TREATMENT VS DISPOSAL
Out of sight, out of mind? Eco-friendly development and responsible home and land owners should not think like this anymore. Properly designed systems will TREAT and CLEAN wastewater, while overloaded or improperly designed systems simply DISPOSE wastewater into the ground and contaminate and destroy soils and groundwater.
In the past, most acreage home owners (and installers) simply put a septic tank into the ground and then buried 100' of weeping tile per bedroom, and this served as their "septic system". Many are still operational today, but many have failed horribly.
The industry has recognized that SOILS onsite are what dictate how much effluent waste we can distribute over an area. It is actually the SOIL and the microbes within that clean our sewage. If we overload the onsite soil beyond its capacity, effluent can surface and cause ponding. This can "drown" the microbes, saturate and destroy the soils, and treatment will not occur. Each soil type is lab tested and we have values for each. A properly designed system will remove almost 99% of contaminants (not pharmaceuticals and other chemicals, unfortunately), and return the water back to the environment in a safe and responsible way. And its the microbes in the soils that do most of this work! Today, with the new regulations, each site must first have a site evaluation by a certified designer/installer. Test pits are dug and soil samples are analyzed and sent to the lab. A certified design is then created for your unique needs and lot requirements.
Most designs today consist mainly of a septic tank and a treatment field. Most septic tanks have two compartments. The first compartment (Working Chamber) catches all the sewage (from toilets, showers, sinks, dishwasher, etc) from the home, and must be sized correctly to give approx 24hrs of "quiet" time to allow solids (sludge) to sink and for fats, oils and grease (scum) to float. This is the first clarification of the water. This water (effluent) then passes into the second chamber (or Dose Chamber), where it waits to be sent to the field. It can be sent to the field via a syphon/gravity setup or a pump (pressurized) setup.
Typical 2 compartment septic tank
The soil analysis / results from the site evaluation will determine what type of treatment field options you have. Most common are a buried field or a sand treatment mound. There are other options as well. Buried fields can accept effluent via gravity or pressure (pump), while sand mounds can only accept effluent via pressure (pump). Pressurized (pump) systems are preferred as they help to evenly distribute the effluent and prevent overloading the soil at the beginning or end of a field, which commonly happens with gravity systems. To the right is an example of a typical setup: septic tank + buried treatment field.
WHAT'S IN WASTEWATER (SEWAGE)?
Domestic sewage (wastewater) includes:
1) "Black Water" - everything that goes down the toilet
2) "Gray Water" - everything else; from sink, dishwasher, laundry, showers, etc
There are organics, nutrients (phosphorus, nitrogen,) and pathogens (bacteria, viruses, protozoa, helminths). Properly designed soil-based treatment fields will treat and remove most of these elements.
Pharmaceuticals (medications) as well as household chemicals are very difficult to remove from domestic wastewater, and excess use therefore should be avoided whenever possible.
Domestic Wastewater DOES NOT INCLUDE, and these should not enter your system:
1) Ground Water
2) Water from weeping tile
3) Industrial waste (paint, fuel, other chemicals and cleaners)