Across the developed world failures in coagulation and filtration have led to outbreaks of Cryptosporidiosis and other illnesses caused by organisms such as Cryptosporidia and Giardia.
Continuous monitoring of the turbidity at the outlet of a filter is essential and even a legal requirement in some countries. Turbidity is a good measure of the clarity of the water and gives a single, understandable output for operators and is most sensitive to smaller particles (particles <1µm in size).
Particle Counters look at larger particles (usually larger than 2µm) and provide additional information over and above that provided by turbidity meters, particularly information regarding the break down of a filter and the passing of Crypto sized particles, often undetectable by a turbidity meter.
In the past many water companies, water authorities, local county councils, etc. have put turbidity meters on filters but not particle counters, largely due to the higher cost of particle counters.
Coagulation Failure Vs Filter Breakthrough
In most Cryptosporidium outbreaks there has been a failure of both coagulation and filtration. If coagulation fails then un-coagulated particles can pass straight through a filter. A turbidity meter would pick this up and show the operator that there was something wrong.
If, however, the filter starts to pass large, crypto sized particles, or to break down, or to ‘channel’ (a channel opens in the filter from top to bottom) it is unlikely that this will be picked up by a turbidity meter, but can clearly be seen with a particle counter.
In the past, to install a bank of 8 filters with a particle counter would have meant a capital cost of approximately €45,000 which has been a stumbling block for many.
Now Pi has made a multipoint analyser providing the same functionality for approximately €25,000 taking away much of the price objection.
Particle Counter – ParticleSense
Particle Counter Vs Turbidity…..Which One?
Turbidity Meters are more sensitive to smaller particles which are present if coagulation fails.
Particle Counters are more sensitive to filtration failures.
So which do you need?
You need both.
Why not contact us and see what we may be able to do to help you reduce your risk of a Cryptosporidia outbreak.