Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Technology, Agricultural Engineering, Biotechnology & Applied Microbiology, Energy & Fuels, Agriculture, Adsorption/bio-oxidation system, Dissolved air flotation (DAF), High-rate activated sludge (HRAS) system, Sludge thickening, Waste activated sludge (WAS), WASTE-WATER TREATMENT, RATE CONTACT-STABILIZATION, ANAEROBIC-DIGESTION, MEMBRANE BIOREACTOR, A-STAGE, BIOFLOCCULATION, MANAGEMENT, CARBON, FLOCCULATION, PERFORMANCE, Biofuels, Flocculation, Sewage, Waste Disposal, Fluid, Biotechnology, 3001 Agricultural biotechnology, 3106 Industrial biotechnology, 3107 Microbiology

Abstract:

High-rate activated sludge (HRAS) systems typically generate diluted sludge which requires further thickening prior to anaerobic digestion (AD), besides the need to add considerable coagulant and flocculant for the solids separation. As an alternative to conventional gravitational settling, a dissolved air flotation (DAF) unit was coupled to a HRAS system or a high-rate contact stabilization (HiCS) system. The HRAS-DAF system allowed up to 78% removal of the influent solids, and the HiCS-DAF 67%. Both were within the range of values typically obtained for HRAS-settler systems, albeit at a lower chemical requirement. The separated sludge had a high concentration of up to 47 g COD L-1, suppressing the need of further thickening before AD. Methanation tests showed a biogas yield of up to 68% on a COD basis. The use of a DAF separation system can thus enable direct organics removal at high sludge concentration and with low chemical needs.