Costs of sludge processing in Waste Water Treatment Plants with Upflow Anaerobic Sludge Blanket reactors and aerobic post-treatment: resources for Conception Studies

ABSTRACT

This research assessed the implementation costs (CAPEX) and the operational costs (OPEX) of different sludge dewatering and disinfection alternatives, considering WWTP with UASB reactors and aerobic post-treatment, aiming to provide resources for Conception Studies. The following technologies were considered: Drying Beds, Centrifuges, Sludge Drying Reed Beds (SDRB), Alkaline Stabilization Process (ASP), and Heat Drying. Cost functions for wastewater flows ranging from 5 to 750 L.s⁻¹ were elaborated, while disregarding area acquisition and sludge final disposal costs. It was determined that the Centrifuge’s CAPEX could be lower than the Drying Bed’s for WWTPs inflows above 80 L.s⁻¹. Nonetheless, Drying Beds remained cheaper when OPEX was considered. A hybrid alternative with Drying Beds and Centrifuges in parallel was evaluated, but their combined costs remained higher than each option considered individually. Moreover, SDRB’s CAPEX was higher than the Centrifuge’s for WWTPs above 120 L.s⁻¹, but the former remained the cheapest dewatering alternative when considered CAPEX + OPEX. Finally, Heat Drying had lower CAPEX than ASP for WWTPs above 500 L.s⁻¹. Nonetheless, considering OPEX, the former remained more expensive up to 750 L.s⁻¹, even when considering fully UASB biogas reclamation.

Keywords
implementation costs; centrifuges; prolonged alkaline stabilization; drying beds; operational costs; heat drying; sludge drying reed beds