A reutilização de águas residuais em Cabo Verde. Análise crítica da situação actual em Santiago. Caso de estudo de Santa Cruz

Mestrado em Engenharia do Ambiente - Instituto Superior de AgronomiaThe potential of urban wastewater reuse was analyzed, based on the socioeconomic and environmental characterization of Santiago island (Cape Verde), aiming to contribute to a better understanding of the concerns of integrating this alternative on the management policy of the country’s water resources. To achieve this, a brief characterization of water resources availability and its uses in Santiago was made. The amount of per capita water consumption, the network coverage of water supply and sewerage and wastewater treatment plant (WWTP) coverage were studied as factors affecting the potential of wastewater reuse. It was estimated the amount of water needs for agricultural irrigation for each municipality on the island, according to their respective agricultural area with suitability for irrigation. It were considered two scenarios of water needs of the most important crops in terms of area and specific water demands (sugar-cane and banana). It was we studied the potential of treated wastewater (TWW) to meet such needs at each one municipalities of the island. The potential of TWW use for irrigation in 2020 was evaluated predicting improvement of water supply and sewage drainage and wastewater treatment conditions, admitting that it be will reused, by that time, 50% of treated wastewater. The situation of TWW reuse in Santa Cruz, one of Santiago’s municipalities, was particularly studied, in what concerns the WWTP operation. It was qualitatively and quantitatively analyzed the affluent and the effluent of treatment plant, useful information for assessing the suitability of TWW for irrigation. The farms sit near to WWTP were characterized through the evaluation of soils, crops, and irrigation water used. The acceptance of TWW use in irrigation, the current knowledge and perspectives about irrigation with TWW were also evaluated through a survey directed to farmers and Santa Cruz inhabitants in general. It was found that volume of TWW in Santiago is actually low compared to water needs for irrigation, but this volume will increase significantly until 2020 reaching 50 times higher values