Exam 2-Chapter 20 Flashcards
How does the presence of sewage or organic materials in water affect the level of dissolved oxygen (DO)?
It depletes DO. Raw sewage has a BOD value of 250 ppm. If added to water with 10 ppm DO, it can take away all oxygen and severly affect the stream’s biology.
What is the source of most eutrophication?
Nutrients like nitrogen and phosphorus from fertilizer
Why must sewage be treated before release?
So it has a low BOD and may improve water quality.
What is biochemical oxygen demand (BOD)?
measures the amount of organic material in the water based on how much oxygen it will require to break down that material.
Submerged aquatic vegetation (SAV) vs. phytoplankton
SAV grows underwater and needs clear water for light to penetrate, and gets nutrients from the bottom sediments. Phytoplankton are bacteria containing chlorophyll and float on the surface of the water, and get nutrients from the water.
What is point-source pollution?
Source easy to identify, monitor and regulate like factories, power plants, and mines.
What does the presence of E. coli suggest?
water is contaminated with fecal waste.
How can pollutants be bioaccumulated?
Increase in concentration of a pollutant from the environment to the first organism in a food chain/microbeads and plastics can aid in bioaccumulation/ if fish mistake pollutants for food these chemicals leach into the tissues of organisms.
About water treatment process (three phases)
Primary-remove sludge (grit and debris) with bar screen for debris and grit chamber for grit. Secondary-treats clarified water by filtering thru rocks or activated sludge system (detritus-feeding organisms) to get to 90% material removed. Final cleansing and disinfection-with chlorine gas, clorox or ozone gas before discharge.
Why do agencies screen for the presence of E.coli in water?
To protect the public health against diseases.
What is nonpoint-source pollution?
Source is poorly defined and scattered like agricultural runoff, atmospheric deposition.
How can pollutants be biomagnified?
Incrementally higher doses because pollutants have a tendency to concentrate as you go up the food chain.
What dangers are there to human health from water contaminated with fecal waste?
Diseases. E. coli may contain disease-carrying bacteria, viruses and parasites.
How does eutrophication lead to hypoxia?
Zoo plankton eat the excess growth of phytoplankton and multiply. These dead organisms are eaten by bacteria which consume oxygen. Eventually oxygen is used up causing hypoxia (or dead zone).
Types of pollution (about each)
Nutrients (become pollutants when they stimulate undesirable plant growth in water. Sediment (when washed in water/muddy and murky reduce photosynthesis/can clog gills of fish. Chemicals (by humans-pesticides, solvents, detergents)
