Lesson Ten

Question 1

Waste Stabilization Ponds - Definition

Answer 1

Economical alternative to mechanical treatment. Uses natural processes to stabilize wastewater. Lower cost, simpler operation, high-quality effluent (if managed well).

Question 2

Stabilization Ponds - Natural Treatment Processes

Answer 2

Heavy solids settle (anaerobic bacteria decompose).
Suspended solids/organic matter stabilized by bacteria in suspension.
Dissolved N & P are used by algae for growth (algae use CO2/bicarbonates).

Question 3

Stabilization Ponds - Typical Use

Answer 3

Smaller communities, often located outside municipal boundaries. Can be single or multiple ponds.

Question 4

Benefits of Waste Stabilization Ponds (List - 8)

Answer 4

Limited expensive equipment.
Lesser operator skill needed.
More economical (construction & operation) vs. mechanical.
Effluent quality equal to or better than mechanical. Adaptable to changing hydraulic/organic loads.
Effluent can be used for land application (if suitable).
Less energy required.
Fewer possible problems than other processes.

Question 5

Limitations of Waste Stabilization Ponds (List - 5)

Answer 5

Seasonal/overload odours.
Requires large land areas.
Potential groundwater contamination (if not careful).
Treatment efficiency depends on climate.
May have high suspended solids in effluent.

Question 6

Bacteria & Algae in Stabilization Ponds - Role

Answer 6

Microorganisms use organic matter/nutrients for growth/respiration (needs oxygen). Bacteria decompose, algae photosynthesize (release O2, use CO2).

Question 7

Aerobic Ponds - Characteristics

Answer 7

Shallow, good oxygen distribution. Oxygen from wind action and algal photosynthesis. Primarily aerobic bacteria.

Question 8

Anaerobic Ponds - Characteristics

Answer 8

Deeper, less surface area. Anaerobic bacteria at the bottom consume settled organic matter (produce CO2, N2, organic acids).

Question 9

Facultative Ponds - Characteristics

Answer 9

Aerobic near surface, anaerobic at bottom (3-8 feet deep). Aerobic, anaerobic, and facultative bacteria present. Oxygen from photosynthesis and aeration. Most common type.

Question 10

Algae in Ponds - Function

Answer 10

Uses sunlight/CO2 for growth, releases O2 (photosynthesis). Present in upper layers. O2 used by bacteria.

Question 11

Bacteria in Ponds - Function

Answer 11

Release CO2, methane, nutrients, ammonia. CO2 used by algae. Interdependent relationship with algae for stabilization.

Question 12

Pond Aeration - Natural

Answer 12

Surface winds create turbulence, adding air/oxygen. Oxygen transfer depends on turbulence and oxygen solubility (higher in colder water).

Question 13

Dissolved Oxygen in Ponds - Daily Variation

Answer 13

Lowest in early morning (bacteria used it overnight). Increases during day (algae produce O2), highest midafternoon (if sunny). Lower on cloudy days.

Question 14

Dissolved Oxygen in Ponds - Winter

Answer 14

Ice cover can lead to extremely low DO levels. Ponds kept at max depth to prevent freezing.

Question 15

Biological Zones - Photosynthetic/Aerobic Zone

Answer 15

Upper layer, dominant algae and aerobic bacteria. Depth depends on water clarity and sunlight penetration

Question 16

Biological Zones - Facultative Zone

Answer 16

Below photosynthetic zone, dominant facultative bacteria. Oxygen mainly from pond aeration.

Question 17

Biological Zones - Anaerobic Zone

Answer 17

Bottom layer, no sunlight penetration. Anaerobic bacteria digest organic matter (produce volatile acids, methane, CO2, ammonia, H2S).

Question 18

Treatment Factors - Physical (Examples)

Answer 18

Type of soil (containment), surface area, depth, wind action, sunlight, temperature, short circuiting, inflow variations.

Question 19

Treatment Factors - Chemical (Examples)

Answer 19

Organic material (loading), pH, solids (type/concentration), concentration/nature of waste.

Question 20

Treatment Factors - Biological (Examples)

Answer 20

Type of bacteria (heterotrophic important), type/quantity of algae, activity of organisms, nutrient deficiencies (N, P), toxic substances.

Question 21

Pond Colour - Warm Weather Indicators

Answer 21

lear dark green: Well-balanced facultative pond (high algae).
Clear light green: Facultative storage ponds (less algae).
Dark “pea soup”/blackish green: Blue-green algae.

Question 22

Pond Colour - Other Conditions

Answer 22

Dark green to black: Anaerobic wastewater.
Brown: Anaerobic wastewater, low DO.
Grey: Dead algae.
Red or pink: Purple sulfur bacteria (anaerobic) or red algae (aerobic).

Question 23

Disinfection of Pond Effluent - When Necessary

Answer 23

Discharge to water course leading to public water supplies and/or recreational use.

Question 24

Accepted Disinfection Methods for Pond Effluent

Answer 24

Chlorination or complex ultraviolet (UV) light system.

Question 25

Chlorination Requirements for Pond Effluent

Answer 25

Minimum 2.0 mg/L residual chlorine after a 20-minute contact time.

Question 26

Discharge of Chlorinated Water

Answer 26

Prohibited into fish-bearing streams under federal law. Dechlorination required before discharge.

Question 27

Aerated Waste Stabilization Ponds - Definition

Answer 27

Economical alternative to regular stabilization ponds and mechanical treatment. Less land needed. Uses mechanical aeration for oxygen.

Question 28

Aerated Ponds - Bacteria & Algae

Answer 28

Bacteria are similar to activated sludge. Algae are less significant due to high mixing from aeration.

Question 29

Aerated Ponds - Oxygen Supply

Answer 29

Primarily from mechanical aeration equipment (less from algae compared to stabilization ponds).

Question 30

Aerobic Aerated Ponds - Mixing

Answer 30

Complete mix, particles do not settle to the bottom.

Question 31

Aerobic Aerated Ponds - Final Step

Answer 31

Requires a polishing pond (non-turbulent area) for microbial solids to settle before discharge.

Question 32

Aerobic Aerated Ponds - Treatment Efficiency Factors

Answer 32

Organic loading (higher load = lower quality), Oxygen (more needed with higher load), Temperature (colder = lower microbial activity).

Question 33

Aerobic-Anaerobic Aerated Ponds - Mixing

Answer 33

Not completely mixed. Large portion of solids settle, undergoing anaerobic decomposition at the bottom.

Question 34

Aerobic-Anaerobic Aerated Ponds - Decomposition

Answer 34

Bacteria decompose organic matter (some oxidized to nitrates, sulfates, CO2; rest used for cell growth). Bacteria excrete polymers/slime, promoting floc formation for settling.