- Biological wastewater treatment relies on the ability of bacterial populations to breakdown organic materials and nutrients into end products, and toxic ingredients into harmless substances. In addition to bacteria, bacteriophages (viruses that infect bacteria) are ubiquitous in many ecological systems including bioreactors for wastewater treatment. This leads to predator–prey dynamics between these populations, which should be taken into consideration when modelling and applying biological treatment processes. In this study, the predator–prey relationship between bacteria and phages isolated from a wastewater treatment bioreactor was investigated. Using microtiter plates, which served as multiple micro scale eco-systems, shifts in the bacterial population were monitored using a microplate reader. Based on this set of data, a mathematical model incorporating phage-bacteria interactions was developed and calibrated using Matlab; the calibration process was analyzed. The microplate reader was shown to serve as a useful tool for parameter calibration and basic modelling of phage–bacteria behaviour in bioreactors.