Rural, Onsite & Small Community Wastewater & Waste

Management

Facultative & Anaerobic Lagoons

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

Anaerobic Lagoons

Natural continuation of the breakdown of food in the body

Digestion without oxygen

Acid Formers

Tough

Can produce organic acids over a wide range of environmental conditions

Organic acids Lower pH of lagoon Smell bad !!!

Methane Formers

Delicate

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

Anaerobic Digestion

1 Stage Anaerobic Lagoon

2 Stage Anaerobic Lagoon

Startup

Start in Summer

About 1/2 full of clean water

Slowly add waste at first Design loading after 1 year

Loading

Continuous

Check pH Add lime if below 6.7

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

Anaerobic Lagoons

Natural treatment system

No power required

Tend to be large Dilution Long treatment time

Low, but daily management

Stabilization Pond

Sometimes called facultative lagoon

Digestion with oxygen

Used to treat wastewater

Stabilization pond

Shallow basin

Microorganisms at natural concentration

Stabilization Pond

Role of Algae

Design

BOD loading

Hydraulic residence time 3 to 12 months

Loading

Can tolerate fluctuations in loading

Keep inlet below surface to control odors

Management

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

Management

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

Discharge

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

Sludge Management

Debris may wash up on banks Pretreat with screens

Small amounts of stabilized sludge can be entrained in irrigation system

Stabilization Ponds

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

Stabilization Ponds

Large Treatment takes a long time Affected by winter conditions

Relative Size

FixedFlim1x

Lagoon6x

Reduce the Size?

Stirring Improves air transfer Increases contact between micoorganisms and

waste

Stirred Pond

Impact of Stirring

Pond can be Smaller Deeper Shorter residence time

Impact of Stirring

Power required

More operator time & training

More sludge is generated

Readings

Hammer & Hammer 413 - 419

MWPS 18 Section 7.1