PROJECT DESCRIPTION
BACKGROUND
The scarcity of water resources is a chronic problem in many southern regions of the European Union, which forecasting models incorporating the effects of climate change predict will worsen and extend to northern regions. These water resources maintain the environmental quality of rivers and wetlands, but they are being rapidly reduced due to human activity. Pressure on natural water resources could be reduced by the generation of good quality water resources from non-conventional sources in an environmentally sustainable and economically viable way. Treated sewage is an unconventional water resource that, with adequate post-treatment, can guarantee a quantity and quality of water suitable for environmental uses. This is one of the uses envisaged in the Spanish legislation on reclaimed water reuse (RD 1620/2007). The European Proposal for water reuse only considers the use for agricultural irrigation (COM/2018/337). The Urban Waste Water Treatment Directive (91/271/EEC, UWWTD) is the framework for ensuring minimum quality requirements for the effluents from wastewater treatment plants (WWTP). Nevertheless, competent water authorities must ensure compliance with the environmental objectives set out in the Water Framework Directive (2000/60/EC), including the achievement of good surface water status. However, the requirements for the discharge of phosphorus established in the UWWTD (1 or 2 mg P/l) are insufficient for using treated water to feed wetlands or other lentic water bodies, due to their vulnerability to eutrophication. Furthermore, when drinking water is produced, one of the main wastes generated is the sludge from the physical-chemical water treatment. The cost of managing this Drinking Water Treatment Sludge (DWTS) could be reduced if a reuse is found. One option is to use its adsorbent capacity as a phosphorous sorbent in sewage post-treatment.
OBJECTIVES
The general objective of LIFE RENATURWAT is to demonstrate that it is possible to obtain reclaimed water from WWTP effluents through the combination of nature-based solutions (NBS) and industrial waste, to produce a high-quality water resource suitable for environmental uses, such as the recovery/conservation of wetlands.
Specific objectives are to:
Demonstrate the feasibility of reusing Drinking Water Treatment Sludge (DWTS), produced during one stage of the urban water cycle, in another stage, so valuing this waste and transforming it into a raw material; Optimise this reuse by using it as the filling material of Vertical subsurface Flow Constructed Wetlands (VFCW), thus favouring biological processes that occur in the plant roots; Demonstrate that the combination of VFCW, whose substrate is the DWTS, with a Free Water Surface Constructed Wetland (FWSCW) that host diverse environments (free-surface areas and vegetated zones) gives better environmental results than if only one FWSCW is available at the exit of the wastewater treatment plant (WWTP); Improve the quality of WWTP effluents, reducing their concentration of nutrients, emerging pollutants, priority substances and pathogens. Consequently, increasing their biological biodiversity (e.g. aquatic invertebrates, amphibians and insects); and thus improving the biodiversity associated with ecosystem services, such as pollination and insects for pest control in agriculture; Demonstrate that these NBS can become sanctuaries for endangered species and places for educational use; Develop specific design and operation guidelines for renaturation systems, to be included by competent authorities among the proposed improvements in tenders for WWTP maintenance contracts; Carry out a life cycle analysis (LCA) and cost-benefit analysis of this kind of facility to demonstrate the suitability of its implementation; Establish water quality criteria for environmental uses, contributing to the development of Spanish law and European proposals on water reuse to recover or maintain ecosystem services. The project contributes to the objectives of the EU Water Framework Directive and the Habitats Directive (92/42/EEC). By turning sludge into a resource, the project also contributes to EU waste management and circular economy policy. It provides a good example of the integration of EU policies in water, waste and biodiversity.
RESULTS
Expected results:
Creation of a renaturation treatment system in the Valls dels Alcalans WWTP (Valencia, Spain), managed by GOMSL, with the creation of wetland habitats over an estimated area of 300 m2, thus providing environmental services such as landscape integration, carbon sequestration and biodiversity enhancement; Demonstration that the proposed treatment significantly improves the environmental quality of WWTP effluent. Specifically, the following removal efficiencies, based on pilot plant studies, are expected: total phosphorus (>50%), ammonium (>60%), organic matter (>25%), emerging contaminants (20-50%), pathogens (>80%); Improved aquatic biodiversity by enhancing the taxa richness in, at least, 50 aquatic invertebrate taxa and favour the colonisation of the constructed wetland by species of amphibians, reptiles, fish, birds and terrestrial insects; Production of a renatured water flow between 50 and 250 m3/d, a figure equivalent to a population of about 1 500 inhabitants. This flow will feed the receiving river (Magro River in Valencia, Spain), contributing to an improvement of its status in accordance with the Water Framework Directive; Implementation of an economically and environmentally viable method to process and transport the DWTS; Implementation of a design and management tool for the proposed treatment scheme based on water quality numerical models, which will facilitate the implementation of this cost-efficient technology anywhere under similar conditions; and Elaboration of a guide for the design, construction, maintenance and operation of WWTP effluent renaturation systems, which helps competent authorities propose improvements in future WWTP tenders.
