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 Fixed Flim 1x Lagoon 6x

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 MWPS 18 Section 7.1