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A study of oxygen transfer efficiency (OTE) in aeration basins, using measurements of oxygen depletion in offgas collected from them, was carried out over a period of several years by collaborations between the University of California, Los Angeles and the Bureau of Sanitation Research Group of the City of Los Angeles. Measurements were taken of dissolved oxygen (DO), water temperature, oxygen depletion, and air flux at each sampling location as part of the process to obtain standardized OTE. Field instruments, permanently located near the tanks and galleries, are connected to the control room that automatically records return activated-sludge flow, influent flow, tank DO sensor readings, and air flow. Data from the control room and field instruments were collected for the times of the samples to provide context and some degree of quality control for the samples obtained by the measurement team.The combined air flux and OTE measurements not only agree with the familiar inverse relationship between OTE and air flux but have allowed detection of strong evidence that serious leakage has developed in a few weeks in the air distribution systems of tanks 4 and 5, which was indirectly confirmed by observation of water ejection from the air release valves on the tanks. However, the detail provided by OTE measurements allows more specific understanding of the magnitude of the problem and its significance for the operation of these tanks. Analysis of the OTE measurements made at the site since 1991 also indicates that the diffusers in some of the tanks may now be in need of cleaning or replacement. Water Environ. Res., 72, 363 (2000).

The main objective of this investigation is to determine whether or not it would be feasible to use the measured values of biochemical oxygen demand (BOD) of wastewater obtained by an online instrument at the Los Angeles/Glendale Water Reclamation Plant (California) for controlling its activated sludge process. This investigation is part of a project to develop online BOD monitoring for process control in the City of Los Angeles wastewater treatment plants. Tests studied the Siepmann und Teutscher GmbH (ISCO-STIP Inc., Lincoln, Nebraska) BIOX-1010, which uses a bioreactor containing a culture of microbes from the wastewater to measure soluble BOD in 2 minutes. This rapid approximation to the operation of secondary treatment allows anticipation of system response. Calibration measurements allow the operators to find a conversion factor for the instrument's microprocessor to compute values of BOD that agree well with the standard 5-day BOD (BOD 5 ) measurement, despite the differences in the details of the two testing methods. This instrument has recently been used at other wastewater treatment plants, at a number of airports in Europe and the United States to monitor runway runoff, and is also being used on waste streams at an increasing number of food processing plants.A comparison was made between the plant influent BOD values obtained by the BIOX-1010 online monitor from the end of August, 2000, to late January, 2001, and the individual and average values obtained for the same period using the standard BOD 5 , 208C test, to determine the effectiveness of the Biox-1010 to identify shock loads and their duration. Individual BOD estimates and averages over periods of overly high biological loads (shock loads) were compared, and the instrument readings were evaluated for their effectiveness in detecting shock loads. The results were highly satisfactory, so the instrument was used to trigger a shock-load warning alarm since late September, 2000. This allowed flow diversion and temporary storage to prevent process upsets. Water Environ. Res., 80, 298 (2008).

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