Extraction of biomass attached to a support media in a moving bed biofilm reactor: mechanical agitation and ultrasound

ABSTRACT

Quantification of attached biomass in Moving Bed Biofilm Reactors (MBBR) is essential for performance assessment and process control. However, it is observed that such quantification is performed using the most diverse techniques, which hampers comparisons between results. In this investigation, two of the main techniques used (mechanical agitation and ultrasound) were compared for removal of the biomass attached to the support media of an MBBR reactor without the use of chemical agents. The experiments were planned following full factorial designs using the two independent variables: Exposure time (T) from 15 to 60 min; and Volume of distillate water used for extraction (V) from 100 to 400 mL. The results revealed that ultrasound is superior to mechanical agitation regarding detachment of the total suspended solids (%TSS) and though neither T or V contributed significantly within the interval tested, based on the response surface, a new experiment was performed using an increased T range from 5 to 90 min. Then, exposure time contributed significantly to the %TSS detachment, with the best result at 90 min. The use of ultrasound is therefore recommended, with volume that is easier to handle (250 mL) and time equal to 90 min. Additional tests are recommended for method standardization.

Keywords:
sewage; MBBR; support media; fixed biomass; total suspended solids; ultrasound