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Waste
water discharge
Nutrient load
from point sources
Biological
quality of small rivers
Waste
water treatment
Waste water discharge
The total amount of waste water discharge has
decreased by more than two times between 1991 and 2000. The
greatest decline occurred between 1991 and 1995, a period of
falling industrial and agricultural production. The decrease in
waste water amounts after 1995 indicates the efficiency of
environmental protection policy which has promoted implementation
of environmentally friendly technologies and efficient (decreased)
water consumption.
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Nutrient load from point
sources
The total discharge of nitrogen with waste water
rapidly decreased between 1991 and 1995, but stabilized after 1996
when the rate of economic production began to grow. However, since
1997 there has been a rapid increase in nitrogen discharge to some
river basins (Venta, Saka, Irbe and Bārta).
While the total phosphorus discharge in waste
waters to river drainage basins has decreased, this reduction has
been less than the decrease in the total amount of waste water.
This is to a great extent due to specific sources of phosphorus (for
example, synthetic washing detergents). During biological
treatment processes in waste waters, the phosphorus content
decreases less than the nitrogen content. Phosphorus is the
limiting element in eutrophication of freshwater ecosystems, and
therefore an increase in discharges is a significant threat to the
quality of inland waters.
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Biological quality of
small rivers
The biological quality of small rivers was studied
at 3920 monitoring stations during 1998-2000. The study was based
on the composition of macrozoobenthic organisms. In general, it
can be concluded that the river condition is good: two-thirds of
the rivers were classified as slightly polluted, one-fifth as
clean to slightly polluted, and only 3% are classified as polluted
rivers.
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Waste water treatment
National environmental policy has directly
resulted in a substantial increase (by two times) since 1991 in
the proportion of waste waters that are treated. The national
standards meet the requirements set by the Urban Waste Water
Treatment Directive (91/271/EEC).
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