## **Box  5.7  Mendoza, Argentina—creating a special area for direct wastewater irrigation**

The greater Mendoza metropolitan area has one million inhabitants, with 75% of the population connected to sewers in 1997, and coverage projected to increase to 95 percent by 2010. Mendoza is located in an arid region in the foothills of the Andes in the western part of Argentina. The city's wastewaters have traditionally been used indirectly for irrigation. The Campo Espejo treatment plant was built in 1976 and upgraded in 1993 (see Box 5.9) and provides 1.7 m<sup>3</sup> /s of effluent for direct irrigation.

The treated effluent from the _Campo Espejo_ treatment plant is conveyed to a special 1,900 ha restricted irrigation area, _Area de Cultivos Restringidos Especiales_ (ACRE). Farmers with properties within the special area receive treated effluent free of charge and are obliged to follow the irrigation regulations established for ACRE. About one quarter of the irrigated area is devoted to the production of grapes, another quarter to the cultivation of tomatoes and squash, and the remaining area to the cultivation of alfalfa, artichokes, garlic, peaches, pears, and poplar biomass. The quality of the agricultural produce and the health of the agricultural workers are monitored by a special office of the _Departamento General de Irrigación_ . An agreement of cooperation was recently signed between OSM and the ACRE farmers to study concerns of mutual interest, including the possibility of building effluent storage reservoirs that would optimize wastewater use during the dry season without requiring changes in the treatment plant operations, as well as the possibility of charging farmers part of the cost of treatment.

_Sources:_ Idelovitch and Ringskog, 1997; Kotlis, 1998; Barbeito, 2001; Egocheaga and Moscoso, 2004.

# _A new paradigm for wastewater treatment decision-making_

Technical standards for the design of municipal wastewater treatment systems often derive from environmental legislation that calls for the removal of organic matter and nutrients, and is focused primarily on pollution control and protecting the receiving water body (river, lake, wetland, groundwater, coastal zone). The resulting plants are built and operated for the downstream control of physical (temperature, pH, total solids, suspended solids), chemical (metals, oils, polymers, anions, and cations), and biological (biochemical oxygen demand (BOD5) and in-stream dissolved oxygen) parameters (Egocheaga and Moscoso, 2004). In developing countries, these sanitation solutions are often viewed as costly means of preparing wastewater for unproductive disposal, and as a result resource-constrained governments seldom rank wastewater treatment high on their agendas (Murray and Buckley, 2010).

There is a need to shift the paradigm so as to see wastewater as an asset, and to manage water, wastewater, pollution control, and effluent irrigation in an integrated way while ensuring public health protection (Bahri, 2009). In this paradigm shift, treatment facilities are not designed for waste disposal but to conserve resources in wastewater and reduce pathogen risks (Murray and Buckley, 2010). Such solutions, based on appropriate technologies, are cheaper than conventional WWTPs designed purely for disposal.<sup>32</sup> To minimize wastewater treatment costs, to safeguard public health, and to obtain the maximum possible agricultural benefit from nutrients and organic matter contained in wastewater, treatment plant design for irrigation use should focus primarily on reducing priority pathogens – particularly helminth eggs that threaten farmers’ health – while preserving nutrients. Conventional secondary 32 Appropriate technologies for wastewater treatment are defined by Libhaber (2007) as simple treatment processes of proven technology, of low investment costs and especially of low operation and maintenance costs, simple to operate and with the capacity of yielding any required effluent quality. The author describes a gamut of such processes that exist and are especially suitable for developing countries with warm climates, since biological processes perform better at higher temperatures.

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