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
