Process and control today | Online monitoring of nitrates and organic impurities optimizes water quality

05/03/2022 Burkert Fluid Control Systems

From bottled beverages to textile manufacturing processes, optimizing water quality and safety requires reliable measurement of nitrates and dissolved organic impurities. Continuous online monitoring offers the highest measurement reliability, and Bürkert’s new sensors offer a cost-effective solution to improving water quality and reducing the time required for testing.

Greg Wainhouse, Industrial Account Manager for Water Applications at Bürkert, examines the challenges of monitoring nitrates and organic impurities.

To ensure public health, the quality of the water we consume, whether it comes directly from the tap, bottled spring water or from producers of processed foods and beverages, must reach safe limits of its compositional elements. A group of compounds in water that should be within safe limits include nitrates (NO3-), and although they occur naturally in vegetables and the human body, excessive levels pose a health risk. health. With up to 50 parts per million (ppm) considered safe for children and adults with immune system vulnerabilities, the UK and EU have set this figure as a maximum level in water intended for the consumption. In addition to nitrates, drinking water must also be disinfected to leave only safe levels of bacteria.

Essential for the food industry, taste is also impacted by nitrate levels and organic impurities. These compounds and organics must also be closely monitored to ensure the quality of the end product for other sectors that depend on pure water, such as pharmaceutical production. Even industries that only use water to enable a process need to ensure that nitrate levels do not negatively affect the end result, for example in textile and paper manufacturing, where color can be affected.

The challenge of reliable testing

The most common source of nitrates in water is from agricultural production, with nitrates from fertilizers and manure seeping into the soil, flowing into the supply of boreholes, streams, natural springs and reservoirs . Whether capitalizing on the benefits of a local source for provenance and taste, such as bottled spring water and beer, or using a private source to remove the higher cost of utility supply, organizations with their own water supply assume responsibility for testing for nitrates and organic impurities. Even for water companies, in water source areas sensitive to higher nitrate concentrations, they also need to be able to quickly and accurately check if more accurate nitrate testing is needed.

For most organizations, the financially viable and typical nitrate testing method is a periodic spot check, with a sample taken at intervals rather than continuously. Depending on the capabilities and facilities of end users, samples may be tested with their own analyzers or sent to a laboratory for analysis. To monitor organic impurity bacteria levels, the five-day pot test is the typical biological oxygen demand (BOD) pollution check, with a two- to three-hour test to check the chemical demand in organic oxygen (COD). Both tests measure a sample from a single instant. Whether an individual sample is tested by the end user or sent to a laboratory, the environmental conditions do not remain the same for long and a changing situation, such as overnight rain, could quickly increase the level of nitrates and impurities. . Any water produced between test results may be wasted if the parameters are found to have been exceeded. Therefore, reducing this period to almost zero avoids any waste.

Online monitoring

To increase the frequency and accuracy of measuring nitrates and organic impurities in water, giving a more reliable overall picture of levels, Bürkert has added two new sensor probes to its online water analysis system and in real time. The type MS09 nitrate sensor provides a constant and high precision measurement of nitrate with an accuracy between 0 and 50 mg/l. By using a xenon flash lamp to measure nitrate by UV optical absorption, organic and turbidity compensation eliminates negative influences to optimize measurement reliability.

Additionally, the MS08 SAC254 sensor, using 254 nm Spectral Absorption Coefficient (SAC) UV light, provides optical absorption measurement of organic impurities with reliable LED technology. Providing continuous monitoring of dissolved organic compounds including BOD and COD matter, the sensor also measures TOC (Total Organic Carbon) with monitoring of activated carbon filters to determine saturation levels.

Out-of-the-box integration

Continuous, automated monitoring eliminates the resources needed for periodic testing and the time spent waiting for lab test results. This technique also protects against the potential for high volume scrap. The sensors are also quick to install and configure, with plug-and-play operation with Bürkert’s online water analysis system via the included fieldbus gateway. With no moving parts, the sensors are also maintenance-free and the optical measurement guarantees long-term operation.

Bürkert’s online analysis system, available in the compact modular platform Type 8905 and cabinet format Type 8906, monitors all important water parameters on a single platform, now adding nitrates and from organic impurities to the measurement of pH, chlorine/chlorine dioxide, conductivity, redox potential, turbidity and temperature. Based on highly reliable CANbus, the popular protocol in the automotive sector, Bürkert’s EDIP network enables rapid integration with the PLC and Ethernet network of your choice.

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