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European Water Disinfection Practices Parallel U.S. Treatment Methods

By Gerald F. Connell

European water disinfection practices are very similar to those in the United States and Canada. The formation of disinfection by-products (DBPs) also is a source of concern for European water suppliers, and it is expected the European Union (EU) will be implementing uniform maximum DBP levels in the near future.

A study conducted for the EU in 1996 and 1997 (Premazzi, et al. and European Commission Directorate) documented the methods of treatment for both surface water and groundwater.

Chlorination Widely Practiced

As in the United States, a large number of treatment plants use chlorine for disinfection in the treatment process and in the distribution system, although ozone is more frequently used for taste and odor control.

In over 90% of the surface water included in this study, chlorine was used as the primary disinfection technique. In addition, almost all of the public water suppliers use chlorine at some point in distribution systems. For most groundwater supplies, chlorination was the only treatment used. The study defines chlorine as chlorine gas, calcium hypochlorite and sodium hypochlorite (liquid bleach).

The accompanying table summarizes the various disinfection techniques used in the 15 countries of the EU that were studied. Eleven of the 15 countries predominately use chlorine for water treatment. Two other countries identify chlorine as a common practice, and two do not specify any particular type of disinfection method.

 

Summary of Disinfection Practices in European Union Countries

Country

Chlorine

Chlorine Dioxide

Chloramines

Ozone

UV

Austria

1

3


3

3

Belgium (a)

1

3


3

3

Denmark






Finland

1

3

3

3

3

France

2

2


2


Germany

1

1


2

3

Great Britain

1

3

3

3

3

Greece

1





Ireland

1



3


Italy

1

1


3


Luxembourg






The Netherlands (b)

2

2


1

3

Portugal

1





Spain

1

3

2

2


Sweden

1

3

2



Disinfection Methods -- 1. Dominant Practice, 2. Common Practice, 3. Occasional Practice
(a) Strong shift from chlorination to UV, particularly in ground water with THM formation potential
(b) UV implementation is expected.

 

Controlling Disinfection By-products

The reduction of DBP precursors is universally required of all surface water sources. All countries have established either a maximum admissible concentration (MAC) for total trihalomethanes (comparable to maximum contaminant levels in the United States) or a guide value (similar to U.S. maximum contaminant level goal). The MAC for various European countries ranges from 30 to 100 parts per billion with the guide value for some set at 1 part per billion.

Current practices to achieve recommended MAC levels vary among countries depending on the type and quality of their water sources.

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