Water and Waste Water Quality and Treatment
What is Water and Waste Water Quality and Treatment?
The amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period.
Key formula / rule: Settling Velocity (Stokes' Law)
Key points
- Identify and interpret key water and wastewater quality parameters.
- Describe the purpose and mechanisms of different water and wastewater treatment processes.
- Understand the principles behind biological and chemical treatment methods.
- Differentiate between various stages of water and wastewater treatment.
Common exam trap
Confusing BOD and COD values or their implications.
Definitions
- Term
Biochemical Oxygen Demand (BOD)
- Meaning
The amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period.
- Term
Chemical Oxygen Demand (COD)
- Meaning
A measure of the amount of oxygen required to chemically oxidize the organic compounds in water.
- Term
Dissolved Oxygen (DO)
- Meaning
The amount of free oxygen dissolved in a water body, essential for aquatic life and aerobic decomposition.
- Term
Turbidity
- Meaning
A measure of the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye.
- Term
Activated Sludge Process
- Meaning
A biological wastewater treatment process that uses aeration and a settled flocculent suspension of microorganisms to remove dissolved and suspended organic matter.
- Term
Disinfection
- Meaning
The process of eliminating or reducing harmful microorganisms from water or wastewater.
Learning objectives
Identify and interpret key water and wastewater quality parameters.
Describe the purpose and mechanisms of different water and wastewater treatment processes.
Understand the principles behind biological and chemical treatment methods.
Differentiate between various stages of water and wastewater treatment.
Analyze the suitability of different treatment technologies for specific applications.
Formulae
- Name
Settling Velocity (Stokes' Law)
- Note
vs = settling velocity, g = acceleration due to gravity, d = particle diameter, ρp = particle density, ρw = fluid density, μ = dynamic viscosity of fluid.
- Expression
vs = (g * d2 * (ρp - ρw)) / (18 * μ)
- Name
BOD exertion
- Note
Lt = BOD at time t, L0 = ultimate BOD, k1 = deoxygenation rate constant, t = time.
- Expression
Lt = L0 * (1 - e^(-k1 * t))
- Name
Oxygen Sag Curve
- Note
Dt = DO deficit at time t, k2 = reoxygenation rate constant, D0 = initial DO deficit.
- Expression
Dt = (k1 * L0 / (k2 - k1)) * (e^(-k1 * t) - e^(-k2 * t)) + D0 * e^(-k2 * t)
- Name
Surface Overflow Rate (SOR)
- Note
Q = flow rate, A = surface area of settling tank.
- Expression
SOR = Q / A
- Name
Hydraulic Retention Time (HRT)
- Note
V = volume of tank, Q = flow rate.
- Expression
HRT = V / Q
Prerequisites
Basic Chemistry (pH, oxidation-reduction, chemical reactions).
Basic Biology (microbial activity, aerobic and anaerobic processes).
Fluid Mechanics (settling velocity, flow rates).
Basic Mathematics (algebra, unit conversions).
Common mistakes
Confusing BOD and COD values or their implications.
Incorrectly applying treatment processes to specific pollutant types.
Underestimating the importance of disinfection and its limitations.
Ignoring the role of sludge management in treatment plants.
Not considering the variability of wastewater characteristics.
Keywords
Water Quality
Wastewater Treatment
BOD
COD
DO
Turbidity
Sedimentation
Activated Sludge
Disinfection
Filtration
Nutrient Removal
Stokes' Law
Oxygen Sag Curve
Practice preview
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