ABSTRACT
Several accurate manometric devices capable of measuring gas consumption or production by microbial activity were used in the biological sciences laboratories since the turn of the century. Some of these manometers were designed to measure oxygen demand i.e., respirometers during microbial respiration. Employment of respirometers designed for biological sciences laboratories has had limited success in the environmental sciences. Respirometric devices are used to monitor progressive oxygen uptake by microorganisms in a wastewater sample. The sample may be seeded using a large population of acclimated organisms, or unseeded, depending on the particular application. The Pneumatic Computerized Bod (PCBOD) apparatus introduces several unique features into the field of respirometry. First, a vacuum switch replaces the conventional U-tube or pressure transducer used by other respirometers. The PCBOD is an innovative constant pressure respirometer that is not affected by barometric pressure variations or sample evaporation losses. Thus, correction to compensate for these interferences becomes unnecessary when using this respirometer.
