CES | Challege Environmental Systems, Inc.

The Challenge OLR on-line respirometer operates by measuring the amount of oxygen input needed to maintain a constant oxygen partial pressure in contact with a mixture of wastewater and microorganisms. The culture can be supplied from an operating aeration basin or a managed culture. The wastewater input can be from the influent to the aeration basin or from a candidate stream. Both wastewater and microorganism culture can be pumped into the reactor continuously or intermittently to provide either continuous or batch operation. A stream of air or oxygen enriched air is injected into the reactor at a controlled rate to flush carbon dioxide and inert gases from the headspace volume. A mass balance of oxygen input and wastewater flow is used to compute the total oxygen uptake rate. Adjustments for background endogenous respiration provides a measure of oxygen uptake due to waste synthesis alone and gives a measure of short term BOD.

The Challenge OLR allows operation at headspace oxygen concentrations ranging from that of air (21%) to 95% or greater, thus allowing simulation of processes that use oxygen enriched air.

The Challenge OLR does not rely on the oxygen dissolved in the influent wastewater but adds oxygen in amounts equal to the uptake of the culture confined in the reaction vessel. Thus the reactor can be operated under conditions that are essentially the same as used in the treatment plant being monitored. Oxygen uptake rates as high as 300 mg/l./hr can be measured directly without dilution of the mixed liquor or the wastewater being added to the reactor.