One of the greatest challenges in delivering Section 82 is land access. As most storm overflow sites are on private land, water companies will need to engage with landowners for permission to install instrumentation as well as ongoing maintenance and calibration visits. There are no statutory rights afforded to water companies in the Act. Therefore, building relationships with landowners will take time and incur additional costs.

Further to the requirement for land access, planning permission will also be required to deploy technology into the river.

Hydrological modelling of the watercourse is required before monitors are installed to help with understanding mixing zones as part of the site profile and to ensure correct positioning of the monitors.

Biofouling is the build-up of sediment, biofilms, or even barnacles on sondes due to algae, silt, and microorganisms from harsh aquatic environments. This is a year-round problem, but especially prevalent in summer months. This biofouling can skew data, making it near worthless. Regular field visits to clean equipment can be costly. It is estimated that maintenance costs due to biofouling can consume up to 50% of operational budgets.

Alternatively, technology such as central wiper systems and sapphire glass surfaces can provide anti-fouling in low-power applications without the need for an in-person site visit.

Ammonia monitoring is the primary issue with Section 82 legislation. Accuracy is hard to deliver consistently. Wet chemistry and colorimetric analysis are still the most common methods used for quantifying aqueous ammonia in the laboratory. However, as with any optical engine / spectrometry, it's great in controlled conditions in a laboratory, but when used in the field, there can be associated problems with fouling of the lenses and, in certain cases, turbidity may affect the light intensity. Find out more about solving the problems of ammonia monitoring here.

Sondes, battery packs, and solar panels are all expensive pieces of equipment and are at risk of vandalism or theft. Some locations will be on private land and easier to manage. Some will be publicly accessible and water companies and suppliers will need to think carefully about how to manage this risk.

Sondes left in the water will require a power source to ensure continuous monitoring. For the reliability in the stream of data, fixed kiosks would benefit from being mains-powered, with backup generator power where possible. Solar power could be an option to top up the battery and allow the unit to run for longer periods. The level of wattage of the solar panel will impact the ability to continuously power the unit, as well as cost and mobility.

Calibration is required prior to install as well as periodically to ensure the sonde is working effectively. Sondes can be pre-calibrated before they are installed, or on-site during installation. Sensor drift (when a sensor starts to become unreliable and needs recalibration) requires consideration regarding the length of time between recalibration visits.

Once sondes are installed, ongoing maintenance will be required periodically to ensure they continue to work effectively. Water companies will need to appoint suppliers who can deliver this service on a regular and continuous basis.

That is the question. Is the sonde the correct solution? The sonde has been used since 1993. And since then, many new products have been designed to measure more parameters, with greater accuracy. However, suppliers and water companies alike need to work together to understand if sondes are the answer to Section 82, or if an alternative solution will be more efficient and effective.

The traditional approach of boots-on-the-ground monitoring works for reactive monitoring. However, monitoring 23,000 sites nationally will surely require an alternative, fixed-site approach.