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A new version of Intellitect Water’s water quality monitoring system, the Intellisonde FE, has been installed on the final effluent of Wessex Water’s Holdenhurst wastewater treatment plant.

The new system can continuously monitor final effluent without the need for chemicals or frequent maintenance and calibration, according to the company.

The unit has been operating at Wessex Water’s Bournemouth facility since January 2010 and initial results indicate that this technology could bring the advantages of online monitoring to a larger proportion of wastewater treatment plants.

The Intellisonde FE is a very small, multi-parameter monitor that is able to run unattended for weeks.

Intellitect Water claims that low capital and operational costs will mean that it will become possible to install continuous monitors at plants for which the costs were previously considered prohibitive.

The Bournemouth trial was conducted adjacent to traditional online monitoring instruments.

Mike Robinson, Wessex Water’s regional waste scientist, said: ‘The trial is proceeding very well, with the Intellisonde FE producing measurements that closely mirror data from our other monitors and from manual tests.

‘For example, we employ traditional, online, single-parameter monitoring instruments at the outfall and we also utilise portable instruments to measure parameters such as clarity and ammonium,’ he added.

The Intellisonde FE is located in a flow-through chamber that is fed by a submerged sampling pump located in a sump.

A level gauge ensures that the sump does not pump dry.

The trial unit has been fitted with a small strainer to prevent any possible accumulation of dirt in the measurement chamber.

However, it has been necessary to occasionally remove small stones and snails, although these did not have any effect on the measurements.

Inside the sonde head, tiny solid-state sensors continuously monitor conductivity, pH, temperature, turbidity and ammonium.

The unit can simultaneously log at intervals between one minute and one hour on all parameters.

Measurements are retained on an internal data logger, but data is transmitted via GPRS to a dedicated server, which feeds a website to enable 24/7 access to almost-live water quality information.

The units are also able to provide an analogue output that could interface with a water company’s regional telemetry system, providing a closed-loop system for data protection.

The graph shows recorded data during February and March 2010, and Robinson reported that no calibration or maintenance was necessary during this period.

The data shows several weeks of unattended use, with reported ammonia levels working well with a second instrument installed at the same point.

The simultaneous monitoring of other parameters can indicate possible causes of variations in effluent quality, which may, in turn, lead to more efficient treatment management.

For example, reduced conductivity may indicate a correlation between rainfall and ammonia.

Without this data, it would be more difficult to diagnose causes of variations in effluent quality, particularly at unmanned treatment works where data is restricted to discrete samples during the day.

The ammonium peaks in this data are recorded during the night.

David Vincent, Intellitect Water’s technical director, believes that recent changes in monitoring requirements will enhance the demand for the new Intellisonde FE.

He said: ‘The Environment Agency [EA] is currently engaged in a programme of passing the responsibility for collecting, analysing and reporting discharge quality to operators.

‘At the same time, the level of monitoring required will depend on the level of pollution risk that each discharge represents.

‘Consequently, operators such as the water industry and the process industries will have to develop a monitoring strategy that meets the requirements of the EA,’ added Vincent.

The EA conducts infrequent audit checks on the plant effluent.

However, the responsibility for maintaining effluent quality lies with the water company and Robinson believes that continuous monitoring offers operational benefits.

He said: ‘One of the main advantages of 24/7 data is that it helps to identify spikes and enables process operators to determine the cause of the problem and thereby to adjust the treatment process.

‘Continuous data also helps with the identification of treatment deficiency and data for multiple parameters provides a better understanding of the whole process.

‘For example, conductivity and temperature can provide useful supplementary data,’ added Robinson.

Occasional sampling and analysis can be lower in cost than online monitoring; however, the main disadvantages are that a pollution incident could go undetected between sampling times and infrequent data does not support process optimisation.

In contrast, however, Vincent said that the Intellisonde FE will provide continuous access to effluent quality data and thereby help to further raise compliance levels.

The Intellisonde FE will also provide financial advantages; it is priced for volume deployment, well below traditional effluent monitoring systems, which means that it will be cost effective for a larger proportion of works and will save the cost of sampler visits and analysis.

Intellitect Water

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