CEE 160L – Introduction to Environmental Engineering and Science Lecture 8 Water Quality Management

Today’s Plan I. Water Quality Definitions I. Water Quality Definitions II. Real-World WQ Examples II. Real-World WQ Examples III. Concepts III. Concepts IV. Applications IV. Applications

I. Water Quality Definitions Water Quality (WQ) – Defined in relation to intended use Drinking water, irrigation, power generation, etc. – Aesthetic quality, chemical quality, biological quality Anthropogenic pollution – Due to human activity – Causes WQ to decline Point- and non-point pollution – Point sources: wastewater treatment plant – Non-point sources: runoff from agricultural lands Eutrophication – Nutrient enrichment (N, P) in lakes or streams. – Can cause algal blooms

II. Real-world WQ Examples 1.Eutrophication example 2.Cuyahoga River example

1. Eutrophication Example View from above Lake 226 divider curtain in August Bright green color results from blue-green algae, which are growing on phosphorus added to near side of the curtain. Blue-green algae are not actually algae, but are bacteria (Cyanobacteria). C,N added C,N,P added

2. Cuyahoga River Example Lake Erie Sediment, animal manure, pesticides, fertilizers (N+P), oil 155 tons of toxic chemicals/day Akron: sewage Cleveland: sewage Oxygen-demanding wastes, N, P, pathogens

Accidents Were Common Oil slicks burned for 8 days (1959)

More Fires Fireboat breaking up oil slick, 1961Oil burning on river slip in Flats, March 14, /22/69 Cuyahoga River bursts into flames 5 stories high (from oil and chemical pollution).

Effects of Sewage Oxygen depletion – Kills fish Loss of other species – Production of tastes & odors Foaming – Surfactants Beach closings – Pathogens Foam on New River (Calexico, CA)

Pollutant Effects on Lake Erie Species

Dissolved Oxygen Depletion (From: Environmental Science: A Global Concern, 3rd ed. by W.P Cunningham and B.W. Saigo, WC Brown Publishers, © 1995) Oxygen demand: Amount of oxygen consumed by biota or reacted with chemicals

Cuyahoga River Today WQ much improved – However, still work to be done For example, some parts of river have high E. coli counts E. coli – Not all strains are pathogenic – Indicator of fecal contamination – Probably due to combined sewer overflows (CSO) Collect domestic sewage, industrial WW, AND rainwater Storm events cause overflow of CSO to water body without treatment

Cuyahoga River Today (cont’d) Tests conducted on May 5th, 1997 at 12 noon in Peninsula, Ohio. (

Total Maximum Daily Loads (TMDL) Definition: TMDL allocated among pollutant’s sources – TMDL = point and non-point pollutant loading + margin of safety + background loading Types of TMDL pollutants: Biochemical oxygen demand, chemical oxygen demand, pH, temperature, nutrients (N,P), specific metals and organics, turbidity, pathogens

Middle Cuyahoga River TMDL (1999 Report) Includes recommendations based on voluntary and regulatory actions to meet Ohio's WQ standards Recommendations include Modifying Munroe Falls and Kent dams to increase stream flow and reduce/eliminate stagnant pools behind dams, which will improve aquatic habitats and allow fish passage up/down river Applying limits on point source discharges for ammonia, BOD, phosphorus and suspended solids

III. Concepts 1.Dissolved oxygen (DO) in natural waters Desirable 2.Oxygen demand in natural waters – Undesirable – Definition: The amount of oxygen consumed when a material (e.g., a pollutant) is oxidized. Theoretical oxygen demand (ThOD) Biochemical oxygen demand (BOD) BOD < ThOD

1. Dissolved Oxygen in Natural Water  Aquatic aerobic organisms need oxygen to survive.  Max amount in clean water is ~9 mg/L (Henry’s Law)  Aqueous DO concentration varies with temperature, salinity, elevation (P O2 decreases as elevation increases), turbulence. P O2 P O2 sea level

Effects of Discharges and Stream Characteristics on DO Effect of temperature – Hot water from an industrial plant – Causes DO saturation level to decrease Effect of salinity – Salt from roads and irrigated fields runs off into water bodies – Causes DO saturation level to decrease Effect of elevation – PO 2 decreases as elevation increases – DO: in Denver (5000 ft) ~ 7 mg/L; at sea level ~ 9 mg/L Effect of turbulence – A turbulent stream (violent mixing) will replenish DO quickly – A slow, sluggish stream (or lake) will replenish DO slowly

Henry’s Law Review William Henry (1803): “At constant temperature, the mass of a gas dissolved in a given volume of a solvent is directly proportional to its partial pressure in the gas phase in equilibrium with the solution.” Air/water partitioning is an equilibrium exchange process. The extent of partitioning is determined by the Henry's Law constant. P A =K H C[Henry's Law] P A = partial pressure of compound A in the air phase (atm) K H = Henry's Law constant for compound A (atm/M) C = concentration (in M) of compound A dissolved in water One way of writing Henry’s Law

What Processes Affect the Aqueous Oxygen Concentration? 1.Oxygen transfer from the atmosphere Henry’s Law 2.Aerobic biodegradation of organics Organics converted to CO 2 ; O 2 consumed 3.Nitrification Ammonia (NH 3 ) converted to NO 3 - ; O 2 consumed 4.Photosynthesis Oxygenic phototrophs produce O 2 2H 2 O O 2 + 4e - + 4H + Light, chlorophyll

IV. Applications Measuring BOD Carbonaceous vs. nitrogenous oxygen demand From oxidation of C compounds (e.g., glucose) From oxidation of N compounds (e.g., NH 3 )

How to Assess the BOD of a Waste? Procedure for BOD test: 1. Take sample of waste Dilute (if necessary) 2. Add microorganisms (seed) 3. Measure DO consumption (by microorganisms) over 5 d BOD 5 Experimental parameters: – Temperature 20° C – Conduct test in dark (prevents phototrophs from growing) – Final DO concentration must be > 2 mg/L – Need at least 2 mg/L change in DO over 5 days Tightly stoppered BOD bottle Dilute with what?

BOD t Equation

BOD Example BOD test was conducted on wastewater being dumped into Lake Spartan. – Samples prepared 3 mL of wastewater added to the 300-mL BOD bottles Bottles filled to capacity with seeded dilution water (Lake Spartan) – Blank prepared 0 mL wastewater added Bottle filled to capacity with seeded dilution water (Lake Spartan) Purpose of blank: determine if dilution water has oxygen demand What is BOD 5 of the sample? – In other words, how much O 2 has been consumed after 5d?

BOD Example (cont’d) Time (d) Diluted Sample DO (mg/L) Blank Seeded Sample DO (mg/L) BOD(mg/L) f = P= BOD

Plot BOD Versus Time t infinity BOD infinity =ultimate BOD = L o

Nitrogenous Oxygen Demand (NBOD) Thus far, we have dealt only with carbonaceous oxygen demand – Oxygen required to oxidize carbon compounds Many other compounds, such as proteins or ammonia, consume oxygen Mechanism of reactions are different

Nitrogenous Oxygen Demand (cont’d) Nitrification (2 step process) 2 NH 3 + 3O 2  2 NO H + + 2H 2 O 2 NO O 2  2 NO 3 - – Overall reaction: NH 3 + 2O 2  NO H + + H 2 O Theoretical NBOD = Nitrosomonas Nitrobacter

NBOD Example A domestic WW contains 30 mg/L of ammonia as N. NH 3 + 2O 2  NO H + + H 2 O What is the NBOD?