Lesson Nine

Question 1

Primary Objectives of Wastewater Treatment

Answer 1

Protect the Public,
Preserve Aquatic Life,
Preserve the Receiving Water Environment,
Preserve Water Quality

Question 2

Original Goal of Wastewater Treatment

Answer 2

Prevent the outbreak of communicable diseases transmitted in water (the relationship between water and disease).

Question 3

Protect the Public - Focus

Answer 3

Prevent communicable diseases (typhoid, cholera, dysentery, polio, hepatitis) from untreated wastewater. Disease-causing organisms are called pathogens.

Question 4

Preserve Aquatic Life

Answer 4

Maintaining sufficient dissolved oxygen (DO) in receiving waters for the fish and aquatic life respiration.

Question 5

Preserve Aquatic Life - Impact of Organic Matter

Answer 5

Increased organic matter leads to increased bacteria, which consume DO during oxidation, potentially depleting it.

Question 6

DO Levels & Aquatic Life

Answer 6

DO below 5 mg/L can seriously harm or kill fish. High organic loads reduce DO.

Question 7

Preserve Receiving Water Environment - Concerns

Answer 7

Untreated wastewater can cause: loss of clarity/colour, floating scum, excessive algae/weed growth (due to added nutrients), reducing aesthetics and recreation.

Question 8

Preserve Water Quality - Industrial Wastewater Issues

Answer 8

Can be highly acidic/alkaline and contain toxic substances, hazardous to aquatic life and public water supplies (taste/odour).

Question 9

Sources of Wastewater - Smaller Communities

Answer 9

The majority is domestic (residential) wastewater (60-80% of per capita water consumption).

Question 10

Sources of Wastewater - Commercial

Answer 10

From businesses frequented by the public (shopping centers, restaurants, hotels, etc.).

Question 11

Sources of Wastewater - Industrial

Answer 11

May contain toxic compounds and heavy metals. Often requires pretreatment before discharge to municipal systems.

Question 12

Sources of Wastewater - Institutional & Recreational

Answer 12

Essentially domestic. Hospitals may have high pathogen levels. Recreational flows are seasonal.

Question 13

Sources of Wastewater - Infiltration

Answer 13

Groundwater and stormwater are entering the collection system, increasing volume. Depends on the soil, precipitation, and pipe condition.

Question 14

Sources of Wastewater - Inflow

Answer 14

Surface water entering the collection system through sewers or access points. Influenced by system layout and drainage.

Question 15

Wastewater Characteristics - Composition

Answer 15

Over 99.9% pure water, less than 0.1% solids (organic & inorganic).

Question 16

Wastewater Characteristics - Fresh vs. Septic

Answer 16

cloudy, grey, musty odour. Septic (stale): black, foul smell, black solids (indicates blockage).

Question 17

Total Solids in Wastewater - Categories

Answer 17

Organic solids (from plants/animals, decompose) and Inorganic solids (sand, gravel, silt, don’t decompose).

Question 18

Types of Solids (Further Breakdown)

Answer 18

Suspended solids (small particles held in suspension) and Dissolved solids (in solution). Also Settleable solids (larger particles that settle).

Question 19

Regulations - Provincial (Alberta Environment)

Answer 19

License to Operate or Code of Practice issued. Includes system classification (Class I-IV), operator requirements, volume allowed, sampling/testing/reporting, effluent standards.

Question 20

Federal (Fisheries Act)

Answer 20

Illegal to discharge “deleterious” substances to fish-bearing waters (administered by DFO).

Question 21

Regulations - WSER

Answer 21

Wastewater System Effluent Regulations may require reporting of effluent quality and quantity to the federal government.

Question 22

Wastewater Collection - Sanitary Sewers

Answer 22

Gravity sewer pipes transport wastewater to treatment plants. Size/grade depends on flow and infiltration/inflow.

Question 23

Wastewater Collection - Combined Sewers

Answer 23

Older systems carrying both wastewater and stormwater. Often lead to bypasses during storms.

Question 24

Wastewater Collection - Trunk & Outfall Sewers

Answer 24

Trunk: collect from large areas. Outfall: major sewer to the treatment facility (carry combined flows).

Question 25

Wastewater Collection - Lift Stations

Answer 25

Pump wastewater to higher elevations when gravity is uneconomical (wet well, sewage pumps, force main).

Question 26

Wastewater Collection - Low Pressure Systems

Answer 26

Holding tanks & small pumps at each household, pumping to a low-pressure main. Solids removed periodically.

Question 27

Class I Wastewater Treatment Facilities

Answer 27

Wastewater ponds and aerated lagoons. Basic treatment: solids removal and organic matter stabilization (bacterial breakdown).

Question 28

Bacteria in Waste Stabilization Ponds (Types)

Answer 28

(use dissolved oxygen), Anaerobic (get oxygen from compounds), Facultative (can use both).

Question 29

Waste Stabilization Ponds - Best Use

Answer 29

Smaller communities with lower land costs. Lower operating skill needed than mechanical plants.

Question 30

Mechanical Plants - Best Use

Answer 30

Larger communities with higher land costs. Continuous discharge to receiving streams (requires sufficient flow).

Question 31

Mechanical Plants - General Pretreatment

Answer 31

Screening (remove large debris) Grit removal (remove sand/gravel) Pre-aeration (freshens wastewater, adds DO)

Question 32

Primary Treatment - Main Process

Answer 32

Sedimentation in primary clarifiers to remove settleable solid matter (sludge/biosolids) and floatable material (scum). Detention time ~1.5-2 hours.

Question 33

Secondary Treatment - Main Goal

Answer 33

Remove dissolved and non-settleable organic material (biological process using microorganisms).

Question 34

Secondary Treatment - Common Processes

Answer 34

Rotating Biological Contactors (RBC) and Activated Sludge processes.

Question 35

Rotating Biological Contactors (RBC) - Key Feature

Answer 35

Rotating plastic discs are partially submerged in wastewater, developing a biological slime (aerobic bacteria) that consumes organic matter.

Question 36

Activated Sludge - Key Feature

Answer 36

Forced aeration to introduce oxygen, mixing microorganisms with organic matter in aeration tanks. Sludge is recycled.

Question 37

Secondary Clarifier - Purpose

Answer 37

Solids/liquids separation after secondary treatment, removing microorganisms and humus. Effluent then disinfected.

Question 38

Dissolved Air Flotation (DAF) - Secondary Treatment

Answer 38

Alternative to secondary clarifiers. Fine air bubbles attach to solids, causing them to float and be removed from the top.

Question 39

Suspended Biofilm Reactors (SBR)

Answer 39

Small plastic discs suspended in aerated tank, biofilm grows on discs, wastewater flows through screens to keep discs in tank.

Question 40

Membrane Bio-Reactor (MBR)

Answer 40

Uses manufactured films with fixed pore sizes to filter solids. Requires effective pretreatment. High effluent quality possible.