Ozone reactor combined with ultrafiltration membrane: A new tertiary wastewater treatment system for reuse purpose

In the present research, a new technology using the application of ozone (O_³) together with an ultrafiltration (UF) membrane was tested for the tertiary treatment of wastewater. The primary and secondary wastewater-treatment systems were a septic tank and anaerobic filter. The experiment was divided into two stages: the first including only the application of O₃ in the reactor, and the second, inclusion of the UF membrane. During the first stage of the study, where only the ozone was applied, a time of 40 min was chosen, with removal levels for chemical oxygen demand (COD), five-day biochemical oxygen demand (BOD₅), total organic carbon (TOC), turbidity and ammonium (NH₄⁺) of 39.5%, 45.4%, 32.4%, 44.85% and 68.4% being recorded. During stage 2, the UF membrane inside the reactor was activated after 40 min of ozonation. The values for the removal of COD, BOD₅, TOC, turbidity, NH₄⁺ and total phosphorus were 89.13%, 95.41%, 82%, 93.4%, 14.75% and 79.67%, respectively. The use of O₃ + UF removed 100% of total coliforms and viruses from the secondary wastewater. In accordance with North American and European guidelines, the water resulting from the treatment process is fit for reuse. The operating costs can vary between 0.859 € m^-3 and 2.440 € m^-3 depending on the cost per kWh in each country. The experiments were conducted under batch-mode conditions, further evaluations about the real scale operation would require a previous pilot stage that would develop more tools for operations specifications and their costs. The results recorded here show that the performance of this new reactor design is effective in the tertiary treatment of wastewater, and should be available for use in the near future.