Effect of bicarbonate alkalinity on gravimetric solids analysis in anaerobic wastewater treatment

Bicarbonate alkalinity plays an important role in the stability of biological reactors used in wastewater treatment, primarily in anaerobic systems. As some wastewaters tend to acidify readily, addition of an external alkali source may be necessary to maintain process stability. An assessment was made of the effect of sodium bicarbonate addition on the determination of solids concentration. The methodology consisted in accompanying a series of solids concentrations (total solids, TS; total volatile solids, TVS; and total fixed solids, TFS) in samples containing cheese whey and volatile acids used to simulate anaerobic reactor effluents. TS, TVS and TFS showed to be strongly affected by NaHCO3 addition, mainly due to an increase in TFS. This effect could be quantified by relating the experimental values to the theoretical ones from the stoichiometric equations for NaHCO3 decomposition and other compounds (sodium acetate and sodium propionate) formation with temperature increase. In this way, as one of the main parameters of assessing liquid effluent treatment systems is the reduction in solids present in the medium, the concentration of solids can be quantified more adequately by determining fixed solids from the inorganic salts present. This methodology showed to be adequate in cases where a significant amount of alkali is added.32961061

Hydrodynamic analysis of an anaerobic sequencing batch biofilm reactor with liquid-phase external circulation

An assessment was made of the hydrodynamic behavior and organic matter removal of a fixed bed anaerobic sequencing batch reactor with liquid-phase circulation, containing 0.5cm polyurethane foam-cubes. The hydrodynamic study was performed without biomass and with superficial rates ranging from 0.16 to 0.80cm/s, employing continuous operation to quantify the flow behavior in the bed and discontinuous operation to quantify mixing time. In the continuous mode the bed showed a piston flow behavior. In the discontinuous operation mode the mixing time obtained in all conditions may be considered negligible when compared to the total cycle time to be employed in the assay with biomass. In the assay regarding organic matter removal, 8h cycles were employed in sequencing batch mode using anaerobic biomass. The reactor was maintained at 30 1C, treated glucose-based synthetic wastewater with a concentration of approximately 500mgCOD/L. Reactor performance was assessed for the condition without liquid circulation as well as at a superficial circulation rate of 0.19cm/s. The reactor presented better performance and stability for the circulation condition, achieving efficiencies as high as 95% organic matter removal.304188