Nutrient Monitors Shine in Final Effluent Trial

The levels of nutrients, such as ammonium and phosphates, entering natural water resources is of great concern because these nutrients can either remove vital oxygen or lead to excessive plant growth and algal blooms, which harm wildlife through eutrophication. In addition, high levels of phosphate or nitrate in abstracted water significantly add to the cost of drinking water treatment. The management of nutrient levels is therefore dependent on the ability to monitor accurately and reliably, and as a result, a group of UK water companies organised a joint monitoring trial to determine the best instruments.

The trial involved the installation of turbidity, phosphate and ammonium monitors from the market’s leading manufacturers at two designated final effluent plants within the UK. HACH LANGE (UK) provided an AMTAX sc ammonium analyser, a PHOSPHAX sc phosphate analyser and a SOLITAX sc turbidity analyser for the trial.

The SOLITAX sc performed better than any of its competitors and as a result, Severn Trent Water has adopted the instrument in a framework agreement.

Summarising the report on the AMTAX sc and PHOSPHAX sc, John Moroney says “We are delighted to report that these analysers came first in almost all of the key performance measures, which included correlation to diurnal data, variance to laboratory data, and maintenance requirements. However, the panel decided to take the List Price as opposed to current framework prices for the commercial part of the assessment. However, the overall results are extremely encouraging and I know that our customers are very impressed with the technical performance of these units coupled with such low levels of maintenance. The manufacturers did not have access to their equipment during the trial, but over the 4 month period, the AMTAX required 2 hours of maintenance and the PHOSPHAX just one hour!”

The whole life costs of the Amtax sc for Ammonium and Phosphax sc for orthophosphate have been drastically reduced as a result of the chemistries employed. With the Amtax sc, a gas sensing electrode is utilised which means that reagent consumption is halved in comparison with traditional colorimetric analysers. For the Phosphax sc, the stability of the vanado-molybdate method, means that calibration is not necessary and therefore no calibration standards are required.

The results of this trial will be of great interest to process managers who have to comply with tighter discharge consents as a result of the Water Framework Directive. Couple this with the fact that HACH LANGE can now offer sample preparation systems that deliver continuous samples from the inlet all the way through to final effluent, John Moroney firmly believes these analysers lead the way in reliability, accuracy, stability and the lowest whole-life costs.