Predicting fecal coliform inactivation in a mixotrophic algal wastewater treatment system

Abstract Our previous reports have detailed the development of a pilot-scale algal wastewater treatment system (A-WWTS) utilizing a mixotrophic strain, Galdieria sulphuraria. This A-WWTS has consistently achieved discharge standards for organics and nutrients in a single step, concurrently reducing coliform bacteria to undetectable levels. Here, we present an approach to predict i) the fate of fecal coliform in this A-WWTS; and, ii) the fed-batch processing time required for a desired inactivation level. Specifically, a process model was developed to predict fecal coliform reduction under the synergistic effect of temperature, pH, and sunlight in terms of their individual first order inactivation rates. First-order temperature dependent inactivation rate at 20 °C (k20) was established as 0.05 h−1 with a temperature coefficient (θ) of 1.08. Inactivation coefficient due to the combined effects of sunlight was established as 0.647 m2/MJ. The proposed approach was validated with experimental data from five scenarios; the quality of predictions of log removals spanning over five orders of magnitude (r2 = 0.947; n = 12) was comparable to or better than those reported previously in inactivation studies. Utility value of this approach in forecasting fed-batch processing time under field conditions is illustrated.