Using Custom Sensors and Electrodes for Water Quality Monitoring

What is the Environment Act 2021 and what is Section 82?

The 2021 Environment Act is aimed at improving how water quality is measured, monitored, and managed in real-time, particularly in rivers, lakes, estuaries, and coastal waters. The Environment Act 2021 introduced several measures to improve environmental protections, and continuous water quality monitoring is a critical part of these efforts, especially for the management of wastewater and storm overflows. Section 82 of the Environment Act 2021 focuses on improving monitoring regarding water quality, specifically targeting how sewerage undertakers (i.e., water companies responsible for managing public sewer systems) handle wastewater discharges, including storm overflows, into rivers, streams, and coastal waters.

Sewerage undertakers are required to install and maintain monitoring equipment on storm overflows and combined sewer overflows to track how often they discharge untreated sewage into water bodies. Sewerage undertakers must ensure that any discharge from their sewer systems does not breach water quality standards, particularly in sensitive areas such as bathing waters and protected ecosystems.

The government guidance details the types of technologies and methodologies that sewerage undertakers should use to monitor water quality effectively. This includes specifications for:

• Flow meters and sensors for measuring discharge volumes.
• Water quality sensors for detecting pollutants (e.g., ammonia, pH, DO2, etc.).
• Data collection and management systems for storing and reporting monitoring data.

The legislation in place dictates that sewage undertakers must monitor their waste output upstream and downstream, of their asset being monitored, once per hour or every 15 minutes during a high-risk event. These changes are required to be rolled out as soon as practicably feasible and have started by 2025 with complete monitoring completed by 2035.

How can Sentek Help?

Electrochemical sensors play a significant role in supporting the Continuous Water Quality Monitoring Programme and compliance with the Environment Act 2021, particularly for sewerage undertakers in implementing Section 82. These sensors are designed to measure various chemical properties of water in real-time, offering precise and reliable data essential for maintaining water quality and detecting pollution. Sentek can provide a range of electrochemical sensors suitable for measuring common sewage works contaminants and key indicators of a water courses health:

• pH Levels
• Temperature
• Dissolved Oxygen
• Turbidity/Conductivity
• Ammonia – An increase in Ammonia is a common indicator of sewage contamination.
• Chlorine – Chlorine sensors can detect the presence of disinfectants that may be released from wastewater treatment plants.

Nitrate sensors help track nutrient levels, which can cause issues like eutrophication (excessive nutrient enrichment in water bodies leading to algal blooms and oxygen depletion).
As one of the leading UK sensor manufacturers, Sentek can support clients with design of custom electrochemical sensors, probes and sondes to meet their specific water quality monitoring requirements. These can be installed at combined sewer overflows and other wastewater discharge points to monitor when and how often untreated wastewater is being released into rivers or coastal waters. Sensors provide early detection of changes in water quality. For example, if a sensor detects a sudden rise in ammonia or a drop in dissolved oxygen, this could indicate a pollution event such as a sewage spill. Early detection allows companies to respond quickly and mitigate the environmental impact before it escalates.

Sentek electrochemical sensors have been used for long-term deployment across the globe, providing continuous monitoring that ensures companies remain compliant with the environmental regulations over time. By tracking trends and long-term changes in water quality, sewerage undertakers can identify problem areas, manage wastewater systems more effectively, and make informed decisions on infrastructure improvements.

Sensors from Sentek can be integrated with remote monitoring systems and data platforms, enabling seamless collection and transmission of water quality data. This integration is particularly useful for large-scale, continuous monitoring across multiple locations, such as river systems or coastal areas.

The sensors can also be incorporated into smart monitoring networks, where data is aggregated and analysed to provide insights into overall water quality trends and potential sources of pollution.

Sentek electrochemical sensors could significantly enhance water quality monitoring efforts by providing reliable, real-time data that helps sewerage undertakers meet their obligations under the Environment Act 2021 Section 82. These sensors enable proactive management of water resources, ensuring timely detection of pollution and helping to maintain high environmental standards.

Ammonia vs Ammonium

Ammonia is just one component in sewage that can be particularly harmful to aquatic life, it can be very challenging to monitor, particularly in the field. Ammonia ISE are available but presently are only practically useable in a lab-based setting.

Ammonia is only present as the deprotonated form NH3 in a basic pH greater than 7, below this it is mostly in the less harmful ammonium ion (NH4+). Ammonium is unable to cross cellular membranes so is therefore much less toxic than ammonia. As pH and temperature increases the proportion of ammonium being deprotonated to the smaller and more harmful ammonia increases so by monitoring NH4+, pH and temperature we can relatively accurately infer the ammonia concentration in the water. The table below shows the percentage of ammonia vs ammonium at varying pH and temperature.

This can be plotted onto a curve also shown here.

Schematic model of ammonium ion (NH4 + ) and neutral ammonia (NH3) proportions in function of the pH. At acidic and neutral pHs, NH4 + is the most abundant species. However, NH3 is dominant in highly alkaline solutions. Scientific Figure on ResearchGate. Available from: https://www.researchgate.net/figure/Schematic-model-of-ammonium-ion-NH4-and-neutral-ammonia-NH3-proportions-in_fig2_358973331

Calibration and Maintenance

Sensors or sondes can be pre calibrated prior to installing but will need periodic recalibration to maintain a high degree of accuracy. Over time the sensor will begin to drift away from the calibration point. Each sensor type will drift at a different rate as they age – the longer the sensors go without calibration the greater degree of uncertainty the measurement will have.

Regular maintenance will also be required to ensure that the sensors or sondes are working at their best, giving that monitoring a water way will naturally lead to an amount of biological fouling to the sensors. Contamination of the sensor junctions or plates will lead to increased resistance which in turn will skew measurements, so it is important that these are periodically cleaned off and recalibrated.

For more information on the Environment Act 2021 Section 82 and sensors used to measure chemical properties of water, contact a member of the team.

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Types of pH Meters

It is important to define the difference between a pH meter and pH probe in order to understand their overall functions. A pH meter is an instrument that measures the overall acidity or alkalinity of a liquid or solution. This is measured on the pH meter scale of 0 to 14, with 7 being neutral. Anything below 7 is considered acidic, and conversely above 7 is considered alkaline. A pH probe definition describes the entire measuring component that connects to the meter itself. The probe consists of an electrode, housing unit, and preamplifier with a temperature sensor often included for compensation. The pH element itself is defined as a thin glass membrane permeable by hydrogen ions. Having defined what the pH meter principle is, we should look at the different types of pH meters and how they work.

Types of pH Meter

There are three main types of pH meter available, each with their own applications:

• pH electrodes, also known as pen testers, are the cheapest and easiest to use on the market. The electrode is housed in a glass pen-like container with a tip that is sensitive to hydrogen ions. The small size of the electrode meter means that it can be transported and used anywhere, although it does have limitations compared to heavier grade meters. pH electrodes are often used on the go for testing in construction, hydroponics, food manufacturing and swimming pool maintenance.
• Handheld pH meters are more heavy duty than their pen tester counterparts. These meters consist of a handheld device for display and calibration features as well as an interchangeable electrode probe component. Handheld pH meters are often used in field work by environmental officers and in aquaculture, agriculture and water treatment industries. Many recent models also feature Bluetooth and wireless technology for easy transmission of data to mobile devices.
• Benchtop pH meters are often found in laboratories and professional industries. These are the largest types of meter available and are usually either desk or wall mounted. Benchtop meters provide the highest degree of accuracy when measuring pH levels and are commonly found in food processing facilities, quality assurance, water testing and environmental testing.

Calibrating and Using a pH Meter

Regardless of the types of pH meter used, here are the steps you should take to ensure accurate readings:

1. Turn on the meter and allow it to warm up.
2. Clean the electrode by rinsing it with distilled water. Avoid contaminating the electrode by touching it or letting it come into contact with other solutions.
3. Prepare your buffers for calibrating the meter, pouring each into separate containers and allowing them to reach the same temperature. You should have one neutral buffer of a pH meter scale of 7 and at least one other with a pH close to that of the expected sample. High pH buffers are useful in testing alkaline bases, low pH buffers for acidic solutions.
4. Test your pH meter in the neutral buffer to begin calibration.
5. Adjust the pH meter value according to the reading from the neutral buffer.
6. Rinse the electrode again in distilled water.
7. Test your pH meter in the buffer that matches the sample pH level.
8. Adjust the pH meter value again according to the reading from the sample pH buffer.
9. Rinse and clean the electrode in distilled water.
10. Use the meter in the sample and begin testing.
11. Measure the pH level on your meter.
12. Clean the electrode after use.

Sentek

Since 1991 Sentek have been manufacturing probes, pH electrodes, sensors and other equipment for a range of industries. We have a range of excellent quality pH probes available through our online store, plus we can create custom probes for bespoke applications. To find out more contact our expert team online or via phone. For reliable and superbly designed pH probes, contact Sentek today!

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What is pH Adjustment?

The science of everyday things

Sentek is one of the UK’s leading manufacturers of probes, pH electrodes and sensors, specifically designed for use in a range of manufacturing and other procedures, including pH adjustment. Although these instruments are essentially scientific in nature, their use is fundamental to a variety of everyday processes.

pH in water, for example, is a measurement of how much alkaline or acid is present. In terms of suitable drinking water, the pH level can be critical. It may require neutralisation, which is also known as pH adjustment. The type of highly specialised probes manufactured by Sentek are an integral part of this process.

The importance of pH

Though the majority of people are relatively unaware of it, pH plays a crucial role in our everyday existence. Our blood, the food we eat, and the paint we use to decorate our homes are all affected by pH. The ‘p’ represents power or potential, while the ‘H’ represents the Hydrogen atom. The term pH is used to denote the level of Hydrogen ions (H+) in a given solution.

As we’ve seen above, in the case of clean drinking water a pH adjustment is simply a matter of adjusting the pH level to make the water drinkable. It is within this process and many others that Sentek’s precise pH probes are used. Other processes include the manufacture and testing of biofuel, where a Biofuel Probe would be used.

The pH value of every aqueous solution can be measured using pH probes and pH meters, a process that is critical before a pH adjustment can be made. These precise scientific devices are used in the testing of a wide range of everyday products. This includes food items such as bread, dairy products, meat and fish; items such as cement, cosmetics, paint and photographic materials; and in other areas related to blood products, education, and soil.

The use of pH probes and meters

Sentek’s pH probes are highly sensitive instruments used in the process of measuring pH levels. A pH probe is made up of a pH electrode within a transparent housing, often a temperature sensor for temperature compensation, and a preamplifier; a thin glass membrane which is permeable by H+ ions makes up the pH element.

A pH meter is an important instrument when used in conjunction with pH probes, and is the most accurate way of measuring the pH level of a given substance or solution. The process involves the preparation of the materials to be assessed, as well as methodical calibration and testing.

The electrical potential of the solutions inside and outside the thin glass membrane of the probe creates an electromotive force in relation to the difference in pH. This difference is precisely measured by the pH meter. pH adjustment chemicals are then used to make the necessary changes or ‘adjustment’.

Sentek has been manufacturing a range of electrochemical sensors for laboratory and industrial use since 1991. Over that time the company has acquired a wealth of knowledge and experience in the field. The team at Sentek is also happy to advise on the manufacture of custom probes for specific applications.

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How to Pick the Right pH Testing Equipment

Most people, even if they don’t work in a specialist profession, have a bit of knowledge about pH and its significance. It is one of the first lessons taught in school chemistry because knowing how to measure acidity and alkalinity is relevant to all kinds of scenarios. Ultimately, pH plays a vital role in many different aspects of life, so it’s a very useful tool.

The range of businesses which utilise pH testing equipment is surprisingly broad. The food and drink industry is one of the biggest clients, but the cleaning sector comes a close second. Everything from scrubbing carpets to washing swimming pools requires just the right pH balance for success. It is why high quality pH probes and electrodes are always in demand.

If your business is in need of premium testing equipment, the first step is working out what kind of pH probe or other instrument you require. Keep reading to find out more.

The Makeup of a pH Probe

From a technical perspective, pH probes and electrodes have changed very little over the decades. The basic internal setup is the same, though advanced features and new additions have been used to extend their value.

Inside the probe, there is a reference solution. This is made up of silver or potassium chloride. It is designed to provide a constant electric potential so that the probe can identify the potential in the sample and calculate the difference between the two. This gives the pH reading.

Electrodes and probes are very delicate things. They must be cared for and maintained in a specific way, in order to guarantee accurate measurements. Some, like glass bulb probes, are actually reusable as long as the reference solution is refilled at the right times.

The Different Types of Probe Available

Today, there are all kinds of pH probes on the market, and they are suited to a wide variety of applications. They include combination, gel filled, double junction solid state, ion selective, epoxy body electrodes, and more. Let’s take a closer look at some of these tools.

Single Junction

This is the most common probe, so it is considered to be the ‘standard’ choice. It contains that all-important silver chloride reference solution, and it is compatible with everything but heavy metal samples (like iron or lead), proteins, sulphides, organics, and low ion concentrations.

Double Junction

The double junction works in much the same way as the single junction, but it contains two reference channels. The purpose of this is to filter contaminants out of the reference solution. So, silver chloride can be used with heavy metals, but only when part of a double probe.

PTFE Resin Junction

This next pH probe is a very specialist instrument. It is primarily used in situations where the sample may cause obstructions. So, for example, testers of paint, sauces, and other types of paste use these for quality control procedures. They are highly resistant to clogs and jams.

For more information on pH testing and the use of pH probes, contact us or, call 01376 430 456 to place orders for high quality conductivity, reference, and pH electrodes.

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