Welcome to Our Factory for a Visit! Free customized disinfection solutions
Have you ever noticed that tap water can sometimes carry a faint unusual odor?
At such times, even if chlorine dioxide has already been dosed during treatment, the taste and odor control effect may still be unsatisfactory, and the sensory quality of the treated water may show little improvement.
Why does this happen?
In drinking water treatment, chlorine dioxide is a water treatment agent that provides both oxidation and disinfection functions.
It can be used for microbial control and for the oxidation of certain compounds responsible for taste and odor problems. Compared with free chlorine, chlorine dioxide can generally reduce the formation of some typical halogenated organic disinfection by-products. However, chlorite, chlorate, and other related transformation products still need to be controlled during use.
For this reason, chlorine dioxide is used in some drinking water treatment and pre-oxidation applications.
One important application of chlorine dioxide is the oxidation and control of certain taste- and odor-causing substances in water.
For example, when raw water contains certain phenolic compounds, free chlorine may react with them and form chlorophenolic compounds with noticeable odors.
Because chlorine dioxide follows a different reaction pathway, it can oxidize some phenolic odor precursors and, under suitable water quality and operating conditions, help reduce the risk of chlorophenolic odor formation.
Chlorine dioxide can also oxidize certain reducing odor compounds such as some sulfides.
However, its treatment effectiveness varies significantly among different algal metabolites. It should not be assumed that simply dosing chlorine dioxide can remove every type of odor.
Chlorine dioxide is not a universal odor-control agent that works equally well for every compound.
Its actual performance can vary considerably depending on the source water, target contaminant, and operating conditions.
Therefore, when treatment performance is unsatisfactory, the first question should be:
What substance is actually causing the odor?
The first response should not simply be to increase the chlorine dioxide dose.
First, the composition of raw water varies greatly from one region to another.
Natural organic matter, reducing inorganic substances, and other oxidizable constituents can create different levels of chlorine dioxide demand. This consumes part of the applied chlorine dioxide and reduces the amount that remains available to oxidize the target odor compounds.
For example, in source waters with a high natural organic matter load, a fixed chlorine dioxide dose may be insufficient if the actual oxidant demand of the water is not taken into account. In such cases, a large portion of the chlorine dioxide may already have been consumed before the target odor compounds are adequately controlled.
In chlorine dioxide treatment, particular attention should also be paid to chlorite and chlorate as relevant transformation products.
Their formation and concentrations may be affected by raw water quality, chlorine dioxide generation method, generator operating conditions, and actual dosage.
Therefore, by-product issues associated with other oxidation processes should not be directly transferred to chlorine dioxide systems without distinction.
Temperature is another important factor.
At lower temperatures, the rates of some oxidation reactions may decrease, which can affect the reaction efficiency between chlorine dioxide and certain odor compounds.
However, seasonal changes in water odor should not be attributed to low temperature alone. They may also be related to source-water switching, algal variation, reservoir stratification, organic loading, and distribution-system water age.
Many different compounds can cause taste and odor problems in water, and chlorine dioxide does not react with all of them at the same rate.
For certain reducing sulfur compounds and some phenolic compounds, chlorine dioxide may show relatively good oxidation reactivity.
However, for two important causes of earthy and musty odors—geosmin and 2-methylisoborneol (2-MIB)—the direct oxidation capability of chlorine dioxide is generally more limited.
Therefore, if the main odor problem in the raw water is caused by geosmin or 2-MIB, simply increasing the chlorine dioxide dose or extending contact time may not provide an ideal technical or economic result.
Excessive dosing may also lead to:
higher chlorine dioxide residuals;
increased chemical consumption;
greater pressure to control chlorite and chlorate.
In such cases, it is often more appropriate to evaluate activated carbon, ozone, or other enhanced treatment processes according to the actual water quality.
In addition, some organic odor precursors may form new intermediate products during oxidation.
As a result, the sensory quality of treated water does not necessarily improve under every condition.
If a new abnormal odor appears after chlorine dioxide treatment, the cause should be identified through water quality analysis and specific odor-compound testing rather than by inferring a fixed reaction pathway based only on smell.
The chlorine dioxide dose, dosing point, and contact conditions directly affect taste and odor control performance.
If the dosage is too low, the oxidant demand of the raw water may not be satisfied, and the target odor compounds may not receive sufficient oxidation.
If the dosage is too high, or if mixing and reaction conditions are poorly controlled, chlorine dioxide residuals may become excessive and affect the odor and sensory quality of the drinking water.
Therefore, the goal should not simply be to “dose more,” but to establish an appropriate chlorine dioxide demand and dosing control range based on actual source-water conditions.
The removal efficiency of chlorine dioxide for different odor compounds should also not be described using fixed universal percentages.
Actual removal performance can be affected by:
initial contaminant concentration;
chlorine dioxide dose;
pH;
water temperature;
contact time;
natural organic matter;
and other competing reactants.
For this reason, rather than stating that a certain compound will always be removed by 95%, 90%, or 60–80%, it is more appropriate to determine the actual removal performance through site-specific water quality and process testing.
When dealing with complex taste and odor problems, water treatment personnel should first identify the source of the odor and then develop a targeted treatment strategy based on source-water characteristics and the target contaminant.
Seasonal monitoring should include raw-water algae, odor compounds, temperature, organic matter, and other key water-quality indicators.
During periods of elevated algal risk, the response should not simply be to increase chlorine dioxide dosage in advance.
A more appropriate approach is to adjust pretreatment and oxidation strategies according to the specific algal species, algal density, odor compounds, and potential toxin risks.
If toxin-producing algae are involved, the potential for oxidation to damage algal cells and release algal toxins should also be evaluated.
Water treatment plants can gradually build historical datasets for different seasons and source-water conditions, including:
chlorine dioxide demand;
actual dosage;
contact time;
chlorine dioxide residual;
changes in odor compounds;
chlorite and chlorate concentrations;
and overall treatment performance.
Based on these data, an appropriate dosing control range can be established and dynamically adjusted as raw-water conditions change, rather than relying on a fixed dosing rate throughout the year.
For compounds such as geosmin and 2-MIB that may not be consistently controlled by chlorine dioxide alone, source-water-specific evaluation can be conducted for:
powdered activated carbon;
granular activated carbon;
ozone;
and other combined treatment processes.
For example, ozone–activated carbon treatment may be considered as an enhanced option for certain odor problems.
However, combined processes also introduce additional control requirements.
For example, when ozone is applied to bromide-containing source water, bromate formation should be carefully controlled.
Therefore, combined treatment processes should not simply be copied from another water treatment plant. They should be selected based on the actual source-water quality and validated through process testing.
Fluctuations in chlorine dioxide taste and odor control performance do not necessarily mean that the chemical has suddenly “failed.”
In many cases, what has actually changed is:
source-water quality;
the target odor compound;
water temperature;
chlorine dioxide demand;
contact conditions;
or the overall treatment process.
Therefore, when a water treatment plant encounters an odor problem, the first step should not be to blindly increase chlorine dioxide dosage. It should first answer:
What is the odor? Where does it come from? What compound is causing it? Is chlorine dioxide suitable for treating it?
Only after the target contaminant has been identified can the appropriate oxidant, dosing conditions, and combined treatment process be selected.
China’s GB 5749-2022, Standards for Drinking Water Quality, establishes requirements for the sensory characteristics of drinking water and related water quality parameters.
Therefore, water treatment plants should confirm compliance through actual monitoring of finished water and distribution-system water rather than simply assuming that water will be free of unusual taste and odor under normal conditions.
Ultimately, chlorine dioxide is not a universal odor-removal agent that is equally effective against every taste- and odor-causing compound.
Its value depends on one key principle:
Identify the source of the odor first, then match it with the appropriate dosing strategy.
When chlorine dioxide alone cannot provide satisfactory control, activated carbon, ozone, or other enhanced treatment processes should be considered, while chlorite, chlorate, and other related by-products are controlled at the same time.
Only by combining source-water monitoring, target-contaminant identification, dosing control, and appropriate treatment combinations can chlorine dioxide perform more consistently in the applications where it is best suited and provide more reliable technical support for drinking water taste and odor management.
Chlorine dioxide can efficiently disinfect drinking water, is not easy to generate carcinogenic disinfection by-products, and will produce chlorite and other residues, which must comply with the national standard limits. It shall be accurately added according to the water quality and equipped with qualified equipment and process. The safety of compliant use is high. Water supply enterprises need to do a good job in control and monitoring to ensure the safety of water quality.
Chlorine dioxide is a who Certified grade A1 safe disinfectant with high sterilization efficiency, few harmful by-products, strong water quality adaptability and multiple water purification functions; Compared with traditional chlorine disinfection, it is safer and more environmental friendly, and can be widely used in drinking water, sewage treatment, food and beverage disinfection and other fields.
Chlorine dioxide can sterilize and remove odors in water treatment plants and is unlikely to generate trihalomethanes. However, in practical applications, it can fail to remove odors or even produce new unpleasant smells. Organic matter in the water source, bromide ions, and low temperatures can affect treatment effectiveness. Furthermore, its removal capacity for geosmin and 2-methylisoborneol is limited, and improper dosage can also cause odor problems. Water treatment plants need to strengthen water quality monitoring, dynamically adjust dosages, and, when necessary, combine ozone-activated carbon processes to ensure that the odor of the treated drinking water meets standards.
When adding chlorine dioxide to the water pumping station to maintain residual chlorine in the pipeline network, it is necessary to avoid pipeline corrosion caused by local high concentrations. The dosage should be accurately controlled by flow-linked dosing, pipeline mixing, and online residual chlorine monitoring, while also paying attention to under-scale corrosion, thus balancing disinfection and pipeline protection.
Pipeline network renovations can easily alter the hydraulic conditions of the network, increasing flow velocity and creating stagnant zones that consume chlorine dioxide, leading to fluctuations in water quality. Water plants can ensure the quality of water supplied to the end points through monitoring and prediction, dynamic chemical dosing, pipeline flushing, and the activation of contingency plans.
Traditional chlorine disinfection is prone to producing carcinogenic halogenated by-products; chlorine dioxide oxidizes and kills bacteria, with almost no such by-products, good inactivation effect, and the ability to remove odor and inhibit algae, but it generates by-products such as chlorite, requires higher raw material and operation and maintenance costs, and is suitable for water plants that can be upgraded and managed in a coordinated manner, rather than being simply and directly replaced.
This study simulates a scenario where a small town's water plant experiences a sudden pollution outbreak caused by medical wastewater and the failure of chlorine dioxide disinfection. It analyzes the reasons why pollutants consume disinfectant and provides four-step emergency response measures. Furthermore, it proposes long-term improvement suggestions in terms of monitoring, supplies, contingency plans, and drills to enhance the emergency response capabilities of small and medium-sized water plants.
Switching from sodium hypochlorite to chlorine dioxide disinfection in water plants is not just about replacing equipment; it's a complete system upgrade. Chlorine dioxide disinfection is more effective, produces fewer byproducts, and has lower overall costs. However, many water plants only replace the hardware, neglecting personnel training and adapting management systems. The core of this transformation is shifting from experience-based to scientific operation.
The actual dosage of chlorine dioxide at water treatment plants often exceeds the theoretical value, influenced by factors such as reducing agents in the water, sediment in the pipe network, water quality fluctuations, and byproduct consumption. By leveraging monitoring and local operational data to optimize dosage, we can provide water quality assessments and customized dosage solutions.
A water plant in a county in Qinghai Province with a capacity of 30,000 cubic meters per day was found to have excessive byproducts from sodium hypochlorite disinfection. It was upgraded to a Xiuba chlorine dioxide dosing system. Four on-site tests showed that residual chlorine dioxide in the effluent was within acceptable limits, achieving stable compliance. Water treatment upgrades need to be tailored to specific on-site conditions to create a complete closed-loop disinfection process.
Northeast of Huangshan Road and Chuangye Intersection, Small and Medium sized Enterprise Entrepreneurship Industrial Park, Shanwang Town, Linqu County, Weifang City, Shandong Province
Copyright © 2025 by Shandong Huashi Pharmaceutical Co., Ltd All Rights Reserved
Language
中文
Русский
Chlorine Dioxide Disinfectant Manufacturer
