Multi-criteria analysis for site selection for the reuse of reclaimed water and biosolids

Low pH soils with insufficient organic matter can benefit from the application of reclaimed water (RW) and biosolids. The presence of nutrients also aids plant growth. This paper presents the results of two integrated research studies, both carried out in the Beira Interior Region (Covilhã, Portugal); one used RW for irrigation, the other applied paper mill sludge to agricultural land. In both cases, multiple criteria based on GIS tools were used for site selection. In the first study, the characteristics of RW analyzed over 2 years were found suitable for crop irrigation. The RW had moderate organic content, low electrical conductivity (CE), high nutrient content (N, P), and low concentrations of nitrate, metals and phytotoxic elements (Al, B, Cl and Na). The multi-criteria analysis was carried out taking into account environmental, technical and economic criteria and a suitable area of 30.5 ha was found for RW irrigation. In the second work, the paper mill sludge was considered suitable for application to agricultural land. Its concentrations of N, P and heavy metals did not a present risk for soil contamination and were suitable for soil improvement and crop production. A multi-criteria analysis based on similar criteria was conducted and a suitable area of 253 ha was found for sludge application.