Attention, water utilities! Since July 1, 2024, stricter limits apply to chlorate ion levels in drinking water. But what exactly is the chlorate ion? Why is it a problem? How can its concentration be reduced? And what can a utility or operator do to comply with the new rules?
What is chlorate ion and how does it enter drinking water?
The chlorate ion (ClO₃⁻) is a decomposition byproduct of sodium hypochlorite (NaOCl), commonly known as bleach. Sodium hypochlorite is widely used for disinfecting drinking water.
The issue begins when:
- bleach is stored for long periods,
- kept in warm environments, or
- used in high concentrations.
These all accelerate decomposition – increasing chlorate levels in the solution, and ultimately in the water supply.
New limit: 0.25 mg/l
Az ivóvíz minőségi követelményeiről és az ellenőrzés rendjéről szóló 5/2023. According to Government Regulation 5/2023 (I.12.) on drinking water quality and monitoring requirements, the maximum permissible chlorate ion concentration is 0.25 mg/l, 2026. mandatory for all water suppliers starting January 12, 2026. This regulation aligns with the provisions of the (EU) 2020/2184 directive on the quality of water intended for human consumption.
This is especially critical in areas where:
- breakpoint chlorination (high-dose bleach) is used,
- ammonium or iron–manganese removal technologies are applied.
Why is chlorate ion a problem?
Accumulation of chlorate in drinking water may pose health risks, particularly for:
- young children,
- individuals with kidney disease,
- and those with thyroid disorders.
In addition, exceeding the legal limit during regulatory inspections can lead to serious consequences – fines, reputational damage, or even water supply restrictions.
What can be done? – Step-by-step solutions
- Optimize storage conditions
- Reduce the storage time of bleach – order smaller batches more frequently
- Store in a cool, dark place in sealed containers
- Use lower-concentration solutions (e.g. 45 g/l instead of 90 g/l)
- Regularly monitor chlorate ion levels
- Technological modifications
- Switch to chlorine gas disinfection (no chlorate, but high investment and complex permitting)
- Use potassium permanganate or ozone as oxidizing agents (they don’t generate chlorate)
- Innovative solution: on-site chlorine generation
On-site systems like our ClearGenX generators produce active chlorine from ordinary salt tablets via electrolysis. These:
- generate fresh chlorine with no chlorate accumulation
- eliminate the need for transporting or storing hazardous chemicals
- operate with cloud-based control and SCADA integration
- are safer and more cost-effective in the long run
In summary: Proactive response is key
The chlorate ion issue is not an isolated case – it’s a growing technological and regulatory challenge for many water utilities. The good news? Forward-thinking, practical solutions already exist.
