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The nature of off-mains drainage often means the vast majority of the works we undertake are carried out in rural areas, this invariably also increases the chance of having to work in environmentally sensitive or protected areas. With this comes a moral code of practice to ensure ecological and environmental compliance in more ways than one!

Whilst some sites require simple due diligence, others require more stringent levels of caution – subsequently these jobs can take longer to make active progress prior to the start on site. With careful planning and design even environmentally sensitive areas can benefit from certain categories of work.

We were originally requested to attend site back in 2021 to investigate the efficiency of the existing system in place. When our contracts manager first attended site, it was immediately clear that the setup was not treating the effluent to the desired standard and therefore meaning compliance was not being achieved!

The old septic tank unit on site had been previously retrofit with an aeration unit (by others) to try and improve the outfall quality however this still remained much below the required levels.

Due to the environmentally sensitive nature of the project we hoped to limit any excavation works where possible, therefore our first proposal was to utilise the existing unit and convert it into a Twin Crude pump station. Several parts were required to carry out the conversion including internal pipework, pumps, guiderails etc but before any of this work could begin the structure had to be checked as suitable to be adapted.

The waste was then pumped to a 9,150 litre Primary Settlement Tank which provided a vital part in the operation of the whole proposed set up, this unit slowed the incoming flow from the pump station allowing a vast number of solids to settle. The outfall from the settlement tank then gravity flows to a 22,000 litre Balance tank. This unit was installed with an Air-lift forward feed system to regulate the flow entering the new sewage treatment plant.

The second to last link in the chain but arguably the most important was the new sewage treatment plant, our recommendation was the installation of a Klargester BD BioDisc package sewage treatment system – this is our ‘go to’ where effluent is of the highest importance.

Within the commercial BioDisc itself there are a number of different elements that build up to the operational efficiency that gained this system not only BS EN 12566-3 (Standards covering treatment plants up to 50 population)/ BS EN 12255 (standards covering treatment plants over 50 population) but also BS EN13725 (Odourless operation). The four sections within the unit are the primary settlement chamber, first stage biological treatment, second stage biological treatment and then the final settlement chamber.

The BioDisc is suitable to discharge to either a watercourse or to a drainage field of which the latter is the proposed outfall for this system. For the correct design to be identified we carried out percolation tests in the proposed drainage field location, during the initial project discussions we attended site to identify the ground conditions and porosity levels.

Thankfully the material uncovered proved to be ideal for the application, the loam-based sand/ gravel subsoil meant the percolation value was at a sufficient level to allow the treated effluent to disperse evenly and the soakaway to be constructed in line with BS 6297:2007.

Compliance does not merely occur at the point the new system is installed, to be compliant with the General Binding Rules/ any permits you must ensure that the system is operating as designed. There are many ways in which this has to be regulated.

The first stage of system checks needs to be carried out by the site, there are number of things that need to be checked on a regular basis. Systems can come with a selection of alarms such as audible, visual and telemetry, if any of these have identified a fault you should notify your service provider as soon as possible.

For the correct treatment process to take place it is important to check that there is a constant electrical supply to the unit, unfortunately any lapses over an extended period of time can mean the system will not be treating the waste and only acting as a septic tank instead. In instances where an IPS/ Pump station is involved, any break in the electrical supply is considered as an emergency as they will not be able to flow away under gravity and it won’t take long for your drains to start backing up.

Another consideration for the operators is that you should always be careful what enters the drainage system, this applies not only to sewage treatment plants but also the mains sewer network! Within all of our Installation completion packs our customers are issued with a handy ‘Dos and Don’ts’ flyer however a general good rule of thumb to follow is that you should aim to only flush the 3 Ps (Pee, Poo, and Paper!).

It is your responsibility to ensure that your sewage treatment plants, pump stations, separators etc are routinely serviced. The frequency in which a system is serviced is dependent on the size of the unit and the manufacturer’s recommendations, this should always be carried out by an experienced engineer.

Alongside servicing there is a requirement for these units to be emptied, this frequency is generally outlined by the tank manufacturer, however this many need to be adjusted dependent on usage/ what has entered the system. All empties are required by law to be undertaken by a registered waste carrier and a transfer note should be supplied complete with information on the point of disposal.

As complicated as this sounds, here at R A Dalton we are always on hand to help our customers and many thousands entrust us to carry out their work to the highest of standards.