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Effluent ammonia increasing – trouble shooting and finding the correct response

1/4/2023

 
Picture
qPCR curves used to calculate % AOB and % NOB
What can cause sudden increase in effluent ammonia
  • Rapid increase in loading – Ammonia & TKN
    • Look at influent loadings – total nitrogen loading is needed
    • As both AOB/NOB are slow growing it can take time to catch up to influent increase
  • Inhibition – slowing of AOB & NOB metabolism
    • D.O. being < 2 mg/L
    • COD/BOD inhibition – Rule of Thumb – 80% COD needs to be removed before AOB/NOB tend to fully function in WW
    • pH < 7.0 or >8.5
    • Alkalinity
    • Temperature <12 or >38 Deg C
    • Enzyme cofactors – trace metals lacking or being bound
    • UV radiation (sunlight)
  • Washout
    • Slow growth and short MCRT – can lead to AOB/NOB washout (population drop as reproduction is not fast enough)
    • This often goes along with inhibitory factors slowing growth rates
  • Acute toxicity – kill of AOB/NOB
    • Some compounds have acute toxicity – thiourea, carbon disulfide, sulfide, cyanide, phenol
    • Total loss of aeration for extended periods with septicity 
    • Not that common in most WWTP 

Tools to directly monitor AOB/NOB populations
  • Aster Bio uses molecular tools to track for potential inhibition & washout
  • qPCR for wastewater organisms – use primers based on actual WWTP data can directly enumerate populations
  • MCA – total microbial census gives data on both AOB & NOB as % of total reads
  • Answers questions – total toxicity, inhibition, or insufficient populations for current loadings
 
What to do if you suddenly see an increase in effluent ammonia
  • Run qPCR to identify the root of the problem
  • If influent ammonia/TKN increase is the issue
    • Slow influent flow if possible, this will give time for AOB/NOB growth
    • Adjust environmental conditions in the biological unit to maximize AOB/NOB growth
    • Add nitrifiers – decrease time required to adjust to full AOB/NOB population
  • Toxicity – loss of all AOB/NOB populations
    • Find out what happened!
    • Remove problems from influent & increase wasting if it builds up in the MLSS
    • Adding nitrifiers or outside MLSS can help but only if inhibitors/toxic agents are removed
  • Washout
    • Usually not a sudden increase – this is a gradual process, and you have warning
    • Reduce wasting rates
    • Enhance environmental conditions for AOB/NOB
 Key points
Check as to why you are seeing increased effluent ammonia
  • Something had to change!
  • Was it gradual or sudden
  • Influent TKN is important - as much as influent ammonia
  • If toxicity or inhibition is found, you must eliminate it as much as possible! Added nitrifiers from commercial blends are just as susceptible to inhibition as indigenous.
  • qPCR is best tool to find out direct information on the AOB & NOB populations
  • If adding nitrifiers, the dose depends upon growth rates and how much ammonia needs to be oxidized. We want to give the best growth environment possible.
 


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    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

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