Wastewater reuse to increase soil productivity

Often wastewater is considered a pollution problem. However, Mexican experience shows that it can constitute a way to increase soil productivity. This was demonstrated by the use of the wastewater from the Valley of Mexico, which is a mixture of domestic and industrial discharges and rainfall, for irrigation purposes on a surface of 85,000 ha, being an unique experience worldwide. However, this practice - also applicable to agroindustrial effluents - comprises sanitary risks for which a means of control is proposed herein. The process applied is an advanced primary treatment which, thanks to the newly synthesized polyelectrolytes, employs relatively lower doses of ferric chloride (50 mg/l), alum (110 mg/l) or calcium hydroxide (250 mg/l). With this process the required characteristics (pathogenic organisms and metals) for reusing water in agriculture without negative secondary effects are achieved and soil productivity is maintained. Copyright (C) 1996 IAWQ. Published by Elsevier Science Ltd.