Comparison of Sand Filter Type Septic Systems to Aerator Type Systems

Sand Filter Systems

• There are three primary types of sand-based septic systems: sand filter, recirculating sand, and sand mound systems. Sand-based septic systems are used in locations with shallow soil. They are essentially boxes filled with sand, and walls of the box are made of concrete or PVC. Effluent waste is pumped through the septic tank pipes into the sand where it is chemically treated simultaneously. An underdrain moves the treated wastewater to a drainfield where the waste finally filters through the soil. A recirculating sand filter system has a second layer of sand so that the waste is treated twice. A sand mound system has a drainfield raised above the natural soil surface filled with sand and gravel and pressurized pipes. The effluent is pumped through the pipes and distributed through the mound and into the soil.

Aerator Systems

• Aerator type systems use oxygen to break down organic matter. The technical name for these systems is Aerobic Treatment Units (ATUs). They are used in environmentally sensitive areas where conventional or gravity flow systems cannot be utilized because the water table is too high for a drainfield to function effectively. ATUs are like scaled-down versions of municipal wastewater treatment systems for homes. They decompose organic solids using a process called “suspended growth.” Waste is piped from the septic tank into an aeration chamber where air is forced to mix with the wastewater. The process creates a suspended growth environment, where bacteria float in the liquid and digest solid waste. Some units have a second chamber into which undigested solids float and settle. Water from both chambers will float back and forth, like a refining process to clean the wastewater.

Similarities

• Wastewater management is an important process that impacts the health and safety of your family and your community. All septic systems are regulated by local, state and federal agencies. If you are installing a new system, you must use the type dictated by your local municipality. The agencies inform you whether a sand fill or ATU system is appropriate for where you live. Proper permits are typically required before installation, and, in most cases, the system will have to be inspected before you are granted a certificate of approval to operate a sand or ATU system.

Comparison

• While both systems require monitoring to make sure they are operating properly, ATUs are more complicated than sand fill systems. ATUs require quarterly fecal testing, monitoring of fecal matter, periodic inspection of the effluent to make sure that it is a clear, brownish color and not gray or black, which indicates that oxygenation is not occurring. Sand-filled units are less sensitive. The pump chamber and floats should be checked annually to determine whether parts need repairs or replacement, and the drainage area should be checked periodically for odors and to ensure surfacing sewage does not accumulate over six inches. Contact your local municipal agency if problems need to be addressed.