Climate change isn’t just reducing the amount of water available – it’s also impacting the quality of source water and putting a strain on Australia’s treatment facilities.
As hotter and drier weather becomes the new norm, climate change is opening the doors to severe bushfires, and unpredictable storms and floods.
While the risk of water scarcity looms large due to less rainfall over time and extended droughts, these long dry periods followed by heavy rains can also impact the health of our waterways and disrupt the quality of our source water.
At the same time, Australia’s population is booming, which not only increases the demand for water, but increased urbanisation also means more surfaces that are impervious to water, like roads and buildings, which prevent rainwater from soaking into the ground and being naturally filtered. Instead, more pollutants such as oil, metals and sewage are carried into our water supply, particularly during heavy rainfall events.
These issues aren’t isolated, however; climate change increases the risk of bushfires, the ash then hinders the soil’s ability to absorb water and makes it prone to erosion1 – then if an extreme flooding event comes along afterwards, that soil is washed into the waterways. This soil is often full of chemicals used in fire suppression activities, while the ash and charcoal release numerous nutrients, metals and toxins into the waterways that otherwise wouldn’t be there.
At best, this disrupts the balance of metals and chemicals – such as ammonia, fluoride, aluminium, iron, manganese and phosphate – found in source water, and at worst it introduces dangerous toxins that prevent the use of that catchment entirely, exacerbating water scarcity.
Customer expectations around the quality of drinking water are also higher than ever, and as cost-of-living increases water treatment facilities are also feeling the pressure to tackle these challenges while ensuring prices remain as affordable as possible.
Good measure
The climate, population and geographical conditions of source water greatly determines the amount of chemicals that need to be used during the treatment process.
The Australian Drinking Water Guidelines (ADWG) sets out a strict limit for the amount of certain chemicals that can be in our drinking water – but if the quality of the source water varies considerably then it must be closely monitored to ensure optimal treatment.
To navigate these challenges and take immediate action when an issue arises, utilities need to be able to analyse the current process conditions in real-time. Manual testing methods are not only time consuming, but they take up operators’ precious time. Continuous water quality analysers like the ABB Aztec 600 series arms water treatment facilities with the information they need to adapt to any changes in water quality – but as every treatment facility has its own unique challenges water authorities need to choose a solution that can work the way they work.
Starting from the source
Depending on the nature of your facility, automatic water quality analysers can typically assist with all the key stages of the water treatment process – and in ABB’s case, the Aztec 600 series is designed to work both as a single system or part of a multi-stream configuration, and can even be integrated with existing analysers2.
As raw water enters a treatment facility, the initial levels of ammonia, iron, manganese, phosphate and aluminium can be measured before the application of treatment processes including aeration and chemical dosing.
As the levels of these substances fluctuate depending on conditions like climate, ground erosion, thermal changes and disturbances of water sources, closely monitoring these initial levels helps streamline the treatment process, optimise resource and avoid wasted chemicals.
Ammonia can be found naturally as a result of biological degradation and can enter both ground and surface water through runoff of waste products, such as fertiliser. It is also used as part of the treatment process – carefully measured doses of chlorine and ammonia are added to water to monochloramine, which works as a disinfectant.
However, it’s essential to have just the right balance of the two chemicals – too much ammonia can encourage the growth of nitrifying bacteria, whereas too little can reduce the efficacy of the disinfection process and create harmful byproducts.
Similarly, water scarcity has led to a rise in the levels of naturally occurring minerals like manganese, aluminium and iron in raw water sources – however a range of factors causes variation in these quantities, not just between different service areas, but on a day-to-day basis.
Elevated concentrations iron and manganese can impact the taste and colour of drinking water, as well as stain of pipes and fittings. Iron can also be introduced via corrosion of cast iron water mains, and damage to these assets exacerbates this issue.
Aluminium is also used as a flocculant to remove impurities during water treatment processes, and helps reduce the turbidity and bacterial content of water prior to the final stages of treatment and disinfection.
The ADWG strongly encourages authorities to keep acid-soluble aluminium concentrations as low as possible, preferably below 0.1mg/L, but levels must not exceed 0.2mg/L3. While the there is no health-based guideline set for aluminium at this time, according to the National Water Quality Management Strategy there is considerable evidence that aluminium is neurotoxic.
While a key component in fertiliser, polyphosphates, such as sodium hexametaphosphate, are also sometimes used to prevent corrosion in water treatment facilities.
Under the ADWG, sodium hexametaphosphate should be used in such a way that any contaminant or by-product formed by the use of the chemical does not exceed guideline values for that particular chemical4.
By arming themselves with real-time information about the quality of the water going into the facility, operators can ensure a high level of accuracy in the dosing stages and reduce the additional costs associated with overdosing. If an issue does occur, then crews are empowered to immediate action to prevent failure.
ABB’s Aztec analysers uses advanced optics to ensure that measurements remain precise, even in challenging conditions. Each Aztec 600 analyser incorporates automatic LED intensity adjustments during calibration, compensating for drift and fouling to provide stable readings even in environments with high suspended solids, a problem common in water sources following bushfire events or heavy rainfall.
VIP treatment
Close control of treatment processes can help reduce energy consumption, optimise chemical usage and minimise wastage from incorrectly treated water.
After any pre-treatment processes have been completed, analysers can once again be used to monitor things like iron or manganese concentrations. Where a clarification process is used, water may also be monitored to assess whether coagulants used in the treatment process are being under or overdosed.
Online monitoring provides plant operators with an early warning of any changes to the treatment process, enabling operational decisions to be made in near real-time. This level of process control is not possible with manual testing alone, where potentially important events that occur between less frequent manual sampling can be missed.
Colourmetric analysers like the Aztec 600 that include automatic two-point calibration enable operators to verify analyser’s performance against standards of known concentration.
Self-cleaning abilities can also improve accuracy by ensuring the optical cell and analyser tubing used for sample measurements remain free of residual particles between each analysis. The Aztec 600, for example, includes patented mechanical cleaning function uses the piston movement to wipe the optical cell with every measurement – which is particularly important when measuring raw waters where optical contamination can be a real issue.
The Aztec 600’s piston and optical sensor use air to mix the sample and reagents, eliminating the cost and maintenance associated with mechanical or electrical stirring systems. The inherent product design and auto-calibrating features means that maintenance is only required annually.
The finishing touch
After the filtration process is complete, continuous analysers can then take a final sample to ensure that the treated water meets the required standards and can also assist with the fluoridation process.
The ADWG say that fluoride has been shown to improve dental health, however high concentrations can result in a range of health issues5 – so accurate dosing is vital.
However, underlying levels of natural fluoride in certain areas as can complicate this – and aspects like climate, water consumption and groundwater quality need to be taken into account to determine the optimal approach.
Situating a sampling point for any online monitoring instrument in a location where the sample is likely to have been sufficiently mixed but before the water is drawn off to the distribution network can help maximise accuracy.
Again, solutions like the Aztec 600 Fluoride offer built-in alarms prevent incorrect dosing of fluoride, and can detect process failures before they affect the quality of the water leaving the plant. This process optimisation also increases plant efficiency; reducing capital and operating costs, as well as chemical and energy usage – cost savings than can then be passed on to customers
To aid in a smooth integration into existing infrastructure without causing significant downtime or operational challenges, the Aztec 600 analysers are designed easy installation and minimal maintenance.
The system’s advanced communication protocols – such as Ethernet connectivity, Profibus DP v1.0 and SD memory cards for data storage – allow for easy integration into existing control systems, offering real-time monitoring and enabling remote data access.
Online instrumentation takes the guesswork out of water quality management, and continuous analysers like the Aztec 600 are the key to overcoming treatment challenges and ensure a secure water supply for all Australians. But with a host of variables to consider, utilities need a solution that can work the way they need it to.
For more information, visit the ABB website or contact bella.garg@au.abb.com for expert advice
