Two years monitoring of the natural system for wastewater reclamation in Santa Lucía, Gran Canaria Island

The objective of this work is to describe the performance of the Santa Lucía natural system for wastewater reclamation (NSWWR) in its first two operating years, where it was run under distinct conditions from the initial design. This plant, located in the island of Gran Canaria, has yielded a wealth of information on the implementation of low-cost technologies in subtropical areas with water scarcity, both ecologically as well as socially sustainable, and the option of installing similar plants in coastal zones. The system also served as a local pilot plant for a natural technology of wastewater reclamation, alternative to conventional solutions, whether centralized or onsite, usually applied for the treatment of domestic wastewater in rural areas. In fact, over the years local wastewater treatment has demonstrated clear advantages: no need for electricity, no leakage of raw sewage along the sewerage systems, social and landscape integration, exploitation of by-products like macrophyte-derived material for local handcrafts, and reuse of reclaimed water for irrigation. Remarkably, the plant operated under forced conditions of a hydraulic overload of 200%; however, the influence of a climate with stable mean temperatures and mild winters may have contributed to a satisfactory overall performance. Mean removal efficiencies were even higher than expected: more than 80% for biochemical and 75% for chemical oxygen demand (BOD5 and COD), and 90% for total suspended solids (TSS). Mean decrease of nitrogen and phosphorus were 50 and 30%, respectively, while abatement of fecal indicators attained 2 log units. The data collected from the Santa Lucia wastewater reclamation system represent an exceptional case study, which may be potentially transferred to other rural or littoral communities that lack sanitation and reclamation systems. Moreover, the option of wastewater reuse and zero discharge is particularly attractive for arid zones.