coordinated by the Walloon Agricultural Research Centre (CRA-W) and funded by the Société Publique de Gestion des Eaux (SPGE). The diagnosis method is inspired of the AQUAPLAINE method (Arvalis, France), and is composed of four steps: 1/preparing the diagnosis using existing data, 2/diagnosis using data bank completed by field observations, 3/meeting and discussion with the pesticide users, 4/final diagnosis and remediation proposal. In a rural district of Walloon Region, a water producer who possesses two catchments ("Les marroniers" (P1) and "Puits N2" (P2)) has problems with pesticides. The pollution started in 1998 with atrazine and bromacile detected in the two catchments. In 2004, 2,6-dichlorobenzamide, metabolite of dichlobenil, was also detected in the catchments. At present, all these pesticides are still found in the catchment P1 and only the 2,6 dichlorobenzamide is found in the other catchment. These active ingredients are not used in agriculture expect atrazine. Indeed, the main user of these products is the public sector. An investigation was realised to locate the main sites which are treated with these pesticides in this commune. The conclusion of this study is that the local authority used dichlobenil, bromacile and atrazine to weed the public areas. In more, the filling and the cleaning areas of sprayer, used for the treatment, are located near the catchments.

Biofilters to treat the pesticides wastes from spraying applications: results after 4 years of study.

Biofilters were developed in order to eliminate or reduce the quantity of pesticides from rinsing and cleaning waters of sprayers. Biofilters consist in 1, 2 or 3 plastic containers of 1 m3 placed in a vertical pile and containing a substrate elaborated from a homogenised mixture of local soil, chopped straw and compost able to absorb and degrade the pesticides. Biofilters are installed near the area for cleaning and rinsing the sprayer and the waste waters are pumped into the system. Since 2002, a pilot study is carried out in Belgium in order to evaluate the efficacy of these systems. Twenty pilot systems were installed since 2002 until 2004 in several farms, agricultural technical centres or schools and in a municipal maintenance service. The efficacy of the biofilters was studied for several chemical classes of herbicides (sulfonylurea, aryloxyalcanoic acids, chloroacetanilides), insecticides (pyrethroids, carbamates) and fungicides (dicarboximides, phenylamides, triazoles and strobilurines). The balance of the inputs and the outputs of the pesticides was determined by monitoring the elutes. The degradation kinetic of pesticides into the substrate was evaluated by analysing the pesticides into the substrate. The microbiological activity of the substrate was also evaluated by measuring respiration and some indirect parameters like dry matter content, Kjeldahl nitrogen content, organic carbon content and biological oxygen demand (BOD). Results obtained until now after four years of experiments have showed an overall good efficacy (retention) of pesticides by the biofilter and a high degradation rate for the majority of pesticides. Biofilters permit to reduce highly the quantity of pesticides from rinsing and cleaning waters of sprayers and contribute significantly to the reduction of the contamination of surface water. Biofilters are now registered by the Ministry of Agriculture and Environment of the Walloon Region in Belgium and are recommended to pesticides users.

The heterogeneity of sprout inhibitor application with chlorpropham.

The CIPC or chlorpropham is used on potatoes as "sprouting inhibitor". These lasts years, some set of belgian potatoes treated by CIPC exceeded the Maximum Residue Limit (MRL), fixed at 5 mg/kg. The heterogeneity of sprout inhibitor application would be one of the causes of over-dosage. In order to estimate the distribution of CIPC between potatoes, according to the formulation used (DP, EC and HN), a research project financed by "le fond budgétaire des matières premieres" has been set up. In order to evaluate the distribution of CIPC into the pile of potatoes, the efficiency of the different formulations as well as the residues caused by their application on tubers, some tests have been placed in the storage hall. These tests consist in taking off some samples at different places into the pile of potatoes during storage and destocking. The content of CIPC is analysed by capillary gas chromatography with detection by mass spectrometry detection (GC-MS) or nitrogen specific detection (GC-NPD). To estimate the efficiency, the sprouting are observed every month and samples of potatoes are taken off on the top of the pile to control the evolution of CIPC content. Considering the results of the tests, the inhibitor treatment with the formulation DP+HN seems to be the more efficient. As for the residues, the formulation DP leads to a higher content of CIPC than HN, that has a very low concentration. After treatment, the quantity really applied on tubers depends on the formulation used. In fact, 50% of CIPC applied by DP formulation are found on tubers but hardly 10%, after gas application.

Study of potatoes' sprout inhibitor treatments with chlorprophame.

Studies carried out in 1999 by the University of Ghent showed that 36% of potatoes' samples contained Chlorprophame (CIPC) residues and that 7.9% of them exceeded the maximal limit of residues (RML), fixed at 5 ppm. The heterogeneity of sprout inhibitor application would be one of the causes of over-dosage. However, this heterogeneity would also cause under-dosages leading to problems when controlling the sprouting in potatoes stored over 6 degrees C. This study aims at determining some technical causes of the heterogeneity of CIPC sprout inhibitor treatments when storing potatoes. The study concerns two treatment techniques: dusting and spraying. To draw up an inventory of mechanical treatments in Belgium, a survey has been conducted among 28 farmers throughout Belgium. 35 samples have been taken at random in the different storage rooms to analyse the content of CIPC residue. In order to do so, a method of analysis: the gas chromatography in capillary phase with detection by mass spectrophotometry, has been developed. Tests have been carried out by changing several parameters such as the material, the product or the place in the storage line, in order to assess the CIPC application techniques. The survey made it possible to analyse qualitatively, from the declarations of farmers, the causes of heterogeneity linked to treatment techniques. An almost systematically over-dosage of the CIPC quantity has been noticed. However, out of the 35 samples analysed, only 2 had residue contents higher than the RML. The comparative analysis of the quantities applied and the residues contained in the samples made it possible to quantify the heterogeneity of the applications depending on the techniques. The tests carried out show in a general way that mechanical dusting, even though having a less constant flowrate than sprayers, leads to less important variation of the residue between samples. In testing conditions, the heterogeneity of the antigerminative treatment decreases when applied by means of a mechanical duster. In practise, these results are distorted by topical applications of CIPC. The combination of this practise with a too high heterogeneity of the treatment are to be avoided in order to have a good preservation and meet the residues standards.

Comparative study of anti-drift nozzles' wear.

When spraying, the drift is a restricting factor which reduces the efficiency of pesticides treatments and increases their impact on the environment. The use of anti-drift nozzles is the most common technique to reduce the drift effect. The basic principle of all anti-drift nozzles is to produce bigger droplets (Imag DLO, 1999) being less sensitive to the wind. The increase of the droplets' size is possible whether by reducing the spraying pressure (anti-drift fan nozzle) or by injecting air in the nozzle (air injection nozzles). This study aims at comparing the performances of the main anti-drift nozzles available on the Belgian market (Teejet DG and AI, Albuz ADI and AVI, Hardi ISO LD et AI). The study made it possible to compare thirteen different nozzles' sets according to their trademark, type and material. The study is based on the analysis of macroscopic parameters (flowrate, transversal distribution and individual distribution) as well as on the analysis of microscopic parameters (spraying deposit on artificial target). The evolution of these parameters is analysed according to the nozzle's wear. The wear is carried out artificially according to the "ISO 5682-1" standard (ISO 5682-1, 1996). The results confirmed the major influence of the manufacturing material on the nozzles' wear, ceramic being the most resistant material. Macroscopic as well as microscopic parameters variated according to the utilization time without any direct correlation. Indeed, most parameters variate in an uncertain way. It was however possible to establish a correlation between the wear time and the recovering rate and flowrate parameters. The utilization length is different depending on the type of nozzle, air injection nozzles being more resistant. At last, the analysis of microscopic parameters (spraying deposit) (Degré A., 1999), shows that the number of impacts is stable depending on the wear, while the size of impacts and the recovering rate increase.

Rinsing and management of pesticides' containers.

In order to reduce the effects on the environment, it is necessary to improve the management of pesticides' containers. Usually, users burn or bury empty containers. These methods, even though decreasing must be avoided or even forbidden. Since 1996, empty containers are systematically collected in Belgium and are specifically removed by the firm Phytofar Recover created by the Belgian Federation of pesticides' manufacturers. Since the beginning, the recovery rate (percentage of containers recovered compared with the containers sold) goes on increasing to exceed 85% in 2001. These action and results are a world first (more than 500 tons of empty containers are collected yearly). Once collected, empty containers are subjected to the European Policy about toxic wastes since they contained dangerous products. Their removal must follow a specific removal process by incineration at very high temperature (> 1200 degrees C) with a specific filtration of the smoke. The treatment cost is high and reaches 2 Euros per kg of container. If the container is rinsed and the residue does not exceed 1000, 10,000 or 30,000 mg per kg of container (depending on the dangerousness of product: very toxic, corrosive or toxic), it will be considered as domestic waste and will therefore follow a much more economical energy production process. The study aims at determining the quantities of residue contained in empty containers and the parameters reducing the rinsing efficiency: the formulation (EC, WP, WG), the container's size, packaging's type (plastic container or paper bag), the rinsing technique. Almost 150 tests and analyses of residue have been carried out. A manual rinsing procedure has been set up in order to meet the standards about residue. Rinsing three times with an average volume of water (20 to 30%) allows to reach the lowest residue level. As bags containing powder (WG or WP) container not be rinsed, it is necessary to empty them completely. It is however difficult to reach the 1000 ppm residue limit.

Fast, simultaneous simulation of the integrated urban wastewater system using mechanistic surrogate models.

The urban wastewater system components (sewer, treatment plant, and river) are often modelled using complex mechanistic models. Mechanistic surrogate models are introduced here as simplified models that still contain some physical knowledge. Surrogate models are faster, but are less but still sufficiently accurate, and require more data to be calibrated. The possibilities of replacing actual field data by virtual data generated with a complex mechanistic model for calibration of the surrogate model are examined. As an example, a series of tanks with variable volume is shown to approximate sufficiently well the flow propagation in the river Zwalm (Belgium) as predicted by the "de Saint-Venant" equations. The three surrogate models can be implemented in the WEST simulator, which makes a simultaneous simulation of the system possible. In this work a connection is made between the ASM1 and the new IWA River Model No. 1 (RWOM1) by using a translator between the models in such a way that both mass and elemental balances remain closed for the overall system. This approach is illustrated with a case study on the river Lambro (Italy). The dispersion process in this river with steady flow could be modelled by using a tanks in series model, while the water quality in the river was predicted to improve substantially with an increase in hydraulic capacity of the treatment plant. The simulation results with the upgraded plant still need to be checked by field data.