Chlorates in drinking water

Water utilities play an essential role in modern society: It is hard to imagine how difficult our daily lives would be with no access to clean water flowing on demand from a tap. Unfortunately, despite recent progress, 24% of people lacked access to safely managed drinking water services in 2020, according to United Nations figures.

Before this water reaches us, it typically needs to be treated to meet safe drinking water criteria. These treatments depend on the water’s origin, for example whether it is groundwater or water taken from a lake or a river. Applied treatments vary according to source water composition and local regulations, but in essence they consist of removing contaminants through a combination of physical, chemical, and biological processes, and then keeping it safe until it reaches the consumer. 

Over the years, advances in technology and medical knowledge have led to treatment improvements, as well as changes in water quality requirements. For instance, microplastics or endocrine disruptors were not considered at all just a few decades ago, while nowadays they are an area of increasing concern. Today, greater attention is also taken in both the choice of disinfection method and in limiting the corresponding disinfection by-products (DBPs) resulting from the treatment. Limits and recommendations vary depending on local and regional regulations, which is why it is always recommended to familiarise oneself with these.

One of these regional regulations is the Drinking Water Directive from the European Union. A list of new parametric values is included with the 2020 publication. Among these values is chlorate, which is a known DBP from chlorinated disinfection, but it can also be found naturally in sourced water due to its use in pesticides a few decades ago.

In this paper, we will share insights on the regulatory environment, we will discuss the parameters to be considered in order to minimise chlorates and we will review the most common technologies used for drinking water disinfection.