Contribution of non-conventional technologies for sewage treatment to improve the quality of bathing waters (ICREW project)

Abstract

The new EU Bathing Water Directive (2006/07/EEC) suggests that for a better management of the quality of these waters is necessary to be established the coordination with others directives such as The Urban Wastewater Directive (71/271/EEC) aiming the adequate treatment of the urban wastewater. Within the framework of the interregional European project “ICREW: Improving Coastal a Recreational Waters” nine small-scale wastewater treatments plants and a wastewater experimental plant in small rural areas were investigated in order to evaluate their effectiveness for treating municipal effluents. Suspended solids, organic matters and microbiological pathogen ( E. coli and intestinal Enterococci) parameters were monitored during 12 months. Sewage treatment plants based on non-conventional and conventional technologies located in Occidental Andalusia and Canary Islands were compared. Most of the treatment plants monitored present a BOD 5 and COD removal values higher than those established in the Directive 91/271/EC. The pathogen removal rates varied from one technology to another, fluctuating between 1.0 and 3.5 log units. The higher E. coli (more than 2 log units) and intestinal Enterococci (more than 3 log units) were achieved for Constructed Wetland, Stabilization Ponds and Rotating Biological Contactors with Sand Filters or Peat Filters. An entitled guide “Guideline of urban wastewater treatments for small communities” has been produced. The aim of this guide is to support the decision-making process in public or private organizations when selecting sewage treatment technology to obtain the final effluent quality required.