Using UV Fluorescence technology to monitor for organic pollutants in Flood Water

Climate change, Urban sprawl, reduced spend on infrastructure and poor historical planning have all led to an increase in flooding events and the increased severity and duration of such events.

Flood water afflicts not only physical damage on property and the environment but also carries a heavy burden of pollution which can have just as far reaching effects.

Flood events are here to stay - climate change will not be reversed in our lifetimes -if ever- and there will always be man made events caused by burst water mains and ruptured sewers.

Flood water will by its very nature seek out and fill below ground pipes, drains, septic tanks, sewers and culverts collecting discharge water from homes and industry and spreading the resulting mix of water, faecal matter, fats, oils and grease into everything it touches. The result not only a public health risk but also an absolute catastrophe for home owners and businesses whose homes and premises are now toxically polluted.

Although in many cases the evidence of pollution is all too evident this is not always the case and many will assume that because the water flooding their homes "looks" like clean water that it must be safe. This is of course far from the truth, bacteria and parasites can have severe implications on human health at concentrations where the human eye will not be able to detect them and only instrumented testing will reveal the true quality of the water.

For many years the water industry has relied on traditional sampling techniques to monitor water quality in a wide range of environments. Traditional tests such as BOD, PH, Dissolved Oxygen and Ammonia have formed the bedrock of monitoring parameters. There is however other ways to establish water quality and UV fluorescence offers an up to date solution for the investigation of Organic pollutants such as those found in flood waters.

UV Fluorescence works by using a light source to excite a water sample and cause certain compounds in the water to fluoresce. This fluorescence is then measured using a detector and filter which eliminates the excitation wavelength and passes the wavelength of the fluorescent material. The technique of course relies on the water sample having a fluorescent constituent and there are only a limited number of fluorescent compounds which are useful in determining water quality.

Large and expensive bench top instruments have now been replaced with small, lightweight field portable instruments such as the SMF4 from STS Instruments ltd which have the same sensitivity but give an instant reading in the field.

Currently operators have to make visits to a site in order to collect samples, log and send them in a prescribed format and under regulated conditions to the lab, wait for the samples to be processed and then collate the data generated into a usable format. The benefits to such a regime are that there is an on-going record and audit trail which can be used for evidence; however the overriding cost implication born by the water companies far outweighs these simple markers. Man hours for the operator, vehicle costs, equipment costs, consumables, lab overheads, lab staff, data collection and analysis all contribute to the real cost of monitoring.

The advantage therefore of taking the measurement in the field with the SMF4 is in getting an instant answer and being able to act immediately on that evidence whilst massively reducing the cost overheads associated with such sampling regimes.

UV fluorescence has been shown to be a particularly effective tool when looking for signs of organic pollution derived from human waste. Unlike standard 5 day BOD tests a fluorescent detector can be left in situ to monitor over a number of days or weeks and the data gathered will show a true representation of the water quality over time. It is impossible using a 5 day BOD to know that you are taking a representative sample of the normal state of a water body and the potential to miss a pollution event is clear. Further a BOD sample taken which returns a high figure is merely an indication of a moment in time - returning to the site to carry out further sampling may reveal little as the event may have already passed or be cyclical and not discharging at the time of sampling.

The SMF4 gives the operator the ability to take instant readings, make a quick analysis of the results and determine if further investigation is required. The difference is that the sample now has a history and a provenance which shows a much more significant picture than a single grab sample could ever do.

Fluorescence can also be of help where investigations into cross or mis-connections is required. Any built up urban area will have its particular issues but the certainty is that a percentage of all properties will have mis-connections between rain water run off to storm sewers and services destined for foul sewers. These mis-connections often occur where an extension or refurbishment has been completed and the services are mistakenly plumbed into the wrong sewers. There is a huge and ever growing scheme of investigations into sewer connections by teams of contractors paid by the water companies to identify and eliminate them.

Providing these teams with the instruments with which to carry out these tasks has, in many cases, previously been limited to rudimentary caging and visual assessment with sampling only carried out at the outfall into a watercourse.

Enabling these teams to actually physically map out the pollution flowing through a network of rain water sewers will vastly improve the efficiency and rapid resolution of cross connections. Rapid on site detection and quantification gives the operator an indication not only of the presence of pollution but also the severity of pollution leading to a more appropriate response in keeping with the situation at hand.

Embracing new technology is always a difficult step, but it is imperative that innovation is seen not as a weird science but as a means of improving what we do and how we do it for both a financial and environmental benefit.

For more information on the STS SMF4 fluorimeter please contact:
Jim Ward
Operations Manager
STS Instruments Ltd
01344 483563

For further information please email STS Instruments Ltd

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N.B. The information contained in this entry is provided by STS Instruments Ltd, and does not necessarily reflect the views and opinions of the publisher.

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