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Water Resources and Pollution
Dr. Raymon Shange Department of Agricultural and Environmental Sciences
Earth’s Water Resources
Water Pollution Lecture Objectives
S Understand the Difference between Point Source and Non-point source pollution
S Know the Types and Nature of Major Water Pollutants
S Know the Sources of Major Water Pollutants
Point vs. Non-Point Source Pollution
S Point Source Pollution: S Can be traced to a particular source such
as industrial site, septic tank, smokestack, wastewater treatment plant
S Non-Point Source Pollution: S Results from large areas and not from a
single source and includes both natural and human activities.
Sources: Nutrients
S Mainly from agricultural and Domestic Sources
S Major types: Nitrate and Phosphates
S Fertilizers from agriculture and domestic sources
S Results in Eutrophication
Sources: Oxygen Demanding Wastes
SOrganic matter vs. Dissolved Oxygen. S DO affected by OM decomposition S Most fish and aquatic organisms affect at
DO < 4 mg L-1 S Fresh Water 8-15 mg L-1 (30-0oC) S Sea Water 6-11 mg L-1
Oxygen Demanding Wastes
S Biochemical Oxygen Demand (BOD)
S Amount of O2 used over course of time, usually 5-20 d as O2 is oxidized both biologically and chemically.
S Most commonly used parameter for analysis of O2 resources in H2O.
Oxygen Demanding Wastes
SChemical Oxygen Demand (COD) S Measure of decomposable material S Used for industrial wastes S Provides a direct measure of the impact of
O2 consumption on O2 content of water body.
Oxygen Demanding Wastes
Sources of Organic Materials:
Wastewaters Added to Soils S Domestic-Sewage effluents can contain 300-
400 mg L-1 of organic compounds S 6% are degraded by microbial community S Leads to decrease in DO S Industrial Wastes
Oxygen Demanding Wastes
SSewage Sludge S Residual sewage solids waste from
Municipal sewage systems.
S Contain OM, N, P, Micronutrients
S Main Problem: Pathogens and Heavy Metals e.g. B, Cd, Pb, Se, Hg, Cu
Oxygen Demanding Wastes
Animal Manures S Contain soluble salts in addition to N, P,
and heavy metals
S Euthrophication from N and P
S Possible source of pathogens
Oxygen Demanding Wastes
S Municipal Wastes, Composts and Sanitary Landfills S Possible source of toxic substances S Gases from anaerobic decomposition
S Food-Processing Wastes S Main problem water pollution by N
Pesticides
SPesticides S 600 commercially important pesticides S 1500 registered for sale S About 70% used in agriculture S 7 % at home S FIFRA regulates pesticide in Agriculture S FFDCA in food
Pesticides
Estimated Annual Use of Pesticides in 1985
Herbicides Insecticides Total
Agricultural 238 102 390
Non-Agric. 52 18 80.05
Home/Garden 14 16 35.05
Total 304 136 505.1
S *Total includes Fungicides and other; Source EPA 1987
Inorganic Pollutants
Metals:
SMainly from Industrial Sludge and Solid Waste S Mining S Metal Smelting and refining S Coal Burning Power Plants (Flue Gas
sludge), Paints
Organic Compounds
S Mainly from industry
S Includes greases, solvents and by-products in manufacturing e.g. benzene, toluene and other petroleum based products
Inorganic Pollutants
SNonmetallic Salts S Sources: S Oil Drilling S Irrigation S Industrial Sludges S High concentration in soils kills plants
Inorganic Pollutants
S Potential groundwater contamination destroys freshwater.
S Accumulation can lead to hazardous concentration of Selenium, Boron, Arsenic and molybdenum.
Inorganic Pollutants
Acids and Bases
SMain sources: Industry and Mining S Mine spoils S High in arsenic, Very acidic S Burning of fossil fuel
Soil Sediments
S Erosion of agricultural soils can lead to soil loss.
S Construction also a major cause of sedimentation.
S Destroys soils
S Fills dams and reservoirs
S Reduce sunlight penetration in water
Soil Sediments
S Adsorbed Chemicals
S Carries toxic chemicals to water
S 80 % of P and 73% of N loadings in water from eroded soils
Water Quality Laws
S Two major laws on water:
S 1. Clean Water Act S Goal: To restore and maintain chemical, physical
and biological integrity of the surface waters of the United States.
S Vision: To make all surface waters of the U.S. swimmable and fishable
Safe Drinking Water Act (SDWA)
S Goals: S To protect Drinking Water S Mandates the establishment of uniform
standards for drinking water quality S Provides a system for regulating underground
injection of wastes and other substances that could contaminate underground water sources.
Safe Drinking Water Act (SDWA)
Drinking Water Standards
S Primary Standards S The primary standards are set for
contaminants deemed to pose a threat to human health and also to the environment.
S The maximum contaminant level (MCL) set for primary contaminants are enforceable under the law.
S MCL for nitrate is 10 ppm, Pb is 15 ppb
Safe Drinking Water Act (SDWA)
Secondary Standards
SSecondary Standards are only advisory and nor enforceable by federal government. S Normally concern physical characteristics which are
not health hazards S Set Maximum Contaminant Levels consistent for the
protection of the public