|
|
|
|
|
|
A septic tank system includes an underground tank and leach field A well designed and maintained concrete, fiberglass or plastic tank should last about 50 years. Because of corrosion problems, steel tanks may only last a decade or less. Most typical is a two compartment septic tank. The size of the tank will vary depending upon local codes, but a typical tank for a family of four would have a liquid capacity of 1,500 gallons. On the left is the input pipe from the dwelling, on the far right is the output pipe to the leach field. The tank itself is water tight and divided into two semi-compartments. This division allows for improved digestion of the waste materials. When the waste flows into the tank, the heavy solids (primarily feces) sink to -the bottom to form a layer of 'sludge'. Lighter materials (grease, fats, small food particles ' etc.) float on the surface forming a layer of "scum'. Between these two layers is a soup of suspended materials and water soluble chemicals (urea from urine and many household chemicals). The division into two chambers increases the efficiency of the system at removing suspended solids. The second compartment receives its "load", or liquid mixture, already substantially clarified (much of the solid material has settled out of the liquid). There is little turbulence in the second chamber either, because the load enters more slowly. Both of these factors allow settling of finer suspended solids than can occur in the first chamber where incoming material acts to churn up the chamber contents. more info
The process of digestion in the tank is carried out primarily by microbes
excreted from our, gastrointestinal tracts (E. coli, for instance). Digestion
is an anaerobic process, meaning -that oxygen is not required. Gases (hydrogen
sulfide and methane) are produced and must be vented. Basically the same
-thing that happens in a septic tank also occurs in our guts and in centralized
waste water treatment plants, however a properly operating septic system
probably is the most efficient of the three. In the septic system, the
gases help to stir the sludge, scum and liquid layers which promotes further
digestion of the solids. A properly functioning tank will convert the bulk
of solids into liquid waste through the processes of digestion and hence,
decomposition. more
info
Tank Size Household size (number of people)
| (Gallons) | 1 | 2 | 3 | 4 | 5 | 6 |
| 500 | 5.8 | 2.6 | 1.3 | 1.0 | .7 | .4 |
| 750 | 9.1 | 4.2 | 2.6 | 1.8 | 1.3 | 1. |
| 900 | 11. | 5.2 | 3.3 | 2.3 | 1.7 | 1.3 |
| 1000 | 12.4 | 5.9 | 3.7 | 2.6 | 2.0 | 1.3 |
| 1250 | 15.6 | 7.5 | 4.8 | 3.4 | 2.6 | 2. |
| 1500 | 18. | 9.1 | 5.9 | 4.2 | 3.3 | 2.6 |
| 1750 | 22.1 | 10.7 | 6.9 | 5.0 | 3.9 | 3.1 |
| 2000 | 25.4 | 12.4 | 8.0 | 5.9 | 4.5 | 3.7 |
| 2250 | 28.6 | 14.0 | 9.1 | 6.7 | 5.2 | 4.2 |
| 2500 | 31.9 | 15.6 | 10.2 | 7.5 | 5.9 | 4.8 |