Monitoring & metering D
esigned and manufactured in Switzerland, Swan’s water quality analysers have a global reputation for accuracy and long-term reliability, but as the company’s John Saxton says:
“The accuracy of a measurement can only be as good as the quality of the sample, and this can be one of the more challenging aspects of wastewater monitoring. We have therefore worked closely with specialists in this field to develop the new Sample Filtration Cabinet, which combines the quality of a Swan Analytical analyser with a best-in-class sampling system.” Phosphate is an essential nutrient, and is necessary for example, in low concentrations in biological wastewater treatment, but excessive concentrations can cause significant ecological harm. It is therefore common for phosphate to be included in environmental permits at municipal and industrial wastewater treatment plants. Phosphate can be removed from wastewater by dosing with precipitants such as Ferric Chloride. However, dosing to excess can be very costly and inefficient, so it is common practice to continuously monitor phosphate levels for dosing control, and for demonstrating discharge compliance. Swan’s online AMI Phosphate instruments combined with the Sample Filtration System, have been designed specifically for both applications.
BACKGROUND
Phosphate is a key nutrient in the maintenance of aquatic animal and plant life. However, it is also considered to be one of the most important pollutants in surface waters. Excessive quantities, through natural accumulation or derived from human activities such as wastewater treatment and agricultural runoff, can stimulate the rapid growth of algae, resulting in algal blooms. This reduces the amount of light available for plants and can lead to oxygen depletion, bacterial growth and eutrophication. In addition, some algal blooms produce toxins that are harmful to other organisms. High phosphate concentrations can therefore cause enormous ecological and aesthetic damage to streams, lakes, rivers and oceans.
In England, the Environment Act 2021 and
“With this technology, wastewater process managers can
minimise precipitation costs, optimise performance and maintain regulatory compliance.”
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WASTEWATER PHOSPHATE MONITORING… IT IS ALL ABOUT THE SAMPLE!
Swan Analytical Instruments has launched a new Sample Filtration Cabinet which ensures the reliable provision of representative samples to its continuous phosphate analysers. The climate-controlled cabinet houses all of the key instrumentation and employs innovative sampling technology to ensure reliable, regulatory compliant measurements.
the supplementary Environmental Targets Regulations 2023 have set targets for reducing the levels of phosphorus, and other contaminants, that are released into fresh and coastal waters. As a consequence, phosphate limits in treated wastewater discharged into water courses are being tightened.
MONITORING PHOSPHORUS – THE CHALLENGE
The most prevalent compounds of phosphorus are derivatives of the phosphate (PO4) anion, with orthophosphate being soluble and the only bioavailable form. Orthophosphate is therefore a key measurement parameter in wastewater process control. Inlet variation of orthophosphate concentration is common in sewage and wastewater treatment plants, which increases the necessity for monitoring to inform dosing control. In addition, some of the organically bound phosphorus and polyphosphates are converted into orthophosphate during the wastewater treatment process, which can influence the total orthophosphate concentration over time. This conversion is specifically optimised by some wastewater treatment plants to improve the overall balance of phosphorus recovery. For these reasons, orthophosphate concentration is the appropriate control parameter for optimising precipitation treatment.
Precise dosing of precipitants is extremely
important for phosphorus elimination/recovery to avoid over- or under-dosing. The key to cost-efficient precipitant dosing is robust online measurement analytics that can determine the orthophosphate parameter accurately and reproducibly. Orthophosphate precipitation typically takes place in three process locations:
1. Pre-precipitation (before the biological stage) – early elimination of orthophosphate.
2. Simultaneous precipitation (in activated sludge) - combining biological and chemical processes.
3. Post-precipitation (after the biological stage) - reduces residual phosphate in effluent.
With high levels of contamination, these process sampling points are always very demanding. A highly effective filter mechanism is therefore necessary to ensure that there are no blockages and that samples are truly representative.
MONITORING PHOSPHORUS – THE SOLUTION
Swan’s Sample Filtration Cabinet is an all-in-one solution for orthophosphate analysis in wastewater, facilitating problem-free sampling and analysis in
August 2026 Instrumentation Monthly
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