Different sludge growth

Hello,

We have at our treatment three Uplift Anaerobic Slib Beds (UASB).

Currently we are experiencing problems with one of the reactors.

The sludge in this reactor does not form a granular structure as it normaly does. Insteed it forms loose flakes that are easily washed out, hence we are losing sludge at a fast rate.

It does however produce biogas at a comparable rate than the other reactors. The fatty acids are also under control, as well as pH and temperature.

The reactor was only startup about a year ago and received somewhat similar sludge than the second reactor. For a period this evolved in the same way but in the last couple of weeks this has changed dramaticaly.

Does anyone have any idea why the sludge can be so different if al the other parameters are the more or less the same?

Sincerely,

Marijn

Taxonomy

• Treatment
• Anaerobic Digestion
• Bioreactor
• Biological Treatment
• Industrial Wastewater Treatment
• Waste Water Treatments
• waste water bacteria

6 Answers

1. If you want to reduce sludge volume, Please consider of ELODE system. www.elode.co

2. 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

   1. 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.

3. The granular formation will not happen as there might be due to higher TSS. try to remove as much as TSS in primary process and feed into the Digester, so that there wont be any suspended sludge formation which will lead to overflow from the top;

   1 Comment

   1. Currently we do not have a primary process to remove TSS wich has been a problem before the expansion of the waste water treatment.

      Due to further expansion of the factory this is however in a casestudy right now.

4. Hello Marjin,

   Sounds like you on top of the laboratory parameters. I would check the plant to see if all valves and pumps are correct. Are there any chemicals that are pumped to each digester as apposed to the common line.

    

   1 Comment

   1. The reactors all receive the same water, the pH correction happens in a buffertank before the reactors.

      The pumps & valves will be checked though.

5. I would recommend you to do a test with sludge to evaluate gas production versus DQO and sludge mass inside the reactors. Kind regards

   1 Comment

   1. Thank you for the advice.

      We are not able to perform a gas production analysis ourselfs but i will contact our external partner for an analysis.

6. One of the variables is sludge age in relation to the influent MLSS, have you checked this and compared the two reactors? This means the F/M ratios might be out of balance for the anerobic floc or CFUs available.

   1 Comment

   1. Due to the washout of the sludge we do have a different MLSS, the feed to the reactor has however already been adapted to compensate for this.

      As such the biogas production is also somewhat lower but relatively speaking comparable to the other reactors.