Conventional Treatment System means an on-site liquid waste system utilizing both conventional treatment and conventional disposal, including privies, holding tanks, pipe and gravel trenches, proprietary drainfield products (eg. chambers), absorption beds, seepage pits and vaults.
Conventional Treatment means a septic tank where primary treatment occurs.Primary Treatment means a liquid waste treatment process that takes place in a treatment unit (tank) and allows those substances in wastewater that readily settle or float to be separated from the water being treated.Primary Treatment Standards means the primary treated wastewater does not exceed 200 mg/l BOD, 100 mg/l TSS, 60 mg/l total nitrogen or 60 mg/l fats, oils and grease.
Conventional Disposal means a subsurface soil absorption system with gravity distribution of the effluent, with or without a lift station, constructed in accordance with the standards set forth in this regulation, including privies, holding tanks, pipe and gravel trenches, proprietary drainfield products (eg. chambers), absorption beds, seepage pits and vaults.
| Conventional Treatment | Advanced Treatment | |
| Primary Treatment | Secondary Treatment | Tertiary Treatment |
| 2 Compartment TankAllows for settling of solids to form “Sludge” layer in bottom of tank.Flotation of Fats, Oils, Greases (FOG) to form “Scum” layer. | Aeration (aerobic)In addition to Primary Treatment, also includes:Reduction in TSS and BOD | Aeration (aerobic)In addition to Secondary Treatment, also includes:Reduction in TN (as calculated) |
| Treatment Standards | ||
| BOD 200 mg/LTSS 100 mg/LTN 60 mg/LFOG 60 mg/L | TSS 30 mg/LBOD 30 mg/L | TN (mg/L) = [lot size(in acres)/design flow (in gpd)] x 30,000 |
Typical Parameters for Measuring Wastewater Strength
BOD = Biochemical Oxygen Demand means the rate at which organisms use the oxygen in water or wastewater while stabilizing decomposable organic matter under aerobic conditions.TSS = Total Suspended Solids means the measurable component of solid matter suspended in water or wastewater.TN = Total Nitrogen means the combined organic nitrogen, ammonia, nitrite and nitrate contained in the wastewater or effluent.FOG = Fats, Oils and Grease
Concrete Seepage Pit rings.
Click on tank icon to download a slide show that demonstrates how a two compartment septic tank handles solids, liquids and gases.