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Harnessing reclaimed water to improve river health

Oct 17, 2023

Discover an interview with Dr. Antoni Munne, a distinguished Water Ecologist and PhD from the University of Barcelona. Dr. Munne currently heads the Water Quality and Control Department of the Catalan Water Agency and plays a crucial role in safeguarding Catalonia’s water resources. In this interview, you will learn about the valuable contributions of a co-creation project for water management and ecosystem health, aimed at improving the overall health of rivers.

Could you explain to us what is your responsibility as Director of the Environmental Management Area of the Catalan Water Agency?

As Director of the Environmental Management Area of the Catalan Water Agency, my team and I are responsible for monitoring and controlling the status of the different bodies of water in Catalonia and regulating discharges resulting from human activity. This includes protected waters, bathing waters, and waters that will later be treated to be potable. We collect groundwater and surface water samples from rivers, lakes, reservoirs, and coastal waters to assess their microbiological, morphological, and physicochemical status. We also carry out additional controls, such as microbial controls, in drinking water and in risk areas where there is a catchment. Our aim is to ensure that the water in Catalonia is safe and complies with all relevant water directives.

Considering the current climatic context, when do you plan to use reclaimed water to restore the minimum flow of the lower course of the Llobregat River?

In recent years, due to climate change, there has been a reduction in water inputs, significant afforestation in the river basins of Catalonia, an increase in ambient temperature causing evaporation, and a decrease in rainfall, which has led to a significant reduction in water availability. On average, some rivers have seen a 7% decrease every ten years, and models predict reductions of up to 18% and possibly 22% in some areas of available resources by mid-century. The objective is to prepare for this scenario.

Can you tell us about the details of the proposal?

In 2008, an alert was issued due to a major drought that led to the implementation of various measures, and in the last two years (2021-2023), we have again suffered an even more prolonged drought situation. After the 2008 drought, measures were taken to address the problem. One of the measures included the construction of a pipeline to transport treated water from the Sant Joan Despí treatment plant in the Metropolitan Area of Barcelona to upstream areas, where it can be used for irrigation or other purposes. Currently, 53 treatment plants in Catalonia discharge a significant amount of water to marine areas that are not reused. The proposal suggests redirecting this water to the headwaters of rivers to give it a second life for irrigation or other uses and increase river flows.

Is this type of practice being applied in other parts of the world?

Similar practices exist in various parts of the world, especially arid areas such as southern California, Israel, northeastern Australia, etc., but in most cases, the reclaimed water is mainly used for infiltration and groundwater recharge or directly discharged into reservoirs. However, in our case, we propose to return the reclaimed water to the river a few kilometers away from the catchment area, with a low dilution ratio, which can be as low as 1:1. Although this method is more efficient in terms of water gain, it also requires a more rigorous control and forces us to guarantee the quality of the water through exhaustive analysis of various compounds.

When were the first tests conducted?

In 2019, before the onset of the drought, we conducted some tests in the summer season. These tests were aimed at reducing reservoir releases, especially those of the Llobregat River. Our goal was to achieve a dilution ratio of 1:1, meaning that we added two cubic meters of river water for every two cubic meters of reused water. We formed a team of expert advisors composed of chemists, microbiologists, reclaimed water technology specialists, public health professionals, communication experts and environmentalists. We also created a working group with representatives from Public Health, the plant operators, AMB, Aigües de Barcelona, and ourselves. The pilot test lasted two months under these conditions.

What kind of controls did you perform?

We performed several water controls, including chlorination and non-chlorination processes. We selected a number of compounds that could enter the treatment plant. The Department of Health provided a comprehensive list of key drugs that can be prescribed in medical facilities. We compiled information on compounds discharged from various sources, such as industries, domestic use, and cleaning products used in parks, gardens, and city streets. We collected more than a thousand compounds and analyzed more than 300 of them, from the treatment plant’s inlet to the outlet of the treatment plant, secondary and tertiary stages, discharge to the river, dilution, catchment, purification, and network. We performed these tests with and without chlorination and studied the most common microbiological indicators, including coliphages.

As a result, we obtained authorization from the Health Department for this project in case of drought. Our goal is to analyze between 20 and 25 indicator compounds since most of these 300 analyzed compounds always present concentrations below detectable levels.

Did the tests give the expected results?

The tests have yielded positive results for both the reclaimed and drinking water treatment systems, ensuring that the water entering the network meets optimum quality standards. This is especially important during drought in the Barcelona Metropolitan Area, where the use of reclaimed river flows as additional water sources helps slow down reservoir depletion. The intention is to use this method during alert stages, in combination with other sources such as aquifers or desalination plants.

What was the methodology followed?

To carry out the project, two groups were formed: one made up of expert advisors and the other of ACA technicians, technicians from the treatment plants, AMB, Aigües de Barcelona, and Public Health, who were in charge of setting the work guidelines. Each time an internal consensus was reached, the proposals of the technical group were shared with the expert advisors, who provided their comments and suggestions for improvement. The technical team then executed the plan, averaged the results, and presented them to the expert advisors for further evaluation.

Were the coliphages tested?

We searched several libraries to identify the presence of pathogens in the water. We also compiled a list of viruses that might be present in the water. However, we did not find viruses at significant levels. Through two or three tests, we found that coliphages are reliable indicators of viral contamination. If coliphages are present, it indicates the presence of viral contamination in the water, and if they are not found, it suggests that the water is not contaminated or that the level of contamination is below levels hazardous to health.

Water treatment is an efficient process.

An interesting issue to consider during treatment is the log decay of microbiological indicators. Reclaimed water restrictions usually require a reduction of 6 log units, and we can observe a significant decay during the wastewater plus reclaimed water treatment process. Once the treated water is discharged to the river, it is mixed with water at a level of 3 logarithmic units, which means that it does not need to be reduced beyond two logarithmic units. Therefore, there is no need to chlorinate the water at the reclaimed water plant, which helps to avoid adding more chemicals (disinfection by-products) to the river.

What is the public opinion on these practices?

Effective communication is crucial to avoid social rejection and promote the use of reclaimed water. To this end, we had an expert journalist in science communication within the group of expert advisors who helped us develop a communication strategy for our institutional relations department. This strategy allowed us to explain our proposal in the best possible way to both experts and non-experts. We did not face social rejection or opposition thanks to our efforts. We also published a scientific article and used various communication channels to make the public aware in detail of the controls performed and their results and to gain confidence in our proposal.

Dr. Antoni Munne

Biologist. PhD in Water Ecology (University of Barcelona). Currently working at the Catalan Water Agency in Catalonia (NE, Spain) the public water authority in charge of managing water resources and watersheds in Catalonia. In charge of Monitoring and Water Quality Department, responsible for assessing water quality status in Catalan basins. Redactor of the water management plan of the Catalan River Basin District and participating in the first and second phases (2006-2008 and 2009-2011) of the EU intercalibration exercises for biological quality assessment in the Mediterranean Geographical Intercalibration Group (Med GIG). Also involved on various programs of measures aimed at improving the quality status of water bodies according to the European Water Framework Directive – WFD (2000/60/EC): environmental flows, water reuse, invasive species, restoring river ecosystems, etc. Author of several papers related to ecological status assessment in Mediterranean water bodies and WFD implementation. Editor of the book titled: “Experiences from Water Quality Monitoring: The EU Water Framework Directive Implementation in the Catalan River Basin District”. Handbook of Environmental Chemistry. Published by SPRINGER in 2016.

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