A study using online monitoring with an MSL 100 L tank respirometer in the MAT2000 (mobile analytical trailer) was performed from 1999-2002 at various wastewater treatment facilities across the United States. The seven facilities discussed in this study varied in size, process, and included both domestic and industrial sources. The respirometer provided data 24/7 and was accessible remotely to readily communicate with the onsite staff. The instrument calculates an oxygen uptake rate (OUR), oxygen demand, diurnal variation, and by reviewing the shape of the curve on the graph or respirogram various conclusions can be drawn to assess the state of the biomass.

The results from the study showed examples of how the aeration capacity of a facility can be determined quickly and plant process changes can be made with the results from the changes being seen rapidly using the respirometer in order for staff members to react to any changes being too drastic. The respirometer also gave the required detention time for a facility based on the loading coming into the plant thus capacity could be adjusted to reduce power costs of oversized aeration volumes. Also observed during the study was the ability of the instrument to readily identify toxic conditions or inhibition of the autotrophic biomass. This was especially interesting in facilities where it was assumed that nitrification was taking place. The instrument proved effective in assessment especially in terms of diagnosis time which would have certainly taken more manpower, cost, and most importantly time to obtain the same results using laboratory sampling and traditional process control calculations.

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