Circulating fluidized bed bioreactor: A cost-effective technology for wastewater treatment

This study was focused on evaluating the economic feasibility of a newly developed technology, the Circulating Fluidized Bed-Bioreactor [CFBBR] compared to alternative technologies e.g. activated sludge process [AS], moving bed bioreactor [MBBR], and sequencing batch reactor [SBR] for municipal wastewater treatment. The CFBBR combines a circulating fluidized bed and a fixed-film process for an enhanced solid-liquid mass transfer that provides higher removal rates of nitrogen and phosphorous compared to the AS, MBBR, and SBR processes. Both lab-scale and pilot-scale CFBBRs demonstrated > 90% COD, > 80% N and 70% P removal at a hydraulic retention time of 2 h without primary clarification. Furthermore, the observed sludge yields of 0.12-0.16 g VSS/g COD consumed in the CFBBR resulted in 75% reduction in total biosolids production compared to conventional activated sludge non BNR treatment processes. The CFBBR demonstrated the potential for significant capital cost reduction, compliance with stringent regulations, reduction of biosolids, and up to 80% reduction in space requirements. Cost modules have been developed using CapDet Works 2.5 for the different processes employing reactor sizes designed for an average daily flow of 2.6 MGD (10,000 m³/d). The cost modules consist of screening, grit chamber, primary clarifier, biological nutrient removal units, secondary clarifier, UV-disinfection, thickening, anaerobic digestion, energy recovery, dewatering and sludge handling and disposal. The CFBBR was determined to be the most cost effective technology compared to the conventional BNR-AS and other available technologies for a completely new wastewater treatment facility. Even though the CFBBR does require high recirculation volume (12 times influent flow) to fluidize particles, energy consumption of 0.33 kWh/m³ in the CFBBR is less than the energy required in the MBBR (0.39kWh/m³), SBR (0.41 kWh/m³), and in the same range of the BNR-AS (0.31 kWh/m³) for biological nutrient removal from municipal wastewater.