Water / Wastewater - UK Focus iii
Water quality monitoring networks – issues to consider…
1. Timing
When asked about the anticipated timing of monitor installations, Philip Dunne MP said: “During the next pricing review period, which begins in January 2025, we will start to see these monitors being installed, and I would hope by the end of that fi ve-year period we should have close to full coverage of the outfalls which need to be monitored.”
In the short-term it is likely that WaSCs will wish to conduct pilot monitoring projects in the locations of greatest priority. These locations will be those that are already used for bathing purposes or for other water-based recreational activities such as fi shing, canoeing, kayaking, sailing etc.
2. Measurement Equipment
Mains power and communications may not be available at many measurement sites, so the monitors will need to be low- power; to run from solar panels, and offer fl exible communication options. These challenges have faced the Environment Agency for decades and have resulted in the development of portable and kiosk- based monitors that rely on multiparameter water quality sondes.
There are two main options for sonde
OTT HydroMet remote water quality monitoring station for long-term deployment
deployment. (1) directly in the river, attached to a structure and protected by a stilling well. (2) inside a fl ow-through chamber, testing pumped water samples.
Ideally, it should be possible to install the monitors without the requirement for capital works. This lowers costs and speeds up installation times. It also allows fl exibility in the choice of monitoring location because it would be simple to move the monitor if necessary.
HACH WQM Kiosk
In most lowland situations, multiparameter sondes such as the Hydrolab HL4 and HL7 will be appropriate for ammonia measurements. However, in some situations, such as upland rivers, greater sensitivity will be required, so the HACH Amtax SC Ammonium Analyser may be more appropriate.
The monitoring parameters required by the Section 82 will detect most pollution incidents, but if further investigation and laboratory analysis is likely to be necessary, it would also be possible to install a water sampler that could be triggered in the event of a pollution incident.
3. Datalogging and Communications Equipment
Most multiparameter water quality sondes also feature internal dataloggers so that data can be stored locally. However, in order to leverage the value of the data, it should be possible to transfer raw data and processed data (averages, maxima, minima, calculated values etc.) to a central server in almost real-time.
These sondes should also be able to issue alerts when pre-set conditions arise.
The method by which routine data and alarms are transmitted is likely to vary from site to site. In most locations cellular communications will suffi ce, however, coverage in remote locations can be poor so it should also be possible to utilise alternative methods, using OTT and Sutron technology such as radio or IRIDIUM® satellite.
4. Data Management and Display
The challenge for data management and display will be (1) the volume of data from such large numbers of continuous monitors, (2) extracting useful insights from the data, and (3) being able to present the data to stakeholders with different needs.
WaSCs will be able to extract a wide variety of useful insights from the data, such as:
• baseline water quality over different seasons • the level of harm (if any) of different outfalls • infl uence of other pollution sources • pollution alerts
• data to inform investment at wastewater treatment sites (especially smaller sites) • protection for drinking water treatment plants
The data should also provide visibility of water quality for the public. Here, a traffi c light display is likely to be more useful; helping river users to determine, for example, if it is safe to swim. However, the public should also be provided with an opportunity to drill down to measurement values in almost real-time.
Aquarius water data management software is being used to gather, manage and display data from thousands of measurement points in other countries, so it would be a good candidate for becoming the ‘National Environment Data Hub’ referred to by Water UK in May 2023.
OTT HydroMet Service 6. Site location
Practical considerations will vary from site to site. For example, landowner permission may be necessary at some sites, and at others there may be vandalism or theft concerns, dictating that the sonde will need to be submerged out of sight. The optimal monitoring location should be chosen to ensure that the difference between upstream and downstream water quality is accurately measured. However, fl exibility will be necessary to accommodate site variability.
Naturally, the location of the downstream monitor is of particular importance; it should be located at the fi rst suitable point downstream. To ensure data validity, the downstream monitor must not be more than 500m downstream from the point of cross-sectional mixing of the target discharge outlet.
Of the four statutory parameters, the maximum point of harm arising from ammonia is to be used as the key determinant for siting decisions. Ammonia was selected as the determining metric as it should be easier to identify the point of maximum harm, which is the fi rst point of full cross-sectional mixing.
The Defra consultation also listed the local factors that should be considered:
• river features or geography, including catchment type, variable annual fl ow, sources of dilution, and sources of diffuse pollution;
• the infl uence of other pollutant sources or signifi cant sources of dilution on the end data; and,
• health and safety considerations for access for maintenance or repair.
7. Leveraging the value of the data
Naturally, the availability of real-time continuous data will provide all stakeholders with a clear understanding of river water quality at any moment in time. It will also enable the water companies to target and schedule improvement measures, and to subsequently check the success of improvement measures.
AQUARIUS cloud-based software provides alerting and public notifi cation for events like toxic algal blooms
5. Service and Calibration
Many storm overfl ows are located at remote sites, so monitoring equipment should be able to operate unattended for extended periods of time. However, it will be necessary for sondes to be recalibrated regularly in order to maintain data quality. The sensor with the shortest calibration period is usually the ammonium ISE sensor, from which total ammoniacal nitrogen can be automatically calculated using values from the pH and temperature sensors. Typically, this sensor requires recalibration every 4 to 8 weeks. This work could be undertaken in the fi eld, but most practitioners simply swap sondes in the fi eld with pre- calibrated sondes, and return the fi eld sonde to a laboratory. This provides an ideal opportunity for sondes to be checked, cleaned and recalibrated. This will necessitate investment in calibration laboratories and suffi cient service engineers to conduct site visits at the required frequency.
Conclusions
The size and complexity of the new monitoring requirements will impose a requirement for cooperation among potential suppliers, so OTT HydroMet and HACH will be well-placed to help meet the requirements.
The recent publicity surrounding storm overfl ows will help to raise awareness of key issues such as:
• reducing peak fl ows during storm events • natural fl ood management • sustainable urban drainage • limiting toilet waste to the 3 Ps • identifying the root causes of river pollution
Improvement measures will be costly, so it is essential that decisions are underpinned by accurate reliable data. The new monitoring networks will provide a comprehensive picture of not just the impact of storm overfl ows, but of river water quality generally. This will dramatically improve our understanding of the factors affecting water quality so that improvement measures can be targeted and effective.
Author Contact Details
Sutron XLink 500 transmits water quality data back to the offi ce via cellular or IRIDIUM® satellite.
Dr Liam Goodes - Sales & Business Dev. Manager, OTT HydroMet • Tel: +44 (0)7512 319704 • Email:
liam.goodes@
otthydromet.com •
www.otthydromet.com
WWW.ENVIROTECH-ONLINE.COM
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