Identifying sustainable rehabilitation strategies for urban wastewater systems: A retrospective and interdisciplinary approach. Case study of Coronel Oviedo, Paraguay

Many wastewater managers in developing countries struggle with the daily operation of urban wastewater systems. Technically well-designed wastewater collection and treatments are often degraded and/or not properly functioning. In this paper, a realistic rehabilitation strategy is developed for the urban wastewater system of Coronel Oviedo (Paraguay), in which the actual performance is unsatisfactory, as revealed by a detailed technical assessment, including water quantity and quality monitoring data. Understanding the history, starting from the initial planning and design process, allows to explain the current failing status of the urban wastewater system of Coronel Oviedo. The key information for the specific local rehabilitation strategy was extracted from an interdisciplinary assessment of shortcomings of urban wastewater systems in Paraguay which were revealed by a survey of all existing wastewater systems. Opting for a stepwise rehabilitation strategy allows the wastewater manager to gradually improve the performance of the wastewater system. Reusing the wastewater in agriculture and recovering the energy of methane gas are possible advantageous options for attracting external financial resources. Finally, the crucial role that the wastewater manager must play for sustainable wastewater management to become effective in practice is discussed, and recommendations are provided on how decision makers, researchers and consultants can contribute by anticipating the challenging circumstances inherent to developing countries.

► Human factors can undermine the sustainability of well-designed wastewater systems.
► Urban wastewater managers should opt for a stepwise rehabilitation strategy.
► The active participation of stakeholders during rehabilitation must be stimulated.
► More robust wastewater treatment systems are needed in developing countries.