A large utility provider serves communities across the northern region of Sydney, Australia. The company operates a sewage treatment facility that receives wastewater from homes and businesses and removes solids, nutrients and other contaminants through a combination of primary treatment, biological treatment, clarification and biosolids processing. The treated effluent is then discharged in accordance with environmental licence requirements.

As a key part of the regional wastewater network, the plant helps protect local waterways and catchments while providing reliable wastewater treatment for a large and growing population.

At the wastewater treatment plant (WWTP), ferrous chloride (FeCl₂) is dosed into the anoxic zone immediately downstream of primary sedimentation to support phosphorus removal and improve settling performance. Ferrous chloride reacts with dissolved phosphorus in the wastewater, forming insoluble compounds that are removed with the sludge, thereby reducing nutrient concentrations in the final effluent. It also promotes the formation of larger, denser flocs that settle more effectively in downstream clarifiers. This improves effluent quality, reduces suspended solids carry-over, and helps maintain stable and efficient plant operation.

Accurate dosing is critical, as under-dosing can compromise nutrient removal efficiency, while over-dosing increases chemical consumption and operating costs. In addition to process performance, chemical dosing systems present significant operational and safety challenges. Ferrous chloride is a corrosive chemical that is typically stored and transferred within bunded containment areas. As a result, technicians often need to enter these areas to perform inspections, maintenance, flow verification, or troubleshooting activities.

Application parameters

Such tasks may require additional personal protection equipment (PPE), chemical handling precautions, permit controls, and can increase exposure to slip hazards, chemical contact, and confined working conditions. Frequent manual intervention around dosing infrastructure not only increases maintenance costs but also elevates health and safety risks.

Flow instrumentation therefore plays a pivotal role in both dosing efficiency and occupational safety. Reduced confidence in flow measurement can lead to more frequent field inspections and manual verification, increasing technician exposure to hazardous areas and reducing operational efficiency. Because many conventional flowmeters struggle to maintain long-term reliability in aggressive chemical dosing applications, the plant operator placed particular emphasis on selecting the right flowmeter when the ferrous chloride dosing system was due for refurbishment.

The utility selected the OPTIFLUX 5400. KROHNE’s latest-generation electromagnetic flowmeter is fully designed to address these application challenges. It features a ceramic measuring tube with fused Cermet electrodes, providing excellent resistance to corrosive chemicals. Its optimised flow sensor design delivers reliable and accurate measurements in demanding low-flow chemical dosing applications, making it particularly well suited to ferrous chloride dosing systems.

The OPTIFLUX 5400 was supplied in DN6 (~¼") for installation on the dosing skid. The flow sensor features a stainless steel connection box and a protective coating for enhanced corrosion resistance. Instead of flanged connections, the wafer-style (or “sandwich”) version was selected, allowing the flowmeter to be installed between counter-flanges in a cost- and space-saving manner. The field-mounted version (F) allowed the signal converter to be mounted on the vertical dosing panel, providing good visibility of the backlit display and enabling operators to check readings from a distance.

The flowmeter features enhanced device and process diagnostics, with OPTICHECK technology integrated into the device (OPTICHECK technology built-in). Combined with integrated Bluetooth^® communication and the OPTICHECK Flow Mobile app, these functions enable straightforward parameterisation, commissioning and flow monitoring, as well as on-site verification supported by continuous self-diagnostics. A verification report can be generated at the touch of a button, without interrupting the process. Alternatively, the OPTICHECK DTM allows the device to be accessed from the control room for verification.

In addition, the OPTIFLUX 5400 incorporates MPO (Multi-Phase Operation) functionality. MPO uses advanced signal processing to maintain measurement operation even during significant process disturbances that can push conventional electromagnetic flowmeters to their limits. As a result, the flowmeter delivers reliable, repeatable measurements even in the presence of high levels of entrained gas or electromagnetic disturbance. This helps operators maintain confidence in dosing accuracy, improve process reliability and reduce unnecessary site visits and manual intervention in areas where hazardous chemicals are handled.

The KROHNE flowmeter provides highly accurate flow measurement of ferrous chloride, supporting precise dosing control of this corrosive chemical. This helps the utility maintain effective phosphorus removal while avoiding unnecessary chemical consumption.

With its ceramic measuring tube and fused-in electrodes, the OPTIFLUX 5400 offers excellent chemical and mechanical robustness. It significantly reduces the risk of leakage compared with electromagnetic flowmeters featuring conventional liners and electrode material, helping to lower whole-of-life ownership costs.

In addition, the magmeter features advanced signal processing, further enhanced by MPO (Multi Phase Operation). This helps maintain reliable, stable measurement even during major process disturbances.

A key advantage of the OPTIFLUX 5400 is that operators and maintenance personnel can perform function checks, commissioning, diagnostics and verification from outside the bunded chemical storage area using the integrated Bluetooth^® communication and a handheld or smart device running KROHNE’s OPTICHECK Mobile app. This reduces the need for personnel to enter areas where corrosive chemicals are handled, potentially reducing PPE requirements, permit-to-work procedures and exposure to chemical hazards. It also improves maintenance efficiency and reduces the time spent on site.

The OPTIFLUX 5400 is just one of many instruments in KROHNE’s extensive process instrumentation portfolio. This includes flowmeters based on six different measurement technologies, level and pressure transmitters, liquid analytical instruments and a comprehensive service portfolio – providing water and wastewater utilities with a single source for their process instrumentation needs.