The debate on the alternatives to traditional water treatment plants It is no longer just a technical issue, but a political and environmental priority for many European cities. Zaragoza has become one of the clearest examples of this change of course by launching a plan to thoroughly rethink how it treats its wastewater.
Far from simply replacing old equipment, the City Council wants to study more advanced, flexible and sustainable purification modelscapable of complying with demanding European regulations, reduce energy consumption and adapt to the urban and industrial growth projected for the coming decades.
A new wastewater treatment model for Zaragoza: why alternatives are being sought
The Zaragoza City Council has launched a tender for a contract for more than 537.000 euros to thoroughly analyze their wastewater treatment system and define a renewed model. The commission includes both a diagnosis of the current facilities and a study of different technological and infrastructure alternatives.
As detailed by the Councillor for Urban Planning, Infrastructure, Energy and Housing, VÃctor Serrano, the goal is comply with the most demanding European standards In terms of sanitation, this involves ensuring the economic and environmental sustainability of the system. It's not just about continuing to treat water, but about doing so with a more efficient, resilient, and future-proof approach.
In practice, the contract will allow you to decide if it is more suitable expand and modernize the existing wastewater treatment plantsbuild new plants or combine both options. The result will be a water management model that addresses the city's regulatory, environmental, and population growth challenges.
These types of in-depth review processes are not unique to Zaragoza: they are being explored in much of Spain and Europe. circular economy criteria and alternatives to classic wastewater treatment plant schemes, incorporating cutting-edge technologies and circular economy criteria to minimize the impact of sanitation on the environment.
Six major objectives: radiography, alternatives, and efficiency
The contract is structured around six key objectives that set the course for the future wastewater treatment system of Zaragoza and for possible alternatives to the current treatment plants.
First of all, a comprehensive overview of existing facilitiesThe Wastewater Treatment Plants (WWTPs) in the municipality, some of which have been in operation for about 35 years, will undergo a detailed technical assessment: the condition of the civil works, the useful life of structures and equipment, energy consumption, and the actual capacity to continue meeting the new discharge requirements.
Secondly, a objective evaluation of treatment alternativesThis includes comparing different purification processes, from improved conventional technologies to advanced systems such as membrane bioreactors (MBR), moving bed reactors (MBBR), or advanced oxidation, which allow for the removal of emerging contaminants and improve the quality of treated water.
The third objective involves defining a new, more innovative cutting debugging modelThis model should integrate tertiary and quaternary treatments to obtain higher quality effluent, promoting the energy neutrality of the plants —taking advantage of biogas or solar energy, for example— and applying a circular management of sludge, reducing waste and promoting its valorization.
The fourth pillar of the contract focuses on the administrative agilityThe winning company must deliver technical documentation prepared to initiate the various legal and environmental procedures, so that the City Council can quickly move from preliminary studies to the actual execution of the works when the time comes.
Fifth, a strategic investment roadmapThis plan will prioritize actions according to technical, environmental, economic and urban planning criteria, allowing for the organization of future investments and avoiding improvisation in the expansion or renewal of the sanitation system.
The sixth objective is to have a detailed economic forecast that realistically quantifies the investments needed to carry out the transformation. This information will be key to balancing municipal budgets, exploring potential European funding, and planning the implementation schedule without surprises.
Three phases until 2027: from diagnosis to preliminary projects
To organize all this work, the City Council has divided the contract into three major interrelated phaseswith a timeline extending to 2027. The idea is to move forward step by step: first, understand the situation, then compare alternatives, and finally prepare the documents to put the works out to tender.
La Phase The study will focus on the diagnosis and complete technical characterization of the current system. Intensive analytical campaigns will be carried out on the wastewater, measuring everything from basic nutrients to emerging pollutantsThe condition of the infrastructure will be assessed through non-destructive testing of concrete and structures.
At the same time, the energy efficiency of wastewater treatment plantsanalyzing consumption and assessing the integration of renewable energies such as biogas or photovoltaics. The capacity of the Almozara-Cartuja joint system will also be modeled to verify its compliance with future landfill regulations, and a study will be conducted on how to integrate new technologies into the urban and environmental context of Zaragoza.
La second phase It will start with all that data on the table and its mission will be study of alternatives and the selection of the optimal solution. Options such as the expansion and renovation of existing WWTPs, the construction of new facilities, or combined approaches will be evaluated, supported by tools such as Multi-Criteria Analysis (MCA), cost-benefit studies, and risk analyses.
Once the alternative that best balances cost, environmental impact, treatment capacity and future flexibility has been chosen, the following will be developed specific flood studies and environmental impactincorporating corrective and protective measures against possible extreme episodes of rain or river flooding.
Por último, la third phase will be dedicated to the writing of preliminary designs and complete technical documentationReports, hydraulic and process dimensions, models, geological and geotechnical studies, construction plans, estimated budgets and the basic health and safety study will be prepared, leaving the project ready to start the next phases of bidding and execution.
The planned schedule aims to have the diagnosis finalized by the end of 2026The plan is to have the alternatives study ready by spring 2027 and the preliminary designs available in the last quarter of that same year. This gives Zaragoza a reasonable timeframe to ensure the change in model is well-founded before committing to larger investments.
What do the alternatives to traditional wastewater treatment plants entail?
Beyond the deadlines and technical documents, the process initiated by Zaragoza opens the door to different ways of understanding purification in the city, aligned with the trends observed in Spain and the European Union.
On the one hand, the possible incorporation of technologies such as MBR, MBBR or advanced oxidations This involves moving from systems designed only to remove organic matter and nutrients to approaches capable of addressing emerging contaminants, and greater demands on the quality of treated water, something increasingly required in complex urban environments.
On the other hand, the commitment to the energy neutrality and the circular economy This means that wastewater treatment plants will no longer be seen solely as a fixed cost and will become infrastructures capable of generating energy (by harnessing the biogas from the sludge). recover resources and reduce its climate footprint. This vision aligns with European policies on ecological transition and decarbonization.
The emphasis on long-term planning and flexibility It is also part of the alternatives to the classic model: the aim is not just to find a large facility that solves everything, but a scalable system, adapted to urban and industrial growth and prepared for climate change scenarios, episodes of intense rainfall or variations in the polluting load.
Finally, the combination of more advanced treatments, better sludge management, and streamlined administrative procedures It facilitates the rapid implementation of future policy decisions when funding is available, whether municipal, regional, state or European.
With this approach, Zaragoza is positioning itself along the path of other European cities that are reviewing their sanitation systems to incorporate alternatives to conventional water treatment plants, opting for more efficient, resilient facilities aligned with the EU's climate and environmental objectives.
