CHAPTER 8 Water Quality Katherine L. Thalman and James M. Bedessem CONTENTS Section 8A Water Quality. . . 8-1 Section 8B Drinking Water Quality Standards United States 8-33 Section 8C Drinking Water Standards — World . 8-54 Section 8D Municipal Water Quality. . . 8-71 Section 8E Industrial Water Quality . . . 8-105 Section 8F Irrigation Water Quality . . . 8-115 Section 8G Water Quality for Aquatic Life . . . . . 8-129 Section 8H Recreational Water Quality . 8-176 Section 8I Water Quality for Livestock and Aquaculture . . 8-183 Section 8J Water Treatment Processes . 8-189 Section 8K Water Treatment Facilities . 8-218 8-1 q 2006 by Taylor & Francis Group, LLC SECTION 8A WATER QUALITY Table 8A.1 Summary of Quality Inputs to Surface and Groundwaters Contributing Factor Principal Quality Input to Surface Waters Meteorological water Dissolved gases native to atmosphere Soluble gases from man’s industrial activities Particulate matter from industrial stacks, dust, and radioactive particles Material washed from surface of earth, e.g., Organic matter such as leaves, grass, and other vegetation in all stages of biodegradation Bacteria associated with surface debris (including intestinal organisms) Clay, silt, and other mineral particles Organic extractives from decaying vegetation Insecticide and herbicide residues Domestic use Undecomposed organic matter, such as garbage ground to sewer, grease, etc. (exclusive of industrial) Partially degraded organic matter such as raw wastes from human bodies Combination of above two after biodegradation to various degrees of sewage treatment Bacteria (including pathogens), viruses, worm eggs Grit from soil washings, eggshells, ground bone, etc. Miscellaneous organic solids, e.g., paper, rags, plastics, and synthetic materials Detergents Industrial use Biodegradable organic matter having a wide range of oxygen demand Inorganic solids, mineral residues Chemical residues ranging from simple acids and alkalis to those of highly complex molecular structure Metal ions Agricultural use Increased concentration of salts and ions Fertilizer residues Insecticide and herbicide residues Silt and soil particles Organic debris, e.g., crop residue Consumptive use (all sources) Increased concentration of suspended and dissolved solids by loss of water to atmosphere Contributing Factor Principal Quality Input to Groundwater Meteorological water Gases, including O 2 and CO 2 ,N 2 ,H 2 S, and H Dissolved minerals, e.g.: Bicarbonates and sulfates of Ca and Mg dissolved from earth minerals Nitrates and chlorides of Ca, Mg, Na and K dissolved from soil and organic decay residues Soluble iron, Mn, and F salts Domestic use Detergents (principally via septic tank Nitrates, sulfates, and other residues of organic decay systems and seepage from polluted Salts and ions dissolved in the public water supply surface waters) Soluble organic compounds Industrial use (not much direct disposal to soil) Soluble salts from seepage of surface waters containing industrial wastes Agriculture use Concentrated salts normal to water applied to land Other materials as per meteorological waters Land disposal of solid wastes Hardness-producing leaching from ashes (not properly installed) Soluble chemical and gaseous products or organic decay Note: This list includes the types of things that may come from any contributing factor. Not all are present in each specific instance. Source: From McGauhey, Engineering Management of Water Quality, McGraw-Hill, Copyright 1968. THE WATER ENCYCLOPEDIA: HYDROLOGIC DATA AND INTERNET RESOURCES8-2 q 2006 by Taylor & Francis Group, LLC Table 8A.2 Conditions That May Cause Variations in Water Quality Climatic conditions Runoff from snowmelt—muddy, soft, high bacterial count Runoff during drought—high mineral content, hard, groundwater characteristics Runoff during floods—less bacteria than snowmelt, may be muddy (depending upon other factors listed below) Geographic conditions Steep headwater runoff differs from lower valley areas in ground cover, gradients, transporting power, etc. Geologic conditions Clay soils produce mud Organic soils or swamps produce color Cultivated land yields silt, fertilizers, herbicides, and insecticides Fractured or fissured rocks may permit silt, bacteria, etc., to move with groundwater Mineral content dependent upon geologic formations Season of year Fall runoff carries dead vegetation—color, taste, organic extractives, bacteria Dry season yields dissolved salts Irrigation return water, in growing season only Cannery wastes seasonal Aquatic organisms seasonal Overturn of lakes and reservoirs seasonal Floods generally seasonal Dry period, low flows, seasonal Resource management practices Agricultural soils and other denuded soils are productive of sediments, etc. (See third item under Geologic conditions.) Forested land and swampland yield organic debris Overgrazed or denuded land subject to erosion Continuous or batch discharge of industrial wastes alters shock loads Inplant management of waste streams governs nature of waste Diurnal variation Production of oxygen by planktonic algae varies from day to night Dissolved oxygen in water varies in some fashion Raw sewage flow variable within 24-hr period; treated sewage variation less pronounced Industrial wastes variable—process wastes during productive shift; different material during washdown and cleanup Source: From McGauhey, Engineering Management of Water Quality, McGraw-Hill, Copyright 1968. WATER QUALITY 8-3 q 2006 by Taylor & Francis Group, LLC Table 8A.3 Principal Chemical Constituents in Water — Their Sources, Concentrations, and Effects upon Usability Constituent Major Sources Concentration in Natural Water Effect upon Usability of Water Silica (SiO 2 ) Feldspars, ferromagnesium and clay minerals, amorphous silicachert, opal Ranges generally from 1.0 to 30 mg/L, although as much as 100 mg/L is fairly common; as much as 4,000 mg/L is found in brines In the presence of calcium and magnesium, silica forms a scale in boilers and on steam turbines that retards heat; the scale is difficult to remove. Silica may be added to soft water to inhibit corrosion of iron pipes Iron (Fe) 1. Natural sources Igneous rocks: Amphiboles, ferromagnesian micas, ferrous sulfide (FeS), ferric sulfide or iron pyrite (FeS 2 ), magnetite (Fe 3 O 4 ) Generally less than 0.50 mg/L in fully aerated water. Groundwater having a pH less than 8.0 may contain 10 mg/L; rarely as much as More than 0.1 mg/L precipitates after exposure to air; causes turbidity, stains plumbing fixtures, laundry and cooking utensils, and Sandstone rocks: 50 mg/L may occur. Acid water from thermal imparts objectionable tastes and colors to Oxides, carbonates, and sulfides or iron clay minerals springs, mine wastes and industrial may contain more than 6,000 mg/L foods and drinks. More than 0.2 mg/L is objectionable for most industrial uses 2. Man-made sources: Well casing, piping, pump parts, storage tanks, and other objects of cast iron and steel which may be in contact with the water Industrial wastes Manganese (Mn) Manganese in natural water probably comes most often from soils and sediments. Metamorphic and sedimentary rocks and mica biotite and amphibole hornblende minerals contain large amounts of manganese Generally 0.20 mg/L or less. Groundwater and acid mine water may contain more than 10 mg/L. Reservoir water that has “turned over” may contain more than 150 mg/L More than 0.2 mg/L precipitates upon oxidation; causes undesirable tastes, deposits on foods during cooking, stains plumbing fixtures and laundry and fosters growths in reservoirs, filters, and distribution systems. Most industrial users object to water containing more than 0.2 mg/L Calcium (Ca) Amphiboles, feldspars, gypsum, pyroxenes, aragonite, calcite, dolomite, clay minerals As much as 600 mg/L in some western streams; brines may contain as much as 75,000 mg/L Calcium and magnesium combine with bicarbonate, carbonate, sulfate, and silica to form heat-retarding, pipe-clogging scale in Magnesium (Mg) Amphiboles, olivine, pyroxenes, dolomite, magnesite, clay minerals As much as several hundred mg/L in some western streams; ocean water contains more than 1,000 mg/L and brines may contain as much as 57,000 mg/L boilers and in other heat-exchange equipment. Calcium and magnesium combine with ions of fatty acid in soaps to form soap suds; the more calcium and magnesium, the more soap required to form suds. A high concentration of magnesium has a laxative effect, especially on new users of the supply Sodium (Na) Feldspars (albite), clay minerals, evaporates, such as halite (NaCl) and mirabilite (Na 2 SO 4 10H 2 O), industrial wastes As much as 1,000 mg/L in some western streams; about 10,000 mg/L in sea water; about 25,000 mg/L in brines More than 50 mg/L sodium and potassium in the presence of suspended matter causes foaming, which accelerates scale formation THE WATER ENCYCLOPEDIA: HYDROLOGIC DATA AND INTERNET RESOURCES8-4 q 2006 by Taylor & Francis Group, LLC Potassium (K) Feldspars (orthoclase and microcline), feldspathoids, some micas, clay minerals Generally less than about 10 mg/L; as much as 100 mg/L in hot springs; as much as 25,000 mg/L in brines and corrosion in boilers. Sodium and potassium carbonate in recirculating cooling water can cause deterioration of wood in cooling towers. More than 65 mg/L of sodium can cause problems in ice manufacture Carbonate (CO 3 ) Commonly 0 mg/L in surface water; commonly less than 10 mg/L in groundwater. Water high in sodium may contain as much as 50 mg/L of carbonate Upon heating, bicarbonate is changed into steam, carbon dioxide, and carbonate. The carbonate combines with alkaline earths— principally calcium and magnesium—to form Bicarbonate (HCO 3 ) Limestone, dolomite Commonly less than 500 mg/L; may exceed 1,000 mg/L in water highly charged with carbon dioxide a crustlike scale of calcium carbonate that retards flow of heat through pipe walls and restricts flow of fluids in pipes. Water containing large amounts of biocarbonate and alkalinity are undesirable in many industries Sulfate (SO 4 ) Oxidation of sulfide ores; gypsum; anhydrite; industrial wastes Commonly less than 1,000 mg/L except in streams and wells influenced by acid mine drainage. As much as 200,000 mg/L in some brines Sulfate combines with calcium to form an adherent, heat-retarding scale. More than 250 mg/L is objectionable in water in some industries. Water containing about 500 mg/L of sulfate tastes bitter; water containing about 1,000 mg/L may be cathartic Chloride (Cl) Chief source is sedimentary rock (evaporates); minor sources are igneous rocks. Ocean tides force salty water upstream in tidal estuaries Commonly less than 10 mg/L in humid regions; tidal streams contain increasing amounts of chloride (as much as 19,000 mg/L) as the bay or ocean is approached. About 19,300 mg/L in seawater, and as much as 200,000 mg/L in brines Chloride in excess of 100 mg/L imparts a salty taste. Concentrations greatly in excess of 100 mg/L may cause physiological damage. Food processing industries usually require less than 250 mg/L. Some industries—textile processing, paper manufacturing, and synthetic rubber manufacturing—desire less than 100 mg/L Fluoride (F) Amphiboles (hornblende), apatite, fluorite, mica Concentrations generally do not exceed 10 mg/L in groundwater or 1.0 mg/L in surface water. Concentrations may be as much as 1,600 mg/L in brines Fluoride concentration between 0.6 and 1.7 mg/L in drinking water has a beneficial effect on the structure and resistance to decay of children’s teeth. Fluoride in excess of 1.5 mg/L in some areas causes “mottled enamel” in children’s teeth. Fluoride in excess of 6.0 mg/L causes pronounced mottling and disfiguration of teeth (Continued) WATER QUALITY 8-5 q 2006 by Taylor & Francis Group, LLC Table 8A.3 (Continued) Constituent Major Sources Concentration in Natural Water Effect upon Usability of Water Nitrate (NO 3 ) Atmosphere; legumes, plant debris, animal excrement, nitrogenous fertilizer in soil and sewage In surface water not subjected to pollution, concentration of nitrate may be as much as 5.0 mg/L but is commonly less than 1.0 mg/L. In groundwater the concentration of nitrate may be as much as 1,000 mg/L Water containing large amount of nitrate (more than 100 mg/L) is bitter tasting and may cause physiological distress. Water from shallow wells containing more than 45 mg/L has been reported to cause methemoglobinemia in infants. Small amounts of nitrate help reduce cracking of high-pressure boiler steel Dissolved solids The mineral constituents dissolved in water constitute the dissolved solids Surface water commonly contains less than 3,000 mg/L; streams draining salt beds in arid regions may contain in excess of 15,000 mg/L. Groundwater commonly contains less than 5,000 mg/L; some brines contain as much as 300,000 mg/L More than 500 mg/L is undesirable for drinking and many industrial uses. Less than 300 mg/L is desirable for dyeing of textiles and the manufacture of plastics, pulp paper, rayon. Dissolved solids cause foaming in steam boilers; the maximum permissible content decreases with increases in operating pressure Source: From U.S. Geological Survey, 1962; amended. THE WATER ENCYCLOPEDIA: HYDROLOGIC DATA AND INTERNET RESOURCES8-6 q 2006 by Taylor & Francis Group, LLC Table 8A.4 Relative Abundance of Dissolved Solids in Potable Water Major Constituents (1.0 to 1000 mg/L) Secondary Constituents (0.01 to 10.0 mg/L) Minor Constituents (0.0001 to 0.1 mg/L) Trace Constituents (generally less than 0.001 mg/L) Sodium Iron Antimony a Beryllium Calcium Strontium Aluminum Bismuth Magnesium Potassium Arsenic Cerium a Bicarbonate Carbonate Barium Cesium Sulfate Nitrate Bromide Gallium Chloride Fluoride Cadmium a Gold Silica Boron Chromium a Indium Cobalt Lanthanum Copper Niobium a Germanium a Platinum Iodide Radium Lead Ruthenium a Lithium Scandium a Manganese Silver Molybdenum Thallium a Nickel Thorium a Phosphate Tin Rubidium a Tungsten a Selenium Ytterbium Titanium a Yttrium a Uranium Zirconium Vanadium Zinc a These elements occupy an uncertain position in the list. Source: From Davis and DeWiest, Hydrogeology, John Wiley & Sons, Copyright 1966. Table 8A.5 Characteristics of Water That Affect Water Quality Characteristic Principal Cause Significance Remarks Hardness Calcium and magnesium dissolved in the water Calcium and magnesium combine with soap to form an USGS classification of hardness (mg/L as CaCO 3 ) insoluble precipitate (curd) and 0–60: Soft thus hamper the formation of a 61–120: Moderately hard lather. Hardness also affects 121–180: Hard the suitability of water for use in the textile and paper industries and certain others and in steam boilers and water heating More than 180: Very hard pH (or hydrogen-ion activity) Dissociation of water molecules and of acids and bases dissolved in water The pH of water is a measure of its reactive characteristics. Low values of pH, particularly below pH 4, indicate a corrosive water that will tend to dissolve metals and other substances that it contacts. High values of pH, particularly above pH 8.5, indicate an alkaline water that, on heating, will tend to form scale. The pH significantly affects the treatment and use of water pH values: less than 7, water is acidic; value of 7, water is neutral; more than 7, water is basic (Continued) WATER QUALITY 8-7 q 2006 by Taylor & Francis Group, LLC Table 8A.5 (Continued) Characteristic Principal Cause Significance Remarks Specific electrical conductance Substances that form ions when dissolved in water Most substances dissolved in water dissociate into ions that can conduct an electrical current. Consequently, specific electrical conductance is a valuable indicator of the amount of material dissolved in water. The larger the conductance, the more mineralized the water Conductance values indicate the electrical conductivity, in micromhos, of 1 cm 3 of water at a temperature of 258C Total dissolved solids Mineral substances dissolved in water Total dissolved solids is a measure of the total amount of minerals dissolved in water USGS classification of water based on dissolved solids (mg/L) and is, therefore, a very useful Less than 1,000: Fresh parameter in the evaluation of 1,000–3,000: Slightly saline water quality. Water containing less than 500 mg/L is preferred 3,000–10,000: Moderately saline for domestic use and for many 10,000–35,000: Very saline industrial processes More than 35,000: Briny Source: From Heath, R.C., 1984, Basic groundwater hydrology, U.S. Geological Survey Water-Supply Paper 2220. THE WATER ENCYCLOPEDIA: HYDROLOGIC DATA AND INTERNET RESOURCES8-8 q 2006 by Taylor & Francis Group, LLC ALASKA HAWAII Re g ional data not available PUERTO RICO Regional data not available Less than 120 PPM 120 to 350 PPM More than 350 PPM Figure 8A.1 Dissolved solids in surface water. (From U.S. Water Resources Council, 1968.) 150 Stn 028015 Tennessee R. United States Stn 001005 R. de la Plata Stn 054002 Chao Phrya R. Thailand Argentina Stn 033004 Murray Darling Australia Stn 075006 Ebro En Mendavia Spain Stn 080007 Sagami R. JJJASOND 3050 2520 1990 1460 930 400 225 190 155 120 85 50 100 80 60 40 20 0 33100 29240 25380 21520 17660 13800 1400 1150 900 650 400 150 1225 980 735 490 245 0 FM MA JJJASONDFM MA JJJASOND TDS (mg L –1 ) Discharge (m 3 s –1 ) FM MA JJJASONDFM MA JJJASONDFM MA JJJASONDFM MA 140 130 120 110 100 700 630 560 490 420 350 140 130 120 110 100 90 215 190 165 140 115 90 165 150 135 120 105 90 450 380 310 240 170 100 Japan Figure 8A.2 Seasonal variation of total dissolved solids (TDS) and water discharge at selected world river stations for selected years. (From United Nations Environment Programme, Global Environment Monitoring System Water Programme (GEMS/WATER), The annotated digital atlas of global water quality, www.gemswater.org. Reprinted with permission.) WATER QUALITY 8-9 q 2006 by Taylor & Francis Group, LLC Dissolved Oxygen Explanation Trend in concentration in percent Upward, >15 Upward, 0–150 None Downward, 0–15 Downward, >15 Nationwide Concentration deficit > 4.0 mg/L Concentration < 6.5 mg/L Water year Water year 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1980 1981 1982 19831984 1985 1986 1987 1988 1989 100 90 80 70 60 50 40 30 20 10 0 100 90 80 70 60 50 40 30 20 10 0 Percentage of stations where 20 percent or more of the concentrations were less than 6.5 mg/L Percentage of stations where 20 percent or more of the concentrations were less than or greater than the values shown Land use 0 0 Agriculture, 119 stations Urban, 26 stations Forest, 98 stations Range, 100 stations 500 Miles 500 km Fecal Coliform Nationwide Water year Water year 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 100 90 80 70 60 50 40 30 20 10 0 100 90 80 70 60 50 40 30 20 10 0 Agriculture, 83 stations Urban, 20 stations Forest, 77 stations Range, 80 stations Land use 0 0 Percentage of stations where the annual average concentration was greater than 200 colonies per 100 millieliters Percentage of stations where the annual average concentration was greater than the concentration shown 1980 19811982 1983 1984 1985 1986 1987 1988 1989 200 colonies per 100 milliliters 1,000 colonies per 100 milliliters 500 Miles 500 km Explanation Trend in concentration in percent Upward, >50 Upward, 0−50 None Downward, 0−50 Downward, >50 Concentration and trends in dissolved oxygen in stream water at 424 selected water-quality monitoring stations in the conterminous United States, water years 1980−89. Concentration and trends in fecal coliform bacteria in stream water at 313 selected water-quality monitoring stations in the conterminous United States, water years 1980−89. Figure 8A.3 Concentration trends in dissolved oxygen and fecal coliform bacteria in United States rivers, 1980–1989. (From USDA, Natural Resources Conservation Services, 1997, Water Quality and Agriculture, Status, Conditions, and Trends, www.nrcs.usda.gov. Original Source: Smith, R.A., Alexander, R.B., and Lanfear, K.J., 1993, Stream water quality in the conterminous United States – status and trends of selected indicators during the 1980’s in National Water Summary 1990–91 – Stream water quality, U.S. Geological Survey Water-Supply Paper 2400, www.usgs.gov.) THE WATER ENCYCLOPEDIA: HYDROLOGIC DATA AND INTERNET RESOURCES8-10 q 2006 by Taylor & Francis Group, LLC [...]... 1 985 : 1 984 data; FRA) Data refer to hydrological year (September–August) Loire: since 1 988 data refer to another station; 1 980 and 1 985 ; 1 982 and 1 984 data; DEU) Rhein 1 984 –1 989 and 95–97: upper limits: Elbe: data refer to dissolved concentrations; 1990– 1991: upper limits Weser 1 988 –1997, and Donau: upper limits; GRC) Strimonas 1 986 –1 987 , 92–94, Axios 1 986 –1 987 , Axeloos 1990, 92–96 and Nestos 1 986 , 92–97:... milligram per liter Land use 500 km 100 90 80 70 Agriculture, 88 stations Urban, 24 stations Forest, 82 stations Range, 89 stations 60 50 40 30 20 10 0 1 980 1 981 1 982 1 983 1 984 1 985 1 986 1 987 1 988 1 989 Water year Concentration and trends in nitrate in stream water at 344 selected water- quality monitoring stations in the conterminous United States, water years 1 980 −1 989 Figure 8A.4 Concentration trends... constrcted Pre-causeway Gilbert Bay at Saltair Boat Harbor gage Post-causeway 185 0 187 3 187 9 188 9 189 4 1900 1903 1907 1930 19 58 1961 1964 1966 19 68 1970 1972 1974 1976 19 78 1 980 1 982 1 984 1 986 1 988 1990 1992 1994 1996 19 98 Salinity (percent) 24 Figure 8A.6 Salinity in the Great Salt Lake, Utah 1950–19 98 The Salinity of Great Salt Lake is determined by the amount of inflow (and its salt content) and the amount... to the mouth and farther away from Sevilla influence; TUR) 1 980 : 1 982 data q 2006 by Taylor & Francis Group, LLC THE WATER ENCYCLOPEDIA: HYDROLOGIC DATA AND INTERNET RESOURCES 1996 Average Last 3 yrs (b) WATER QUALITY BOD: MEX) 1 985 : 1 984 data 19 98: the data s variations can be explained by fluctuations of meteorological conditions and the CNA’s actions on control of residual water discharges; JPN) Data. .. 1. 78 X 1.34 1.49 X 1.37 1. 68 X 9.2 8. 8 10.2 3.9 9.5 9.1 9.6 4.9 8. 7 9.3 9.6 6.3 8. 2 8. 6 8. 8 5.5 8. 8 9.0 9.3 5.6 1.3 3.7 2.0 2.2 1.1 3.2 2.7 2.0 1.3 3.5 2.4 5.5 1.3 3.4 2.2 3.3 1.2 3.4 2.4 3.6 1.45 1.37 2.90 1.15 1.20 1.42 1.70 0.57 1.15 1.43 7.53 0.29 1.21 1.50 5.05 0.06 1.19 1.45 4.76 0.31 10.2 10.7 8. 5 8. 1 9 .8 11.0 10 .8 8.0 7.7 9.1 10 .8 10.3 9.6 8. 2 — 10.5 — 8. 7 8. 2 — 10 .8 10.6 8. 8 8. 0 9.2 3.0 2 .8. .. Land use 100 90 80 No data 70 60 Agriculture,110 stations Urban, 28 stations Forest, 98 stations Range, 100 stations No data 50 40 30 20 No data 10 0 1 980 1 981 1 982 1 983 1 984 1 985 1 986 1 987 1 988 1 989 Water year Nitrate HDSN Percentage of stations where the annual average concentration was greater than the concentration shown Concentration and trends total phosphorus in stream water at 410 selected water- quality... from the mouth of the river due to the tidal influence; AUT) 1 985 : 1 984 data; FRA) Data refer to hydrological year ¨ (September–August) Loire—1 980 : 1 982 data: since 1 982 data refer to another station Seine: station under marine influence Rhone: sicne 1 987 data refer to another station; GRC) Strimonas: 19 98 and 1999 data refer to ortho-phosphate; IRL) Boyne: Data refers to ortho-phosphate; ITA) Po: Data. .. upstream from the mouth of the river due to the tidal influence; AUT) 1 985 : 1 984 data Donau 1 980 , 82 , 86 , Inn 1 982 , 84 and Grossache 1 980 , 86 : limit of detection values; CZE) Labe: from 1 988 to ¨ 1993 data are upper limit values Morava: 1995 data is an upper limit value; FIN) Tornionjoki and Kymijoki: include limit of detection values; Kokemaenjoki 1 980 : 1 981 data; FRA) Data refer to hydrological year... 1 984 1 985 1 986 1 987 1 988 1 989 Water year Explanation Trend in concentration in percent Upward, >50 Upward, 0−50 0 0 500 Miles 500 km None Percentage of stations where the annual average concentration was greater than 500 mg/L Land use 100 90 80 Agriculture, 86 stations Urban, 21 stations Forest, 77 stations Range, 81 stations 70 60 50 40 30 20 10 0 1 980 1 981 1 982 1 983 1 984 1 985 1 986 1 987 1 988 1 989 Water. .. the mouth of the river due to the tidal influence; AUT) Donau 1 980 : figure is approximate: Donau 1 982 , 86 87 , 91 and 93, Inn 1 984 , 86 , 88 –90, 94 and Grossache 1 980 , 82 and 84 : upper limits 1 985 : 1 984 data; BEL) Meuse (Agimont): 1994–1996 are upper limits; CZE Labe:from 1990 to 1993 data are upper limit values Morava: 1993 figure is an upper limit value; FIN) Tornionjoki and Kymijoki: upper limits; 1 985 : . mg/L Concentration < 6.5 mg/L Water year Water year 1 980 1 981 1 982 1 983 1 984 1 985 1 986 1 987 1 988 1 989 1 980 1 981 1 982 1 983 1 984 1 985 1 986 1 987 1 988 1 989 100 90 80 70 60 50 40 30 20 10 0 100 90 80 70 60 50 40 30 20 10 0 Percentage. >50 100 90 80 70 60 50 40 30 20 10 0 100 90 80 70 60 50 40 30 20 10 0 1 980 1 981 1 982 1 983 1 984 1 985 1 986 1 987 1 988 1 989 1 980 1 981 1 982 1 983 1 984 1 985 1 986 1 987 1 988 1 989 Water year Water year 1. . . . . . 8- 1 29 Section 8H Recreational Water Quality . 8- 1 76 Section 8I Water Quality for Livestock and Aquaculture . . 8- 1 83 Section 8J Water Treatment Processes . 8- 1 89 Section 8K Water Treatment