Dear Reza

It depends mainly on the reactor operating condition. It was reported that ammonium oxidation rates of up to 500 gN m−3day−1 with greater than 90 % conversion to N2 have been achieved in a pilot study using online ammonia sensor, with continuous aeration at dissolved oxygen concentrations

Dear Reza,

I agree with Ata if your objective would be ammonium oxidation using shortcut BNR (via nitrite) as we apply in full scale plants since almost 30 years..

However if your main objective would to acclimate your micro-population to saline wastewater along with bio-oxidzing organics (BOD, COD) then I would first make sure that there are sufficient nutrients (macro + micro) and then apply on-line specific oxygen uptake rate (SOUR) analysis to determine to optimal DO concentration profile over the SBR cycle (from high to low oxygen demand).

Regards,

Bruno

 Dear Ata

Thanks so much for your helpful answer and references.

Dear Bruno,

Thanks so much, your explanation was very helpful. As you noticed my main objective is acclimation along with COD removal. What would happen if DO concentration is more than optimum value in bioreactor and is there any standard or defined range for DO in bioreactors?

Regards,

Reza 

Dear Reza,

In most cases, the optimal DO for BOD and COD removal is around 2 ppm. High DO  (more than 5 ppm) is inefficient (waste of aeration energy) and may also result in the disintegration of activated sludge flocs especially in saline wastewaters containing high levels of monovalent cations (Na+, K+) as compared to bivalent ones (Ca++, Mg++, ...).

Regards,

Bruno

Thanks, I would like to know if excess DO has any effects on bio-oxidation reaction, activity of microorganisms and biomass flocs. 

Regards,

Reza

You may want to check this somewhat related discussion: https://www.researchgate.net/post/what_are_negative_consequences_of_increasing_dissolve_oxygen_in_aeration_tank_in_waste_water_treatment_plant

 Dear Carlos,

Thanks so much, It was so helpful and informative.

regards,

 Dear Reza

As mentioned by most workers, maintaining DO level at 2 mg/L is the usual practice. The first phase is aerobic digestion during which time you will be stripping C as CO2 and by bacterial assimilation. By bacterial assimilation alone one could convert 50% of the C into solids. The above process may require 1-1.5 kg O2 per 1 kg BOD and sufficient NH4 and PO4 which are available at this stage.

As the workers identified, maintaining greater DO level is wasteful and energy taxing. However, sometimes high BOD wastewater or systems with low HRTs may require higher DO than 2 mg/L.

Once much of the bacterial assimilation is completed (when BOD is

Dear Selva,

Thanks so much for your comprehensive explanation.

Regards,