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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