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Suspended solids
Reduce water clarity
Settle out & interfere with aquatic life
Clog soil & equipment
Septic Tank Pumping
•Tank size (gal) •2 •4 •6
•500 •2.6 •1.0 •0.4
•1000 •5.9 •2.6 •1.5
•1500 •9.1 •4.2 •2.6
Filtering out solids
How deep in soil?
A few inches to 1 foot
Wastewater will be clear
Is it fully treated?
Organic Matter (BOD) & Ammonia
Microorganisms Organic matter & ammonia is their food
Create ideal environment for microorganisms Surface to attach to Air Water Food
Organic Matter & Ammonia Removal
How deep in soil?
2 feet of unsaturated soil
Wastewater is clear with no odor
Is it fully treated?
Bacteria
Remove by Filtering action of biological film Chemical attraction to soil particles
Soil particles and bacteria both have a surface electrical charge
They attract like the opposite poles of a magnet
Bacteria Removal
How deep in soil?
1 1/2 to 2 feet of unsaturated soil
200 to 400 feet in saturated soil
Wastewater is clear, has no odor and is free of bacteria
Is it fully treated?
Viruses
Too small for filtration
Removed by adsorption onto soil particles
Organic matter interferes with adsorption
Must remove the organic matter from wastewater first
Depth of Soil
Ohio Code - 4 feet above Ground or perched water table Bedrock Compacted soil layers Sand and gravel layers
Soil too Shallow?
Environmental impact?
Layer of sand on top of soil Sand allows for flow of air & water Substrate for biofilm No surface chemistry for adsorption of bacteria
or viruses
Removal in Sand
Suspended solids, BOD and Ammonia
Widrig, Peeples & Mancl (1996) After 24 inches of sand
BOD - 12 mg/l SS - 10 mg/l Ammonia - 0.5 mg/l
Disinfection of Sand Treated Wastewater
Through a layer of soil Called a mound system 2 feet of soil under 2 feet of sand
Soil too Shallow for Mound?
Environmental Impact?Filter through sand SS, BOD & ammonia removal
Disinfection system Bacteria & virus removal Classes 15 & 16
Disperse through irrigation Class 17
Sand Bioreactor System
Water tight container of sand
Wastewater applied in doses
Collected and disinfected
Dispersed in soil 1 foot deep
Soil too Shallow for Irrigation?
Hydric soil - wet soil Saturated several months each year Within 1 foot of surface
Environmental Impact?