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Continuous monitoring of water quality

04 August 2019

Greg Wainhouse discusses the issue of continuous monitoring of various aspects of water quality as it enters the food and beverage production process.

Water is an essential element in the manufacture of food and drink, from washing produce to being the main ingredient and every application will have different water quality requirements. Having access to reliable, up-to-date data on water quality parameters is an important step in improving productivity and the quality of the final product.

In most cases, water will be supplied by the local water authority, which has the responsibility to provide a service within certain parameters. However, demands on treatment plants, seasonal changes and the age of the network can all result in variability in the quality of mains-supplied water. 

It is possible for the local authority to be unaware of an ‘out-of-consent’ incident until it is reported by consumers, but for some industrial customers, this notification will have come too late. Further, water authorities are required to add sufficient levels of chlorine to reach the furthest points of the network. This means that those closest to the water treatment works may receive some free-chlorine, which can damage sensitive equipment such as reverse osmosis membranes.

The alternative is a bore hole – usually on or near the manufacturing site – but this source can be affected by temperature, rainfall and local agricultural activities, which means it needs to be tested for quality at least every month, preferably more frequently. On-site treatment should be looking to remove sediment, dissolved iron, nitrates and bacteria.

Filtration systems
Whichever source is used, manufacturers employ a wide range of water treatment processes. Carbon filters can remove chlorine, biological contaminants and flavours, while a sand filter will remove iron. Ion-exchange processes are used to soften the water and both pH and conductivity monitoring can take place at this point.

Finally, filtration is used to remove unwanted particles, organic matter and bacteria. Depending on the quality of water required, manufacturers may use ultra-filtration, nano-filtration or reverse osmosis and each process can be equipped with sensors for turbidity, chlorine and pH to provide feedback on water quality.

Many businesses will use third-party services to monitor the water quality and address any issues on a regular basis. The problem with this approach is the frequency of the interventions and the reporting. In many cases, a monthly visit is deemed appropriate, so an issue could reasonably go undetected for over three weeks, which could affect a significant volume of products.

To resolve this situation, manufacturers need an accurate but flexible system that can be built around their application and connect directly into their control infrastructure. Some will only need pH and turbidity, while others require a more comprehensive solution that includes iron, chlorine, conductivity and oxidation reduction potential (ORP).

The latest sensing technologies may offer a solution. The Type 8905 online analysis system from Bürkert, for example, offers a multi-channel unit that can offer a solution to measure pH, ORP, conductivity, free chlorine and turbidity, chlorine dioxide and iron. The introduction of a chlorine monitor is an important addition as this chemical is often used in the disinfection process as a microbicide, disinfectant and sanitiser.

Bürkert has also developed an auto-cleaning process for the sensor cubes that uses a solution of clean, filtered water and mild citric acid, primarily to flush the turbidity sensor cube. The accuracy of the water analysis equipment can be checked using a hand-held cleaning and calibration module that connects to the unit. This enables operators to follow step-by-step maintenance instructions and procedures for using calibration fluids. All the while, the base unit continues to monitor the process and record the necessary data.

Simple installation
Investment in water quality monitoring equipment needs to be carefully assessed and often supporting evidence is required to obtain the capital expenditure. With this in mind, Bürkert offers short-term rental solutions for its online analysis technology enabling users to build a water quality profile while also creating a case to support a capital submission process.

For every business that needs to maintain high water quality standards and ensure the integrity of on-site water treatment facilities, taking advantage of advances in analysis technology can deliver benefits. 

Greg Wainhouse is UK water segment manager for Bürkert.

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