APES Chapter 21

Water Pollution

• Sewage – wastewater carried off by drains or sewers; contains human wastes, soaps, and detergents

o Problems from Sewage

� Enrichment – fertilization of a body of water caused by the presences of plant and algal

nutrients such as nitrogen and phosphorus

� Oxygen Demand - cellular respiration breaks down the organic matter, which requires oxygen;

this causes a higher biological oxygen demand (BOD) – the amount of oxygen needed by

microorganisms to decompose the waste. The amount of dissolved oxygen (DO) cannot be

replenished fast enough through photosynthesis.

• Disease causing agents – infectious agents such as viruses and bacteria that come from the wastes of infected

animals

o Monitoring Sewage

� Fecal coliform test – tests for E. Coli

� Bacterial source tracking (BST) – attempts to identify where the bacteria is from

Some Human Diseases Transmitted by Polluted Water

• Sediment Pollution - excessive amounts of suspended soil particles that eventually settle our and accumulate on

the bottom of a body of water; as a result of erosion

o Causes problems reducing light penetration, covering gills, insoluble toxic pollutants into the water,

filling in waterways

• Inorganic plant and algal nutrients – nitrogen, phosphorus, and other substances that stimulate plants and algal

growth; from animal wastes, plant residues, and fertilizer runoff

o Dead Zone in Gulf of Mexico – runoff from Mississippi fertilizer, causes eutrophication

� Hypoxia – oxygen free condition when algae grow rapidly because of the presence of nutrients

such as nitrates in the water.

• Organic Compounds – carbon-containing chemicals that are usually synthetic and often toxic to aquatic

organisms

• Inorganic Chemicals – contaminants, such as acids, salts, and heavy metals, that contain elements other than

carbon

o Lead – linked to hypertension or high blood pressure

o Mercury – metal can vaporize at room temperature;

• Radioactive substances – wastes from mining, refining, and use of radioactive metals.

o Radon – lung cancer

• Thermal pollution – heated water produced during certain industrial processes

o Less DO; more food required; increased BOD

Eutrophication:

• Oligotrophic – minimal levels of nutrients – un-enriched

• Eutrophication – the enrichment of a body of water by inorganic plant and algal nutrients such as phosphorus;

then called eutrophic

• Artificial eutrophication or cultural eutrophication – human caused problem

Sources

• Point source pollution – discharged into environment through pipes, sewers, or ditches from specific sites such

as factories or sewage treatment plants

• Nonpoint source pollution – polluted runoff – land pollutants that enters bodies of water over large areas

rather than a single point

• Agriculture – fertilizers, pesticides, chemicals

• Municipal waste pollution –

o combined sewer system – human and industrial waste are combined with urban runoff; NYC, Pittsburgh,

Boston, San Francisco – heavy rain causes problems – overflows directly into waterway

• industrial waste – heavy metals + other pollutants

Groundwater Pollution – 50% people get water from groundwater; pesticides, fertilizers, organic compounds; seep from

storage tanks, golf courses, landfills, and farms

Drinking Water

• reservoirs – artificial lakes that hold water

• Chlorine – linked to cancer, miscarriages, rare birth defects

• Fluoridation – cancer, kidney disease, birth defects

Septic Systems

• Tank slows the flow and separates sludge, wastewater, and scum

• Treated wastewater flows into a drainage field where it reenters the ground

Laws controlling Water Pollution

• Refuse Act – 1899 – intended to reduce the release of pollutants into navigable rivers

• Safe Drinking Water Act – 1974 – set uniform federal standards for drinking water in order to guarantee safe

public water supplied throughout the country

o EPA set a maximum contaminant level – maximum permissible amount of any water pollutant that

might adversely affect human health

• Clean Water Act – eliminate the discharge of pollutants into US waterways and to attain water quality levels

that make these waterways safe to fish and swim in

o EPA set up national emission limitation – max permissible amounts of water pollutants that can be

discharged from sewage treatment plants, etc.

o National Pollutant Discharge Elimination System – point source polluters must obtain permits from this

organization

• Resource, Conservation, and Recovery Act –storage and disposal of hazardous wastes and helps prevent

groundwater contamination

• Great Lakes Toxic Substance Control Agreement – coordination between 8 states and 2 provinces to stop

pollution in the lakes

Other Polluted Countries

• Lake Maracaibo – Venezuela – oil pollute and human wastes

• Po River – Italy – treated and untreated sewage

• Ganges River – India – ashes, sewage, drinking water, bathing

• Kwale – Kenya – disease causing organisms

• Arsenic in Bangladesh – wells built in the 80s contain arsenic

Sewage Treatment

• Primary treatment – removes suspended solids; removes primary sludge

• Secondary treatment – uses microorganisms to decompose suspended organic material in waste water;

removes secondary sludge

• Tertiary treatment – biological, chemical, physical processes to remove phosphorus and nitrogen

• Sludge is disposed in landfills; or decomposed to make methane

• 1988 – Ocean Dumping Ban Act – barred ocean dumping of sludge and industrial waste