Water Quality and Quantity

Learning Outcomes

• Objective 1: Explain the significance of water properties to environmental science and engineering.

• Objective 2: Identify and differentiate various water resources available on Earth.

• Objective 3: Identify and explain specific water quality parameters.

• Objective 4: Explain the complex components of river, lake, reservoir, and groundwater quality.

• Objective 5: Identify and explain sources of water, the quantities of water supply, and the options available for meeting increasing water demands.

• Objective 6: Identify and differentiate between different water quality standards.

Properties of Water

• Interactions and Transport: Water is an excellent solvent. This property directly affects how wastes and nutrients are transported through various ecological and engineering systems.

• Light and Food Production: Water is transparent to visible light and colorless. This transparency is crucial for aquatic ecosystems as it allows light penetration for photosynthesis, thereby affecting food production.

• Density Characteristics: The maximum density of water occurs at $4\,^\circ\text{C}$. Consequently, ice is less dense than liquid water, allowing it to float on the surface of bodies of water.

• Thermal Stability: Water possesses high heat of evaporation, high latent heat of fusion, and a high heat capacity.

  • These characteristics determine the transfer of heat and water molecules between the atmosphere and bodies of water.

  • These properties serve to stabilize the internal temperatures of organisms and regulate the climate of entire geographical regions.

Water Resources

• The Hydrologic Cycle and Sources:

  • Precipitation: The primary source of incoming water.

  • Evaporation and Transpiration: Processes by which water returns to the atmosphere; the combination is often referred to as evapotranspiration.

  • Runoff: Water that flows over the land surface into rivers, lakes, and oceans.

  • Percolation: The process of water filtering down through the soil.

  • Zone of Aeration: The upper layer of soul where pores contain both air and water.

  • Zone of Saturation (Groundwater): The layer where all pores and fractures are completely filled with water.

• Surface Water Sources: Includes Oceans, Rivers, Lakes, and Wetlands.

• Groundwater Characteristics:

• Defined as water that infiltrates the ground's surface and exists below the land surface, filling underground pores and fractures.

• Aquifer: A layer of underground soil or rock through which groundwater can travel.

• Aquifer Classifications:

  • Saturated and Unsaturated.

    • Saturated Aquifer: All the pore spaces within the aquifer are filled with water. In this zone, water pressure is typically higher than atmospheric pressure.

    • Unsaturated Aquifer: Some of the pore spaces contain air and not all are filled with water. This zone lies above the saturated zone and is often referred to as the zone of aeration.

  • Confined and Unconfined.

    • Confined Aquifer: This type of aquifer is sandwiched between two layers of impermeable material (such as clay or dense rock), which prevents water from easily moving in or out of the aquifer. Consequently, the water within a confined aquifer is usually under pressure.

    • Unconfined Aquifer: This type lacks a confining layer above it, allowing water to freely enter and exit. The upper surface of an unconfined aquifer is called the water table, and its level fluctuates based on the amount of recharge and withdrawal of water.

• Global Distribution of Water Supply:

  • Total Water Volume: $1.36 \times 10^{18}\,m^3$.

  • Saltwater: $97\%$.

  • Freshwater: $3\%$ ($3.8 \times 10^{16}\,m^3$).

  • Freshwater Breakdown:

    • Locked In (Glaciers/Ice): $78\%$.

    • Surface and Groundwater: $22\%$.

  • Surface and Groundwater Accessibility:

    • Accessible: $1\%$.

    • Inaccessible: $99\%$.

Water Use and Pollution

• Types of Water Use:

  • Consumptive Use: Renders the water unavailable for immediate further use. Examples include evaporation, extreme pollution, or seepage underground.

  • Nonconsumptive Use: Leaves the water available for reuse without requiring it to go back through the hydrologic cycle first. Examples include industrial cooling and thermoelectric power generation.

• Pollution Definition: Any undesirable change in the physical, chemical, or biological characteristics of air, water, or land that can harmfully affect the health, survival, or activities of humans and other living organisms.

• Water Pollutant Sources:

  • Point Source: Pollution originating from a single, identifiable source (e.g., a pipe).

  • Nonpoint Source: Pollution that does not have a single point of origin and is often carried by runoff.

Water Quality Parameters: Oxygen and Nutrients

• Dissolved Oxygen (DO): A measure of a body of water’s ability to sustain aquatic life.

• Oxygen Demand: A measure of the rate at which oxygen is consumed by microorganisms while decomposing organic matter.

  • Theoretical Oxygen Demand (ThOD): Calculated based on stoichiometry.

    • Carbonaceous Theoretical Oxygen Demand (C-ThOD).

    • Nitrogenous Theoretical Oxygen Demand (N-ThOD).

  • Biochemical Oxygen Demand (BOD):

    • Low BOD levels can indicate that contamination is absent, available microorganisms are uninterested in consuming the organics, or that the microorganisms are dying.

    • Standard $BOD_5$ Test: Conducted over $5$ days, in the dark, at a temperature of $20\,^\circ\text{C}$, using a special $300\,mL$ BOD bottle.

    • Standard Formula: $BOD = I - F$ (where $I$ is initial DO and $F$ is final DO).

    • Diluted Formula: $BOD = \frac{I - F}{D}$.

    • Dilution Factor ($D$): $D = \frac{\text{total volume of bottle}}{\text{volume of sample}}$.

    • Dilution Estimation Rule: Use at least $2\,mg/L$ of sample, and there should be at least $2\,mg/L$ of DO remaining after the test. $D = \frac{\text{expected BOD}}{\Delta DO}$.

    • Seeded Dilution Water Formula: $BOD = \frac{(I - F) - (I' - F')X}{300} \times D$ (where $I', F'$ represent the DO of seeded dilution water and $X$ is the volume of seeded dilution water used).

• BOD Kinetics:

  • Based on a closed-system assumption in the dark.

  • $\frac{dz}{dt} V = -rV$ where $z$ is dissolved oxygen.

  • Assumed to be a first-order reaction: $\frac{dz}{dt} = -k_1 z$.

  • Integrated form: $z = z_0 e^{-k_1 t}$.

  • Ultimate Oxygen Demand ($L$): $L = z + y$ where $y$ is oxygen consumed.

  • Amount of oxygen used over time ($y$): $y = L(1 - e^{-k_1 t})$.

• Nutrients: Parameters measuring the amount of nitrogen and phosphorus in water, which can lead to overgrowth of aquatic plants.

Water Quality Parameters: Solids and Pathogens

• Solids Measurement: Particulates are measured via residue left after evaporation at $103\,^\circ\text{C}$.

  • Total Solids (TS): $TS = \frac{W_{ds} - W_d}{V}$ where $W_{ds}$ is weight of dish + dry solids, $W_d$ is weight of clean dish, and $V$ is volume in L.

  • Suspended Solids (SS): Material retained on a filter aided by vacuum. $SS = \frac{W_{df} - W_d}{V}$.

  • Dissolved Solids (DS): $DS = TS - SS$.

  • Fixed Solids (FS): Residue not volatilized at $600\,^\circ\text{C}$. $FS = \frac{W_{du} - W_d}{V}$.

  • Volatile Solids (VS): Material volatilized at $600\,^\circ\text{C}$. $VS = TS - FS$.

• Bacteriological Measurements:

  • Pathogens: Disease-causing microorganisms. Examples: Salmonella, Shigella, hepatitis virus, Entamoeba histolytica, Giardia lamblia, Escherichia coli, Cryptosporidium.

  • Indicator Microorganisms: Used as a proxy for pathogens. They are normal inhabitants of digestive tracts of warm-blooded animals, plentiful, easily detected, generally harmless, and hardy (surviving longer than pathogens).

River Water Quality

• Oxygen Deficit ($Def$): The difference between saturation and actual concentration. $Def = S - C$.

• Kinetics in Rivers:

  • Deoxygenation = $k_1 L$.

  • Reoxygenation = $k_2 Def$.

  • Rate of change: $\frac{dDef}{dt} = k_1 L - k_2 Def$.

• Streeter-Phelps Equation: Provides the deficit at time $t$.

  • $Def = \frac{k_1 L_0}{k_2 - k_1} (e^{-k_1 t} - e^{-k_2 t}) + Def_0 e^{-k_2 t}$.

  • Critical Time ($t_c$): The time at which the maximum oxygen deficit occurs.

  • $t_c = \frac{1}{k_2 - k_1} \ln \left[ \frac{k_2}{k_1} \left( 1 - D_0 \frac{k_2 - k_1}{k_1 L_0} \right) \right]$.

Lake and Reservoir Quality

• Thermal Stratification: The division of water into layers, restricting mass transport and influencing chemical cycling.

  • Epilimnion: Warm, well-mixed surface layer.

  • Hypolimnion: Cold, well-mixed bottom layer.

  • Metalimnion: Transition region where temperature varies at least $1\,^\circ\text{C}$ per meter of depth.

  • Thermocline: The specific plane in the metalimnion with the steepest temperature-depth gradient.

• Oxygen Depletion: Occurs when organic matter from the surface settles and decomposes at the bottom. During stratification, oxygen resupply is limited.

  • Effects: Cycling of iron and phosphorus from sediments, generation of hazardous species ($NH_3$, $H_2 S$, $CH_4$), and loss of fish/macroinvertebrates.

• Eutrophication: Nutrient enrichment leading to increased organic matter.

  • Oligotrophic: Nutrient-poor, low algae, transparent, abundant oxygen.

  • Mesotrophic: Intermediate zone, often abundant fish life.

  • Eutrophic: Nutrient-rich, high algae, poor transparency, often oxygen-depleted in the hypolimnion.

• Engineered Lake Management:

  • Point Source Control: Advanced wastewater treatment.

  • Nonpoint Source Control: Reduction of $P$ and sediment from croplands.

  • Diversion: To land application.

  • Dredging: Mechanical removal of sediments.

  • Chemical Inactivation: Addition of alum.

  • Hypolimnetic Aeration: Bubbling oxygen into bottom waters.

  • Herbicides: To eliminate invasive species.

Groundwater Quality and Water Supply

• Sources of Groundwater Contamination:

  • Intentional Input: Deep well injection, fertilizer/pesticides, land application of waste.

  • Unintentional Input: Septic tanks, cesspools, unlined landfills, leakage from confining zones, sewer leakage, waste lagoons, factory spills.

• Remediation Strategies:

  • Pump and Treat.

  • In situ Chemical Oxidation.

  • Natural Attenuation.

  • Phytoremediation.

• Options for Meeting Water Demands:

  • Supply Side: Dams, water diversions, desalination (Distillation, Reverse Osmosis/RO), aquifer recharging, use of icebergs, relocation.

  • Reuse and Conservation: Better treatment/recycling, reduction of evaporation, water conservation techniques.

• Water Quality Standards:

  • Drinking Water: Philippine National Standards for Drinking Water of 2017.

  • Surface Water/Effluent: Water Quality Guidelines and General Effluent Standards of 2016.

Sample Problems (SP)

• SP 01: What is the theoretical oxygen demand in liters of air for a $50\,mg/L$ solution of acetone, $CH_3 COCH_3$, to decompose completely?

• SP 02: What is the theoretical oxygen demand in liters of air for a $300\,mg/L$ solution of methylamine, $CH_3 NH_2$, to decompose completely?

• SP 03: A series of BOD tests were run at three different dilutions ($100$, $200$, and $400$). Initial DO was $10\,mg/L$. Final DO readings were $2.5$, $6.0$, and $7.5\,mg/L$ respectively. Determine the BOD.

• SP 04: Five-day BOD of an industrial influent is expected to be $800\,ppm$. Determine the sample volume to be used if initial DO is $10\,ppm$.

• SP 05: Calculate $BOD_5$ for a sample at $20\,^\circ\text{C}$. Saturation initial DO. Dilution is $1:30$ with seeded dilution water. Final DO of seeded water is $8\,mg/L$. Final DO of sample/seed mix is $2\,mg/L$.

• SP 06: A waste with a 5-day BOD of $200\,mg\,O_2/L$ and a rate constant of $0.1/\text{d}$ is discharged to a river at $1\,m^3/s$. Calculate ultimate CBOD ($L_0$) before discharge, ultimate CBOD after mixing (river flow $9\,m^3/s$, upstream CBOD $2\,mg/L$), and downstream CBOD ($50\,km$ downstream, width $20\,m$, depth $5\,m$).

• SP 07: A stream has a reoxygenation constant of $0.4/\text{d}$ and velocity of $0.85\,m/s$. Pollutant is discharged into oxygen-saturated water ($10\,mg/L$). Ultimate demand below outfall is $20\,mg/L$, deoxygenation constant is $0.2/\text{d}$. Find DO at $48.3\,km$ downstream.

• SP 08: Determine DO at $48.3\,km$ downstream given: Waste ($DO = 1.5\,mg/L$, flow $0.5\,m^3/s$, temp $26\,^\circ\text{C}$, ultimate BOD $48\,mg/L$) and Streamwater (flow $2.2\,m^3/s$, saturated DO, temp $12\,^\circ\text{C}$, ultimate BOD $13.6\,mg/L$).

Learning Outcomes

• Objective 1: Explain the significance of water properties to environmental science and engineering.

• Objective 2: Identify and differentiate various water resources available on Earth.

• Objective 3: Identify and explain specific water quality parameters.

• Objective 4: Explain the complex components of river, lake, reservoir, and groundwater quality.

• Objective 5: Identify and explain sources of water, the quantities of water supply, and the options available for meeting increasing water demands.

• Objective 6: Identify and differentiate between different water quality standards.

Properties of Water

• Interactions and Transport: Water is an excellent solvent, affecting how wastes and nutrients are transported through ecological and engineering systems.

• Light and Food Production: Transparency of water is crucial for photosynthesis, affecting food production in aquatic ecosystems.

• Density Characteristics: Maximum density is at $4 \, ^\circ C$, causing ice to float on water.

• Thermal Stability: High heat of evaporation, latent heat of fusion, and heat capacity stabilize internal temperatures and climate regions.

Water Resources

• Hydrologic Cycle and Sources:

  • Precipitation: Primary source of incoming water.

  • Evaporation and Transpiration: Water returns to the atmosphere as evapotranspiration.

  • Runoff: Water that flows over land to bodies of water.

  • Percolation: Filtering of water through soil.

  • Zone of Aeration: Upper layer where pores contain air and water.

  • Zone of Saturation (Groundwater): Layer where pores are filled with water.

  • Surface Water Sources: Oceans, Rivers, Lakes, Wetlands.

• Groundwater Characteristics:

  • Aquifer: Layer of soil or rock through which groundwater flows

  • Aquifer Classifications: Saturated/Unsaturated, Confined/Unconfined.

  • Global Distribution of Water Supply:

  • Total Water Volume: $1.36 imes 10^{18} \, m^3$.

  • Saltwater: $97\%$.

  • Freshwater: $3\%$ ($3.8 imes 10^{16} \, m^3$).

  • Freshwater Breakdown:

    • Locked In (Glaciers/Ice): $78\%$.

    • Surface and Groundwater: $22\%$.

  • Surface and Groundwater Accessibility:

    • Accessible: $1\%$.

    • Inaccessible: $99\%$.

Water Use and Pollution

• Water Use Types:

  • Consumptive Use: Water rendered unavailable.

  • Nonconsumptive Use: Water available for reuse.

• Pollution Definition: Undesirable changes that harm health.

• Water Pollutant Sources:

  • Point Source: Identifiable origins (e.g., pipes).

  • Nonpoint Source: Non-identifiable origins carried by runoff.

Water Quality Parameters: Oxygen and Nutrients

• Dissolved Oxygen (DO): Measure of a water body's ability to sustain aquatic life.

• Oxygen Demand: Rate of oxygen consumption during organic matter decomposition.

• Biochemical Oxygen Demand (BOD):

  • Low BOD levels indicate absence of contamination or interest of microorganisms.

  • Standard BOD Formula: $BOD = I - F$ (Initial DO - Final DO).

• Dilution Factor: $D = \frac{\text{total volume of bottle}}{\text{volume of sample}}$.

• Seeded Dilution Water Formula: $BOD = \frac{(I - F) - (I' - F')X}{300} \times D$.

• BOD Kinetics: $\frac{dz}{dt} = -k1 z$, $z = z0 e^{-k_1 t}$.

• Ultimate Oxygen Demand: $L = z + y$.

• Nutrients: Parameters measuring nitrogen and phosphorus levels.

Water Quality Parameters: Solids and Pathogens

• Total Solids (TS) Formula: $TS = \frac{W{ds} - Wd}{V}$.

• Suspended Solids (SS): Material retained on a filter. $SS = \frac{W{df} - Wd}{V}$.

• Bacteriological Measurements: Pathogens such as Salmonella and Escherichia coli.

Problems and Exercises

1. Multiple Choice Questions

   1. What is the maximum density of water at what temperature?

   • A) $0 \, ^\circ C$

   • B) $4 \, ^\circ C$

   • C) $100 \, ^\circ C$

   • D) $25 \, ^\circ C$

   1. Which source of water is primarily underground?

   • A) Lakes

   • B) Rivers

   • C) Aquifer

   • D) Ocean

2. Enumeration

• List the water quality parameters measuring oxygen levels.

• Enumerate the classifications of aquifers.

1. Problem Solving

• Calculate BOD for a sample with initial DO of $10 \, mg/L$ and final DO of $2 \, mg/L$.

• A stream has a reoxygenation constant of $0.4/ ext{d}$ and velocity of $0.85 \, m/s$. Find DO at $48.3 \, km$ downstream if the initial DO is $10 \, mg/L$ and the ultimate demand is $20 \, mg/L$.

Learning Outcomes

• Objective 1: Explain the significance of water properties to environmental science and engineering.

• Objective 2: Identify and differentiate various water resources available on Earth.

• Objective 3: Identify and explain specific water quality parameters.

• Objective 4: Explain the complex components of river, lake, reservoir, and groundwater quality.

• Objective 5: Identify and explain sources of water, the quantities of water supply, and the options available for meeting increasing water demands.

• Objective 6: Identify and differentiate between different water quality standards.

Properties of Water

• Interactions and Transport: Water is an excellent solvent, affecting how wastes and nutrients are transported through ecological and engineering systems.

• Light and Food Production: Transparency of water is crucial for photosynthesis, affecting food production in aquatic ecosystems.

• Density Characteristics: Maximum density is at $4 \, ^\circ C$, causing ice to float on water.

• Thermal Stability: High heat of evaporation, latent heat of fusion, and heat capacity stabilize internal temperatures and climate regions.

Water Resources

• Hydrologic Cycle and Sources:

  • Precipitation: Primary source of incoming water.

  • Evaporation and Transpiration: Water returns to the atmosphere as evapotranspiration.

  • Runoff: Water that flows over land to bodies of water.

  • Percolation: Filtering of water through soil.

  • Zone of Aeration: Upper layer where pores contain air and water.

  • Zone of Saturation (Groundwater): Layer where pores are filled with water.

  • Surface Water Sources: Oceans, Rivers, Lakes, Wetlands.

  • Groundwater Characteristics:

  • Aquifer: Layer of soil or rock through which groundwater flows.

  • Aquifer Classifications: Saturated/Unsaturated, Confined/Unconfined.

  • Global Distribution of Water Supply:

  • Total Water Volume: $1.36 \times 10^{18} \, m^3$.

  • Saltwater: $97\%$.

  • Freshwater: $3\%$ ($3.8 \times 10^{16} \, m^3$).

  • Freshwater Breakdown:

    • Locked In (Glaciers/Ice): $78\%$.

    • Surface and Groundwater: $22\%$.

  • Surface and Groundwater Accessibility:

    • Accessible: $1\%$.

    • Inaccessible: $99\%$.

Water Use and Pollution

• Water Use Types:

  • Consumptive Use: Water rendered unavailable.

  • Nonconsumptive Use: Water available for reuse.

• Pollution Definition: Undesirable changes that harm health.

• Water Pollutant Sources:

  • Point Source: Identifiable origins (e.g., pipes).

  • Nonpoint Source: Non-identifiable origins carried by runoff.

Water Quality Parameters: Oxygen and Nutrients

• Dissolved Oxygen (DO): Measure of a water body's ability to sustain aquatic life.

• Oxygen Demand: Rate of oxygen consumption during organic matter decomposition.

• Biochemical Oxygen Demand (BOD): Low BOD levels indicate absence of contamination or interest of microorganisms.

• Standard BOD Formula: $BOD = I - F$ where $I$ is initial DO and $F$ is final DO.

• Dilution Factor Formula: $D = \frac{\text{total volume of bottle}}{\text{volume of sample}}$.

• Seeded Dilution Water Formula: $BOD = \frac{(I - F) - (I' - F')X}{300} \times D$ where $I', F'$ represent the DO of seeded dilution water and $X$ is the volume of seeded dilution water used.

• BOD Kinetics: $\frac{dz}{dt} = -k_1 z$ where $z$ is oxygen concentration.

• Integrated Form of Kinetics: $z = z<em>0 e^{-k</em>1 t}$ describes oxygen decay.

• Ultimate Oxygen Demand Formula: $L = z + y$ where $L$ is total oxygen demand, $z$ is oxygen at time $t$, and $y$ is oxygen consumed.

• Amount of Oxygen Used Over Time: $y = L(1 - e^{-k_1 t})$.

• Nutrients: Parameters measuring nitrogen and phosphorus levels.

Water Quality Parameters: Solids and Pathogens

• Total Solids (TS) Formula: $TS = \frac{W<em>{ds} - W</em>d}{V}$.

• Suspended Solids (SS): Material retained on a filter, $SS = \frac{W<em>{df} - W</em>d}{V}$.

• Bacteriological Measurements: Pathogens such as Salmonella and Escherichia coli.

Problems and Exercises

1. Multiple Choice Questions

   1. What is the maximum density of water at what temperature?

   • A) $0 \, ^\circ C$

   • B) $4 \, ^\circ C$

   • C) $100 \, ^\circ C$

   • D) $25 \, ^\circ C$

   1. Which source of water is primarily underground?

   • A) Lakes

   • B) Rivers

   • C) Aquifer

   • D) Ocean

2. Enumeration

   • List the water quality parameters measuring oxygen levels.

   • Enumerate the classifications of aquifers.

3. Problem Solving

   • Calculate BOD for a sample with initial DO of $10 \, mg/L$ and final DO of $2 \, mg/L$.

   • A stream has a reoxygenation constant of $0.4/\text{d}$ and velocity of $0.85 \, m/s$. Find DO at $48.3 \, km$ downstream if the initial DO is $10 \, mg/L$ and the ultimate demand is $20 \, mg/L$.