Lecture 24 | Water Pollution

Contamination, BOD in Freshwater & Saltwater, GW Contamination & Treatment, Wastewater Treatments

Case Studies | What major pollutant from AWCC and General Electric contaminated the Hudson River? Why are they such a problem?

pcbs, last forever in environment & bioaccumulate in fish, cause liver disease & cancer

Why is water the most easily contaminated resource?

universal solvent, dissolves many pollutants

Provide examples of pollutants that water can dissolve:

heavy metals, sediment, bacteria, viruses, nutrients

Maximum Contaminate Levels

epa sets regulations to protect drinking water

State regulations must be ______ or _____ than EPA regulations for water

as strict, stricter

BOD

biochemical oxygen demand, amount of o2 in water consumed by decomposers/bacteria

What happens when BOD is too high?

not enough o2 left for other organisms to breathe

Describe how being downstream from a wastewater treatment plant eventually leads to BOD spikes:

wastewater with nutrients causes nutrient spike, algae population spike, decomposers consume more dead algae, use up most of the o2, fish kills

How does BOD create dead zones in areas such as the Gulf of Mexico?

nutrient pollution runs into large water body, algae proliferate, decomposers consume dead algae & o2, suffocates/kills others

Explain how farming along the Mississippi results in the Gulf of Mexico dead zone?

fertilizer = nutrient pollution runs into ocean, algal bloom, increase decomposing & bod spike

Eutrophication

increase in BOD due to influx in nutrients

What nutrient limits freshwater populations and causes eutrophication when introduced?

phosphorus, cleaning

What nutrient limits saltwater populations and causes eutrophication when introduced?

nitrogen, fertilizers

What are two examples of oil spills that polluted water bodies?

exon valdez, deepwater horizon

In what 3 ways does an oil spill pollute aquatic ecosystems?

light hydrocarbons create oil slick on surface, heavier hydrocarbons pollute ocean floor with fallout plumes, ch4 and oil dissolve in water column & stay in water

What problems does sediment loading create in rivers?

bpc: organic sediment increases bod, murky water deceases photosynthesis, too much sediment chokes the river

Which is easier to regulate, point or non-point source water pollution?

point easier because permits, nonpoint harder because runoff everywhere

Surface Runoff

rainwater washes pollutants into surface water bodies, major nonpoint source

List some examples of pollutants that can pollute water via runoff:

farm chemicals, gasoline residue, anything

What is the biggest source of groundwater pollution?

lusts, leaking underground storage tanks

How do LUSTs contaminate groundwater? How can it be removed?

steel rusts & gas leaks, soluble gasoline dissolves in groundwater, insoluble gasoline evaporates into fumes, has to be pumped out

What are other sources of groundwater pollution (other than LUSTs)?

drslmf: dry cleaner solvents, factories raw material & wastes, septic system buildup, landfill leaching, mining tailings, farming chemicals

Why is delineating and treating groundwater pollution so difficult? Describe the process of treating groundwater

can’t see it, dig many wells to determine how far pollution goes & concentrations

Where does all the wastewater that goes down your drain end up?

wastewater treatment plant

Wastewater Treatment Plant

remove pollutants from wastewater before discharging to surface water body

What is the first stage of wastewater treatment?

primary treatment, sediment settles, oil/grease rise, skimmed off & removed

What is the second stage of wastewater treatment?

secondary treatment, remove organic pollutants/nutrients by stimulating bod with bacteria and oxygen

What is the third stage of wastewater treatment?

tertiary treatment, optional, involves disinfection/filtration of viruses and bacteria

What three ways can you disinfect/filter wastewater during the third stage of treatment?

chlorine effective but increases salinity of water, uv sterilizes microorganisms, ozone oxidizes and kills everything