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Water Quality Standards for Different Water Bodies

Water 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.

1)Among those omitted were some of the less common variables including conductivity, total nitrogen, color, manganese and iron.
2)For 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.
3)The 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.
*A lack of BOD monitoring data compared to COD (Mn).
*Water 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.
*The alkali-permanganate method was quite commonly used to monitor organic pollution in coastal waters. Therefore, these data were considered when standards were established.
*Standardized methods for BOD analysis for coastal and lake waters are not well established.
*In 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.
*There are limited data correlating COD (Mn) and BOD, and no fixed relationship between the two was observed.

Water 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.
3)Suspended 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 conditions.
4)Dissolved oxygen (DO)
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 standard.

Water 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.

1)Chemical 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 of environment.
2)Suspended solids (SS)
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.
3)Dissolved oxygen (DO)
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.

Water quality standards for coastal water bodies

Seven 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.

In 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.
2)Chemical 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 .
3)Dissolved oxygen (DO)
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.
The 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.
5)n-Hexane extract
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 waters.
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.