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The assessment of microbial processes is often done in Microbioreactor systems (MBRs), which allow for parallel cultivation in multiple independent wells. MBRs often include dissolved oxygen sensors, which are convenient for process characterization through oxygen uptake rate and other respirometric determinations. In order to assess respirometric potential of MBRs, a complete assessment of the DO fluorescent quenching sensors was done, showing that they presented a typical error of 0.56%, a signal to noise ratio of 189, a response time from 5.7 to 7.2 s and no drift over a period of 24 h. Then, KLa in the MBR was measured with different cassette and cap designs, liquid volumes, agitation rates, gas flow rates, temperatures and ionic strengths. KLa ranged from 8 to 90 h(-1), with a standard deviation between replicates from 2.8 to 17.5%. From these results and a numerical simulation, it was shown that the MBR tested allow the determination of oxygen uptake rates in a range from 0.038 to 3390 mg L(-1) h(-1), with a determination error less than 15%. Besides OUR determination, it was concluded that the MBR tested is also a convenient tool for dynamic pulse respirometry methods, based on experimental confirmation with four different cultures.

BACKGROUND: Centrate treatment using microalgal-bacterial processes might be limited by the hydraulic retention time (HRT) required to achieve satisfactory chemical oxygen demand (COD) and nutrients removal. Moreover, the poor settling of microalgal biomass still limits the technical and economic performance of microalgal-bacterial processes. In this work, the performance of microalgal-bacterial aggregates (MABAs) supplied with flue gas was investigated as an effective strategy to improve the treatment of centrate from anaerobic digestion of winery wastewater. RESULTS: MABAs supplied with flue gas achieved maximum soluble COD, N-NO 3− , P-PO 4 3− and N-NH 4 + removal efficiencies of 95%, 94%, 100%, and 100%, respectively, in five-fold centrate dilution within 7 days of operation. Centrate turbidity or its components did not hinder the performance of the MABAs under the conditions tested and no aggregates were formed in controls without MABAs inoculation. The mean diameter of the MABAs after centrate treatment was the same or even larger than that of the aggregates of the inoculum. Scanning electron microscopy analyses showed that the liquid medium composition influenced the structure and the type of microalgae cells established in the MABAs. CONCLUSION: MABAs-based centrate treatment supported by flue gas is a promising technology for improving COD and nutrients removal from centrate as well as further biomass harvesting.