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Quality Standards for Different Water Bodies
quality parameters considered are pH, DO, BOD, COD, coliform groups and n-hexane
Extract. Total nitrogen and phosphorus were added to the standards to prevent
eutrophication in lakes and coastal waters in 1982 and 1993, respectively. Several
factors were considered in the selection of water quality parameters while some
were omitted intentionally.
those omitted were some of the less common variables including conductivity, total
nitrogen, color, manganese and iron.|
rivers and lakes, parameters such as pH and DO, considered important to agriculture,
were included. For coastal waters, coliform groups and COD (Mn) were given high
priority. Because of its significant effect on fisheries, oil was added to coastal
water quality standards.|
organic index for rivers was based on BOD while that for lakes and coastal waters
were based on COD (Mn). The use of COD (Mn) for lakes and coastal waters was for
the following reasons.|
lack of BOD monitoring data compared to COD (Mn).|
treatment plants rely mostly on potassium permanganate consumption levels at intake
points as an index to the quality of raw water intended for drinking purposes.|
alkali-permanganate method was quite commonly used to monitor organic pollution
in coastal waters. Therefore, these data were considered when standards were established.|
methods for BOD analysis for coastal and lake waters are not well established.|
closed water bodies such as lakes, because of long retention times, biological
degradation of organic matters including phytoplankton is much slower than in
rivers. Therefore, five-day BOD tests were considered unsuitable while COD wasconsidered
to be more apporopriate organic pollution index.|
are limited data correlating COD (Mn) and BOD, and no fixed relationship between
the two was observed.|
Quality Standards for River
Five important water
quality parameters are pH, BOD. SS, DO, and Total Coliforrm. Six water use classes
from AA to E were established for rivers. Reservoirs having less than 10 million
cubic meter capacities are considered rivers rather than lakes. All standards
are defined on the basis of daily averages. Descriptions of each variable for
which standards were established are described as follows :
Generally, pH of rivers in Japan is around 7, except in estuaries. At most intake
facilities the pH is around 7.0. The pH data was taken by water authorities at
intakes having capacities of more than 5000 m3/days. When the pH is
more than 8.5, it interferes with chlorination during water treatment plant. To
ensure prevention of corrosion in the treatment plant and distribution system,maintaining
pH between 6.5-8.5 is desirable. If pH is outside the above-mentioned range, it
may cause irritation of eyes and adversely affects the growth of plants and marine
organisms. Low pH at the roots of rice plants severely affects the plants due
to the dissolution of salts, while high pH causes discoloration of leaves. Generally
speaking, the optimum pH range for proper plant growth is between 6.5-7.5, therefore
the pH standard for agricultural use is set as 6.5-7.5.
Self-purification aspects of rivers were given strong consideration when BOD standards
were established for these water bodies. Waters having a BOD of less than 1 mg/l
can be relatively unimpacted by humans and primary candidates for conservation.
About 31.4% , 29.9% and 13.8% of drinking water sources in Japan, have BOD values
less than 1 mg/l, 2 mg/l and 3 mg/l, respectively.If BOD exceed 3 mg/l, it affects
congulation and rapid sand-filtration processes conventional water treatment plants,
requiring expensive advanced water treatment.Therefore,BOD standards are set at
2 and 3 mg/l, respectively, for alass 2 and 3waters.
For class I fisheries,
BOD is set at less than 1 mg/l, since oligosaprobic fishes such as salmon and
smelt require water with a BOD Iess than 2 mg/l. For class II fisheries, BOD is
set at less than 2 mg/l, since mesoprobic fish such as carp require water with
a BOD Iess than 3 mg/l. For class III fisheries, BOD is set at less than 3 mg/l,
since class III fisheries require water with a BOD Iess than 5 mg/l. For class
E, conservation of environment, BOD is set at less than 10mg/l to prevent odor
caused by the anaerobic decomposition of organic matter.
solids (SS) |
Generally SS should be less than 25
mg/l to prevent any harmful effect to the aquatic environment. SS concentration
of more than 50 mg/l affect the proper functioning of fish gills. Turbidity exceeding
30 Nansan Turbidity Units (NTU), equivalent to 30 mg/l SS adversely affect slow
sand-filtration systems.Therefore SS standards of 50 mg/l and 25 mg/l were adopted
for fisheries and water supply use, respectively.
Suspended solids are also
significant for agriculture water use, because high SS decreases soil pore size
and causes a decrease in permeability. Field results indicate that 3-cm deposition
of SS remains permissible, therefore SS standards for agriculture water are restricted
to 100 mg/l. No SS Iimitations were provided for environmental conservation, but
there should be no solid refuse and floating solids that produce undesirable aesthetic
The DO standards were formulated considering
fisheries criteria. The national comnuittee on water pollution control resources
established guidelines in 1958 for water use DO. Relatively good water bodies
have more than 7.5 mg/l. For fisheries, hatching of salmon and trout rearing,
more than 7 mg/l DO is required. Other general aquatic organisms also require
more than 6 mg/l. In Ohio State, USA, the DO standard for fisheries is 5 mg/l.
The Japanese standard for class 3 fisheries is established at the same level .
Dissolved oxygen should be more than 5 mg/l for agriculture use, because DO Iess
than 5 mg/l interferes with root growth. The DO Ievel for the conservation of
the environment should be kept at more than 2 mg/l to prevent anaerobic conditions
that cause bad odors.
Coliform bacteria themselves are not necessarily harmful to humans, but they have
been used as indicators for pathogenic bacteria. Coliform organisms should be
non-existent in drinking water, and the most probable number (MPN) should not
exceed l/100ml considering the normal expected efficiency of 98% kills during
chlorination. Therefore, the safety limit to control for chlorination is 50 MPN/100ml
The council on living environment in the Ministry of Health and Welfare reports
that removal rate of coliforms is about 99% and 95% in slow and rapid sand filtrations,
respectively. The removal rate in rapid sand filtration can be improved to from
98 to 99% with highly proper maintenance. The standard was set as 1000 MPN/100ml
for class 2 water supply in which rapid sand filtration systems is operated with
conventional maintenance, considering that follow up with chlorination can safely
function at 50 MPN/100ml level. For class 3 water supply in which high level maintenance
can be expected, the limit is around 2500-5000 MPN/100ml. Therefore, the standard
was set as 5000 MPN/100ml. For bathing, 1000 MPN/100ml was established as the
quality standards for lakes
The standards include
both natural lakes and artificial reservoirs having capacities of more than 10
million m3. Seven water quality parameters were used to establish the standards.
Four classes, from AA to C, are set for water quality parameters such as pH and
COD. Five classes are set for nitrogen and phosphorus. Five water quality standards
are defined on the basis of daily average values. However, standards for total
nitrogen and phosphorus are defined as annual averages. Standards for pH and coliforms
have the same scientific basis as those for rivers.
Oxygen Demand : COD (Mn)|
COD (Mn) is used as an
organic pollution index including phytoplankton growth. A COD of less than 1mg/l
is assumed not to be caused by anthropogenic influence. Waters under this condition
are suitable for conservation of the natural environment. According to the drinking
water law, the standard value for KMnO4 consumption is 10mg/l, which is equivalent
to 2.5 mg/l of COD. A survey, conducted by the Ministry of Health and Welfare,
found that most lakes being used for drinking water supply have a COD of less
than 3 mg/ l.
Water quality for fisheries were classified as either oligotrophic
or eutrophic. In oligotrophic lakes, having very clear water, COD should be less
than 1mg/l that is required for oligosaprobic species such as rainbow trout. In
general, the COD of oligotrophic and eutrophic lakes containing oligosaprobic
fish such as smelt, should be less than 3 mg/l. In eutrophic lakes containing
carp, the COD should be less than 5 mg/l (Water Quality Standards for Fisheries,
1965). Less than 8 mg/l COD is desirable for waters used for swimming. High COD
interferes with oxygen transfer to the soil, resulting death of rice plants. Experimental
results show that a COD of less than 6 mg/l are desirable for agriculture use.
In general 8 mg/l of COD is acceptable for most industrial uses and for conservation
Generally speaking, if transparency
(Secchi Depth) is more than 3 meters, the SS concentration is assumed to be less
than 1 mg/l. For oligotrophic lakes, the transparency should be more than 5 m.
The annual average OECD transparency criteria is 1.5-3 m for eutrophic lakes and
more than 6 m for oligotrophic lakes. These standard values were determined based
on the characteristics of various Japanese lakes, including Lake Biwa, Lake Suwa,
and Lake Imba. Therefore, for purposes of conservation of natural environment
the SS concentrations should be less than 1 mg/l. From the viewpoint of conservation
of living environment, no SS Iimitations were provided, but there should be no
solid refuse and floating solids that produce undesirable aesthetic conditions.
Generally, the DO concentration in
clean lakes is more than 7.5 mg/l. The DO standards for fisheries are set at 7.5
mg/l for smelt and salmon and at 6 mg/l for carp and crucian. In some cases existing
plankton cause lower DO at night, therefore the allowable DO limit is 5 mg/l.
For conservation of the environment, DO should be kept at more than 2 mg/l to
prevent anaerobic conditions that cause bad odors.
quality standards for coastal water bodies
water quality parameters were used to coastal water standards. The main use for
coastal waters is fisheries. Oil content, total nitrogen and phosphorus were added
to the standards to control oil pollution and eutrophication. The three classes
A to C were set for general water quality parameters such as COD, while four classes
were set for total nitrogen and phosphorus, Similar to the lake standards, the
standards for general parameters are defined on the basis of daily average values,
while those for total nitrogen and phosphorus are defined as annual averages.
general, the pH of coastal waters varies between 7.8 to 8.3. Standard values for
class A and B were based on natural conditions. Within the 7.8 to 8.3 ranges aquatic
plants and organisms thrive best and the buffer capacity of coastal water is very
high. For class C, a wider pH range of 7.0-8.3 is established for conservation
of the environment.
oxygen demand : COD (Mn)|
This standard is related
to the protection of fisheries trom to red tides. Red tides are recognized when
diatom counts exceed several thousands per liter under stagnant water conditions.
Algal counts of less than 1000/ml and equivalent COD of 1mg/l are indicators to
control red tide. If the COD exceeds 3 mg/l and the DO concentration is less than
5 mg/ l, fish growth is affected. For standard class A, 1mg/l was subtracted from
3 mg/l to account for the influence of algae and red tide. Therefore the standard
is 2 mg/l.
Seaweed culture requires a relatively low COD. Alkali monitoring
methods for COD indicate that the level must be less than 3 mg/l COD for proper
growth of seaweed, while controlling the growth of filamentous bacteria. For industrial
cooling water, the COD should be less than 3 mg/l . A standard of 8 mg/l COD was
set to prevent bad odor caused by anaerobic decomposition .
The DO concentration in coastal water
is lower than that of rivers and lakes due to its high salinity. More than 5 mg/l
DO is desirable for fisheries. Monitoring data showed that more than 7.5 mg/l
DO was normal under natural conditions. To prevent anaerobic conditions that cause
bad odors, the DO should be kept more than 2 mg/l.
standard values are set based on the basis of those for rivers. The permissible
coliform counts for the protection of fisheries class 1 , and for the cultivation
of oysters is set at 70 MPN/100ml. This number is derived from the food and safety
law of the Ministry of Health and Welfare.
The normal hexane extraction procedure is
used to establish the standard for dissolved oils. Oil pollution in coastal waters
produce bad odors in fish, thus affecting their consumption. Oil film on the water
surface interferes with recreational bathing and respiration of marine organisms.
The Science and Technology Agency (STA) reported on the relationship between the
petroleum oil concentrations and the amount absorbed by fish. The limit for oil
concentrations to control absorption by fish is 0.01 to 0.1 mg/l. At the same
time Ministry of International Trade and Industry (MITI) reported 0.2-3 mg/l,
while the Fishery Agency reported 0.002-0.1 mg/l to control fish contamination.
From this it is obvious that fisheries are affected by very low oil concentrations.
Therefore, it is necessary to keep oil concentrations as low as possible in coastal
There is no standard method available for determination of very low
oil concentrations. However, n-hexane extract method (Japan Industrial Standard
Method) has been commonly used in Japan. The detection limit for this method is
0.5 mg/l for a 10-L sample, which is very low, therefore the standard value has
been defined as non-detectable. The present method is not applicable to deterrnining
oil pollution in rivers and lakes, because of the interference of other form of
organic matters. Therefore this method is only applicable for the detection of
oil in marine waters.