Upcoming changes to the laws concerning septic tanks and the green options for replacement and new builds. From the 1st of January 2020 it will become illegal for owners of septic tanks to discharge their effluent to surface water. Surface water refers to rivers, streams, ditches and canals. The offending septic tanks will need to be replaced with a sewage treatment plant (STP) or the discharge moved to a drainage field. This will stop households pumping their untreated waste directly into our waterways.

So what is the difference between a septic tank and STP? A septic tank just separates the waste and then discharges the liquid element (if maintained correctly); it does not treat the effluent. This liquid is not water it is raw sewage. The effluent is only treated if it flows into a correctly installed drainage field. A drainage field is a system of perforated pipe that has to be big enough and not deeper than 700mm to enable anaerobic digestion. The majority of drainage fields I see are not installed correctly, but that’s another story.

STP’s also vary considerably in how they treat the waste water and the quality to which they treat the water. There are minimum standards that are required and all new tanks have to adhere to BS EN 12566-3. The problem is many are inappropriately installed and poorly maintained. Much like a car, a STP should have a yearly MOT where the tank and effluent quality are checked to ensure that the output is still to the required standard. Although the General Binding Rules allude to this requirement, the Environment Agency guidance is a little woolly.

If you are environmentally conscious then I would recommend the Graf systems. You may think that I am biased and this is more of a sales pitch. Don’t get me wrong, I would like everyone to have their tanks installed by my company but the tank you choose does not concern me. I would recommend the Graf because I truly believe they are best tank for people like me, who are environmentally conscious.

The Graf ‘One2clean’ tanks are single chambered injection moulded systems set up to be ultra environmentally conscious from production through to the output. They are also designed with no moving parts or mechanical elements making them reliable, less costly and easier to maintain. The tank comes with a 15-year warranty and 3 yr warranty on the technology.

Sustainability starts with manufacturing, this type of tank tech normally requires 2.7 kWh per kg of plastic to produce, Graf has it down to between 0.38 and 0.5 kWh. Further, all heat generated by the process is recovered and used to heat the companies logistics buildings. All the materials used are 100% recyclable.

Electric usage is kept to a minimum, 36kWh per person per year for the One2Clean and 43kWh for the advanced, a 9w energy-saving bulb uses 78kWh, normal sludge activated systems use 217kWh per person.
Both of the Graf systems only require one pumping process compared to three in normal systems, extending the life of the core air compressor and delivering the energy savings.

The unique way the system treats the waste minimises the level of sewage sludge left over and generates market leading odourless effluent quality. Graf claims this leads to a carbon footprint of 25% of conventional wastewater treatment systems.

The effluent quality is outstanding, up to 99%; the maximum levels of the following as set out in BS EN 12566-3 are allowable in mg/l ; BOD5 (biochemical oxygen demand), 20, SS suspended solids, 30, and NH4-N, 20. The Graf One2Clean results are 7, 14 & 0.5, the popular and very expensive (both to run and buy) Karlegster BioDisc has advertised results of 10,15 & 3.8.

Unfortunately the Graf has a downside; it like many of the tanks on the market requires an excavation of over 2.5meters. In the Avon Valley For instance, the water table makes that depth of excavation very problematic. In these cases we advise the use of a unit called ‘Marsh shallow’, a good tank with good credentials.

Homeseptic are offering free visits for those who are unsure on the system they have or a free no obligation quote for anyone that needs to change their system or wants a new one installed. Also please feel free to call if you just want some advice on 0800 3101092 or visit their website.

An STP is not a septic tank, it’s far more complicated! I would recommend getting an expert to install it.