Carbon dioxide (CO2) has become an increasingly popular option for water treatment applications over the past few years. But what exactly is CO2 used for when it comes to treating water? In this detailed guide, as a professional water treatment supplier, we’ll cover everything you need to know about the role of carbon dioxide in water treatment.

Why Use CO2 in Water Treatment?
There are several key reasons why water treatment plants are turning to CO2 instead of other options like sulfuric acid or sodium hydroxide for pH adjustment and contaminant removal:
- Safer Alternative: CO2 is far less hazardous than caustic alternatives which require extensive safety precautions. This makes operation and maintenance much easier for plant workers.
- Environmental Impact: Being a naturally occurring gas, CO2 has a superior environmental profile compared to synthetic chemicals. There’s less risk of spills or contamination.
- Cost-Effectiveness: Though CO2 requires a higher upfront investment, the long term savings from reduced infrastructure corrosion, simpler operation, and other factors make it cheaper overall.
- Better pH Control: Dissolved CO2 forms carbonic acid which allows for more controlled, gradual pH reduction compared to sudden drops when using liquid acids that can damage pipes.
Now let’s get into the specific water treatment applications where CO2 really shines.
Key Uses of CO2 in Water Treatment Processes
There are three main ways that water treatment plants are utilizing CO2 to enhance treatment efficiency:
1. pH Adjustment
The most common use of CO2 is for pH control. pH is a critical parameter that impacts everything from pathogen inactivation to the performance of clarifiers and filters.
By bubbling CO2 through water, carbonic acid is formed which provides a safe, reliable way to lower pH. The level of CO2 injection can be precisely controlled in response to online pH measurements.
pH adjustment with CO2 is employed at various points in the treatment train – from influent wastewater neutralization to conditioned water stabilization at drinking water plants.
![CO2 pH adjustment process diagram]
2. Remineralization
Another growing use case is remineralization of softened or desalinated drinking water using lime. This is important for stabilizing corrosion control and limiting release of metals from distribution piping.
CO2 helps this process by enabling calcium carbonate saturation for stronger scale-forming potential despite the water being slightly corrosive. The CO2 essentially provides a “buffering” capacity.
3. Disinfection Byproduct Control
Some plants are also finding value in using CO2 to help curb formation of disinfection byproducts (DBPs) like trihalomethanes (THMs) and haloacetic acids (HAAs) which can develop when free chlorine reacts with natural organic matter.
The CO2 helps by lowering pH which shifts the equilibrium away from converting chlorine into more reactive chlorine species that produce these carcinogenic DBPs. This allows utilities to meet regulatory limits without having to reduce free chlorine residual targets.
Implementing CO2 Treatment Systems
If after reviewing the many advantages CO2 offers for water treatment, you’re looking to implement a CO2 dosing system at your plant, there are a few key considerations during design and installation:
- Storage tanks should be robustly designed and kept properly chilled to maintain liquid CO2 supply pressure. Vaporizers are also essential upstream of injection points.
- Diffusers or injectors with proper spreader nozzles should be positioned to promote rapid dissolution and homogeneous mixing throughout the water flow being treated.
- Online instrumentation like pH sensors is critical for dynamically controlling CO2 dosing rates to respond to fluctuating water quality conditions. This allows optimizing CO2 usage.
- Worker training is paramount so staff understand how to properly operate and maintain CO2 equipment as well as handle minor issues that may arise.
Following these best practices will help guarantee your CO2 treatment system can deliver all the benefits highlighted here for years to come. Reach out now if we can help assess whether CO2 is a good fit for enhancing your plant’s treatment strategies.
Key Takeaways on CO2 and Water Treatment
- As a safer, greener, and cost-saving alternative to caustics, CO2 is growing rapidly across municipal and industrial water treatment applications.
- Main uses are pH control, stabilized water for distribution system protection, and regulating disinfection byproduct formation.
- When implemented properly with robust storage, controlled injection, and staff training, CO2 can significantly bolster treatment plant performance and final water quality.
What’s your take on CO2 for water treatment? Have you used it or considered using it at your plant? I’d love to hear your experiences in the comments below!