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.