CovSoc Chair, Trevor Cornfoot, reports back on “an interesting visit”! Trevor writes……
Well, who’d have thought that a visit to the local sewage works could be so interesting?
The visit of 16 CovSoc members to Finham Wastewater Treatment Works on Friday 2 August was one of our more unusual summer visits but was really fascinating.
By way of background the Works treats the waste of a population of about 460,000 from Coventry and Kenilworth plus sludge from Rugby and satellite sites in South Warwickshire. The Works is Severn Trent’s fifth largest. The surprisingly large site is well screened by trees off St Martins Road.
We took in the full process from the main entry sewers to the freshwater exit into the River Sowe. On the way we saw the huge storm water retention tank, once the largest in Europe, and the first process, the screens taking out the ‘rag’ from the incoming sewage – the stuff we should never put down the drain in the first place: wet wipes, nappies, sanitary items and cotton buds. Grit gets removed at this incoming stage.
We passed many of the settling lagoons, which physically separate sludge and liquids before the sludge enters the huge ‘golfball’ anaerobic digester where heating the sludge to high temperatures encourages bacteria to break down the waste. This produces methane (biogas) which generates electricity to power much of the Wastewater Works and with surplus gas sent into the National Gas Grid. The residual inert residue – ‘cake’- is sold as farmland fertiliser.
The waste water is then aerated and passes through final filters, before being returned to the natural environment. We saw pictures of a pike living in the exit channel to the Sowe. So the whole process is very much a modern circular economy.
Many of us recall the horrid rotten eggs smell from the works. This is said to be much reduced due to the anaerobic digestion processes and biofilters (to reduce hydrogen sulphide by 99%) – though some Finham residents and golfers may disagree on summer days!
All in all, this was a most educational visit. Members who missed out should look out for public open days when they too can be surprised by the sequence of processes to return Coventry’s liquid wastewater to augment the flow of the River Sowe.