Sources:
UNSD/UNEP 2001, 2004 and 2006 questionnaires on Environment statistics, Water section.
OECD/Eurostat 2004 questionnaire on Environment statistics, Water
section.
OECD Environmental Data, Compendium 2006, Inland Waters section.
Footnotes:
- Refers to reticulated sewerage.
- Excludes Azores and Madeira Islands.
- OECD secretariat estimates based on regional data.
- Percentage of Homes with sewage system.
- OECD secretariat estimates based on MUD Municipal Waste Water Database.
- Information provided by the sanitary industry that operates in urban sectors to the Supervision of Sanitation Services respect to the percentage of residential buildings connected to the sewage system.
- Information provided by the sanitary industry that operates in urban sectors to the Supervision of Sanitation Services respect to the percentage of connected residential buildings to the sewage system whose collected water receive treatment.
- It corresponds to the city of Santo Domingo and represents 350,063 inhabitants.
- 2005 data.
- Data refers to agglomerations greater than or equal to 500 population equivalent.
- Population connected may include population not connected by pipe.
- No urban wastewater treatment plant.
- Percentages based on population living in individual housing.
- Estimates based on treated waste water.
- Include population not connected by pipe (whose waste water are collected in septic tanks and delivered to urban waste water treatment plants by truck).
- Public treatment: includes septic tanks (5% in 1998).
- OECD secretariat estimates.
- Data based on a sample survey covering 1911 municipalities.
- Data refer to England and Wales and to the financial year (April to March).
Definitions & Technical notes:
Waste water refers
to water that is discharged as being of no further immediate value
for the purpose for which it was used.
Public waste water collection system means a systems of conduits which collects and conducts urban waste water. Collecting systems are often operated by public authorities or semi-public associations.
Population with access to public waste water collection
system is the percentage of the population connected to the public sewerage
system. Public waste water
collection systems may deliver waste water to treatment plants or
may discharge it to the environment, without treatment.
Public waste water treatment plants refer to municipal treatment plants operated by official authorities or by private companies whose main activity is waste water treatment on behalf of local authorities. The treatment applied can be :
- mechanical, i.e. separates sludge through processes such as sedimentation, flotation, etc.
- biological, i.e. employs aerobic or anaerobic micro-organisms to separate sludges containing microbial mass together with pollutants.
- advanced, i.e. all treatments that are not considered mechanical or biological, particularly chemical treatments.
Population connected to waste water treatment is the percentage of the resident population whose waste water is treated at public waste water treatment plants.
Data Quality:
Data on population connected to waste water collection
and waste water treatment can be obtained from municipalities or
through household surveys. Household surveys usually give more accurate
results, since they do not rely on sometimes incomplete information
about or held by municipalities. In general, data quality can be
considered to be fairly good.
Policy Relevance:
Waste water discharged without treatment into rivers or lakes contributes to eutrophication of the water body, affecting the health of the river or lake ecosystem, reducing the viability of the fish, birds and other beneficial organisms, and the livelihoods of populations that rely on these resources. Waste water discharged into the sea without treatment contributes to eutrophication of coastal waters, also affecting ecosystems. Shellfish living near the discharge point will be contaminated, and where these are harvested by the local population, represent a major health risk. Provision of waste water treatment systems is therefore essential for both environmental and public health.
|
