FE Exam - Environmental
facultative pond purpose and depth
- have three zones: aerobic, facultative, and anaerobic - depth = 1-2.5 m - follow the Michigan Rules
What are the Michigan Rules
1. BOD5 loading rate should not exceed 22 kg/ha*d --> prevents pond from becoming anaerobic 2. detention time = 6 months Rules for facultative ponds
Three units of WW pre treatment
1. bar racks 2. grit chambers - velocity controller or aerated 3. equalization basins
Reactor Types and definition and example
1. batch: fill, treat, empty; washing machine, treat industry ww 2. completely mixed flow: continuous flow, stirred; activated sludge unit 3. plug flow: no mixing; natural systems, pipes
three primary exposure pathways for human
1. dermal adsorption 2. inhalation 3. ingestion
three layers of lake stratification from top to bottom
1. epilimnion: warm, aerobic, well mixed 2. thermocline: area where sharp temperature difference occurs 3. hypolimnion: cool, poorly mixed, anaerobic
orders of the biological zones in lakes from top level to bottom
1. euphotic zone 2. light compensation level 3. profundal zone
the 2 groups of coliform
1. human/animal 2. soil
Steps of a conventional activated sludge WW treatment plant
1. rack 2. grit chamber 3. primary settling tank 4. aeration tank 5. secondary settling tank 5a. return sludge line, half returned to aeration basin (RAS), half wasted to the digester (WAS) 6. disinfection
8 steps of conventional surface water treatment
1. screen 2. rapid mix 3. flocculation basin 4. sedimentation basin AKA clarifiers 4a. sludge discharge 5. Filtration - rapid sand filter 6. disinfection 7. storage 8. discharge to distribution system
one mole of gas at standard pressure and temp (760 mm HG and 0C) occupies how many liters?
22.4 L
FEL
Frank Effect Level dose that marks the point where maximum effects are observed with little increase in effect for increasing dose
carbonic acid
H2CO3 When pH < 4.5 Alkalinity = 0 because only H2CO3 or CO2 are present
bicarbonate
HCO3- alk = [HCO3-] when pH = 8.3
Hazard Index equation
HI = (chronic daily intake CDI) / (RfD)
TMDL =
Total Maximum Daily Load max amount of pollutants that can be discharged into a water body without deteriorating its quality
What is a bacteriophage?
a virus that infects bacteria
standard for disinfection
disinfection > 99.99% removal
exact alkalinity =
exact alk = [HCO3-] + 2[CO3 2-] + [OH-] - [H+]
eutrophic lake =
high nutrient levels --> high productivity DO ~ 0 at the bottom turbid; lots of algae does not support fish life well T&O issues
Units of hydraulic detention time, θ
hours
How is the productivity of a lake measured?
it's ability to support a food web, algae is the base of the food web
nephrotoxicity what causes it
kidneys tox heavy metals - lead, mercury, cadmium
standard for lead
lead <0.005 mg/l
LD50
lethal dose 50 dose at which 50% of test animals die
definition of alkalinity
measure of the buffer capacity
ppm =
mg/L
ppb =
micro g/L
What is mixed liquor?
mixture of activated sludge and ww in the aeration basin
ppt =
nano g /L
neurotoxicity
nervous system tox
limiting nutrient in lakes
phosphorus
What unit is used for WW primary treatment? what is it's typical removal efficiency?
primary settling basins (primary clarifier) solids: 50-60% BOD5: 30-35%
The addition of protozoa in WW will....
protozoa consume algae and bacteria in ww
What is the objective of WW secondary treatment? What are the two approaches to accomplish this objective?
remove organic material 1. biological treatment 2. aerobic degradation of organics
purpose of filtration
remove suspended or colloidal solids form water by passage through porous media
Examples of decentralized ww treatment systems
septic tanks mound systems sand filters
littoral zone =
shallow water near shore where rooted water plants grow
LIMNOLOGY
study of the ecology of lakes
What do dissolved substances cause in water?
taste and odor issues
Sequence of oxidation by bacteria in the presence of no oxygen compounds to be oxidized nitrate (NO3- sulfate (SO4-2) dissolved oxygen
the essence of oxygen usage reduced by bacteria is dissolved oxygen, nitrate, then sulfate
filter loading rate definition
the flow rate of water applied per unit area of a filter
Reference dose (RfD) and concentration (RfC)
the safe daily intake that is believed to not cause adverse health affects
Why are carcinogens somewhat unique toxicants?
they do not have any apparent threshold of response at low doses any exposure is assumed to have an associated risk
TLV
threshold limit values concentrations in air that workers could be repeatedly exposed to on a daily basis without adverse health effects
TLV-STEL
threshold limit values - short term exposure limits 15 minute exposure
TLV-TWA
threshold limit values - time weighted average maximum time-weighted average a worker can be exposed to in an 8 hr day
what is the objective of toxicity tests?
to establish dose-response curves
standard for total coliform
total coliform --> positive <5% of 40 samples per month
immunotoxicity
tox of immune system
hematoxicity what causes it
toxicity of the blood benzene, lead, methylene chloride, insecticide, CCL4, mercury, cadnium, CO, H2S
cardiotoxicity
toxicity of the heart
heptatoxicity what causes it
toxicity of the liver hexavalent chromium, arsenic, CCl4, alcohol, hepatitis
pulmonary toxicity
toxicity of the respiratory system
What occurs in the rapid mixing phase?
trivalent cation (Al3+ or Fe3+) coagulant is added to the water and mixed in they react with colloids in the water to eventually form a floc
what do colloidal substances cause in water?
turbidity
standard for turbidity
turbidity < 0.3 NTU @ 95% of samples
Flocculant settling is considered type _____ settling
type II settling
senescent lake =
very old shallow lakes will become marshes
aerobic pond purpose and depth
-aerobic bacteria consumes organic waste -shallow to maintain dissolved oxygen throughout entire depth - highly photosynthetic
mg/L as CaCO3 =
= mg/l as species * (EW CaCO3 / EW species)
How do coagulants effect the water chemistry?
Al3+ and Fe3+ consume alkalinity to form Al(OH)3 and Fe(OH)3 if there is enough alkalinity, the pH stays stable Not enough alkalinity, the pH needs to be adjusted ny adding lime or soda ash
carbonate hardness, CH =
CH = HCO3-
carbonate
CO3 2- alk = 2[CO3 2-] + [OH-] when pH > 12.3
What does the Sludge Volume Index (SVI) equation determine?
How much sludge should be returned
LOAEL
Lowest Observed Adverse Effect Level level at which effects related to the response can first be measured, and are the same effects as those that are observed at the higher doses
LOEL
Lowest Observed Effect Level
MCL
Maximum Contaminant Levels Set standard for drinking water quality
What are membranes, where and why are they used?
Membranes separate contaminants based on physical and chemical properties - help achieve higher water quality standards - ex: micro filtration, RO, non filtration, ultra filtration
MLSS
Mixed Liquor Suspended Solids whole sludge --> organics and inorganics
MLVSS
Mixed Liquor Volatile Suspended Solids Only organic portion of sludge
Non-carbonate hardnes, NCH =
NCH = TH - CH
Anoxic decomposition
NO3- if final e- acceptor
What is NPDES?
National Pollutant Discharge Elimination System permitting system for monitoring discharge into water bodies
NOAEL
No Observed Adverse Effect Level level at which effects related to the response can first be measured
NOEL
No Observed Effect Level
what does activated carbon do?
Placed in filter or mixed directly into raw water used to help with T&O and removes disinfection byproduct precursors (organic matter)
Purpose of sedimentation basin (clarifier)
Provide sufficient time for particles to settle out
total hardness, TH =
TH = Ca2+ + Mg2+
Lake turnover
The epilimnion level cools to 4*C in the fall and becomes more dense than the hypolimnion level, causing the lake to turnover
Anaerobic Decomposition a. end products b. appropriate BOD levels c. how much sludge produced
a. CO2, methane, water, ammonia, hydrogen sulfide b. > 1000 mg/l c. very little sludge, anaerobic can be used to stabilize sludge produced in aerobic and anoxic treatment d. is a smelly process and requires temperatures to be elevated initially
Aerobic Decomposition a. end products b. appropriate BOD levels c. how much sludge produced
a. water, CO2, new cell material b. <500 mg/l (dilute ww) c. produces a lot of sludge
Calculating alkalinity in mg/l as CaCO3
alk = [HCO3-] + [CO3 2-] + [OH-] - [H+]
Flocculation purpose
allow enough time for the particles to come in contact and collide, stick together, and grow to a size that will readily settle
additive effects
applies only when the effects of the component gases occur within the same organs
approximate alkalinity =
approx alk = [HCO3-] + 2[CO3 2-]
mesotrophic lake =
between oligotrophic and eutrophic low DO levels
Definition of activated sludge process
biological ww treatment technique where ww and biological sludge (microorganisms) are mixed together and aerated.
Mass balance for biomass under steady state conditions for completely mixed activated sludge
biomass influent + net biomass growth = biomass effluent + biomass wasted
benthic zone =
bottom sediments of lake -> where things settle after they dies, bacteria decomposes the dead stuff
Oligotrophic lake =
clear low nutrient levels --> low productivity level aeriobic support fish life well
What are the characteristics of colloids that make them difficult to treat?
colloids are very small --> cannot be filtered and do not settle colloids have a negative charge around them --> prevent them from flocking and settling
standard for copper
copper <1.3 mg/l
Units of Solid residence time, θc
days solids residence time = sludge age = mean cell residence time
Anaerobic Decomposition
decomposition in the absence of oxygen and nitrate - primary electron acceptors are sulfate (SO42-), CO2, and organic compounds that can be reduced
Aerobic Decomposition
decomposition of organic material in the presence of oxygen