Graf UK helps Stairhill Developments

September 23, 2024

A Graf UK wastewater treatment system has enabled a Scottish developer to increase the capacity of a farmstead conversion and achieve a higher quality standard of treatment.

Passive house/low-energy specialists Stairhill Developments are currently halfway through the conversion of Dunree Farm near Dalrymple in Ayrshire into 10 dwellings.

The site comprises an original cottage and farmhouse, together with a barn that Stairhill converted in 2008. These used a foul water system comprising a septic tank with reed bed.

But the developer now also has full permission to convert three more barns into low-energy homes, along with outline permission for the construction of a brand-new home and for the conversion of an agricultural barn to a modern home.

This required a wastewater upgrade, from seven to 10 properties, and that is where Graf UK stepped in.

Sustainable drainage solutions supplier Moir Environmental suggested Graf’s One Advanced 45-person system comprising two 10,000-litre tanks installed in series – the first being a primary settlement tank, and the second a treatment tank utilising SBR (Sequence Batch Reactor) technology.

SBR systems run in batch cycles which generally operate twice or four times every 24 hours to ensure the treatment process is identical every time to produce high-quality effluent.

Continuous flow systems operate on a “What goes in, comes out,” basis, so during periods of heavy loading/inflow, the effluent travels through the system much quicker, potentially reducing the effluent quality.

At Dunree Farm, the drainage works were carried out by Stairhill, while Moir Environmental assisted with the installation of the two tanks, pipe and duct connections, above-ground enclosure set-up, and commissioning of the Graf system.

Moir Environmental are members of Graf UK’s nationwide network of “approved” service providers and have designed and installed multiple Graf systems ranging from single houses up to large visitor centres.

Using a 14-tonne track excavator, alongside a tractor and dumper, both tanks at Dunree Farm were backfilled with concrete to around two thirds of their height, with pea gravel over the top. The old septic tank and reed bed system was then removed.

Stairhill Developments’ certified passive house designer Alistair Mair, son of founder John Mair, said: “The Graf system takes up a much smaller footprint, is hidden underground and therefore not unsightly, and has the capacity to cater for the increased numbers now proposed.

“It was recommended by Stewart Moir [Moir Environmental’s designer/consultant and managing director] as a compact system with no requirement for further treatment, which fitted within our site, and minimised the land area required for the system. It was relatively easy to install and we were able to tie into the existing foul drainage system on site.”

He added: “The Graf system is performing well and we were very happy with the service provided. It was our first time using a Graf system but we will certainly use them again, most likely for smaller units for one-off dwellings.”

Stewart Moir said: “Works duration was approximately three weeks, with the tank installation and commissioning taking around one week. As ever, the customer service from Graf was excellent, with the tanks delivered on the date requested.”

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