Effluent ammonia increasing – trouble shooting and finding the correct response

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.