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Innovative methods used in upwater

  1. ·         Monitoring methods

  2. ·         Modelling methods
  3. ·         Mitigation solutions
  4. ·         Prevention methods

Monitoring methods

Monitoring refers to a broad range of methodologies which can include tools to support water balance calculations, techniques to monitor variations in groundwater quantity or quality and the use of innovative natural and human-made tracers.

Grab sampling


In the UPWATER project, we compare grab sampling with different passive
sampling methods. Grab sampling in groundwater monitoring involves collecting
individual water samples at a specific location and time, providing a snapshot
of the water quality at a given moment. This method is used to assess the momentary
chemical and physical characteristics of the groundwater, helping to identify
potential contaminants or changes in water quality.


Passive sampling is an economic monitoring method that involves
the deployment of small sampling devices in water (or another substance, e.g.
air), aiming at the collection of contaminants
an absorption process. The contaminants diffuse through a membrane where they
bind onto a sorbent material. As passive samplers are deployed for several days
to weeks, this process allows the accumulation of contaminants over time, providing
a time-integrated and hence more representative sample of the environmental
concentration. The collected samplers can then be extracted and the
concentration of the contaminants can be analysed in a semi- quantitative


In the UPWATER project, three passive samplers are used: Ceramic
Passive Samplers (CPS), Viral Passive Samplers (VPS) and Diffusive gradients in
thin films (DGT). 

Ceramic Passive Samplers (CPS)
Ceramic Passive Samplers are porous ceramic membranes that hold a sorbent material in the centre which can bind organic contaminants. The CPS have already demonstrated their worth in another project, IMAQUA, where deployment was in raw surface water and drinking water. In the UPWATER project, CPS are tested in groundwater in all three case studies for sampling of contaminants of emerging concern (e.g. PFAS, PAHs, pesticides, pharmaceuticals, industrial compounds). To allow the detection of contaminants in groundwater, where concentrations are much lower, the porous size of the CPS membrane and the sorbent material are adapted for long-term deployment periods.

Viral Passive Samplers (VPS)
Viral Passive Samplers provide an inexpensive and practical way to study the presence and prevalence of viral pathogens in groundwater samples. VPS already proved functional for measuring the presence of a wide diversity of waterborne viral pathogens and SARS-CoV-2 in wastewater. In the UPWATER project, VPS are tested in groundwater for sampling of specific human fecal pollution and viral pathogens like enterovirus, hepatitis E virus or influenza virus, in the case studies Athens and Barcelona. An innovation in this project is the utility of VPS in monitoring viruses in groundwater bodies. Additionally, we couple VPS with a sequencing method based on target enrichment for the characterization of the virome in this type of sample.


Diffusive gradients in thin films (DGT)
The principle of the DGT technique is based on the diffusion of the dissolved species through a membrane-diffusive layer and their accumulation in an ion-exchange resin. A hydrogel and a membrane filter (to protect the gel) are commonly used as the diffusive layer. The resin, which serves as a binding agent, is incorporated into a gel. These three layers are enclosed and sealed in a small plastic device, so that only the membrane is exposed to the solution to be analysed. In UPWATER, DGT will be deployed for the first time in groundwater. The DGT will be optimised to enhance the sorption capacity of trace elements (e.g., Pb, Cd, Ni, Hg, As, Cu and Zn). This optimization is based on the analysis of grab samples obtained from case studies in Athens and Barcelona. 


Viral passive sampler
Passive sampler

Modelling method

Pollution source apportionment modelling

In order to determine the origin and the proportion of each polluted recharge source within groundwater samples, the Stengaarden and Barcelona case study sites will use source apportionment modelling. The two methods involved in source apportionment include End-Member Mixing Analysis (EMMA) and Mixing Ratios Calculations (MIX).

EMMA, the first method, is a commonly applied method to identify and quantify dominant runoff sources. EMMA uses a method called Principal Component Analysis (PCA) to identify the minimum number of sources necessary to explain the chemical composition of each sampling point, only considering mixing processes. EMMA does not identify specific sources, but provides an arbitrary number that must be supported by a good conceptual model.

On the other hand, MIX is a method used to figure out where the different substances in groundwater come from. MIX works by analysing the amounts of the ingredients in the water and trying to find the best combination that matches these amounts. It keeps adjusting and trying different combinations until it gets as close as possible to the real amounts. Also, MIX can tell us if there are any chemical reactions happening in the groundwater, like the water changing colour, minerals dissolving or forming, and other chemical changes. Notably, UPWATER explores the novel application of MIX to aquifers with more than 20 contaminants and a wide array of chemical parameters.


In essence, the aim is to utilise these source apportionment techniques to discern the sources and relative contributions of pollution within groundwater samples, with EMMA focusing on conceptual modelling support and MIX addressing source apportionment in complex situations involving numerous sources and diverse aquifer attributes.

Besos river - Barcelona

Mitigation solutions

Moving Bed Biofilm Reactors (MBBR)

Moving Bed Biofilm Reactors (MBBR) is a wastewater treatment technology (a cleaning system). The centre for advanced water purification of the [KB1] Institute of Environmental Science [KB2] of Aarhus University (AU) is exploring this technology as a mitigation solution in the Stengaarden case study[AR3]  (Denmark). This innovative approach offers an alternative to energy-intensive remediation methods such as activated carbon treatment or ozonation.

In MBBRs, small floating plastic pieces[AR4] , so-called carriers, are suspended in water. Over time, these carriers get covered with a slimy layer of microorganisms (bacteria and fungi), called biofilms. The biofilms can degrade, remove and mineralise various compounds, including pesticides[1] and pesticide metabolites, in the water. The MBBR system is aerated, constantly blowing air into the moving water which favours the growth and activity of aerobic bacteria. With the carriers being suspended in the water, the biofilms will be operational even in environments with a high concentration of particles (e.g. dissolved organic matter, fine rock material or iron precipitates). 

In UPWATER we use MBBRs for two purposes:

a) to remove pesticide residues from the water.

b) to transform one type of iron (dissolved iron II) into a different kind (particulate iron III). This helps us capture it in sludges and sediments that we can easily remove, protecting the succeeding biofilter  from clogging during pesticide removal.

Labscale MBBRs have already proven their ability to remove Mecoprop,the pesticide of highest concern in Stengaarden. Here, a 30% mineralization[2] was achieved. However, the combination with the iron capture is uncharted territory and can either lead to an increase of the removal efficiency or to a situation where one process blocks the other. Also, previous experiments resulted to some extent in the formation of metabolites, while the ambition is to remove all pesticides including the metabolites. 

[1] Pesticides are chemical or biological products intended to prevent or deter animals, plants or microorganisms from causing damage to crops and other plants.

[2] Mineralization refers to the breakdown of a substance. It is a process of converting a complex organic substance with high effect (in this case, the pesticide residues) into mineral or inorganic forms (CO2, nitrate chloride).


Biofilters are in principle also biofilm reactors; they are also natural
cleaning systems. But instead of the biofilm in MBBR, the biofilter media
(where the biofilm is) is fixed. The water is infiltrated (pumped) through a
cylinder full of fine sand that is saturated with water, so there is a bit of
oxygen but not a lot. The top surface of the filter is planted with

reedgrass to help provide the oxygen needed by the microorganisms.
In comparison to MBBRs, the contact surface of the sand is considerably bigger
than the MBBR, allowing more biofilm to grow. Biofilters have been proven to be
effective at contaminant removal in laboratory experiments. But they have also
proven to be vulnerable to iron precipitation at Stengaarden. They are more
attractive to the public than MBBRs, as the biofilter area can be used as a
leisure area.

The differences between the two systems – MBBR and biofilter –
have an impact on the microbial community. The MBBR biofilm is more similar to
the biofilms present in traditional wastewater treatment plants (sludge)
whereas the biofilm in the biofilter is more closely related to the microbial
communities present in nature (soil, plants, roots).


a) We want to investigate how to use biofilters when there’s a lot
of iron in the water, which has been a problem before.

b) We’re testing if biofilters can work effectively all year, even
in very cold winter temperatures (down to minus 10 degrees Celsius).


c) We’re exploring if using a combination of the two treatment
technologies, MBBR and biofilters, can safely reduce pesticide levels in groundwater
by 99%, making it safe to drink.

Floating root mats and bioelectrochemical hybrid wetlands

Floating root mats in combination with bioelectrochemical hybrid wetlands or as a single treatment are groundwater contamination mitigation technologies that are studied in the Besòs and in the Athens case study sites.

The hybrid constructed wetland consist of a floating root with a surface-water root mat, followed by a saturated reed bed (grass-like plant) containing electroconductive material. For bioelectrochemical wetlands several water saturated columns filled with modified electrochemical supporting materials (coke or biochar) and combined with zero valent iron (ZVI) are being assessed for the removal of CECs. ZVI is a reductant that has been shown to be effective for removing recalcitrant compounds from wastewater and recent studies suggest that its combination with wetland systems may enhance the attenuation of CECs from wastewater. Therefore, we expect that the combination of ZVI with root mat-bioelectrochemical wetlands will help to mitigate groundwater pollution of the most recalcitrant compounds.


The mitigation solution will be first optimised at laboratory-scale and then validated in real field conditions in the Besòs river. The root mat-bioelectrochemical hybrid wetland will be optimised and validated for pollutant removal individually and in combination. CSIC is an expert in assessing the use of constructed wetlands for removing CECs from wastewater and surface water.

Floating root mats and bioelectrochemical hybrid wetlands
Floating rootmats
Bioelectrochemical wetlands

Preventive solutions

UPWATER will also work towards identifying effective strategies for preventing the pollution of aquifers and other water bodies. Through participatory processes with local stakeholders in the three case studies, UPWATER will prompt the evaluation and priorization of existing and innovative non-technological preventive measures ranging from the socio-economic measures to environmental protection legislation and appropriate water governance strategies.

The agriculture pollution in Denmark

Denmark is controlling pesticide1 use by charging fees for their use. These fees have three main reasons and triggers: The first reason is to protect the environment, including non-target organisms. The second reason is to protect groundwater and drinking water sources and the third reason is to ensure the safety of the people working with pesticides, such as industrial workers, gardeners, farmers, etcetera. The tax for each pesticide depends on the amounts (kg) used and the latest scientific knowledge about its toxicity/risks. This approach to regulating pesticide use is entirely unique. The Danish Environmental Protection Agency is currently working towards applying this strategy for urban use of biocides[1] as well. In UPWATER, the aim is to explore the application of additional preventive measures derived from external successful case studies at international level (e.g. special protection zones), as well as to evaluate innovative alternatives suited to the country-specific characteristics and challenges in a mid-term future.

The Region of Athens (Greece)

The Hydrogeology Group of the National Technical University of Athens (NTUA) collaborates with the main local stakeholders in the region. Their focus is to implement relevant EU legislation at the regional level. They will also work on participatory activities in collaboration with local environmental voluntary groups, focusing on flood monitoring. UPWATER will identify and propose the most efficient non-technological preventive measures (e.g. environmental awareness, integral water cycle management, effective records of activities in groundwater) to be applied in a complex groundwater system and highly interconnected with the urban and industrial activities. The analysis involves responsible experts at local, regional, and national levels, with multidisciplinary background.

The Besòs Delta aquifer in Barcelona (Spain)

Several existing plans, programs and procedures are already in place in the Besòs case study. For example, there are the Management Plan and Program of Measures, the Discharge sanitation program, the Declaration of Water Use and Pollution and the Drought plan. The water tax is an end-user environmental tax that supports the financing of water cycle services and accounts for up to 40% of the water bill. The water tax came into effect in the year 2000, coinciding with the creation of the Catalan Water Authority (ACA). Recommendations in form of Policy Briefs are one of the outcomes of the UPWATER project, which might ask for adaptation and changes to existing plans. The project takes advantage of the existing collaborative network in the region of Barcelona (Besòs) to identify innovative and tailored policy options for site-specific challenges. The Besòs case study, can be considered an example for further applications elsewhere. Among others, UPWATER evaluates and updates measures on integral water cycle management, socio-cultural perspectives, and environmental protection as a whole, as well as providing a new view to the economic approach of the groundwater resources.


[1] Biocides are chemicals or microorganisms that are intended to kill or exert a controlling effect on any harmful organisms in a non-agricultural context (building materials, disinfection, etc)

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