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

Nutrient removal from wastewater - new challenges

11/9/2015

 
Due to acute toxicity to aquatic organisms, wastewater permits have long required removal of ammonia nitrogen from wastewater. This process normally relies on Ammonia Oxidizing Bacteria (AOB) which are organisms that derive energy from the conversion of ammonium (NH4) into nitrite (NO2) and finally nitrate (NO3). The focus was to achieve full conversion to nitrate as the nitrite form was also toxic. Later in developing more advanced treatment, the nitrate/nitrite were to be removed via the denitrification process.

Many common wastewater organisms are capable of removing nitrate/nitrite from waste when dissolved oxygen falls to zero (redox potential <0) in the presence of soluble organics (we often term this BOD5). The process relies on the ability of the bacteria to harness the oxygen bound in the nitrate/nitrite when consuming soluble organics. The BOD5 is lowered and nitrate/nitrite are converted to carbon dioxide (CO2) and nitrogen gas (N2). We see this in the small bubbles that float sludge in secondary clarifiers with long residence times and deep sludge beds. It is also seen in settling ponds where in warm weather we have small nitrogen bubbles along with other anaerobic gasses.

Now that we have converted nitrogen in water to gas, another problem nutrient remained in the wastewater for treatment - Phosphorus. While not directly toxic, in most freshwater an excess of phosphate can trigger algae blooms. The algae bloom causes pH and dissolved oxygen swings and in the case of many cyanobacteria can result in toxic byproducts. To remove phosphate multiple technologies were developed including using alum and other chemical binding/solids removal technologies. These require both equipment, operator input, and produce sludge for disposal. Another option explored was to use the natural tendency of bacteria to uptake phosphate into the cell during growth. in nature phosphate is often a limiting nutrient, so when presented with high phosphate levels, bacteria tend to store phosphate for later use. After much testing, a biological process to remove phosphate was optimized. To encourage the best phosphate uptake, requires the use of a anaerobic zone at the inlet where organisms release stored phosphate to move soluble BOD across the cell wall and start anaerobic metabolism. This gives the phosphate storing cells an advantage when they get to an aerobic zone where all bacteria work efficiently. With oxygen plentiful, the Bio-P organisms, phosphate accumulators, uptake excess phosphate into their cells. This fixes free soluble phosphate into the biological solids. For removal of phosphate from the effluent, TSS or biological solids needs to be removed. A big requirement of biological phosphate removal is to keep the phosphate in the cells - which means no anaerobic storage conditions prior to discharge as this starts the natural phosphate release process.


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

    April 2023
    February 2023
    January 2023
    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