The GRAF One Advanced 28 Person Sewage Treatment Plant uses two linked 6,500 litre Carat tanks and treats up to 4,200 litres a day. It serves small developments, holiday parks and rural business units.
The two lines can run together at busy times or one at a time when the site is quiet. In addition, the plant can scale back its cycles automatically when the load drops.
How the One Advanced Plant Works
The One Advanced 28 Person Sewage Treatment Plant is a GRAF SBR (sequencing batch reactor) system. Wastewater flows into the tank, where the plant treats it in batches rather than in a constant flow. First, a compressor blows air through the tank so that bacteria can break down the waste.
Next, the air stops and the activated sludge settles to the bottom, leaving a layer of clear water on top. Finally, the treated water is lifted out and the cycle starts again.
Because the plant is modular, each treatment line can run on its own or together with the others. As a result, lines can be switched off when a site is quiet, which saves power. The convenience package also uses a pressure sensor to spot under-loading and reduce the number of cycles, so the compressor runs less.
Key Features
- GRAF SBR treatment for larger homes, small developments and commercial sites
- Modular design, so lines can run together or on their own
- Upgraded control panel with remote WebMonitor access as an option
- Energy use from 0.95 kWh per day
- Quiet, high-quality compressors
- Add-on packages available for stricter discharge limits
What’s Included
- Two 6,500 litre GRAF Carat tanks with internal treatment parts fitted
- Clear water lifter and aeration system
- Air compressor and control unit
- Mini dome shafts with 150kg pedestrian telescopic lids
Options
- Traffic Telescopic Lid 3.5 Tonne, for driveways and parking areas
- External Cabinet M, for the control unit and compressor when there is no garage or outbuilding to house them
In addition, a raised outlet (fitted before dispatch), a warning beacon and a high level alarm are available on request. Please call us to add any of these to your order.
Where Can the Treated Water Go?
Treated water from the plant can usually discharge to a drainage field or, in many cases, to a ditch or stream. In England, the General Binding Rules set out when you can do this without a permit, so check the rules for your site or speak to the Environment Agency before you order. In Scotland, Wales and Northern Ireland, the local environment regulator sets the rules.
Specification
- Population: up to 28 people
- Tank: Two 6,500 litre GRAF Carat tanks
- Dimensions: 5280 x 2190 x 2390 mm (L x W x H)
- Weight: 530 kg
- Loading: Pedestrian as standard, vehicle with the traffic lid
- Tank warranty: 15 years, with a 50 year design life
- Parts warranty: 1 year from commissioning, or 3 years with an annual service
- Manufacturer: GRAF UK
Commissioning and Delivery
A GRAF-accredited engineer commissions the plant free of charge once it is installed, which also starts the warranty. We deliver the One Advanced 28 Person Sewage Treatment Plant free to UK mainland addresses. However, the plant arrives on a lorry, so you will need to be able to offload it on arrival. You can also download the drawing, data sheet and installation manual from this page.






