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

Microbial Ecology in Wastewater Treatment Systems

9/28/2022

 
Picture
Operators often call the biological treatment units the "bug farm", where they monitor and care for a huge population of living microbes. The organisms growing in the system are present based on:
  • Influent composition & concentration
  • Operating environment - pH, Temperature, D.O., MCRT, F/M, system design

While there is a great degree of variation in the species of microbes, we can classify many organisms based on their ecological niche in the biological treatment unit. Here are the most common functional groups.
  • Heterotrophic Floc Formers – want microbes that uptake soluble organics. Best represented by the sponge analogy. Rapid uptake of organics with actual metabolism as the organisms pass through the system. Ideal organisms form biofilm/floc. This is composed of polysaccharides, proteins, DNA, adsorbed particulate organics, and other biological polymers. Want the “perfect” slime – that gives stable floc without holding too much water (viscous bulking). Manage populations with F/M or MCRT
    • Keeping design F/M favors bacteria with rapid uptake of soluble BOD (organics)
    • Stored organics in EPS used as “food” outside the abundant zone
    • Too little EPS = pin floc or old sludge, too much EPS = non-filamentous or zoogleal bulking
  • Niche Bacteria that require operator attention
    • AOB/NOB – managed by adjusting MCRT & F/M – Alkalinity, D.O. Key concept is that both AOB & NOB are slow growing cultures so need lower F/M and longer MCRT.
    • PAO – function in similar niche to Thauera/Zooglea. Rapid uptake of soluble organic acids for use as “food” later. To favor PAO over Thauera, have true anaerobic zone (no nitrate) with high organic acids.
    • Denitrifying – very common pathway – nitrate/nitrite removal optimized by low D.O. (anoxic conditions) with soluble organics. Relatively high energy yield so these are common and can even thrive inside “aerobic” reactors.
    • Sulfur Oxidizers/Sulfur Reducers - sulfur oxidizers have convert sulfides into sulfur and eventually sulfate. If you have sulfides in the influent, the SOX are important for AOB/NOB growth. The Sulfur Reducers (SRB) are found in anaerobic zones and generate sulfides - often found in collection systems & anaerobic digesters
    • Filaments - Microbes that can grow into high surface area filamentous morphology. Filamentous bacteria in small quantities help floc formation by acting as a biological rebar to strengthen the floc. Once the filaments are bridging floc or extending free into the solution, you start to see filamentous bulking that can be a problem in secondary clarification. 
    • Foaming bacteria - this includes Nocardia and M. parvicella. Problem foaming is caused when influent contains insoluble organics (fatty acids or grease). These organisms use hydrophobic EPS to accumulate the fatty acids to support their growth.  These are slower growing organisms than most heterotrophic wastewater bacteria, so they compensate for slow growth by exploiting their ability to grow on insoluble organics.



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