Above Ground Septic Tank - Septic Tank Sewage Treatment Systems - These come up with the money for a unconditionally slapdash method of treating sewage for properties which are not amalgamated to mains drainage. Many septic tank systems throughout the world are never maintained and as a result reach not pretense properly and pollution direct laws exist to try to limit the amount of environmental and health risks they cause. These laws are getting tighter, and minimum standards have been put in area for other or replacement septic systems. In many cases you will obsession to install a sewage treatment plant system instead. Always acquire the sewage system checked by a waste water system proficient prior to purchasing a property in order to prevent a pollution problem.
Types of Septic Tank Systems Available
There are various types of septic tank systems. They consist of an underground septic tank in differing shapes and sizes, which later connects to a auxiliary soil treatment system, usually a land drainage system in the form of a soakaway or drainfield, or a mound soakaway.
How a Septic Tank works
Raw sewage and waste water from baths, kitchens, etc. discharges into the tank, where the solids are separated from the liquid waste. Fats and oils float to the summit of the tank and form a crust layer. Faeces and food scraps sink to the bottom of the tank and form a sludge layer. Anerobic bacteria which are natural colonisers in the tank "digest" this sludge by taking place to 70%.
The filthy septic water flows out of the tank to a soakaway or drainfield. Baffles or 'T' pipes in the tank support help the purposeless crust and prevent it from entering the outlet of the tank. In order that the sludge and crust layers reach not become too deep, septic tanks should be emptied annually. This also prevents a superior and superior fascination of suspended solids washing out into the soakaway. Solids can block the expose spaces in the soil drainage system, creating a drainage pain and the septic tank effluent will not be competent to soak away or be treated by the natural soil bacteria.
Variations in Septic Tank systems
Traditional septic tanks comprise of two rectangular chambers: the first one beast 2/3 of the whole and the second 1/3, usually built in brick or concrete. Strict design rules are in area and septic tanks must be expected in accordance taking into account BS 6297 1983. The inlet pipe into the first chamber ends in a 'T' pipe which travels by the side of the at least 450mm (18") below summit water level (TWL), and the chamber must be a minimum of 1500mm (5'-0") deep from TWL. This first stage chamber is usually twice as long as it is wide. The pipe from the first chamber into the second chamber consists of an 'H' pipe and the bottom of the pipe is a min. of 300mm (12") below TWL in the first chamber and 450mm (18") below summit water level (TWL) taking into account it enters the second chamber.This second stage chamber is usually square. The outlet pipe from the second chamber of the tank also consists of a 'T' pipe taking into account the bottom of the pipe 300mm (12") below TWL.
Vent pipes should be installed from the first and second chambers for venting the gases, mainly methane and hydrogen sulphide, that are produced by the sludge. strong covers should always be placed unconditionally higher than a septic tank to avoid kids / animals falling into the tank. There are many cases of thcovers collapsing and many people have been killed as a result.
Nowadays, septic tanks are made in GRP and polyethylene which commonly are spherical in fake taking into account a narrow shaft at the summit to a manhole field level. These reach not build the thesame character of effluent as two chamber tanks and cannot be placed in front of many conversion units.
Care should be taken to ensure that problems will not occur due to the tank rising out of the ground, taking into account it is emptied in high water table sites. It is always advisable to install the tank taking into account a tangible surround.
Septic tank effluent still contains nearly 70% of the pollutants in the original sewage and needs other treatment in the soakaway to prevent a pollution problem.
Soakaways and Septic Drainfields
The Septic Tank without help provides the first share of the sewage treatment process. The soakaway is the underground soil treatment system which uses aerobic bacteria found naturally in the field to other treat the effluent. The soil type must be agreeable for a soakaway to pretense properly. Percolation tests are required to determine whether a septic tank soakaway is suitable. If the soil is clay, it is not agreeable for a soakaway and a drainage pain is inevitable. If you have this pain later a sewage treatment plant is the reply as they reach not obsession a soakaway.
The soakaway consists of either a series of trenches containing perforated pipe laid on and surrounded by stone, or an absorption bed, or a soakaway mound, all of which are amalgamated to the septic tank outlet by a pipe. In all cases the soakaway must be a minimum of 1.2 metres above the water table or bedrock at all times. They must also be a minimum of 200 mm. below field level to avoid septic effluent breaking to the surface. The pipes should be laid at a gradient of no more than 1:200 in a drainfield in order that the wastewater does not direct to the stop of the pipe, but is dispersed evenly. The perforations should be larger than 6mm (0.25") to avoid the biomatt, which forms in the trench, blocking the holes. The pipe cannot be the corrugated tubing type as used in land drains as this is not allowed, but must be the precise sound soakaway drainage pipe
The contaminants, pathogens, nutrients, and organic matter in the effluent are dispersed into the gravel where they are digested by aerobic bacteria.
On a leaning site, the effluent may flow into a series of fall boxes or manholes taking into account another outlet to the next pipeline set at a humiliate level. Absorption beds are useful where appearance is limited, but they should without help be used as a second choice.
Sewage Drainage Mounds
A treatment mound is a raised soakaway system. Aggregates are used to lift the soakaway as a result that it is at least 1200mm (4'-0") above the seasonal high water table or bedrock. The mound system must be expected carefully, taking into account the topography of the site, the volume of septic tank effluent to be treated and the porosity of the topsoil to avoid failure of the system and boggy areas around the base of the mound. The design cannot be guessed and must be the end by a trained professional, using test results and calculations.
I have seen terribly expected mounds blast a hole through the side as they have been too little for the job.
Effluent is piped to a pumping station tank, where it is pumped in batches into the mound pipe-work. Septic mounds can see unconditionally handsome and can form share of the landscaping of a garden. You are not allowed to plant shrubs on summit of them, but they can be planted around their base.
Septic Tank Soakaway Pits
In the past, many septic tank systems used soakaway pits, although these pits are no longer acceptable below forward looking building regulations. They consisted of a large hole in the ground, edit at the bottom, either blocked round taking into account gaps amid the blocks to permit seepage of the effluent into the soil, or suitably holes filled taking into account stones. Some soakaway pits were made of large tangible rings taking into account gaps amid the rings and the septic tank effluent was piped into them. They were always covered, usually taking into account a large tangible slab, but they were often a failure, as no calculations were undertaken to determine the porosity of the surrounding soil and they soon were filled taking into account septic effluent. The drains later fill amid the pit and the tank, which backs-up the entire septic system.
Site Conditions and Installation
Most sites in the UK are not agreeable for septic tank systems. Either the soil contains too much clay or is too porous, or the winter water table or bedrock is too close the surface. If the soil is clay, later it will not soak the septic effluent away and if it is too coarse it will not support the effluent long acceptable for treatment. You could decide a non-electric sewage treatment plant instead. Sometimes, it is realizable to become accustomed a septic system to achievement a basically improper site, but this requires careful planning and design by an expert. As a general rule, if the site has either insufficient soil depth, or the incorrect type of soil, it is not agreeable for a septic system. Always edit your Building Inspector before deciding on a septic system.
The size of a septic system, both the tank and the soakaway area, is definite by the number of bedrooms in the house and porosity of the soakaway soil. A septic system cannot pretense if it is overloaded, as a result always bear in mind any plans you may have for extending the property before you decide on the size of the septic system. Increasing the size superior results in a ruined garden.
Finally, always check taking into account the character Agency and you local Building direct before deciding on a septic system. They will have a unconditionally good idea as to whether it is likely to pretense in your area and could keep you thousands of pounds in replacing an improper septic installation.