For decades, chlorine has played an important role in water treatment. Chlorine is the most widely applied disinfectant. The advantage of chlorine is that is can easily be produced and is relatively cheap. Chlorine effectively kills pathogens. It contributes to the reliability of drinking water produced from surface water. Chlorine tablets are used to disinfect water on locations where no collective drinking water treatment takes place. After the discovery of chlorinated by-products, the use of alternative disinfectants has increased.
Most European countries applied drinking water disinfection at the end of the nineteenth century and the beginning of the twentieth century. Chlorine was often used for this purpose. The eldest known application of drinking water disinfection in Europe was the addition of chlorinated bleach in Middelkerke (Belgium). In 1905, the London Metropolitan Water Board started applying drinking water disinfection after researching the disinfection mechanism of chlorine in water purification. The organization thought that chlorine disinfection was a suitable alternative for long-term storage of raw water. During storage pathogenic bacteria died out naturally.
The European Union has a drinking water policy of over 30 years. In 1998, it issued a Directive (98/83/EC) that established the minimum standards for water intended for human consumption. The Directive includes disinfectants and disinfecting by-products limits similar to those recommended by WHO. This Directive ensures that water intended for human use is safe and harmless. The Directive aims to:
The EU Drinking Water Directive (98/83/EC) applies to:
However, the Drinking Water Directive does not apply to:
In the Directive, a total of 48 microbiological, chemical and indicator parameters are encompassed and are subjected to regular monitoring and testing. When implementing the Drinking Water Directive into their own national legislations, Member States of the European Union can include additional requirements, e.g., they may regulate additional substances that are relevant within their territory or set higher standards. Member States are not allowed, nevertheless, to set lower standards. In respect to the prescriptions of the Drinking Water Directive in Europe, most drinking water production companies use chlorine as a disinfectant. It is added to water as chlorine gas, calcium hypochlorite or sodium hypochlorite. Ozone is added for flavor and odor control. For drinking water preparation from surface water, chlorine is used as a primary disinfectant in most cases. For groundwater treatment, which is a simpler treatment process, chlorine is often the only proper disinfectant. Countries in Europe use alternative disinfectants for drinking water disinfection, as well (Fig. 1). France, for example, mainly uses ozone. As early as 1906, ozone was introduced for drinking water disinfection. Italy and Germany use ozone or chlorine dioxide as a primary oxidant and disinfectant. Chlorine is added for residual disinfection. United Kingdom is one of few European countries that use chloramines for residual disinfection in the distribution network and for removal of disinfection by-products. Finland, Spain and Sweden use chloramines for disinfection occasionally.
Fig. 1. Disinfection applications in some EU Members States (Lenntech: http://www.lenntech.com/applications/drinking/drinking_water.htm)
In 1998, the Biocidal Products Directive was also implemented. Furthermore, on 22 May 2012 the Biocidal Products Regulation (BPR, Regulation (EU) 528/2012) was adopted, which repealed the Biocidal Products Directive (Directive 98/8/EC). The last one concerns the placing on the market and use of biocidal products, which are used to protect humans, animals, materials or articles against harmful organisms like pests or bacteria, through the action of the active substances contained in the biocidal product. This regulation aims to improve the functioning of the biocidal products market in the EU, while ensuring a high level of protection for humans and the environment. The BPR aims to harmonize the market at EU level, and simplify the approval of active substances and authorization of biocidal products. According to the BPR, a biocidal product is an active substance or a preparation that contains an active substance, which is intended to kill or deactivate harmful or unwanted microorganisms, by means of biological or chemical resources. Chemical disinfectants for water disinfection are also rated as biocidal products. When a biocidal product is used incorrectly, it may cause damage to human, animal or plant health, or to the environment. The countries of the European Union determine whether a substance can be used for certain purposes. When a company needs permission to apply a certain biocidal product, it must be requested from the government of the country. A demand must also be sent to the EU government. The governments of countries mainly decide whether a substance is permitted. This may cause a substance to be permitted by a certain European country, but restricted by the European Union and vice versa.