Hydrogen Peroxide Turn-key Program Helps Refinery through Aeration Basin Maintenance Outage

US Peroxide’s 27% Hydrogen Peroxide Treatment Program offered the refinery several benefits:

• US Peroxide’s turnkey supply scope provided a safe and cost effective solution for supply of supplemental dissolved oxygen to this large refinery during the maintenance outage.
• The biological treatment system’s performance during the outage  convinced the refinery to maintain the hydrogen peroxide storage and dosing system on site to provide supplemental dissolved oxygen (DO) on as “as needed” basis during periods of high BOD/COD loading, upstream process upsets, and filamentous bulking episodes.

In the summer of 2010, a large refinery complex in the Northeast was a facing a 2-3 month maintenance outage on one of two aeration basins in their activated sludge wastewater treatment system. During the outage, all of the refinery wastewater would need to be routed through the one remaining aeration basin.  Since the refinery periodically had difficulty maintaining dissolved oxygen (DO) levels with both aeration basins in service, they needed a temporary (and non-capital) means to provide the biological treatment system with supplemental DO during the maintenance outage.

Hydrogen peroxide has been used as a source of supplemental dissolved oxygen (DO) in activated sludge treatment systems for decades. In the aeration basin mixed liquor, H2O2 converts to DO according to the following reaction:

2  H2O2   →  O2  + 2 H2O

This decomposition to DO occurs very rapidly due to the catalytic effect of enzymes (i.e. catalase) present in all activated sludge mixed liquors, and thus provides an immediate source of DO to the biomass.  Since hydrogen peroxide is a liquid, and infinitely soluble in water, the amount of DO provided is not limited by mass transfer of oxygen from the gas phase to the liquid as is the case with mechanical aeration.  More information on this application is provided at this link: Supplemental Dissolved Oxygen.

Solution

When the maintenance outage was initiated and wastewater flow was diverted to the lone aeration basin, DO levels rapidly dropped from the target range of 2-3 mg/L to near zero (0.1-0.2 mg/L). Dosing of 27% hydrogen peroxide into the effluent of dissolved air floatation (DAF) unit, just upstream of the aeration basin was started to offset this unacceptable drop in DO. Within a matter of hours, a measurable DO increase was observed and continued to trend upward throughout the day. Within 24 hours of starting H2O2 dosing, the DO levels in the aeration basin in the wastewater treatment process were back in the 1-2 mg/L range, and within 48 hours had reached the refinery targeted 2-3 mg/L range.

Dosing of 27% H2O2 was continued throughout the maintenance outage and maintained the DO levels required for effective BOD removal and nitrification (ammonia removal). It is noteworthy that during the outage the refinery experienced no filamentous bulking episodes. This translated to good clarifier settling, which had historically been a concern when treatment system DOs were experienced.

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Activated Sludge Basin and Dissolved Oxygen