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Dr Chlorine column lead image

The elephant in the room…

DWI annual reports? Not everyone’s cup of tea when it comes to bedtime reading I know. There’s a lot of interesting stuff in there though, especially if you read past the headlines and dig a little deeper.


Of particular interest to me with my Dr Chlorine hat on is the issue of the level of chlorine in the water at the customers tap.


The reports are incredibly detailed and show the number of instances in each company when (and where) residual chlorine levels exceed the regulatory level of 2mg/l (ppm). The incidence was very low with an industry average of 0.2 contacts per 1000 customers per year.


“In addition to investigating any abnormal change in the level of residual chlorine, water companies must also investigate and address any situation where the level of residual chlorine is not acceptable to consumers. Companies therefore have in place protocols for receiving, assessing and

recording contacts from consumers reporting chlorine- related tastes or odours in tap water.”


This is fine as far as it goes. My concern is this. The definition of acceptable is skewed towards “too much”. How many customers would contact a water company to say ” my water doesn’t taste of chlorine”? I’ll hazard an educated guess and say “none”.


Distribution systems are living “breathing” things. Chlorine residuals are known to drop throughout systems due to demand, time (especially in low flow sections of the network) and issues such as ingress at service reservoirs. At the far end of  a system I believe there are potentially instances when the water at the tap contains either no chlorine residual or an immeasurably  small level of chlorine.

These events do not appear to be a direct concern for the DWI. Not surprisingly perhaps then that few water companies have on line monitors in the network that will identify at risk zones.


For me “zero chlorine in the network” is a big elephant in the room.


There are a number of on line solutions to this measurement available and a few water companies are starting to gain valuable insight into the accuracy, reliability and TOTEX of the monitors and the value of the data and information they can provide.


If on line monitoring in networks was the norm, the risk of supplying potentially un-disinfected water could be greatly diminished. Secondary disinfection could be activated when needed, waters could be blended, potentially at risk water could be pumped into a service reservoir until remedial action could be taken.


Without on line measurement none of this is possible. You cannot manage what you do not measure.


Food for thought!



Waste Water and odour control…a subject always at the forefront of Waste Water Treatment Plants.


Q46SThe Environment Agency often impose large fines for odours passing the site boundaries, whilst available budgets limit how much can be done. The Health & Safety Executive are also involved as H2S is a toxic, and potentially flammable, gas.


However, ATi have a solid understanding of detection technologies used in odour monitoring and ultimately odour control.  Perimeter monitoring can be achieved at Parts Per Billion level, and inside the plant they can monitor at Parts Per Million level (and of course Lower Explosive Level).


ATi’s Q46S monitor is a unique sensor that eliminates water vapour bleeding for accurate H2S monitoring, where condensing humidity conditions are normal.  The unit is installed in the stack with no need for sample conditioning and the detection limit is around 20ppb.  At these levels the scrubber is working effectively, but in the event of a breakthrough, the reading will rise and the in-built alarms are activated before the legislative limit is reached.  This means that real time levels can be transmitted remotely, long before it becomes a problem or potential fine. The cost savings can be enormous!


Wet Well Monitoring, Ambient Air Monitoring, Perimeter Monitoring, Waste to Energy Gas Monitoring – ATi can look after all these. Please contact mark.bastable@atiuk.com for further help.


This entry was posted in ATi UK, Chlorine Monitors, Drinking Water, Gas Monitoring, General, Hydrogen Sulphide, Monitoring, Potable water, Training, Water Treatment. Bookmark the permalink.

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