Thank you for the various responses. However there was no real consensus!
Objects
1) The cylindrical objects do look a bit like filter media which may have been used in tower scrubbers, however I’m uncertain that this is by any means conclusive. There is also the possibility that these are catalyst from a more recent gas reformer plant, which is fine (cobalt/Nickel) providing they were not the experimental ones made from depleted uranium ! Just in case anyone should be getting concerned over the risk of depleted Uranium (U238) on former gasworks. It was never used as part of the traditional coal gas process. It relates to the later reforming plants which were generally dependent on refinery based by-products for gas making. Such plant were built either on existing large gasworks or new sites. This Uranium-Nickel catalyst was used on very few sites, being restricted to those operating "high pressure tubular continuous reformers". There were about 40 sites in the UK where this process was used and it was believed that only half of these plants ever used this catalyst. North West Gas Board who pioneered this and a number of other new technologies did use it at one low pressure reforming site, but this was for experimental purposes. It is a poorly document part of gas history, so it’s difficult to find references on the subject matter.
2) It resembles biological filter media with porous / high surface area ratio for maximised media contact. I have seen this first hand in garden pond filters and waste water treatment plants – 2 versions of the same thing! I am assuming therefore it could well have been used in other industrial treatment processes with similar bio-media contact requirements. I have used plastic media in leachate bioreactors to serve the same purpose. Modern plastic forms tend to provide for better circulation and suffer less from bio-clogging. I think the shape / format that you have maybe was an older more traditional form – I recently threw virtually identical looking stuff out of my pond filter and replaced with Alfagrog!
http://www.swelluk.com/swell-alfagrog/?gclid=Cj0KEQjwxbDIBRCL99Wls-nLicoBEiQAWroh6ifozExTXJ_bgLsedjFsBf-lEBvk4oIOE0A6AF2uucoaArDI8P8HAQ
3) I have seen ceramic disks associated with firing of pottery and ceramics as a quality control feature. I think distortion of the disk is taken as a failure of the firing process. If you find ceramic/brick waste in the 1980s landfill that may be an explanation.
4) I am not sure about the former use of the ceramic pipe. It could be related to the gas purification process hence the staining but equally may have picked up the staining from the waste below if it has been used as a fill material. Are there any historical plans of the former layout of the site as this could give a clue as to the process to which they relate?
Blue Staining
5) Gasworks, blue billy staining?
6) The blue staining is Prussian blue, a dye which is a complexed form of iron cyanide formed in the purifiers, the staining usually associated, with storage, disposal or the areas of the purifiers, again this concrete look more recent rather than Victorian.
[Prussian Blue (Ferric Ferrocyanide) is regarded as a non-toxic, non-carcinogenic, non-mutagenic chelating agent, recommended by FDA for the treatment of heavy metal (caesium and thallium) poisoning. It is poorly absorbed into the gastrointestinal tract. https://pubchem.ncbi.nlm.nih.gov/compound/2724251]
7) I know from my previous experience undertaking SI and remediation on former gas works sites that the blue staining is from spent ferric oxide and/or foul lime used to remove sulphur and cyanide impurities from the coal gas. Both types of waste can contain high concentrations of cyanide compounds. Unlike coal tar there was no real economic value in these by-products and so they were commonly used as infill around the gas works.
As a postscript you will all doubtless be relieved to know that all made ground has been excavated and removed to landfill and the remaining natural ground has been encapsulated in geotextile and hardstanding (including service line trenches) to form a cycle path with no access to underlying soils. "Institutional controls" have been put in place to ensure these measures remain effective in perpetuity.
Thank you to all who contributed!
David
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