School opts for aerated technology
A prep school in Oxfordshire has invested in a constructed wetland fitted with forced bed aeration to treat its sewage
St Hugh’s school in Carswell, Faringdon has been working with ARM Reed Beds to replace its existing sewage treatment system with one which works within the existing footprint, is environmentally-friendly and meets its sustainability targets.
Up until recently the school had been treating all of its sewage with a system installed over 20 years ago. Comprising three septic tanks and a filter bed, the system had become overgrown and no longer fit for purpose.
With a tight discharge consent set by the Environment Agency and the welfare of pupils a primary concern, St Hugh’s chose a new system incorporating two septic tanks and an aerated reed bed fitted with forced bed aeration (FBA) technology.
Alistair Hamilton, St Hugh’s bursar, says: “It was important that the new system met a range of criteria set by the school. Not only did it need to meet standards set by the Environment Agency, it needed to be sustainable, cost-effective, require little maintenance and fit within the confines of the existing system.
“As we already had a filter bed, we wanted a similar green solution but it had to have the right capabilities. ARM was able to design a system that met our needs and the use of aerated technology means we have the option of fine-tuning the aeration for maximum treatment during peak times and lowering it during holidays – reducing energy costs.”
With more than 300 pupils and 80 members of staff at the school, the new system includes a new septic tank which takes a combined flow from the prep and middle school on the west side. The new septic tank on the east side of the school takes a combined flow from the upper school house in the manor and the workshop. Previously the workshop had its own septic tank and soak away.
Many schools outside urban boundaries do not have access to the main sewage network, therefore the potential of constructed wetlands as a viable solution is becoming more popular due to advances in technology and treatment capabilities. “The headache for many schools is meeting consent levels. If they fail to meet these, costly fines will be imposed. The sewage treatment solution must be able to meet these tight consents and deal with the challenges that term time and long holidays throw at it,” say Tori Sellers, director at ARM. “Over the past 10 years ARM has invested a lot of resources into providing solutions for a range of clients and the development of aerated reed beds has opened up the possibility of using wetland solutions to treat waste water for many businesses, including schools.
“The requirement is nearly always the same – a need to reduce BOD and ammonia concentrations in the water before it enters the local watercourse. The difficulty with schools is that volume of waste water varies over the course of the school year; therefore aerated wetlands provide the ideal solution as the energy required for the aerated element can be switched on and off to meet demand, thereby reducing energy costs.
“Ammonia requires oxygen to complete the removal process. Once the oxygen is used up, the ammonia removal process stops. In comparison to a passive wetland, an aerated bed can be up to 15 more times effective by ensuring the system isn’t oxygen limited. With this increased treatment capacity, aerated wetlands have a smaller footprint so take up less space than a conventional wetland.
“Schools have limited budgets and if they need a solution which hits sustainability targets, reduces operating costs and requires little maintenance, then aerated wetlands is the only solution,” says Tori.