Biological treatment of dairy industry wastewater in a membrane bioreactor (part 1)

Summary

The results of research study in the field of biological treatment of dairy wastewater are presented. The studies carried out under contact conditions showed that the kinetics of oxidation of dairy wastewater pollutants with activated sludge can be described by enzymatic reactions equation for substrate inhibition; at that, the obtained inhibition constants point at the increase of the wastewater toxicity after chemical flotation for biological treatment processes. The technology has been proved with simulative effluent in a pilot membrane bioreactor. The kinetic dependences of organics oxidation by BOD_full, nitrification and denitrification were determined. The increase of oxidation capacity of the facilities by 1.46 at the sludge concentration increase from 4 to 10 g/l is shown that allows reducing significantly the size of the biological treatment facilities when using MBR technology. In the course of experimental studies at MBR plant and kinetic experiments under contact conditions the coefficients of inhibition with activated sludge metabolism products were determined for the simulative solution of wastewater by BOD_full, for nitrification and denitrification. The temperature constant value for aerobic heterotrophic conversion, for nitrification and denitrification processes has been found.

Key words

wastewater , biological treatment , membrane bioreactor , activated sludge , kinetic constants , dairy factory

Biological treatment of dairy industry wastewater in a membrane bioreactor
(part 2)

Summary

The technology of biological treatment of dairy wastewater is described that provides for meeting the standard maximum permissible concentrations for fishery water bodies. The results of the experimental studies in a pilot membrane bioreactor with real wastewater of «Pestravskii» butter factory are presented. The main process and kinetic parameters of the biological wastewater treatment processes have been obtained that are needed for designing a membrane bioreactor with nitrification-denitrification that provides for meeting the standard maximum permissible concentrations for fishery water bodies or requirements to the effluents discharged into a public sewer. The maximum specific rate of diary wastewater pollutants oxidation V_max at 7 g/l activated sludge concentration and 20 °С temperature is 40 mg/(g·h), Michaelis constant K_m – 15 mg/l, inhibition coefficient of metabolism products – 0.54 l/g, temperature constant X for aerobic heterotrophic conversion – 0.079 deg^–1. Compared to the traditional treatment facilities the use of biomembrane technology at the wastewater biological treatment stage provides for 1.4–1.5 reducing the treatment time, reactor volume and footprint owing to the increase of the oxidation capacity of the aeration units by increasing the activated sludge concentration to 10 g/l; and ensuring almost complete removal of suspended solids by eliminating the tertiary treatment stage. Possible elimination of chemical flotation stage before biological treatment is shown that provides for reducing the expenditures for expensive chemicals and streamlining the process flow scheme.

Ключевые слова

wastewater , biological treatment , activated sludge , membrane bioreactor , kinetic constant , dairy factory