Compact secondary treatment train combining a lab-scale moving bed biofilm reactor and enhanced flotation processes. (1st December 2016)

• Record Type: Journal Article
• Authors: Brosseau, Catherine; Émile, Bettina; Labelle, Marc-André; Laflamme, Édith; Dold, Peter L.; Comeau, Yves
• Is Part Of: Water research. Volume 106(2016)
• Page Start: 571
• Page End: 582
• Publication Date: 2016-12-01
• Subjects: Moving bed biofilm reactor -- Innovative separation process -- Enhanced flotation -- Green coagulant -- Green polymer -- High-rate process; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2016.10.019
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: High-rate wastewater processes are receiving a renewed interest to obtain energy positive/efficient water resource recovery facilities. An innovative treatment train combining a high-rate moving bed biofilm reactor (HR-MBBR) with an enhanced flotation process was studied. The two objectives of this work were 1) to maximize the conversion of soluble organics to particulate matter in an HR-MBBR and 2) to maximize the particulate matter recovery from the HR-MBBR effluent by green chemicals to enhance biogas production by anaerobic digestion. To achieve these objectives, lab-scale MBBRs fed with synthetic soluble wastewater were operated at organic loading rates (OLRs) between 4 and 34 kg COD m −3 reactor d −1 corresponding to hydraulic retention times (HRTs) between 6 and 54 min. Colloidal and soluble chemical oxygen demand (COD) removal efficiency in the HR-MBBR increased with HRT to reach a plateau of 85% at an HRT longer than 27 min. Carrier clogging observed at an OLR higher than 16 kg COD m −3 d −1 (HRT < 13 min) resulted in about 23% loss in colloidal and soluble COD removal efficiency. Thus, the recommended parameters were between 22 and 37 min and between 6 and 10 kg COD m −3 d −1 for the HRT and the OLR, respectively, to maximize the conversion of soluble organics to particulate matter. Total suspended solids (TSS) recovery of 58–85% and 90–97% were achieved by enhanced flotation using green and unbiodegradable chemicals, respectively, corresponding to a TSS effluent concentration below 14 and 7 mg TSS/L. Among the synthetic polymers tested, a high molecular weight and low charge density cationic polyacrylamide was found to give the best results with less than 2 mg TSS/L in the clarified effluent (97% TSS recovery). Green chemicals, although performing slightly less for solids separation than unbiodegradable chemicals, achieved a mean TSS concentration of 10 ± 3 mg/L in the clarified effluent. Graphical abstract: Highlights: A treatment train combining an HR-MBBR with an enhanced flotation process was studied. CS COD removal efficiency increased with the MBBR HRT (inversely with OLR) up to 88%. An MBBR OLR of 6–10 kg COD m −3 reactor d −1 resulted in the best XCOD recovery. MBBR effluent solids were characterized by a bimodal volume particle size distribution. Enhanced flotation with green chemicals allowed to reach 10 ± 3 mg TSS/L in the MBBR effluent.