Water treatment is always challenged by the complexity of water quality. Sudden pollution events, water sources containing mixtures of silt and algae, and water bodies where highly acidic groundwater mixes with surface water can all bring severe challenges to the overall operating environment of water supply systems. In practical water treatment and disinfection, accurately identifying key water-quality variables can help achieve more precise disinfection results. When the pH of water fluctuates, what is the key to ensuring stable disinfection efficiency and compliant treatment results? The answer lies in the proper selection of disinfectants and the scientific design of the disinfection treatment system.

In China, water-source conditions vary greatly because of differences in population distribution and local environments. High-algae, high-pH, high-organic-matter and other complex water-quality conditions differ significantly from region to region. However, the disinfection of complex water sources is often still carried out using relatively standardized treatment models without sufficient adjustment to specific source-water conditions. As a result, it can be difficult to maintain long-term stability in daily water treatment. This is why scientific management of pH fluctuations has become an important issue in water treatment.

I. The Underestimated pH Variable and Hidden Challenges in Water Treatment

In the water treatment industry, pH monitoring is not only used to quantify the basic condition of the source water, but also provides a scientific basis for determining how subsequent disinfection processes should be adjusted.

In many cases, water treatment plants focus primarily on maintaining pH within the target range of 6–9, while overlooking the more subtle effects of pH fluctuations. For example, mildly acidic water may indirectly increase the corrosion risk of metal pipelines, which may contribute to yellow or reddish water after distribution.

In addition, excessive attention to meeting ammonia-nitrogen requirements while overlooking the cumulative effect of pH fluctuations may reduce the system’s ability to withstand sudden changes in influent water quality, forcing the disinfection process to be adjusted again.

Another issue is excessive pH adjustment. Some water treatment plants may consume unnecessary quantities of chemicals because the buffering effects of carbonates and phosphates in water are not fully considered, causing pH to rebound after adjustment and resulting in repeated chemical dosing.

Although pH is only one of many water-quality parameters, it is closely associated with biological activity, chemical consumption and water-quality safety. If pH is not managed as a dynamic variable, the entire water treatment system may remain difficult to control and difficult to keep consistently compliant. This is precisely why pH management deserves greater attention.

II. Advantages of Chlorine Dioxide Reaction Mechanisms under Different pH Conditions

In water treatment and disinfection, chlorine dioxide is often highly regarded as a disinfectant. Although it would be an exaggeration to call it the “standard-setter” of disinfection, chlorine dioxide does demonstrate certain advantages when water pH fluctuates.

Studies have shown that chlorine dioxide can maintain disinfection activity across a relatively broad pH range of 4 to 10. This is mainly related to its single-electron transfer reaction mechanism. During oxidation reactions involving microbial cell structures in water, chlorine dioxide molecules consume relatively little H⁺ or OH⁻.

By comparison, many chlorine-containing disinfectants maintain stronger disinfection activity mainly within a narrower pH range, such as pH 6–8. When water conditions move outside the optimal range, their disinfection performance may decline, resulting in less stable treatment outcomes and potentially increasing the difficulty of controlling disinfection by-products.

III. Differentiated Value of XIUBA Products and XIUBA Solutions

China’s Standards for Drinking Water Quality clearly specify limits for certain disinfection by-products, including a chlorate limit of 0.7 mg/L.

Conventional chlorine-based disinfectants may have difficulty maintaining consistent performance across different water-source conditions. XIUBA chlorine dioxide disinfectants, by comparison, can maintain relatively strong activity even in more alkaline water conditions. In a variety of complex-water experiments, their oxidation performance has produced practical treatment results, which is one of the reasons why XIUBA chlorine dioxide products are used in applications such as hospital wastewater disinfection.

In dynamic water-quality simulation testing, XIUBA chlorine dioxide products achieved a CT value of approximately 60% of that required by chlorine-based disinfectants under the tested conditions, indicating stronger performance in certain pre-oxidation and algae-control applications.

For chlorite control in finished water, test results showed that concentrations could be maintained at around 0.5 mg/L under corresponding operating conditions. This provides additional operational flexibility when water quality fluctuates during different periods.

The disinfection performance of XIUBA chlorine dioxide products is also associated with the product’s high-purity chlorine dioxide generation characteristics and stable oxidation performance. These features support more accurate dosing under different complex-water conditions and help balance disinfection efficiency with compliance requirements.

XIUBA chlorine dioxide disinfection is relatively less affected by pH fluctuations and can therefore provide greater flexibility for different water treatment scenarios. XIUBA currently offers more than ten chlorine dioxide products with different concentration ratios and oxidation capabilities for water-treatment applications, together with online technical support and follow-up service for practical applications.