Many variables at large. Do ...
Published by Martin P. Pelle, Water Technology Advisor, Engineering & Built Project Utility Team EMEA at Cargill
Many variables at large. Do the three reactors receive exactly the same feedwater? That means all three from the same tank? DO you pre-acidify in that tank, or has each reactor its own (pH/level controlled?) buffer. And if still exactly the same, do you control the flow into each reactor so you match the amount of kg of COD /day fed into the reactor, the amount of sludge you have in each of the reactors (like John suggested: F/M ratio). If you overfeed this troubled one, the acidifiers will grow faster than the methanizers, resulting in much faster growth of the acidifiers that are concentrated on the outside of each granule, making them 'lighter' and less compact, so they wash out....also the fast growing acidifiers may freely float around ultimately forming fluffy flocs as you saw...dragging on smaller sized granules...etc
Where is your site located and do you have an external consultant experienced in anaerobic? Who built the reactors, are they the same?
If you still concluded all three are running at the same conditions, you checked the accuracy of your analyses, then I indeed MArks suggestion that something in the internals may be corrupt (internal distribution system not workig correctly, partly blocked or so, settlers ill placed or blocked or actually different from the older reactors.....
Hope it helps.
Good luck
1 Comment
Thank you for your elaborate answer which is most helpful.
The water for the reactors is coming from a common buffer tank where pH is balanced before being sent to the anaerobic system. Temperature is also controlled collectively.
the F/M ratio is adapted according to the measured sludge content of each reactor. This is however with some delay. If there is one single measurement that is lower the feed is not changed since we notice a lot of variation in the measurements due to decent sampling issue's. Not all the strings in reactor constantly receive the same amount of water, via valves this varies. This causes difficulty’s in sampling where there might be a difference when you take a sample 10 minutes later. The feed is thus based on the average measurements. Changes are thus always with a delay.
In brief, it is possible that we are trailing behind and constantly slightly overfeed this reactor.
I was not aware that acidifiers make the sludge lighter nor the fact that it makes them less compact.
We do have an external consultant that could do a microscopic analysis of the sludge to determine whether these are mostly acidifiers.
Thanks again for the valuable information.
Published by Marijn Alliet