Clasificación de Transporte

6.3.4.1 Connection rate and wastewater treatment

Over the past 15 years, significant progress was made in Europe regarding the proportion of the population connected to wastewater treatment and in wastewater treatment technology.

At the end of the 1990s about 80% of the population of the European Union were connected to public sewers and 77% to a wastewater treatment plant. In contrast to this, in the accession countries, only 55% of the population were attached to a public sewage system and 45% to a wastewater treatment plant. In the last 15 years, the focus of attention in the EU shifted from the mechanical (first step) to the biological treatment (second step) and/or to further treatment systems (third step), while in the accession countries, mechanical and biological treatment processes are still predominant (Pau Vall, 2001).

The Urban Wastewater Directive (Directive 91/271/EEC) establishes that the wastewater of all settlements with more than 2,000 PE (PE: Population Equivalent, 1 PE 0,06 kg BOD5/d) must undergo at least a second step treatment, and that discharges in areas that were classified by the member countries as particularly sensitive must undergo a further treatment (second and third step treatment)

Table 6.5 indicates the status of sewer connection and treatment for various countries as it occurred in the late 1990s (Eurostat, cited in Pau Vall, 2001). The data might be partially out-dated as they do not show the improvement of recent years in connection rates and the construction of new wastewater treatment plants as, for example, in Brussels, Antwerp, Milan, etc.

Table 6.5. Connection rate to a sewer system and to a wastewater treatment in some European countries. (Source: Eurostat, cited in Pau Vall, 2001).

Connection rate to a public sewer system

treated

The available data show that independent (private) wastewater treatment has some relevance in Norway, Austria, Hungary, Denmark and Luxembourg, with respectively 20%, 18.5%, 17%, 10.9%, and 7% of population connected (last column in Table 6.5). In this context, independent wastewater treatment means all private wastewater treatment plants (e.g. septic tanks) in areas where there is not a public sewer system. Independent decentralized wastewater treatment can be effective in rural areas and in scattered settlements. Nevertheless, no data about the employed treatment processes are available.

Figure 6.6 depicts the connection rate to sewer systems. A distinction has been made between private and public sewer systems. These are further divided into sewer systems with and without subsequent wastewater treatment. The countries are ranked on the x-axis with decreasing connection to a public sewer system with subsequent wastewater treatment.

Figure 6.6. Percentage of people connected to a sewer system in some European countries.

(Source: Eurostat, cited in Pau Vall, 2001)

6.3.4.2 Wastewater amounts

Wastewaters from point sources come mainly from private households (households and small businesses) and from industry. They are discharged into the environment either directly or after treatment.

Table 6.6 contains data of some countries which describe the wastewater quantities of private households and of the manufacturing industry on a per capita basis. The data show a large amount of wastewater from manufacturing industry in Sweden, Finland and Norway, while among the indicated countries, The Netherlands, Austria, and Slovakia show higher wastewater amounts from private households.

Table 6.7 shows wastewater quantities from different manufacturing businesses from selected countries. The manufacturing businesses need a considerable amount of water for cooling purposes. Process water and cooling water are included in the data. The water is partially discharged into the public sewer system, but mostly treated directly in the industry.

Table 6.6. Wastewater quantities in m³/capita·yr (Source: Eurostat, cited in Pau Vall, 2001).

The Netherlands 1990 30 81

Norway 1999 122 n.d.

Table 6.7. Wastewater quantities in Mm³/yr in different branches of the manufacturing industry for some selected countries (Source: Eurostat, cited in Pau Vall, 2001).

Country year

Belgium 1998 896.6 60.8 477.9 n.d. 15.9 52.0 226.9

Bulgaria 1998 355.3 37.7 95.0 3.1 13.0 30.5 126.0

Finland 1998 658.1 4.0 53.3 - 0.4 521.6 78.8

Germany 1995 6224.0 394.9 897.9 13.9 198.8 670.9 3537.9 The

Netherlands 1990 447.5 n.d. 8.0 n.d. 16.4 16.4 89.4

Norway 1999 540.2 3.1 152.2 - 0.9 1.4 301.9

Poland 1999 560.3 39.1 198.6 5.4 43.8 89.8 113.2

Romania 1999 496.8 22.6 155.9 6.5 11.6 n.d. 300.2

Slovakia 1998 321.0 8.9 28.4 n.d. 1.6 39.0 179.7

Sweden 1995 2054.6 70.1 n.d. n.d. 11.3 882.9 513.6

n.d.: no data

The wastewater quantity depends strongly on the structure of the manufacturing industry.

For the member countries from which data are available, most wastewater originates from the branch ‘Chemical industry, mineral oil production’: in Germany 57% and in The Netherlands 20%. The paper industry produces the most wastewater in Finland (79%) and in Sweden (43%). Also in the accession countries, the greater amount of wastewater stems from the branch ‘Chemical industry, mineral oil production’ (Pau Vall, 2001).

However, industrial water demand and wastewater quantities might differ largely as internal water recycling and water reuse within the manufacturing industry is often not included in the available data (see Box 6.2).

BOX 6.2. What are the right numbers for industrial water use?

Various statistics provide data for water quantities in industry. Many different terms are used, e.g. provided fresh water, utilized water, wastewater, etc. Each of them may or may not include cooling water. Further, the definition of industry may differ as power plants and the mining industry are considered or not.

The example of Germany might illustrate these facts. Table 6.8 lists quantities in Mm³/yr for the year 1998 (Statistisches Bundesamt, 2001).

Table 6.8. Industrial water quantities in Mm³/yr.

Wastewater Water supply

Industry total Of

which cooling

water provided utilized Of which for

cooling use factor Manufacturing

industry 6,008 4,243 6,207 30,226 22,486 4.9

Food 363 162 416 1728 834 4.2

Metal 822 667 873 6,018 4,925 6.9

Vehicle 86 45 93 1,989 1,092 21.5

Textile 175 131 183 242 172 1.3

Paper 547 264 610 3485 816 5.7

Chemical 3,455 2,639 3,422 11,836 10,594 3.6

Power plants (public) 25,984 25,842 26,559 67,734 57,457 2.6

Municipal wastewater 9,695 - - - - -

Table 6.8 indicates the large quantities of cooling water used in power plants. The use factor for water including cooling water is defined as the quotient of utilized to provided water, and it varies between 1.3 in the textile industry up to 21.5 in the vehicle industry. Use factors indicate the extent of water reuse among different industry branches.

The values are increasing, e.g. in the food industry from 3.5 in 1980 to 4.2 in 1998. They might vary in different countries and even in different regions as the driving force for water reuse in industry is quite often economics. Thus, reuse depends on water price and wastewater fees on the one hand, and on water treatment costs for adequate standards for internal reuse purposes on the other hand.