Chapter 6.0: Small Scale Wastewater Treatment Systems Flashcards
Describe a septic tank system
The principle is simple: raw wastewater enters an underground tank where it
is retained for a period of time (typically 3 days). Retention allows scum and grease to float to the top of the water surface and heavier solids to settle to the bottom of the tank where the organic matter is decomposed anaerobically (thus the term “septic”). septic system is typically installed at a single-family home or small business
What is a mound system
A mound system is an option in areas of shallow soil depth, high groundwater, or shallow bedrock. The constructed sand mound contains a drainfield trench. Effluent from the septic tank flows to a pump chamber where it is pumped to the mound in prescribed doses. Treatment of the effluent occurs as it discharges to the trench and filters through the sand, and then disperses into the native soil. While mound systems can be a good solution for certain soil conditions, they require a substantial amount of space and periodic maintenance.
What is a gravel/stone drainfield?
The gravel/stone drainfield is a design that has existed for decades. The name refers to the construction of the drainfield. With this design, effluent is piped from the septic tank to a shallow underground trench of stone or gravel. A geofabric or similar material is then placed on top of the trench so sand, dirt, and other contaminants do not enter the clean stone. Effluent filters through the stone and is then further treated by microbes once it reaches the soil below the gravel/stone trench.
