Full-scale modelling of a food industry wastewater treatment plant in view of process upgrade

A mathematical model for the aerobic part of a food industry wastewater treatment plant (WWTP) was developed and used to assess possible upgrade options. This aerobic part of the WWTP treats two streams. The direct stream is treated in an anaerobic reactor after pre-treatment. The bypass stream is sent directly from the production facility to the aerobic part of the WWTP, without anaerobic treatment. The plant upgrade consists of installing additional volume for nitrification and denitrification, a so-called post-denitrification. An influent characterization translated the available influent measurements into data useful for modelling. It was shown by simulations with the developed model that the physical plant upgrade will result in a 99% decrease in effluent ammonium concentration. In addition a 5% decrease in COD concentration was obtained. However, the effluent nitrate concentration and total nitrogen increased drastically because of the upgrade. Additional control actions, more specifically the increase of the bypass flow rate, were necessary for decreasing this effluent total nitrogen concentration. This was also demonstrated with the developed model.