Parisot - Mini Fosse

SPANC

SPANC.PNG

Two stage mini-fosse

Les fosses et mini fosses septiques.

What does it consist of?

  1. A developed solution for individual or family sanitation
  2. storage and a waste water pretreatment and thus better hygiene
  3. environmental protection in the absence of a public sewer network.

It involves digging a small pit in which we construct a reservoir where sewage or toilet will be stored and undergo natural chemical reactions - a first stage clean. If it processes both "gray" and "black water" (faeces, latrines). then it is called a "septic tank".

Why used?

The method is relatively simple to implement and use anywhere, especially away from central sewerage systems. It avoids construction in areas with limited resources.

What is this process?

The method comprises pretreating wastewater through a settling and anaerobic treatment (without oxygen).

There are generally two compartments as shown in the following diagram.

Fosse_1.PNG

In the first solids will accumulate to undergo a "digestion" (anaerobic fermentation) that will result in the formation of several gases (CO2, NH4 ..).

These require regular emptying (preferably to achieve a professional given the risks of infection). The frequency depends on the volume and use of the pit. It must intervene as soon as the residual sludge solids reach the 2/3 of the first compartment.

Fosse_2.PNG

The second compartmen tejects that is not sufficiently clean. Indeed in the first compartment only 30% of the carbon pollution has been removed; there remains germs, especially bacteria. It is therefore forbidden (in many countries such as France) to eject the water into the environment or even into the sewers because of the many problems that could ensue(for wells pollution, odors and corrosion due to the pretreatment suffered in sewers).

As a result, these 2 stage tanks
require regular emptying (preferably to achieve a professional given the risks of infection). The frequency depends on the volume and use of the pit. It must intervene as soon as the residual sludge solids reach the 2/3 of the first compartment.

Advantages

  1. The pit provides an effective pretreatment and liquefaction releases essential phase of water purification following the pit.
  2. Its cost is low. It does not create odors and prevents flies and mosquitoes
  3. Its lifetime is quite long: 10 to 20 years.
  4. It can be an economical alternative to sewer systems in some cases.

Disadvantages

  1. Septic systems typically cost more than most on-site sanitation systems.
  2. Large amounts of piped water is required (at least thirty liters / person / day) to remove toilet waste feeding the pit.
  3. The water leaving the septic tank is untreated.
  4. Construction such as maintenance of septic systems require specialized labour.
  5. Finally, discharges from septic tanks can pose significant health problems for crop irrigation.
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