A full-scale hybrid vertical anaerobic and aerobic biofilm wastewater treatment system: case study

Abstract

Abstract The first full-scale Hybrid Vertical Anaerobic Aerobic Biofilm (HyVAB) reactor has been set up for treating wastewater from a vegetable processing industry in Grimstad, Norway. The novel HyVAB reactor integrates a bottom expanded granular sludge bed with a top aerobic biofilm stage, resulting in a small footprint and high treatment efficiency. The full scale holistic treatment plant consists of a pretreatment system of a sand trap and an equalization tank, a HyVAB reactor and an effluent sludge settlement tank. The HyVAB system has been operated continuously for 219 days with flow and chemical oxygen demand (COD) fluctuations corresponding to different product seasons. The reactor hydraulic retention time ranges from 32 to 10 hours, with the anaerobic organic loading rate (OLR) reaching a maximum 16 kg-COD/m3·d. The HyVAB removed on average of 90% of the total feed COD, at an operational temperature of 25 °C. Sludge production was low at 0.11 kg-volatile suspended solids/kg-COD removed. Odorless effluent from HyVAB can be discharged directly to a local municipal wastewater treatment plant without sludge handling. Over 82% of feed COD was converted to methane, leaving high methane content (84 ± 2%) biogas out of the reactor. Energy consumption of HyVAB was 0.5 kwh/ton wastewater. The cost of wastewater treatment is 1.5 NOK/kg COD removed (based on rates in Norway).