Water and Wastewater Treatment Review

Flashcards reviewing key concepts in water and wastewater treatment processes for exam preparation.

Environmental Engineering: "Fixing the Past"

Cleaning and protecting the environment from pollution.

Environmental Engineering: "Dealing with the Present"

Controlling waste streams generated as a result of human activities.

Environmental Engineering: "Planning for the Future"

Providing and ensuring safe water, air, and land for future generations.

Major types of water and wastewater treatment processes

Biological, Chemical, and Physical

What are the main objectives of water and wastewater treatment?

Protection of public health, Protection of the environment, Meeting regulations, Cost-effective solutions, Adaptability to new risks

What is the Development of Criteria in the regulatory process for water and wastewater treatment?

Developed based on data and scientific judgement; do not have the force of regulations.

What is the Promulgation of Standards in the regulatory process for water and wastewater treatment?

Considers technical and economic feasibility; set by regulatory agency (enforceable).

What is the Setting Specific Goals in the regulatory process for water and wastewater treatment?

May include constituents not covered by regulations; set by water supplier (more stringent than standards).

What issues influence water and wastewater treatment practices?

Stringent regulations, Increasing population pressures, Need for infrastructure renewals/upgrades

What are the components of an urban water system?

Reservoir, Wells, Water distribution system, Stream, Water treatment plant, Domestic, Industry, Pretreatment, Homes wastewater, Combined sewer overflow, Stream, Industrial wastewater, Sanitary sewers, Combined system, Wastewater treatment plant Separated storm sewer system, Storm sewers

What is the design capacity of municipal water treatment facilities?

Maximum Water Production Rate, Typically in ML/d or USGPD, Determined by the demand for water

What are the water-using sectors?

Residential, Commercial and institutional, Industrial, Public sector

What is per capita demand?

Total demand divided by population served

What is the typical design period for water treatment plants?

Typically 10 to 25 years, Water demand reaches plant capacity at end of design period

What factors are design demand (plant capacity) based on?

Projections of population and per-capita demand, Major industrial/agricultural/institutional water usages, Firefighting requirements, Allowance for in-plant and distribution system losses

What is the best method for estimating projected water usage?

Use past pumping records and growth projections for the municipality

What does seasonal variation in water demand depend on?

Depends on climate

How are water treatment plants designed in relation to daily water demand?

Usually design WTPs for maximum daily flow (typically in July/August)

How is hourly water demand variation addressed?

Supply supplemented from storage

List some examples of inorganic water particles.

Clays, Asbestos fibers, Metal oxides, Carbonates

List some examples of organic water particles.

Powdered activated carbon, Pathogens, Algae, Bacteria, Detritus, NOM, Flocs from coagulant addition

List some methods for measuring water particle concentration.

Turbidity, Mass and Volume Concentration, Surface Area Concentration, Number Concentration

How is water turbidity measured?

Measured using a nephelometer, scattering of visible light, units are NTU, surrogate parameter for the presence of particles

What is mass and volume concentration in water treatment?

Dry mass of particles / unit volume; important with respect to solids loading to treatment plant

What is surface area concentration in water treatment and why is it important?

Concentration in m2 / unit volume; important with respect to the interaction between dissolved species with particle surfaces

What is number concentration in water treatment?

Number of Particles / unit volume; important in determining rate of aggregation, flocculation, and removal

How is taste and odor measured in water?

Measured in threshold odor test; reflects organic/inorganic constituents; TON = diluted volume/original sample volume

How is color measured in water?

Measured as true color units (TCU); due to fine suspended material, colloids or dissolved impurities

What are Total Dissolved Salts (TDS)?

Any minerals, salts, metals, cations, or anions dissolved in water.

What is alkalinity and what does it affect?

Bicarbonate, carbonate and hydroxyl ions; affect the efficiency of certain treatment processes.

List elements that cause hardness in water.

Mg2+, Ca2+, Fe2+, Fe3+, Sr2+

List Priority Pollutants in water.

Pesticides, herbicides, industrial solvents, lead, mercury, arsenic

List Pathogenic microorganisms.

Viruses, Bacteria, Protozoa

What are indicator microorganisms?

E.g. Total and Fecal Coliforms (TC and FC) - Non-pathogenic bacteria that indicate the presence of fecal contamination

What are the standards of Drinking Water Quality, Primary Standards?

Based on protecting public and environmental health.

What are the standards of Drinking Water Quality, Secondary Standards?

Based on other factors – Aesthetics – Best available technology (BAT).

What is Domestic wastewater?

Generated from households and public buildings

What is Inflow in wastewater flows?

Water that enters the sewer through sources such as manhole covers, roof downspouts, yard drains, and cooling-water discharges

What is Infiltration in wastewater flows?

Water entering a collection system from a variety of entry points, including service connections and from the ground through cracks in pipe joints and manholes, services connections, and defective pipes

What factors should be considered for WWTP Design Capacity

Domestic, commercial and industrial sources, Variation in flow rate of wastewater reaching the WWTP

What does WWTP Design flow rate depend on?

Peak hour flow rate for physical facilities, Minimum flow rate for pipes and channels to keep solids in suspension, Mass loadings

How do you calculate mass loading in wastewater treatment?

flow rate x concentration

List the different types of solids in wastewater quality.

Total solids (TS), Total suspended solids (TSS), Volatile suspended solids (VSS), Fixed suspended solids (FSS)

List the components that compose the Chemical Wastewater Quality Characteristics

Chemical oxygen demand (COD), Total organic carbon (TOC), Biochemical oxygen demand (BOD), Total nitrogen

What are the Effluent Standards?

Based on composition of the wastewater treated effluent

What are the Receiving water standards?

Based on water quality goals in the receiving water

What are Selection Considerations for Appropriate Unit Processes for Water/Wastewater Treatment?

Source Water Quality for WTP; Influent Characteristics for WWTP, Regulatory Compliance and Contaminant Removal Requirements, Process Reliability and Flexibility, Initial Construction and annual O&M costs

List one drinking water treatment process configuration - Desalination.

Screen or strainer, In-line coagulation, Train Cartridge filter FeCl3 Ultrafiltration Reverse Osmosis

List some Emerging Processes in Water and Wastewater Treatment

Reduction of trace organic compounds, Reduction of disinfection by-products, Inactivation or removal of disinfection-resistant microorganisms, Reduction of nutrient (nitrates, phosphate) in wastewater, Emerging Contaminants (Micropollutants, Nanomaterials)

What is the objective of Coagulation-Flocculation?

Aggregate small stable colloids into large flocs that settle readily

List Destabilization Mechanisms of Coagulation

Double layer compression, Surface charge neutralization, Inter particle bridging, Sweep Coagulation

What Coagulants are used most often in water treatment?

Alum or ferric iron salts

What happens if too much alum is added?

Provided enough alkalinity exists, More polyvalent cations are formed and adsorb onto the surface of colloids, Can change surface charge from negative to positive, Results in re-stabilization

What are the water Coagulation Operational Strategies?

recycle of sludge - adding PAC (powdered activated carbon) - adding bentonite particles

What the main objectives of rapid or Flash Mixing?

To destabilize colloidal particles, To promote particle contact and aggregation, To form pinpoint flocs

What are some mixers used rapid mixing?

Mechanical mixers (In-line mixers, Impellers in a tank)

What are typical slow mixing (Flocculation) tank types?

Paddle impellers, Turbine impellers, Paddle wheels, Baffled flocculators

what is the main objective of coagulation?

To destabilize colloidal particles

Give the formula of Alum

Al2(SO4)3 · 14H2O

What are some typical Slow Mixing Tanks?

Vertical Turbine Flocculators, Horizontal Paddle Flocculators

What are the types of rapid mixers used in water treatment?

In-line mixers - Impellers in a tank

What are the important layers found In Double-Layer Theory?

Fixed layer (or Stern layer), Surface potential (or Nernst Potential) Shear Plane Diffused Layer Bulk Solution Stern Potential

What is Sedimentation?

Oldest form of water treatment; uses gravity to separate particles

What is Type 1 Settling?

Particles do not interact with each other as they settle

Where is Type 1 settling applicable?

Pre-sedimentation, Grit chambers

What is Type 2 Settling?

Settling of chemically coagulated water

Where is Type 3 settling applicable?

Secondary sedimentation

What are the 4 zones in ideal Sedimentation Basin Theory:

Inlet zone, Outlet zone, Settling zone, Sludge zone

What are Types of sedimentation (water treatment in Alberta, page 2-16, guide) (AB: Alberta)

Horizontal Flow type, Up-Flow Type

What are the advantages sedimentation processes?

Increased Removal Efficiency, Increased Overflow rate

What is Ballasted Sedimentation?

Involves the addition of ballast (e.g. microsand, bentonite, fly ash) to increase the settling velocity

List physical factors influencing sedimentation efficiency

Density currents, Inlet energy dissipation, Wind effect, Outlet currents, Equipment movement

List Filtration Mechanisms

Straining, Interception, Settling, Impaction, Flocculation, Brownian motion

What are some considerations when selecting Granular Filter Media?

Fine material, Coarse material, Uniform materials

Rapid sand loading rate

160 m3/(m2 .d)

What the main indicator of head loss

Pressure drop due to friction losses in filter bed

Describe important components filter backwashing

Fixed and expanded beds during backwashing

What is Disinfection?

Destruction / inactivation of all pathogenic microorganisms

What is Disinfectant applied dose:

Amount of disinfecting agent applied to the water

What is Disinfectant residual:

Concentration of disinfectant remaining in the water

What is Disinfectant demand?

Difference between applied dose and residual

Watson model

k = k'C^n

List of Membrane Processes Used in Water/Wastewater Treatment?

Microfiltration (MF), Ultrafiltration (UF), Nanofiltration (NF), Reverse/ Forward Osmosis (RO/FO), Electrodialysis (ED)

Membrane Containment Vessels

Pressurized, submerged

What approaches are used to management and control of Membrane Fouling?

Chemical cleaning of the membranes; Membrane backflushing

What is Specific Flux

Used to compare different membranes tested at different pressures

What is the goal adsorbtion?

To remove material from process stream (such as bad taste).

What doest BET means in material science?

BET:Brunauer–Emmett–Teller theory