Micropollutants in Water: From Monitoring to Treatment Optimization

6 days ago

5 min read

PFAS, pesticides, pharmaceutical residues and metals: monitoring micropollutants has become a major challenge for drinking water utilities, wastewater treatment plant operators and industry. With tighter regulations and new treatment processes, detecting contamination is no longer sufficient. Timely access to sufficiently frequent analytical results could become an important way to optimize treatment operations.

Control room of a water treatment plant with analytical monitoring and process supervision

Micropollutants: evolving regulations are strengthening monitoring requirements

Micropollutants in water resources and effluents present environmental and public health challenges. These substances have diverse origins and properties, and some require monitoring at very low concentrations.

Since 12th January 2026, EU Member States have been required to monitor PFAS in drinking water under Directive (EU) 2020/2184. The Directive sets a parametric value of 0.10 µg/L for the sum of 20 specified PFAS [1].

Directive (EU) 2024/3019 on urban wastewater treatment also provides for the phased introduction of quaternary treatment to reduce certain organic micropollutants, with milestones between 2033 and 2045 depending on plant size and identified risks [2].

These rules apply in different contexts but point to a common trend: better characterization of contamination and stronger control over treatment performance. How can operators verify that a plant continues to perform adequately over time?

Measurement frequency and result turnaround time: two essential factors

Laboratory analysis remains essential for characterizing contaminants and checking regulatory compliance. However, its use for operational monitoring can face two distinct limitations.

The first is measurement frequency. When sampling intervals are long, variations in contaminant concentrations or treatment performance may go unnoticed.

The second is result turnaround time. Sampling, transport where necessary, analysis and reporting can introduce delays. If operating conditions change quickly, results may be less useful by the time they reach operators.

A study by Furrer et al., published in Water Research in 2025, documented different temporal patterns of organic micropollutants in combined sewer overflows using samples collected every ten minutes [3]. This does not mean that such a frequency is necessary for every contaminant: sampling intervals must suit the phenomenon being studied.

Automated on-site monitoring using scheduled, discrete sampling and analysis could address both challenges: providing more frequent measurements where relevant and reducing turnaround time by bringing analysis closer to the sampling point.

Collecting more samples is not enough if results arrive too late to inform decisions. The objective is reliable, sufficiently up-to-date information that is available when action is still possible.

From regulatory compliance to treatment optimization

Analytical monitoring first answers a fundamental question: does the water meet applicable quality requirements? It can also help operators understand how a treatment plant is performing.

Unexpected changes in contaminant levels may reflect changes upstream, a fault in the treatment line or a gradual decrease in treatment efficiency.

More frequent measurements and faster access to results, considered alongside operating data, could help operators:

Detect anomalies sooner, whether they arise upstream or within the treatment process.
Track performance changes to identify situations that may require intervention.
Improve maintenance planning when treatment media or consumables gradually lose effectiveness.
Explore process adjustments based on pollutant loads and available controls.
Reduce non-compliance risks by identifying certain deviations earlier.

Such data could eventually help avoid unnecessary consumption of treatment media or reagents. These potential benefits, however, depend on the contaminant, analytical reliability and the actual decisions available to operators.

Monitoring creates value through both the timeliness and relevance of data and the decisions that these data can support.

PFAS and activated carbon: understanding changes in treatment performance

PFAS treatment illustrates the issue. Depending on water composition and target substances, treatment options include activated carbon, ion-exchange resins, nanofiltration and reverse osmosis.

Granular activated carbon can retain certain PFAS, but its effectiveness depends on compound properties, the water matrix, flow rate and contact time. Short-chain PFAS are generally less strongly adsorbed than many long-chain compounds [4].

As the medium becomes loaded with contaminants, some substances may gradually appear in the treated water. This phenomenon is known as breakthrough.

Operators therefore face a practical question: when should the filter medium be replaced or regenerated? Replacing it too soon may generate unnecessary costs, while waiting too long may jeopardize treatment performance.

Monitoring concentrations before and after filters, or potentially between treatment stages, could help document changes in removal efficiency and support decisions. Work by the US Environmental Protection Agency (US EPA) provides technical insight into this issue [5].

The challenge is no longer just confirming that a treatment process works, but understanding how its performance changes soon enough to respond.

Drinking water, wastewater and industrial effluents: different needs

In drinking water treatment facilities, monitoring source water and treatment stages can help identify contamination trends and document process performance.

At wastewater treatment plants, the gradual introduction of additional treatment steps for certain organic micropollutants reinforces the case for monitoring adapted to changing pollutant loads and operating conditions.

At industrial facilities, effluent composition can vary with manufacturing processes, production cycles and cleaning operations. Monitoring selected contaminants, including certain metals, can help identify unusual variations and assess their effects on treatment.

Target substances, concentration ranges, matrix complexity and measurement frequency should be defined for each application. The aim is not to increase analysis for its own sake, but to generate operationally useful information.

KLEARIA: bringing analysis closer to water treatment facilities

At KLEARIA, we are developing the microfluidic PANDa platform to bring micropollutant analysis closer to the sites where this information is needed.

Laboratory work has demonstrated detection of copper, nickel and zinc in real wastewater treatment plant effluents, without adding metals to the samples.

This miniaturized analytical approach uses small volumes of samples and reagents. Sample preparation, analysis and data processing are among the most thoroughly tested components of the system to date.

Depending on the application, analysis can take approximately 30 minutes. Where automated sample digestion is required, roughly two additional hours must be allowed. Total time to obtain results also depends on sampling and data transmission.

The proposed monitoring system uses discrete sampling, including a bypass line, rather than continuous physicochemical measurement directly in the pipe. Typical operator needs range from one to a few analyses per day, with higher frequency potentially relevant in some cases.

Development and validation are ongoing for complete automation and field deployment. KLEARIA is also researching additional targets, including PFAS: the PFAS sensor is not yet a field-validated solution.

Towards monitoring that supports operational decisions

Developments in analytical technologies and treatment processes invite us to move beyond a view of monitoring focused only on regulatory compliance.

Two questions become central: how often should measurements be taken, and how quickly can actionable results be obtained? The answers depend on the required decisions, process dynamics and analytical performance.

At KLEARIA, we want to work with operators to develop use cases that assess and ultimately quantify the technical and economic value of automated on-site monitoring, from anomaly detection to potential treatment optimization.

Measuring at the right moment, receiving results promptly and being able to act: together, these capabilities could support more efficient and sustainable water management.