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

Introduction to Wastewater Phosphate Removal Options

2/14/2017

 
With many waterways experiencing problems with algae blooms - including toxin producing cyanobacteria -more wastewater treatment plants have received more stringent nutrient discharge permits. While nitrogen in the form of ammonia and nitrite have long been regulated, facilities are now being required in many areas to bring effluent phosphate below 1 mg/L. 

Effluent phosphorus comes in two main forms, soluble and particulate. The particulate form is bound in the MLSS and can be removed by improving solids separation. Improving solids removal should be the first strategy in meeting effluent phosphorus permits. Often we also have to remove a soluble phosphorus from the effluent which is more difficult.

Biological Phosphorus Removal
In biological phosphorus removal, conditions promoting the growth of phosphorus-accumulating organisms (PAO) must be maintained. The PAOs are facultative anaerobic bacteria that store energy in the form of polyphosphate granules (inside cells). The stored energy powers uptake of volatile fatty acids (VFA) - usually acetic, propionic, & butyric under anaerobic conditions. The uptake of VFAs ends up releasing phosphate into the surrounding water. Once in an aerobic environment, the PAO organisms use the stored VFAs for energy and uptake the free phosphorus in the water and store it as polyphosphate inside the cells. 

PAO organisms do not develop unless their ecological niche exists in the system. So a normal aerobic system will not have an abundance of PAO in the biomass - since conditions exploited by their unique metabolism are not present. What are the required conditions to favor PAO growth:
  1. Must have a true anaerobic zone - without nitrate/nitrite or dissolved oxygen
  2. The anaerobic zone must have volatile fatty acids (VFA) that are used by the PAO
  3. pH must be above 7.0 (GAO organisms start to have an advantage at lower pH - GAO do not uptake phosphorus)
  4. Temperature best below 30oC - as other organisms start to outcompete the PAO (again the GAO organisms)
  5. Anaerobic conditions must be followed by oxygen rich (aerobic) conditions

Chemical Phosphorus Removal
Using alum, ferric salts, or even lime for chemical precipitation is the oldest method for reducing soluble phosphorus in effluents. Today we usually use alum or ferric salts since they function better at the near neutral pH seen in wastewater treatment units. Coagulants can be added at any stage in the waste treatment unit to bind with phosphorus. However, the most common area is to use the coagulants in the secondary or tertiary clarifiers. This avoids removing the phosphorus needed for biological treatment in the biological unit. It also reduces coagulant dosage when compared to dosing at the primary clarifier where other competing materials bind with the coagulants.

The major downside to chemical precipitation is the increased volumes of sludge and metal salts in the sludge.

Constructed Wetlands
Another option for phosphorus removal, that most mimics natural processes, is to construct wetlands that act as a biofilter to remove trace organics, nutrients, and solids before final discharge. Constructed wetlands should be a first choice option in areas with large amounts of land as they have fewer energy, chemical or labor requirements demanded by either advance biological systems or chemical treatment. In many cases, the wetlands can be a natural area or park that benefits wildlife and local residents. Most of the phosphorus removal in constructed wetlands is accomplished through plant and uptake of the nutrients.
Picture
Oxidation Ditch technology can be used for biological nutrient removal. Photo newconcord-oh.gov
Kairi Gainsborough link
3/30/2018 05:39:29 pm

Thanks for explaining how biological and chemical phosphorus removal works. I was wondering how water gets cleaned up. If this is just the process for removing phosphates, I would be interested in how to remove other contaminants.

Vanessa Blair link
7/19/2018 09:45:46 pm

My dad is concerned with his farmland and wants to make sure that the wastewater is regularly removed. It was explained here that there are different types like biological phosphorus and constructed wetlands. Furthermore, it's advisable to consult professional plumbers when considering wastewater removal services.

Camille Devaux link
12/17/2018 01:35:06 pm

It is interesting to hear about the various options that waste water systems have. Using a treatment with chemicals seems like an interesting option. It might be helpful for my sister to know a little more about this as she looks for a system that is right for her.

Dominique Chong link
1/29/2019 03:22:57 pm

This is a thorough explanation of biological phosphorus removal. I have been thinking about how to clean up wastewater for our farm. We are living in a remote area and having such technology is out of our hands. I will consult an expert regarding this matter, this will help me a lot over my farm.


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