Advanced Primary Filtration (APF) Process in Wastewater Treatment: A Techno-Economic and Environmental Assessment

Νumerous WWTPs operate at flow rates or loads above their designed capacity, leading to inefficient and energy-demanding wastewater treatment. Conventional upgrades that involve constructing additional aeration tanks and clarifiers require substantial land and capital investment, which is often not feasible at space-constrained sites, particularly in island regions. The WWTP of Marpissa, Paros, Greece has undergone an upgrade through the implementation of the advanced primary filtration (APF) process. The APF involves the incorporation of a proprietary rotating belt filter, followed by continuous backwash upflow media filters and a lamella clarifier. The innovation of the APF process lies in the early removal of suspended solids upstream of the aeration tank, thereby reducing energy requirements in WWTPs. A techno-economic and environmental assessment was conducted for three scenarios: the existing WWTP (baseline Scenario), the WWTP retrofitted with APF (Scenario 1), and the CAS expansion (Scenario 2). The baseline scenario was evaluated at the average hydraulic capacity (868 m3/d), while the APF and CAS scenarios were assessed at average hydraulic capacity (1,200 m3/d), reflecting the future loading conditions planned for the WWTP upgrade. Different hydraulic flow rates were considered to reflect both the current overloaded conditions of the WWTP and the projected post-upgrade capacity. Despite this increased hydraulic demand, the APF retrofit achieved significant improvements in overall performance. Energy consumption decreased by approximately 25%, greenhouse-gas emissions were reduced by 26%, and sludge production declined by about 40% compared to the baseline scenario. The APF scenario also resulted in the lowest οperating cost of complete wastewater treatment (0.32 €/m3), whereas the CAS expansion led to substantially higher energy use, a large increase in emissions, and the highest treatment cost (0.48 €/m3). The results demonstrate that the APF process offers a technically robust and economically advantageous pathway for upgrading overloaded WWTPs, providing clear advantages over conventional expansion practices.