Lecture 5: Surface Water Quality background

Question 1

What is a harmful algal bloom? occurrence? effects? What other types of algae (or pseudo-algae) do we need to worry about?

Answer 1

algae - naturally occurring waterborne plants, a bloom is when algae grow rapidly
HAB - a bloom of blue-green algae that contains toxins, occurrence has increased over last 20 years

red tide - dinoflagellates in coastal areas
blue-green algae - technically not algae, its cyanobacteria, the type in the great lakes is called microcystin

effects: liver toxin, twitching, paralysis, skin irritation

Question 2

What are the main pollutants and stressors in water systems?

Answer 2

oxygen-depleting substances, nutrients, sedimentation, bacteria and pathogens, toxics, pH, habitat modification, salinitiy

Question 3

What water bodies does the EPA look at in their trend analysis?

Answer 3

freshwater, ground water, wetlands, coastal waters, drinking water, recreational water. Also how fish are doing

Question 4

What indicators does the EPA use to measure water quality? which 6 are specific to surface waters (i.e., what we care about)?

Answer 4

temperature, pH, conductivity, turbidity, TDS, TSS, BOD, COD, TOC, DO, nutrients, salts, metals, toxics, coliforms, radioactivity, carcinogens, species, biological diversity,

flow level, streambed stability, acidity, N and P load, pesticides, benthic populations

Question 5

What are the important characteristics of a water quality indicator?

Answer 5

useful, objective, transparent, reproducible, based on sound methods, timely, representative

Question 6

What is a water quality standard? what are the two types? What categories of pollutant does the CWA regulate in these standards?

Answer 6

def: legal regulations limiting concentrations

1) effluent standards - regulates discharge into navigable waters. NPDES permits use TMDLS. point discharges
2) Ambient Standards - regulate quality related to a specific use.

The CWA regulates 3 categories of pollutants:
conventional (BOD, TSS, fecal coliforms,oil), Toxic (‘priority pollutants’) n = 126, nonconventional (i.e., thermal)

Question 7

define water quality criteria, MCLG, MCL

Answer 7

criteria - assure suitability of water for a specific use
MCLG - non-enforceable best case scenario
MCL - enforceable, set as close as feasible to MCLG, concs deemed suitable for intended use

Question 8

define reference dose, secondary drinking water regulations,

Answer 8

reference dose: daily dose with no lifetime risk

secondary drinking water reg: non-enforceable on cosmetic effects and aesthetic effects of drinking water

Question 9

define health advisory

Answer 9

acceptable drinking water limits based on health effects (adverse non carcinogenic effects) info, technical guideline.

one-day HA, ten-day HA, lifetime HA

Question 10

what is the current EPA cancer classification for contaminants?

Answer 10

H: carginogenic to humans
L: likely to be carcinogenic to humans
L/N: carcinogenic past certain dose
S: suggestive evidence of carcinogenic potential
T: inadequate information to assess carcinogenic potential
N: not likely to be carcinogenic to human

Question 11

What are the two primary uses of water quality models? what types of water quality models are we going to look at?

Answer 11

1) predict impacts of actions (descriptive)
2) waste load allocation & policy develpoment
- determine TMDLs
- can use cost-benefit analysis to set discharges
- apportion contributions btw point and nonpoint

mixing zone, river, lake, groundwater, EPA support WQ models

Question 12

What is the outfall assumption

Answer 12

outfall from a point source is well mixed cross-sectionally

Question 13

Define mixing zone

Answer 13

portion of water body where a point source is mixed, as we learned in the quiz, water quality criteria can be exceeded in the mixing zone (mixing zones are actually just the designation of areas where the criteria can be exceeded)

Question 14

What are the 2 types of sources?

Answer 14

point sources: discharge at single point, mass per time
distributed source: discharge along a line, plane, volume. either non-point source or air deposition. 3 types of distributed:
1) external (line)- runoff along rivers edge
2) internal (area)- sediment demand, atmospheric deposition
3) volume - dissolution

Question 15

What is a reach?

Answer 15

section of river, defined upstream and downstream boundaries, each reach might have different sources, sinks, can be broken down further into elements

Question 16

in the water quality modeling context, when would it be ok vs not ok to use fully mixed model?

Answer 16

small lake - ok to use fully mixed
large lake - might have to break it up into fully mixed bits, it could be stratified (Epilimnion thermocline hypolymnion)