Chapter 21 Water Pollution and Treatment Categories of water pollutants Diseases of drinking water Point vs. non point source pollution BOD Eutrophication Sediment Acid Mine Drainage Aquifer Pollution Waste Water treatment Environmental Laws to protect drinking water
Categories of Water Pollutants Sediment Heavy metals Radioactive isotopes Heat E coli, pathogens, viruses Nutrients Dead organic matter
Introduction US EPA sets standards for over 700 water pollutants Disease free water available in U.S., not necessarily problem except in developing world Sources of surface and groundwater pollution (industry, agriculture, urban) Runoff Spills Leaks Sediment Air fallout Seepage
BOD What is it? Water quality parameter Measured before after at treatment facility and in stream Measure of oxygen for biochemical decomposition processes Amount of oxygen consumed by microorganisms in organic matter breakdown
BOD Trends Natural and unnatural sources BOD 1/3 BOD comes from ag runoff Threshold- <5mg/l water Vocabulary- pollution zone, active decomposition zone, recovery zone
Relationship BOD vs. Dissolved Oxygen plant spill stream BOD concentration low high Return to normal increases Stable amounts Break down organic matter Low O2 species
Water Borne Diseases Outbreaks (sudden occurrences) examples Cryptosporidium - resistant to Cl, caused 100 deaths in Milwaukee sources cattle, sewage, snow melt Installed new filtration system E coli – Ontario, delayed reporting and treatment, boil water, 500 sick, source?- cow manure continuously monitored, <200 cells/100ml water, EPA standard, exceed this amount beach closing and precautions
Nutrients-N and P
Sediment
Acid Mine Drainage
Surface Waters Point vs. Non point
Groundwater Treatment
Septic Tanks Sewage Disposal Systems
Hypoxia
Waste Water Treatment Plants Divided into three categories Primary (30-40% BOD removal) Raw sewage passed through series of screens to remove large materials Grit chamber-removes sand, stones Sedimentation tank- settle out solids (sludge) Sludge- removed to digester
Waste Water Treatment Plants Secondary treatment Waste water from primary treatment enters aeration tank Bacteria in sludge uses oxygen and consumes organics, further reducing BOD Anaerobic bacteria added to further degrade sludge Methane gas (anaerobic digestion) either used for energy or burned off Wastewater treated with chlorine is discharged or used for irrigation 90% BOD removal Sludge- applied to land or special disposal (heavy metals)
Waste Water Treatment Plants Advanced water treatment N, P, organics, and heavy metals require carbon and sand filters, chemical treatment
p.461 Environmental Laws 1899- Refuse Act 1972- Clean Water Act 1974- Safe Water Drinking Act 1984- Amendment to Resource Conservation and Recovery Act 1987- Water Quality Act
LAND APPLICATION OF WASTEWATER