Poo Corner

When I chose to visit a sewage treatment works of my own volition recently, few people could understand why. For my part, I fail to understand why anyone wouldn’t want to visit a sewage treatment works. I find it hard to believe that these remarkable sites, which perform such a fundamental role in modern day society, are simply ignored by the vast majority of the general public.

I’ve stood on the margins of sewage treatment sites on many occasions during my forays into the urban fringe, peering through wire fences and wondering about the arcane processes taking place within, so it was with some excitement that I discovered that tours of the Lilac Grove Sewage Treatment Works in Beeston were to be run as part of the annual Heritage Open Days programme. No stately homes for me… I was intent on discovering the ultimate fate of my poo.

Sewage apparently consists of 99.9% water and 0.1% solids, but my olfactory senses suggested a slightly different ratio as our group assembled at the Lilac Grove site in the early September sunshine. This impression notwithstanding, the smell was not quite as bad as I had expected, and we later learned that this was primarily due to the treatments and systems that are in place for keeping odours to a minimum. As attendees of the 9am tour, though, we undoubtedly got off lightly compared with the next group, who were to be shown around at midday.

I was surprised (although perhaps I shouldn’t have been in this day and age) to discover that the site is not permanently staffed. Modern sewage treatment works are largely automated, and only the main sites require a dedicated manager. The person in charge of the Lilac Grove site, who was also acting as our tour guide for the day, is responsible for several sites in the area and moves between them as necessary, liaising with other Severn Trent employees and contractors when required.

After we had all donned hard hats, hi-vis jackets and rubber gloves and gone through a short induction procedure, our guide, accompanied by his assistant from the Severn Trent Education Department, took us outside to begin the tour.

Despite being bordered on one side by allotments and on the others by industrial land, Lilac Grove Sewage Treatment Works has an otherworldly feel to it. It’s as if there is a perception filter around the perimeter that stops the outside world from paying any attention to this strange landscape. As we gaze out at the mysterious concrete structures before us – somewhat incongruously sited amidst large areas of grass – a rather mangy fox bounds along the periphery of the site and we begin to discover more about the processes that take place here.

Prior to this visit, I had assumed (somewhat embarrassingly) that sewage treatment plants dealt exclusively with the effluent from toilets. As it turns out, sewage has a somewhat broader definition – it can best be described as any water-borne waste that is to be taken away from a community. This includes domestic wastewater, such as that from baths, showers, sinks and washing machines, as well as wastewater from commercial and industrial premises and, in some older areas, rainwater from roofs and roads.

On first entering Lilac Grove, the sewage is passed through screens which are designed to remove larger objects that could damage pipes and machinery. These objects are then washed and sent to landfill. Next, the sewage undergoes an initial settlement process which allows inert material such as grit to be removed while the organic material remains in suspension. As with the larger objects that have already been removed, the inert material is washed and taken to a landfill site.

The next stage involves primary settlement tanks. Here, the, erm, heavier organic material sinks to the bottom and forms a thick sludge, which is removed by scrapers and taken away for further treatment or disposal. As one of Severn Trent’s smaller sites, Lilac Grove does not have sludge treatment facilities, so the sludge is transported elsewhere. It is interesting to note that 68% of the sludge that comes out of Severn Trent’s sewage treatment system is used as agricultural fertilizer after further processing. It is therefore not entirely beyond the realms of possibility that those cornflakes that you had for breakfast were produced with the assistance of one of your own bowel movements.

After the primary settlement stage, the sewage then enters the really clever part of the procedure. Long sprinkler arms, which rotate around the classic circular constructions that most of us are familiar with, direct the sewage onto a filter made up of a bed of stones or other media. The filter contains bacteria and other micro-organisms, which remove organic material from the liquid as it filters slowly downward. This produces a biological film on the surface of the media, which is washed off by the incoming sewage once the film reaches a certain thickness. The water containing the film is then directed to a further settlement tank where the film is taken out as humus sludge, to be added to the primary sludge.

At sites where the Environment Agency requires the final effluent to be of a higher quality, a further treatment stage takes place, involving sand filters or reed beds in combination with chemical or biological processes as necessary, but none of these were in evidence at Lilac Grove.

So that’s it. The end of the journey from derrière to watercourse. We were told that the treated effluent from Lilac Grove is discharged into the Beeston Cut, a branch of the Nottingham Canal that connects the latter to the River Trent at Beeston Lock. A member of our group was insistent that the effluent actually flows into the River Trent, which would make more sense. Either way, the water has undergone a remarkable transformation on its way through the various treatment processes, though I for one won’t be languidly dangling a limb into the canal or the river any time soon.

Reluctantly removing my health and safety garb, I thanked our guide and his helper and collected my Severn Trent goody bag, which contained a pen, a fat trap and an assortment of insomniac-friendly literature. All in all, the visit had been a slightly surreal, yet fascinating experience that provided a privileged insight into a hugely important process that most of us just take for granted.