chapter 22 Flashcards
Why is water treatment essential for public health?
Water can be a source of infectious diseases and chemical intoxications, so ensuring purity is crucial.
What are the main goals of water treatment?
To remove pollutants and ensure water is safe for consumption and use.
How are microorganisms used in water treatment?
Microorganisms help to identify, remove, and degrade pollutants in water.
What is sewage?
It includes domestic sewage and liquid industrial waste that must be treated before disposal.
What is the role of microbes in wastewater treatment?
Microbes are used on an industrial scale for bioconversion of pollutants in wastewater.
What other treatments are included in wastewater treatment?
Physical and chemical treatments are also used in conjunction with biological processes.
What is effluent water?
It is the treated wastewater, suitable for release into surface waters or drinking water purification facilities (but not for direct drinking)
What are the goals of a wastewater treatment facility?
Reduce organic/inorganic materials and eliminate toxic substances.
How is treatment efficiency measured
By the reduction in biochemical oxygen demand (BOD).
What does BOD measure?
The oxygen consumed by microbes to oxidize organic/inorganic matter.
What is wastewater treatment?
A multistep process using physical and biological methods.
What is involved in primary treatment?
Physical separation to remove solid and particulate materials.
What is secondary treatment in wastewater treatment?
A biological process that removes remaining organic material after primary treatment.
What is anoxic secondary treatment?
A process where microbes carry out digestive and fermentative reactions under anoxic conditions.
Where does anoxic secondary treatment take place?
In large enclosed tanks like sludge digesters or bioreactors.
What is aerobic secondary treatment?
A process where microbes perform digestive reactions under aerobic conditions to treat water with low organic material.
What are the most common aerobic secondary treatment methods?
Activated sludge and trickling filters.
What happens in the activated sludge process?
Wastewater is mixed and aerated in large tanks, promoting bacterial growth.
What role do slime-forming bacteria play in the activated sludge process?
Bacteria like Zoogloea ramigera grow and form flocs to treat the wastewater.
What is done to the effluent after secondary treatment?
Most treatment plants chlorinate the effluent to reduce biological contamination.
What is tertiary treatment?
Additional physicochemical or biological treatment to further process secondary effluent.
What are the goals of tertiary treatment?
Remove organic matter and suspended solids
Reduce inorganic nutrients (phosphate, nitrate, nitrite)
Degrade toxic materials
Why isn’t tertiary treatment widely adopted?
It is the most complete method but costly.
What is an example of tertiary treatment?
Phosphorus removal is a key example.
How is phosphorus removed in wastewater treatment?
Chemical precipitation
Enhanced biological phosphorus removal
What is involved in enhanced biological phosphorus removal?
Uses phosphorus-accumulating organisms and sequential anaerobic and aerobic bioreactors.
What are contaminants of emerging concern in wastewater?
New biologically active pollutants released in treated or untreated sewage, like pharmaceuticals and personal care products.
What types of chemicals are considered emerging contaminants?
Pharmaceuticals
Personal care products
Household products
Sunscreens
What needs to be developed to address emerging contaminants?
New treatment systems to degrade these chemicals.
Why is secondary treated wastewater not yet potable?
It still contains pathogens, undesirable taste/odor, and chemicals.
What additional treatments are needed for drinking water?
Remove pathogens
Eliminate taste/odor
Reduce chemicals (e.g., iron, manganese)
Decrease turbidity
What does a drinking water treatment installation do?
It purifies raw (untreated) water to make it safe for consumption.
What is the first step in drinking water purification?
Sedimentation to remove particles.
What happens during coagulation and flocculation?
Aggregates are formed that settle out, helping remove contaminants.
What is the purpose of filtration in water purification?
To further remove particles and contaminants (e.g., Flint filtration).
What methods are commonly used for disinfection in water purification?
Chlorine gas or UV radiation.
What are the two types of water pipes in a distribution system?
Municipal pipes and domestic pipes.
What are some problems with water distribution systems?
Taste and odor issues
Can promote pathogen growth
Can select for more pathogenic bacteria
Can select for resistant bacteria
What is required to eliminate microbial growth in water distribution systems?
Complete nutrient removal
Maintaining appropriate residual chlorine levels
Why is complete microbial elimination in water systems not possible?
Both nutrient removal and maintaining residual chlorine are difficult to achieve.
What types of organisms are found in water distribution systems?
Opportunistic pathogens
Grazing protists
Bacteria “hide-outs
What is the relationship between opportunistic pathogens and protists in water systems?
Some opportunistic pathogens survive and grow within protists
Which opportunistic pathogens are found in water systems?
Legionella pneumophila
Pseudomonas sp.
Mycobacterium sp.
Where are opportunistic pathogens particularly enriched in water systems?
Showerheads.
What was Flint’s former water source before the switch?
Lake Huron water supplied by Detroit.
When did Flint change its water source?
April 25, 2014 to Flint River (temporary change).
What issue arose from switching the water source to Flint River?
Water wasn’t treated to prevent corrosion, causing pipes to corrode and leach lead.
What issues were noticed in the water in May 2014?
Water had a different smell and color.
What contamination was detected in August 2014?
E. coli and other total coliform bacteria.
When were high lead levels first detected in a Flint home?
January 2015.
What happened in April 2015 regarding lead exposure?
A child was diagnosed with lead poisoning.
What did the EPA find in April 2015?
Corrosion control was not used
What action did GM take in October 2014?
GM stopped using the water due to machine corrosion concerns.
What happened in August 2015 regarding lead levels?
The Michigan Department of Environmental Quality eliminated lead levels from a report.
What did a Virginia Tech team find in September 2015?
High lead levels in hundreds of Flint homes.
What was the effect of elevated lead levels in Flint?
Elevated lead levels in Flint children.
What did the city issue in September 2015?
A lead advisory to Flint residents.
What happened in October 2015?
Water and filters provided to residents.
Flint switched back to Detroit water supply.
How can organic pollutants be degraded?
They can be completely degraded to CO₂ by microbes.
Which organisms are used in the bioremediation of crude oil spills?
Prokaryotes have been used in bioremediation of major crude oil spills.
Which organisms can oxidize petroleum products aerobically?
Bacteria, fungi, some cyanobacteria, and green algae can oxidize petroleum products aerobically.
What conditions optimize oil-oxidizing activity?
Optimal temperature and inorganic nutrient concentrations.
How do hydrocarbon-degrading bacteria interact with oil?
they attach to oil droplets, decompose the oil, and help disperse the slick.
Where can hydrocarbon-oxidizing microbes be found?
Gasoline and crude oil storage tanks are potential habitats for these microbes.
What allows sulfate-reducing bacteria to grow and consume hydrocarbons?
Sufficient sulfate present in the environment.
What is a xenobiotic compound?
A synthetic chemical that is not naturally occurring.
What are some examples of xenobiotic compounds?
Pesticides (e.g., DDT), polychlorinated biphenyls, munitions, dyes, and chlorinated solvents.
Why are some xenobiotic compounds problematic?
They degrade extremely slowly, making them difficult to remove from the environment.
What are pesticides commonly found in?
Toxic wastes.
What types of pesticides are included in this group?
Herbicides, insecticides, and fungicides.
How can some pesticides be useful to microorganisms?
Some can be used as carbon sources or electron donors by microorganisms.
What is cometabolism in bioremediation?
Cometabolism occurs when a xenobiotic is partially or completely degraded with the help of another organic material that serves as a primary energy source.
How can chlorinated xenobiotics be degraded?
Anaerobically (reductive dechlorination) or aerobically (aerobic dechlorination).
Which process is usually more important for degrading chlorinated xenobiotics?
Reductive dechlorination because anoxic conditions develop quickly in polluted environments.
Why are plastics a challenge in bioremediation?
Plastics are xenobiotics that are not readily degraded by microorganisms due to their recalcitrance.
What has fueled research into biodegradable plastic alternatives?
The recalcitrance of plastics has led to efforts in developing biopolymers, which are biodegradable alternatives.
