Irrigation of vegetable crops as a means of recycling wastewater: Applied to hesbaye frost

Abstract

Since 1991, a food processing plant which freezes a large quantity of locally grown market garden products, has recycled all its wastewater by irrigating 550 hectares of crops located around the factory. Previously, the 700,000 m3 of wastewater was discharged into a nearby stream apparently devoid of aquatic life. By adopting this solution, the processing plant was able to avoid paying a heavy tax introduced in 1991 to penalize the discharge of industrial effluent. The alternative of building an independent wastewater treatment plant would have required investment costs two to three times higher and would not have achieved the same degree of water purification as the soil. Irrigation guarantees a continuous supply of a vital good quality ingredient, since the short life cycle market garden crops are very susceptible to hydric stress. A 110,000 m3 capacity storage tank acts as a buffer between continuous water consumption and seasonal requirements; in addition, by mixing the wastewaters, it stabilizes their physico-chemical characteristics which vary according to the vegetables treated. This processing plant offers the regional agricultural industry hit by European restrictions, a source of diversification; it is perfectly integrated in an environment it not only respects but relies on for the auto-purifying capacity of its biological medium.