A Mathematical Approach to the Design of Sulphate Reducing Gas-Lift Reactors

In this paper three mathematical steady-state models for the design of gas-lift reactors aimed at sulphate removal from wastewater are proposed. Models 1A and 1B are based on the hypothesis that heterotrophic sulphate reducing bacteria (HSRB) prevail in the biochemical system while Model 2 can be applied if autotrophic SRB (ASRB) are the dominant microbial group in the reactor. Once the effluent sulphate concentration is fixed and the influent wastewater characteristics are assigned, all models give explicit mathematical relationships to determine the bioreactor volume and the effluent concentrations of substrates and products. The models give also explicit relationships to calculate the biomass recycle flow and the bacteria concentrations in the reactor, once the total biomass concentration is fixed. Due to the availability of explicit relationships, the models application is very easy and fast and requires no iterative procedures. If the biological sulphate reduction is performed by ASRB, the model simulations indicate that the required bioreactor volume is much lower than that needed if the prevalent SRB are heterotrophic.