Rural, Onsite

1
Rural, Onsite Small Community Wastewater
Waste Management

• Facultative Anaerobic Lagoons

2
Lagoon Systems

• Objective
• Create an ideal environment for microorganisms to
  consume waste organic matter
• High strength waste - anaerobic lagoons
• Wastewater - Facultative lagoons
• AKA Stabilization ponds

3
Anaerobic Lagoons

• Natural continuation of the breakdown of food in
  the body
• Digestion without oxygen

4
Acid Formers

• Tough
• Can produce organic acids over a wide range of
  environmental conditions
• Organic acids
• Lower pH of lagoon
• Smell bad !!!

5
Methane Formers

• Delicate
• Easily upset by
• Low pH - below 6.7
• High salt concentration (8mmhos/cm)

6
Anaerobic Digestion
7
1 Stage Anaerobic Lagoon
8
2 Stage Anaerobic Lagoon
9
Startup

• Start in Summer
• About 1/2 full of clean water
• Slowly add waste at first
• Design loading after 1 year

10
Loading

• Continuous
• Check pH
• Add lime if below 6.7

11
Pump out

• Annually
• Down to minimum treatment volume
• Avoids salt buildup
• If salts are over 8 mmhos/cm
• Pump some out and add dilution water

12
Anaerobic Lagoons

• Natural treatment system
• No power required
• Tend to be large
• Dilution
• Long treatment time
• Low, but daily management

13
Stabilization Pond

• Sometimes called facultative lagoon
• Digestion with oxygen
• Used to treat wastewater

14
Stabilization pond

• Shallow basin
• Microorganisms at natural concentration

15
Stabilization Pond
16
Role of Algae
17
Design

• BOD loading
• Hydraulic residence time
• 3 to 12 months

18
Loading

• Can tolerate fluctuations in loading
• Keep inlet below surface to control odors

19
Management

• Maintain banks
• Keep weeds from growing in water
• Keep burrowing animals out
• Keep trees from growing

20
Management

• Maintain lnlet Outlet Structures
• Keep sludge from accumulating
• Watch for signs of erosion
• Exercise valves

21
Discharge

• Ideal for irrigation systems
• Appropriate level of treatment
• Storage to maximize flexibility for operator

22
Sludge Management

• Debris may wash up on banks
• Pretreat with screens
• Small amounts of stabilized sludge can be
  entrained in irrigation system

23
Stabilization Ponds

• Reduced management
• No power requirement
• Low labor time and training
• Limited sludge management

24
Stabilization Ponds

• Large
• Treatment takes a long time
• Affected by winter conditions

25
Relative Size
Fixed Flim 1x
Lagoon 6x
26
Reduce the Size?

• Stirring
• Improves air transfer
• Increases contact between micoorganisms and waste

27
Stirred Pond
28
Impact of Stirring

• Pond can be
• Smaller
• Deeper
• Shorter residence time

29
Impact of Stirring

• Power required
• More operator time training
• More sludge is generated

30
Readings

• Hammer Hammer 413 - 419
• MWPS 18 Section 7.1