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Colorimetry for Potability: The Aztec 600

Jon PennApril 15, 2021
Jon Penn, Global Product Line Manager -
Continuous Water Analyzers

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Having ready access to clean, fresh water is something we often take for granted. Very few of us consider the various stages raw water from streams, rivers and lakes are taken through to ensure we have a plentiful supply of water safe to drink from the taps in our homes. Utilities companies are tasked with continuous process improvement, lower prices and keeping pace with growing demand from population growth and urbanisation.


Developments in Continuous Water Analyzers are changing the way the water utilities companies process water. Whilst traditional methods of sampling and testing have served the industry very well over the years, these new opportunities for real-time data are transforming water treatment efficiency.

There are a variety of parameters that require testing when it comes to potable water. In this blog we will look specifically at Aluminium, Iron, Manganese and Phosphate levels which can have a detrimental effect on water quality if left unchecked.
Aluminium levels in water can be attributed either to its natural presence in soil or as a result of its usage as a flocculant to remove impurities during water treatment processes. High levels of aluminium thought to be linked to Alzheimers disease, although aluminium in drinking water represents a tiny percentage of the average person’s total daily intake. Excessive aluminium levels can lead to kidney dialysis problems.
 
Iron in potable water does not present a health hazard. However, it can react with tannins in tea, coffee and some alcoholic drinks, resulting in the formation of a black sludge. It can also cause staining of laundry and items such as crockery and cutlery; discoloration of water fittings such as taps and can clog pipelines, pressure tanks, water heaters and water softeners.Iron may be naturally present due to local geological conditions or will water delivered through runs of cast iron pipes is particularly prone to high levels of iron.
 
Manganese occurs naturally in many sources of water. It has not been proven to pose a risk to human health but failure to properly control manganese levels will result in black deposits collecting in pipe networks which may turn potable water black if disturbed. This can stain laundry or can discolour vegetables during washing or cooking.
 
Phosphates are used by water companies to prevent lead from old pipes dissolving into the water, but can also be attributed to agricultural activities, animal wastes, human sewage, industry and detergents.
High levels can cause eutrophication or excessive growth of plants and algae on the surface of lakes, rivers and streams. By preventing light from penetrating through the water, these growths cause plants beneath the surface to die. Dead plants use up oxygen in the water as they decompose further reducing the oxygen available for other aquatic life.
 
 
Using colorimetric measurement to monitor potable water quality
Colorimetric measurement is used extensively throughout water, power and process industries. Simply described, the technique involves the colour-based measurement of a chemical in a solution. The colour comes from the absorption of certain wavelengths from the visible light spectrum within the range 400 to 700 nanometers (nm).
 
As many of the parameters to be measured are colourless, chemical reagents are used to create a reaction that forms a coloured compound. Adding the reagent creates a dilute solution of molecules that absorb light. By measuring the absorption/ passage of light through the coloured sample, the concentration of the parameter being measured can be ascertained.
 
 
The benefits of continuous online measurement
Continuous measurement using online analyzers replaces spot testing of samples. Spot testing relies on analysis of one sample at a given time and the accuracy is therefore questionable. By increasing the frequency of sampling, online analyzers provide a true indication of water quality under a variety of conditions. 

ABB’s Aztec 600 series of large case analyzers use the principle of colorimetry to measure concentrations of aluminium, iron, manganese and phosphates. Able to measure up to six samples an hour, the analyzers use an LED and detector to measure the passage of light through a sample. A single precisely controlled piston pump provides all the sample and reagent fluid handling for measurement, mixing and disposal. Measurements are taken before and after the addition of reagents to compensate for background color and turbidity. These measurements are compared against the calibrated values to calculate the value of the sample being measured.
The inherent benefits of these analyzers enable them to be used in a variety of applications, including residual coagulant monitoring. Using an online analyzer can help to regulate the dosing of the salts used for coagulation to ensure the treated water meets the required standards.

Cost saving benefits
As a means of continually monitoring water quality throughout the water treatment process, using devices such as those in ABB’s Aztec 600 analyzer series offers a range of cost saving benefits compared to manual sample collection and analysis.  
Foremost amongst these is the ability to optimize plant operation and output consistency through:
·         Reduced failures and maintenance issues caused by underdosing, such as plant shutdowns or increased cleaning of sand filters, or overdosing, such as discoloration or costs of chemical pH correction
·         Reduced operator intervention through the ability to carry out automatic monitoring
·         Decreased levels of sludge, leading to a reduction in the cost and resources connected with sludge disposal
 
Summary
 
The importance of water as a staple of life, coupled with the growing need to conserve water supplies, makes it critical to ensure that its quality is always safeguarded to minimize the risk of contamination. By using continuous online measurement, operators can ensure they are always in possession of the information they need to pinpoint problems and optimize water treatment efficiency. 


As a manufacturer and supplier of a wide range of continuous water quality analyzers and sensors, ABB can help you to choose the right water quality measurement solutions for your application.
 

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