How It Works
Siting The Tank
BS 6297 : 1983 States that sewage treatment plants should be as far from habitable buildings as economically practicable. The direction of the prevailing wind should be considered in relation to any properties when siting the works.
Access should be provided to enable the tank emptying vehicle to operate within its suction lift capacity. Tanks should be placed out of the way from traffic and wherever possible, pumping should be avoided by locating the plant lower than the premises to be served. Treatment plants should not be located in an area subject to flooding or where the water table can rise to such levels to cause flow into the treatment units.
For guidance minimum setback distances for the treatment plant and irrigation area are listed below.
| Treatment Plants | Irigation Areas | |
| 7m | Dwelling Served | 10m |
| 7m | Adjacent Dwelling | 10m |
| 3m | Site Boundarier | 3m |
| 4m | Roads | 4m |
| 10m | Water Course | 10m |
| 10m | Drinking Water Sources | 30-100m |
Principal Of Operation
Stage 1 - Primary Settlement
When sewage enters the primary chamber heavy solids and debris are settled out, floating solids are also retained due to the configuration of the pipe work. Anaerobic digestion also takes place, reducing the B.O.D. of the influent sewage by 30-40% at this stage.
Stage 2 - Aeration
Highly effective aerobibic breakdown generated by the now well proven and reliable aeration produces enhanced purification and excellent nitrified effluents.
Stage 3 - Final Settlement
The final settlement chamber ensures that any carryover of partials are retained and a typical final discharge quality of BOD 18, SS 25, NH 4 which is equal to an improvement of 85-90% before discharge to the percolation drains.
Effluent Disposal
The extent of the treated water disposal is in general based on the quality of the final effluent and the type of ground into which it is to be discharged.
If conditions are suitable, che cheapest and one of the most efficient methods of disposal is by means of a subsurface irrigation system. It is simple to install, but requires careful design and installation to work efficiently. To determine the most suitable siting and area of land required for a subsurface irrigation system, a percolation test in accordance with the British Standard BS 6297:1983 will be necessary.
However, we recommend seeking advice from the relevant Authority whose experience and knolwedge of local conditions can be invaluable.
Laying Land Drains
Ti achieve even distribution, land drains should be laid in a herringbone or similar pattern depending on the site. Rigid Perforated Plastic pipes, or plastic cor-rugated land drain may be used. This is a far more cost effective system than the traditional clayware, which can be used as an option. These products should be laid with a fall of 1 in 200 and at a minimum depth of 500mm. The pipes should be laid on a 150mm layer of clean gravel or broken stone 20mm to 50mm grade and trenches filled to a level 50mm above the pipe and covered with a plastic remainder of the trench can be filled with normal soil.
Maintenance
The standard & satisfactory performance of a sewage treatment plant relies on the plant bein desludged & service once a year, Maintenance & service are available with a Biobubble service contract, after the tank has been commissioned.