Opportunities for rotating belt filters in novel wastewater treatment plant configurations

Abstract

Novel wastewater treatment plants (WWTPs), which are based on a partial nitritation-anammox (PN-anammox) process, enable higher chemical oxygen demand (COD) recovery to produce biogas and lower treatment costs. In this study, rotating belt filters (RBFs) were examined in different configurations to identify the opportunities for RBFs to be included in novel WWTP configurations. RBFs enable recovery of 22–37% of the influent COD and removal of 34–56% of hydrophobic organic micropollutants (OMPs). However, the effluent was not suitable for treatment in a PN-anammox process due to its high COD. Chemically enhanced settling (CES) enabled these limitations to be overcome and caused an increase in OMP removal to 73–94%. However, a dose of 300 mg L⁻¹ of ferric chloride was required to produce a suitable effluent for a PN-anammox reactor. The combination of RBFs and CES not only produced effluents suitable for treatment in PN-anammox units but also decreased the alkalinity consumption and the required chemical dose 3-fold to achieve comparable COD recovery and OMP removal. The methane yield of the combined sludges that were produced (184 L(N) CH₄ per kg COD_influent) was 75% higher than that obtained from a conventional wastewater treatment (105 L(N) CH₄ per kg COD_influent), and the electricity requirements decreased from 0.54 to 0.41 kWh m⁻³ of treated wastewater. The energetic calculations showed that a WWTP incorporating this combined treatment could attain energy autarky with 29% lower operational costs than that of a conventional treatment (0.022 vs. 0.031 € m⁻³) as long as a minimum alkalinity-to-ammonium ratio of 1–1.25 g IC to g NH₄⁺-N was ensured in the effluent of the combined treatment.