Knollands Septic Tanks & Drainage

septic tank design

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Klargester septic tanks are designed to maximise the separation of solids and liquids, minimise turbulence and provide a zone from where discharge is made at a low flow. The purpose of the design is to produce the best quality of effluent and to extend the life of the soakaway or irrigation system. This is very important considering the huge cost of laying a new distribution system.

Process performance is paramount. A septic tank that does not separate the liquid and solids is not doing its job.

Klargester septic tanks have been tested for their sludge retention performance by the British Board of Agrément (BBA) who independently assess construction products. Klargester are proud of their reputation as suppliers of “The Tanks That Outperform The Rest."

Klargester have progressively improved their septic tank internal design over the 35 years they have been manufacturing septic tanks. Most of the spherical septic tanks we supply have one of three different internal baffle designs, all of which include a three stage upward flow route.

a) Submerged Ball

The inlet arrangement directs sewage into the main body of the tank, zone 1. This zone is very large allowing both settleable and floating solids to be retained. Some floating solids may rise out of the zone, but most are retained within the zone by the baffle arrangement and the submerged floating ball. The ball seals zone 1 from zone 3.

Clarified effluent rises through slots in the baffle, from zone 1 into zone 2. Small particles may rise with the clarified effluent and a further scum layer may accumulate at the top of zone 2.

Another baffle positioned higher within the tank, separates zone 2 from zone 3. This baffle has slots positioned at a different orientation to provide a long flow path.

Clarified effluent is discharged from zone 3 into the outlet pipe connected to the irrigation system.

b) Raised/(Red or cream coloured) Neck

The sewage enters the tank via the inlet pipework and is directed into the base of the primary zone 1 where most of the solids settle. Some floating particles rise and a scum develops at the surface. The raised neck of the upper cone is above the normal liquid level and this ensures that scum is retained.

The lower conical baffle arrangement allows liquid to rise at the outside of the tank. Heavy particles sink within the rising liquid. As the liquid ascends, the rate of liquid rise slows, allowing additional time for the smaller and lighter particles to settle.

The baffle design of the second zone allows floating fine particles to be retained against the tank wall, eventually allowing a submerged scum layer to develop. Once formed, smaller fine particles may be collected by this layer, hence a more "mature" unit will work better than one recently installed or just emptied.

There are slots positioned towards the inside of the upper baffle. Liquid rises through these slots into the final zone. The upper baffle is in the form of an inverted cone, the design of which aids consolidation and coagulation of particles. Settleable particles can fall through the same slots and be returned to the primary zone.

c) Plug and Handle

These tanks were provided by Klargester in the 1970's and use a flat plug, held in place with a handle, instead of the submerged ball to retain the floating solids within the main chamber. Their baffle orientation and chamber design is very similar to that described in a) above.

Smells and Odours

Gases can develop when bacteria decompose some of the sewage constituents.

There is usually very limited bacterial activity within the sludge as there is little oxygen available to allow the bacteria to grow.

Any bacterial activity that does occur may obtain its oxygen from bound up chemical compounds such as sulphates (SO4). Hydrogen sulphide gas may be produced, by anaerobic bacterial activity, its smell is particularly distinctive, often described as a sweet rotting cabbage smell.

Gases travel from the top of the liquid level in the septic tank into the vent or to the house's sewer pipe or soil stack, up to the roof terminal where they are vented to atmosphere.

Sometimes the smells detected derive from the irrigation system, or from other sources within the drainage system.

The chart on page 5 offers guidance to help you identify the origin of a smell and suggests ways of eliminating the cause(s).

Septic tank factsheets:

Septic Tanks

Our range of septic tanks are suitable for both domestic and commercial applications and for populations of 1 up to 500 people. The Knollands Bio-Pure septic tank is an innovative and cost effective solution and as a result is our best selling septic tank.

Drainage systems

Wether it be agricultural drainage coil, twin walled CorriPipe™ or Hunter sewer drains, Knollands can offer quality drainage systems for a number of different requirements and are perfect for use with our range of septic tanks and rain harvesting products.

rain harvesting

Knollands supply mainly Graf Carat S underground tanks due to their quality construction and reliable design. Convenient packages that include everything you need to start rain harvesting result in a simple and enjoyable project that benefits you and the environment.

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