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Sustainability and optimisation of treatment and use of wastewater in agriculture

Exploitable results

The treatment of wastewater by Free Water System (FWS) observed a removal efficiency of BOD of 77.00% and 51.25% with recycling and without recycling, respectively. Maturation storage of secondly treated effluents has studied the impact of the capacity of the storage basin on water decontamination. The experiment has showed that the water storage volume has a weak effect on decontamination development. The results about the bacteria indicators during a seasonal storage prove that the long term storage has a beneficial effect on the bacteriological quality of the water. The mean rate for the fecal germs tends to decrease till values undetectable with the analytic method used. The epuvalisation, low cost tertiary treatment technique, is a new treating system which is expected to purify biologically the municipal wastewater and make it apt to be rejected into the sea or used for a non restrictive agricultural use, mainly concerning non edible crops. The irrigation techniques compatible with sustainable agriculture are tested, first with the effect of wastewater on irrigation system. In Tunisia, The experiments show a link between irrigation uniformity and yields. The integrated drippers with a low sensibility to physical clogging, have given the most important yields with both of the water qualities tested, as irrigation uniformity was optimum. Micro-aspersion and auto regulating drippers had the worst irrigation uniformity, due to technological conception, and thus the worst yields obtained for both of water qualities tested. The effect on the soil/plant complex was studied in Morocco on cucurbitta sp. and chrysanthemum sp. crops. Yields results for courgette crop show a difference of 8% between the two tested varieties. Irrigation with wastewater treated by infiltration-percolation (EUI) has generated, for the different doses tested, a mean increase of 28% and 70% next to irrigation with fertilised borehole water (EPF), respectively for 100% and 120% ETM. For the chrysanthemeum crop, irrigation with treated wastewater (infiltration-percolation) increase the aerial biomass of 38% and 23%, respectively for 120% and 100% ETM. The vegetative yield obtained under irrigation with fertilised borehole water at 100% ETM are comparable to those obtained with wastewater treated at 80% ETM. In Israel, two chickpea varieties tested demonstrate that in both varieties, the dry weight and the seeds production in the plots that were not irrigated are lower than the irrigated treatments. The dry matter was significantly low in the non irrigated plot that in the others plots. The seed yield of Icc11299 variety was larger than in the Bulgarian variety. The Nitrogen fertilizer that applied before sowing did not have any effect on any plot parameter. This suggest that the N content in the soil had no influence on the legume, Corn grown in the same plots did respond to N fertilization. Fecal Coliforms were founded in the water and the soil but not on the plans or fruits. In Palestine, the reuse of treated wastewater in agriculture was repeated in this phase on the three different chickpea cultivars used last year with the same two irrigation technologies: Surface drip irrigation, and subsurface drip irrigation. The cultivars Polgarete can be irrigated with TWW without any loss (in some parameters we observe improvement) in the biological indicators. Surface and subsurface drip irrigation gave identical biological results in most cases. However, subsurface irrigation improved plant sanitation and reduced contamination. The complementation irrigation for cereal crops in Morocco reveals on wheat crop, an increasing of the grain yield observed of 9.4 to 31.8 qx/ha, with increasing water supply till 300 mm applied, then a decrease of 94% with 400 mm water supply. The straw yield and the weight of 1000 grain are influenced the same way. Optimisation of the use of Nitrogen fertilisation under irrigation with treated wastewater was tested in Tunisia on eggplant and barley crop. The eggplant yield under irrigation with wastewater lightly increased then decreased to obtain a production inferior to the witness. Yields obtained with wastewater or fresh water are similar. In Belgium, the objective is the adaptation of nitrogen fertilisation for vegetable crops under irrigation with wastewater coming from an agro-food industry. For those two years, the use of the French software Azobil to fix the Nitrogen advice and quantity to apply has allowed a good management of the nitrogen fertilisation for different crops such as spinach, beans and wheat. Using nitrogen fertilisation over the quantity advised, is not traduced by a significant gain of yield, but is responsible of a high nitrogen residue in the soil and increase the risk of the underground water reserves pollution.