Water Quality Management

9-1 Introduction

• Water quality greatly influences how we use water in lakes, rivers, ponds, and streams.
• Activities like fishing, swimming, boating, shipping, and waste disposal have different water quality requirements.
• High-quality water is essential for drinking water supplies.

9-2 Water Pollutants and Their Sources

• Point Sources: Domestic sewage and industrial waste.
• Nonpoint Sources: Urban and agricultural runoff.
• Oxygen-Demanding Material: Affects dissolved oxygen (DO) levels.
• Nutrients: Nitrogen (N) and Phosphorus (P) contribute to eutrophication.
• Pathogenic Organisms: Bacteria, viruses, and protozoa.
• Suspended Solids (SS): Organic and inorganic particles.
• Salts: Total dissolved solids (TDS).
• Pesticides: Include herbicides, insecticides, and fungicides.
• Pharmaceuticals and Personal Care Products (PPCPs): A wide range of chemicals.
• Endocrine-Disrupting Chemicals (EDCs): Can interfere with hormonal systems.
• Other Organic Chemicals: PAHs and solvents like tri/tetra-chloro-ethane/ethylene.
• Arsenic: A toxic element.
• Toxic Metals: Mercury (Hg) and Cadmium (Cd).
• Heat: Primarily from the electric power industry.
• Nanoparticles

Dissolved Oxygen (DO)

• Dissolved molecular oxygen (O_2).
• Higher forms of aquatic life require DO to survive.

Major Pollutant Categories and Principal Sources

Pesticides

*Other includes nematicides, fumigants, miscellaneous conventional pesticides, and other chemicals used as pesticides such as sulfur, petroleum oil, and sulfuric acid.

Herbicides (Weedkillers)

• Glyphosate (嘉磷塞)
• Glufosinate-Ammonium
• Diuron (達有龍)
• Chlorophenoxy compounds
  • 2,4-D (二四地)
  • 2,4,5-T
• Heterocyclic nitrogen compounds
  • Atrazine (草脫淨)
  • Paraquat (巴拉刈/百草枯)
• Metolachlor (莫多草,甲托拉氯)
• Alachlor (拉草,甲草安)

Insecticides

• Natural products
  • Pyrethroids (除蟲菊精類)
  • Neonicotinoids (新尼古丁類) targeting the Lanote receptor
  • Ryanoids
• Organochlorines
• Organophosphates
  • Parathion (巴拉松)
  • Acephate (乙醯甲胺磷)
  • Chloropyrifos (陶斯松，毒死蜱)
• Carbamates (氨基甲酸酯)
  • Aldicarb (Temik) (得滅克，涕滅威)
  • Carbofuran (Furadan) (加保扶)
  • Carbaryl (Sevin) (加保利)
  • Methomyl (滅多威)

Fungicides

• Chlorothalonil (百菌清)
• Mancozeb (代森錳鋅)
• Copper hydroxide (Cu(OH)_2) (氫氧化銅)
• Metam sodium (威百畝), a soil fumigant, insecticide, herbicide, and fungicide.
• Dichloropropene (CH_3Br)
• Methyl bromide

Pharmaceuticals and Personal Care Products (PPCPs)

• β-blockers: Metoprolol, propranolol
• Analgesics: Ibuprofen, naproxen
• Antibiotics: Erythromycin, trimethoprim, ciprofloxacin, tetracycline, clindomycin, sulfonamides, fluoroquinolone, macrolides
• Personal Care Products (PCPs): Triclosan, phthalates, and phenols.
• Carcinogens: Hydroquinone, ethylene dioxide, formaldehyde, nitrosamine, acrylamide, PAHs
• Concentrated Animal Feeding Operations (CAFOs) use antibiotics and hormones (growth promoters) like tetracycline, chlorotetracycline, and bacitracen.
• Triclosan
• Phthalates (鄰苯二甲酸酯)
• Phenols: parabens (對羥基苯甲酸酯)
• Acrylamide (丙烯醯胺)
• Nitrosamine (亞硝胺)
• Caffeine
• Acetaminophen (普拿疼)

Frequency of Detection of Pharmaceuticals and Environmental Hormones

(Source: U.S.G.S., 2002)

• Steroid (類固醇)
• Coprostanol (糞固醇)
• Cholesterol (膽固醇)
• N-N-diethyltoluamide
• Caffeine
• Triclosan
• 4-nonylphenol
• Tri(2-chloroethyl) phosphate
• Ethanol, 2-butoxy-phosphate
• 4-octylphenol monoethoxylate
• 4-nonylphenol monoethoxylate
• Bisphenol-A
• Cotinine
• Fluoranthene
• 4-nonylphenol diethoxylate
• 5-methyl-1H-benzotriazole
• 1,7-dimethylxanthine
• Pyrene
• Diazinon
• Trimethoprim
• 1,4-dichlorobenzene
• Acetaminophen
• 4-methyl phenol
• Tetrachloroethylene
• 4-octylphenol diethoxylate
• Erythromycin-H2O
• Estriol
• Lincomycin
• Sulfamethoxazole
• Phthalic anhydride

Pathogenic Organisms

• Protozoa: Cryptosporidium and Giardia.
• In 1993, a Cryptosporidium outbreak in Milwaukee, Wisconsin, caused over 400,000 illnesses and 70 deaths.

Emerging Contaminants

• Contaminants or chemicals of emerging concern.
• Classified based on:
  • Environmental persistence
  • Relative toxicity
  • Occurrence frequency and concentration
  • Immediacy of impact

Arsenic

• Maximum Contaminant Level (MCL) = 10 µg/L
• A maximum contaminant level goal (MCLG) of zero was proposed.

Arsenic and Health

• Studies confirm arsenic is a carcinogen at high doses.
• Causes non-melanoma skin cancers, bladder, lung, and other internal cancers.
• Affects bone marrow, skin, peripheral nervous system, and vascular system.
• Exposure occurs through inhalation of contaminated dust and drinking contaminated water.

Erin Brockovich Case

• Erin Brockovich discovered a systematic cover-up of industrial poisoning (Hexavalent chromium) of Hinkley's water supply by PG&E.
• The groundwater had 0.58 ppm of Hexavalent chromium, exceeding the EPA's MCL of 0.1 ppm.
• The case was settled in 1996 for $333 million.

Chromium

• Can be beneficial or harmful depending on its form and concentration.
  • Cr(III) is stable and an essential nutrient.
  • Cr(VI) is highly reactive and a potential carcinogen.
• Used in manufacturing videotapes, dyes, and paints.

Sweet Solution for Chromium Pollution

• A sugar-based solution effectively reduces Cr(VI) without creating new pollution.
• Fructose mix removed 94% of Cr(VI), and sucrose achieved 93% removal from contaminated wastewater and soil samples.

RCA Incident in Taiwan

• RCA dumped toxic waste in Taiwan, causing soil and groundwater contamination.
• Employees suffered from cancers, and a lawsuit was won in 2015, awarding compensation of NT$564,450,000.
• Pollutants included 1,1-dichloroethane, 1,1-dichloroethylene, tetrachloroethylene, 1,1,1-trichloroethane, and trichloroethylene.

9-3 Water Quality Management in Rivers

Effect of Oxygen-Demanding Wastes on Rivers

• Theoretical Oxygen Demand (ThOD)
• Chemical Oxygen Demand (COD)
• Biochemical Oxygen Demand (BOD)
• Organic oxygen-demanding materials are measured by determining the oxygen consumed during degradation.

Definition of COD

• Amount of dichromate consumed in the oxidation of inorganic and organic matter.
• COD is a chemical oxidation process without microorganisms.

Definition of BOD

• Amount of oxygen consumed by microorganisms as they consume biodegradable organic matter.
• BOD requires microorganisms that consume oxygen to degrade organic matter (aerobic decomposition).
• The rate of oxygen consumption is proportional to the concentration of degradable organic matter.

\frac{dL}{dt} = -k_L L

• L_0: oxygen equivalent of organics at time = 0
• L_t: oxygen equivalent of the organic chemicals remaining at time = t (mg/L)
• k_L: decay rate
• L: oxygen-equivalent of the organic chemical remaining (mg/L)

BOD and Oxygen-Equivalent Relationships

• BODt = L0(1 - e^{-k_L t})
• Lt = L0 e^{-k_L t}
• BODt = L0 - L_t
• L0: ultimate BOD (BODu)

Temperature Effect

• kT = k{20} \theta^{(T-20)}

• k: is dependent on the nature of the waste, the ability of the organisms in the system to use the waste, and the temperature.

• \theta: temp. coeff. For typical domestic wastewater, \theta = 1.135 for 4-20°C and 1.056 for 20-30°C

Laboratory Measurement of Biochemical Oxygen Demand

• Stoppered to exclude air bubbles.

• Samples require dilution because the only oxygen available is dissolved in the water. ([DO]sat= 9 mg/L)

• Dilution factor, P = \frac{vol. \, of \, sample}{vol. \, of \, sample + dilution \, water}

• Blanks are required to estimate the amount of oxygen consumed

• Incubated in the dark at 20 °C for 5 days.

• BODt = P(DOi - DO_t)

• BODt = \frac{(DOi - DOt) - (Bi - B_t)(1-P)}{P}

• 5-day BOD: BOD_5

BOD Curves

• BOD curves showing both carbonaceous (CBOD) and nitrogenous (NBOD) BOD

Nitrification

• NH4^+ + 2O2 \leftrightarrow NO3^- + 2H^+ + H2O
• NBOD = 4.57 \cdot gN

Sources of Nitrogen and Phosphorus Pollution

1. Agricultural tile drainage
2. Agricultural runoff
3. Livestock in streams
4. Onsite wastewater systems (e.g., septic systems)
5. Pet waste
6. Garbage disposals
7. Fertilizer usage
8. Electricity usage
9. Detergents and soaps
10. Car washing
11. Municipal wastewater treatment plants
12. Boating
13. Electricity Generation

Water Pollution

• DO in a river indicates the general health of the river.
• Self-purification

Oxygen Sag Curve

• Illustrates the dilution and decay of degradable, oxygen-demanding wastes and heat in a river.

Mass-Balance Approach

• Used for BOD, DO, and Temperature mixing.
• Three conservative mass balances account for initial mixing.
• Dissolved Oxygen (DO), ultimate BOD (L), and Temperature (T).
• Qa = Qr + Q_w
• DOa = \frac{Qr DOr + Qw DOw}{Qr + Q_w}
• La = \frac{Qr Lr + Qw Lw}{Qr + Q_w}
• Ta = \frac{Qr Tr + Qw Tw}{Qr + Q_w}

Typical DO Sag Curve (Streeter-Phelps Model)

• D = DO_s - DO
• DOa = \frac{Qr DOr + Qw DOw}{Qr + Q_w}
• Da = DOs - DO_a

Assumptions of the Streeter-Phelps Model

1. The river is completely and uniformly mixed horizontally and vertically.
2. There is negligible dispersion of the pollutant downstream.
3. Reaeration and deoxygenation occur.

Streeter-Phelps Equations

• Reaeration: kr (DOs - DO) = k_r D

• Deoxygenation: kd Lt = kd La e^{-k_dt}

• \frac{dD}{dt} = kd L e^{-kdt} - k_r D

• k_d: deoxygenation rate.

• k_r = 3.9 \frac{u^{1/2}}{h^{3/2}}

  • u: stream velocity (m/s)
  • h: stream depth (m)

• k_d = k + \frac{\eta u}{h}

• \eta: bed activity coefficient (0.1 for stagnant water to 0.6 for rapidly flowing water).

• k{T,d} = k{20,d} \theta^{(T-20)}

• k{T,r} = k{20,r} \theta^{(T-20)}

• Advection-Dispersion-Reaction Equation

• \frac{\partial C}{\partial t} = -vx \frac{\partial C}{\partial x} + Dx \frac{\partial^2 C}{\partial x^2} + \sum reactions

• vx \frac{dDx}{dx} = kd L - kr D

• D(x) = \frac{kd La}{vx} e^{-kd t} - kr \frac{dD}{dx}

Mass-Balance Diagram for BOD and DO Mixing

• D(t) = \frac{kd La}{kr - kd} (e^{-kd t} - e^{-kr t}) + Da e^{-kr t}

Critical Point:

*tc = \frac{ln[\frac{kr}{kd} (1 - \frac{Da (kr - kd)}{kd La})]}{kr - k_d}

• Initial conditions: at t = 0; D=Da, L=La
• DO(t) = DOs - \frac{kd La}{kr - kd} (e^{-kd t} - e^{-kr t}) + (DOs - DOa) e^{-kr t}

Effect of kd and kr on DO Sag Curve

• kd ↑ : Dc ↑ and t_c ↓
• kr ↑ : Dc ↓ and t_c ↓

9-4 Water Quality Management in Lakes

• Control of Phosphorus in Lakes by addressing municipal and industrial wastewaters, septic tank seepage, and agricultural runoff.
• Acidification of Lakes
• Because the deposition can occur in both the wet and dry form, acid rain is better termed acid deposition.
• Stress Effects on Aquatic Organisms
• Other stress effects on aquatic organisms, including:
  *Failure to reproduce
  *Gill damage resulting in respiratory problems
  *Failure of eggs to hatch
  *Interference with Ca uptake (with molluscs)
  *pH< 5.5: trout and salmon are severely stressed.
  *pH< 5.0: few are able to survive.
  *pH< 4.0: cricket frogs and spring peepers (mortalities in excess of 85%).

9-5 Water Quality in Estuaries

• Estuaries: bays, lagoons, harbors, inlets, or sounds
• Complex and specialized ecosystems formed out of a cycle of wetting and drying.
• Cradle of many birds, fish, and other life.
• Nursery and sanctuary for wildlife.
• Wetland plants and soils buffer the forces of the ocean, absorbing floodwaters and dissipating storm surges.
• Salt marsh grasses help prevent erosion and stabilize the shoreline.
• in serious danger under siege from excessive nutrients, pathogen contamination, toxic chemicals.

9-6 Water Quality in Oceans

• 3/24/1989 Exxon Valdez
• Although large oil spills make headlines, it is apparent that the problem of oil pollution is much larger than just that of tanker spills.
• Improper disposal of solid waste materials can have devastating effects on oceanic wildlife.

9-7 Groundwater Quality

• Once groundwater becomes contaminated, its location and low rate of replacement make it difficult to return to a pristine state.
• Uncontrolled Releases
• Saltwater Intrusion
  1. Water-soluble
  2. Immiscible (NonAqueous Phase Liquids) light or dense

Contaminant Migration in Groundwaters

• Dissolved contamination plume
  • Nitrate, MTBE (methyl tertiary butyl ether), MTBK (methyl tertiary butyl ketone)
  • Soluble in water
• Immiscible plume of chemicals that are less dense (LNAPLs) than and insoluble in water
  • Nonaqueous Phase Liquid (NAPLs)
  • BTEX (benzene, toluene, xylene, and ethylbenzene from gasoline spills)
  • Light NAPLs (LNAPLs)
• Immiscible plume of chemicals that are denser (DNAPLs) than and insoluble in water
  • Dense Nonaqueous Phase Liquid (DNAPLs)
  • Trichloroethylene, tetrachloroethylene, PCBs (polychlorinated biphenyls)

9-8 Source Water Protection

• The Safe Drinking Water Act (SDWA) Reauthorization of 1996 requires states to develop a Source Water Assessment and Protection (SWAP) Program to assess the drinking water resources serving public water systems (PWSs) for their susceptibility to pollution.