In the municipal sewage treatment industry, fluctuations in water quality seem to occur at unexpected times, and one of the most easily overlooked issues is the increase in alkaline wastewater. When the pH exceeds the specified range, the biochemical system will become unstable, the equipment may be affected, and ultimately it will also affect the compliance with discharge standards. So, is there a method that can stabilize pH while being safe, economical and environmentally friendly? The answer is gradually becoming clear.
As the industry’s focus on green technologies and sustainable development continues to rise, a method based on CO₂ neutralization has gradually gained attention from municipal plants. It not only reduces the risks brought by the traditional addition of strong acids, but also provides a new solution for sewage treatment plants. This article will start from the actual municipal scenarios, systematically introduce the principle, application and advantages of this method, and help water managers better master the strategies for treating alkaline wastewater.
Why Is Municipal Alkaline Wastewater Worthy Of Attention?
The water sources treated by municipal sewage treatment plants are complex, and the reasons for the increase in alkalinity are not singular. For instance, changes in the incoming water from industrial zones, by-products from chemical deodorization, the reflux of filtrate from sludge dewatering, and even the high alkalinity of the water supply system itself may all cause the treatment system to face a relatively high pH.
When the pH remains persistently high, problems start to arise:
- The biochemical system is affected: The activity of microorganisms decreases, especially for PH-sensitive nitrifying bacteria, which will reduce the removal efficiency of ammonia nitrogen and COD.
- Increased equipment risk: Highly alkaline water can accelerate equipment corrosion, especially in the structure of pumps, pipelines and regulating tanks.
- Discharge compliance pressure: If the discharged water exceeds the standard for a long time, it may face penalties from environmental protection supervision and economic losses.
Therefore, for municipal plants, finding a stable and reliable neutralization method is not only a demand for process optimization but also a necessary measure for safety and compliance management.
The Limitations Of Traditional Acid Neutralization Methods
For many years, municipal plants have often used strong acids such as hydrochloric acid and sulfuric acid for neutralization. Although the method is straightforward, the risks and costs that come with it cannot be ignored.
- Safety risk: Strong acids are highly corrosive and require dedicated storage and operating procedures.
- Obvious pH fluctuations: Once the dosage is not properly controlled, the pH of the water body is prone to overadjustment or rebound.
- By-product impact: Acidic salts can increase the load on downstream water treatment, such as raising the concentration of sulfate or chloride ions in water.
- Accelerated equipment wear and tear: Long-term use may lead to accelerated wear of pipes, pumps and mixers.
These restrictions often make it difficult for municipal plants to maintain operational stability when facing sudden alkaline water volumes or persistently high alkalinity.
The Principle And Advantages Of CO₂ Neutralization
Rather than using strong acids to quickly lower the pH, CO₂ is more like a gentle and controllable way of regulation. After dissolving in water, it forms carbonic acid, which reacts with the alkaline components in water (such as hydroxide and carbonate) to adjust the pH to a stable range. Meanwhile, the formation of bicarbonate forms a buffer system, preventing the water body from experiencing drastic fluctuations during the neutralization process.
The advantage of this method lies not only in its safety but also in its friendliness to the process system:
It will not introduce excessive salt to avoid affecting the subsequent biochemical sections.
The pH adjustment is slow and stable, which is conducive to protecting the microbial community.
Reduce corrosion to equipment and extend its service life.
It can be seen from this that CO₂ neutralization is not only a chemical treatment method, but also a strategy that takes into account both process safety and environmental sustainability.
How Is CO₂ Neutralization Used In Municipal Plants
Although the concept sounds novel, the operation mode of CO₂ neutralization is relatively simple and can be flexibly integrated into the existing processes of municipal plants.
1. The sources of CO₂ are diverse
Municipal plants can choose different sources of CO₂ :
Purchased liquid CO₂ : Convenient for use in short-term or specific projects;
Anaerobic digestion biogas: The biogas produced by anaerobic digestion of sludge contains CO₂ and can be directly utilized.
Surrounding industrial waste gas: such as flue gas from boiler rooms or waste incineration plants, after dust removal and purification, can also become a source of neutralizing CO₂.
2. Injection method
CO₂ is usually added to water bodies through bubble diffusers or pipe mixers. The form of microbubbles can significantly enhance the dissolution efficiency, enabling alkaline water to complete pH adjustment in the shortest time.
3. Automatic control system
To ensure water stability, pH probes are often installed at key locations such as regulating tanks, return water or dewatering filtrate. By adjusting the dosage of CO₂ through the automatic control system, not only can excessive dosage be avoided, but also fluctuations in water volume can be dealt with, achieving refined management.
The Advantages Of CO₂ Neutralization In The Municipal Industry
From the perspective of practical application, CO₂ neutralization has brought multiple benefits to municipal plants:
- Enhanced safety: No need to store or handle strong acids, reducing personnel risks;
- More controllable operation: The buffering effect ensures a stable pH adjustment and prevents water fluctuations.
- More user-friendly process: It does not increase the salt burden and reduces interference with subsequent treatments.
- The cost advantage is obvious: especially for large municipal plants, the cost of CO₂ addition is lower than that of long-term purchase of acid agents.
- Wide application scenarios: It can be used in regulating tanks, return water, dewatering filtrate, and emergency treatment before discharge.
With these advantages, CO₂ neutralization can not only deal with sudden increases in alkaline water but also serve as a long-term pH control strategy for municipal plants.
Final Words
Alkaline wastewater is not the most prominent problem, but it has a profound impact on the stability of water plants, the lifespan of equipment and compliance with discharge standards. With the increasing demands of the municipal industry for safety, cost and environmental protection, CO₂ neutralization technology has gradually demonstrated its unique value.
More importantly, this approach can also utilize CO₂ as a resource, forming a closed loop of carbon reduction and recycling, which is in line with the sustainable development goals of cities. In the future, an increasing number of municipal plants will regard CO₂ neutralization as an important tool for stable operation and environmental management.
By scientifically and systematically applying CO₂ neutralization, municipal plants can not only effectively control alkaline wastewater but also strike a balance among operating costs, safety management and environmental impact, achieving a win-win situation for water quality management and green development.
Molewater offers a complete municipal wastewater treatment system, covering a full-process solution including alkaline wastewater neutralization, sludge dewatering, odor control and automatic pH adjustment. The system design integrates CO₂ neutralization technology, which is safe, environmentally friendly and efficient, and can meet the needs of municipal plants of different scales.If you have any questions about the design, installation or operation of the system, please feel free to contact us at any time for professional consultation and technical support. Molewater will provide your water plant with customized solutions to help urban sewage treatment develop in an intelligent and sustainable direction.
