• Blog
  • Wastewater Testing
  • Bioaugmentation Applications
  • Useful Information
  • About Us
BIOLOGICAL WASTE TREATMENT EXPERT
Contact Us

My SVI or SV30 is too low... what is the cause and fix

2/20/2018

 
The SV30 test uses a dedicated settleometer or 2L graduated cylinder to measure settling velocity and compaction in wastewater treatment biomass. (Note - always use the same size cylinder or settleometer to run the tests). To account for changes in MLSS concentration, the SVI takes the SV30 number and divides by MLSS in grams (some facilities use MLVSS in grams) - just use the same divisor each time.

Now for the SVI or SV30 being too low. Usually compact sludge is a good thing - it means no bulking and clarifiers with not solids carryover. However, if sludge settles too quickly or compacts too much there can be problems including turbidity, recycle (RAS) system troubles, and occasionally floating fines causing effluent TSS problems. Usually the problem is "Old Sludge" where lower F/M conditions over the long term result in bacteria consuming the extracellular polymer substances (EPS). Once the EPS percentage drops:
  • the floc size begins to decrease 
  • floc density increases and settles rapidly
  • "fines" or small solids chunks break off from the floc and enter solution
  • Polymer at the secondary clarifier to reduce TSS or clear up turbidity

How do you investigate and fix the problem
  • Perform microscopic exam - look for smaller floc sizes, high density of floc, presence of low F/M filaments, and increased numbers of multicellular indicator organisms such as rotifers, tardigrades (water bears), and even nematodes.
  • See if SOUR or DOUR has decreased. Lower oxygen uptake rates along with very low SVI are indicative of "old sludge"
  • Determine if low influent organic concentrations is going to be an ongoing phenomenon and adjust target MLSS/MLVSS concentrations
  • Increase wasting in 10% steps while monitoring sludge quality to see if EPS increase is triggered by increasing F/M and lower sludge age (MCRT)
Frederik Wynants
9/12/2018 01:09:39 pm

Very interesting article !


Comments are closed.

    Author

    Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater  facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.

    View my profile on LinkedIn

    RSS Feed

    Click to set custom HTML

    Archives

    December 2022
    November 2022
    October 2022
    September 2022
    August 2022
    June 2022
    May 2022
    March 2022
    February 2022
    January 2022
    November 2021
    October 2021
    September 2021
    August 2021
    June 2021
    April 2021
    March 2021
    February 2021
    December 2020
    November 2020
    October 2020
    September 2020
    August 2020
    July 2020
    June 2020
    May 2020
    April 2020
    March 2020
    February 2020
    January 2020
    December 2019
    November 2019
    October 2019
    September 2019
    August 2019
    July 2019
    June 2019
    May 2019
    April 2019
    March 2019
    February 2019
    January 2019
    December 2018
    November 2018
    October 2018
    September 2018
    August 2018
    July 2018
    June 2018
    May 2018
    April 2018
    March 2018
    February 2018
    January 2018
    December 2017
    November 2017
    October 2017
    September 2017
    August 2017
    July 2017
    June 2017
    May 2017
    April 2017
    March 2017
    February 2017
    January 2017
    December 2016
    November 2016
    October 2016
    September 2016
    August 2016
    July 2016
    June 2016
    May 2016
    April 2016
    March 2016
    February 2016
    January 2016
    December 2015
    November 2015
    October 2015
    September 2015
    August 2015
    July 2015
    June 2015
    May 2015
    April 2015
    March 2015
    February 2015
    January 2015
    December 2014
    November 2014
    October 2014
    September 2014
    August 2014
    July 2014
    June 2014
    May 2014
    April 2014
    March 2014
    February 2014

Proudly powered by Weebly
Photos used under Creative Commons from Picturepest, marcoverch, perzonseowebbyra, Picturepest, Picturepest, dsearls, dungodung, Massachusetts Office of Travel & Tourism, aqua.mech, vastateparksstaff, hile, Aaron Volkening, amishsteve, Neil DeMaster, mklwong88, KOMUnews, Picturepest, kaibara87