Killing two birds with one stone – innovation to deal with wastewater and heating in rural Scottish communities.

It’s not something we often think about – where does our water come from and where does it go once it has been through our bodies? We must deal with wastewater, but the current collective approach is often not suitable for smaller, island or rural communities, where overflowing septic tanks are the norm.

Bill Sloan, Professor of Environmental Engineering at Glasgow University and chair in emerging technologies with the Royal Academy of Engineering, is leading a multi-disciplinary team of academics, social scientists, lawyers, economists and communication specialists to address water issues in Scottish rural and island communities.

He says the current system is a legacy of a response to a public health crisis in cities in the 19th century with many treatment works now 50-60 years old, and pipes often 100 years old. This collective approach is energy intensive; Scottish water is by far the largest user of electricity in the country – using around 5% of the country’s electricity to pump drinking and wastewater and then run large-scale treatment works.

Bill says rural communities have been very much neglected in water and wastewater provision in Scotland and England, and many other places in the world, where a lack of treatment is viewed as a rural failing, rather than a national infrastructure problem.

‘Where governments try and implement the same sort of technologies in rural communities, the cost is enormous, like seven or eight orders of magnitude higher per capita’, says Bill. ‘So there’s a reluctance to do that’.

He was almost fed up with trying to get innovation in the water industry, but now sees there is a real opportunity to be innovative in smaller communities.

We met Bill at the Science festival on Barra and he shared some of the solutions that multi-disciplinary team is considering. The key to this innovation? Bugs. Of the trillon (at latest estimate) of different microbes on the planet, there are some that specialise in munching methane, called methanotrophs.

‘We’re looking at capping septic tanks with a composting bioreactor, populated with these methanotrophs’, says Bill. ‘The heat from that reactor returns to the septic tank, which increases the activity, so you get positive feedback. This cycle stops methane emissions and creates heat for your household. We think we can do that by retrofitting existing infrastructure’.

Given that there are around 2 billion septic tanks on the planet – that’s a lot of waste to be captured and turned into heat. It also has real practical application for those not close to a centralised treatment system. Currently, to empty a septic tank on the Western Isles, a tanker sucks up the waste and it is transported to the mainland and Glasgow for treatment.

‘It’s a hugely energy intensive process, but without much treatment being done on the island. A lot a lot of the septic tanks are never emptied, so they’re discharging directly into the sea’, adds Bill.

‘If we start treating water at the point of use in the landscape, then these technologies may come into play’, Bill says, excitement in his voice. ‘Currently, we take water from the mountains, have a single pass system where we go through our households. Often it’s treated in big wastewater treatment plants, and discharged as almost drinking-quality water into the sea. We’re effectively putting water through the landscape as quickly as possible’.

This one-pass system often means water shortages for those in the Outer Hebrides. And Bill says climate change will cause more water shortages, meaning more tankers supplying clean water to the islands.

‘ We think we’re water rich, but I can guarantee you that in the next 20 years, we’re going to suffer some real water shortages. We should be looking at holding the water in the landscape and treating it close to where it’s being extracted’.

Whilst Scotland is wet it doesn’t have large groundwater reserves – it’s all surface water, meaning little resilience to drought. ‘It’s something island communities are getting pretty concerned about’, says Bill. ‘If you treat wastewater locally to a reasonably high quality, then it can be used for irrigation, for example. It’s amazing how much plant watering goes on, even in these Scottish Island communities’.

Not only would a localised system assist with reducing greenhouse gas emissions, local heating and water supply – the prototype of this work in the Outer Hebrides could be an example that cities can learn from.

‘The more we work on these decentralised technologies, the more I think that even in our cities, we should be thinking about them’, says Bill. ‘We’re ahead of the game by looking at these Island communities and how you do things very locally’.

‘If we can make a big difference on one of the islands or coastal communities, I think it might permeate and change the way things are done, especially if we can recycle water at a very local scale. That would make a huge difference to all sorts of issues like flooding and drought’.

Novara’s role in to support Bill and his team to find funding when they’re at the stage to launch the prototype and implement their ideas, as well as linking Bill and his team to other communities around the world who are looking for ways of dealing with wastewater.