Project description:The biomass concentrator reactor (BCR), a gravity flow membrane bioreactor (MBR) design, was evaluated for use in treating a municipal wastewater stream. The BCR operates with less than 2.5 cm of pressure head and uses a 3 to 4 mm thick tortuous path membrane with pore size ranging from 18 to 28 ?m to achieve solids separation. A two-stage, aerobic/anoxic reactor was evaluated for the removal of chemical oxygen demand (COD), ammonia, total nitrogen, and solids separation. The reactor was fed 72 L/day, with a hydraulic retention time of 9.3 hours, and had a solids retention time of 20 days. The influent COD was reduced by 93%, whereas, influent ammonia was reduced below 0.1 mg/L and total nitrogen was reduced by 53.7%. A lack of readily biodegradable COD limited denitrification and thus total nitrogen removal. The reactor solids were retained completely in the reactor by the membrane for the duration of testing.
Project description:Municipal wastewater effluent can impact its receiving environment. In the St. Lawrence River, male fish living downstream from Montreal exhibit increased hepatic vitellogenin, intersex, delayed spermatogenesis and altered immune function. Few studies have examined genome-wide effects associated with municipal effluent exposure in fish to decipher the mechanisms of toxicity. The present objective was to identify hepatic cellular signaling pathways in fathead minnows following exposure to municipal wastewater effluent. Immature minnows were exposed for 21 days to either 0% (Control) or 20% municipal effluent, the highest concentration in the St. Lawrence River. Hepatic RNA was extracted and used to hybridize a fathead minnow oligonucleotide microarray containing approximately 15K gene sequences.
Project description:Although membrane bioreactor (MBR) systems provide better removal of pathogens compared to conventional activated sludge processes, they do not achieve total log removal. The present study examines two MBR systems treating municipal wastewater, one a full-scale MBR plant and the other a lab-scale anaerobic MBR. Both of these systems were operated using microfiltration (MF) polymeric membranes. High-throughput sequencing and digital PCR quantification were utilized to monitor the log removal values (LRVs) of associated pathogenic species and their abundance in the MBR effluents. Results showed that specific removal rates vary widely regardless of the system employed. Each of the two MBR effluents' microbial communities contained genera associated with opportunistic pathogens (e.g., Pseudomonas, Acinetobacter) with a wide range of log reduction values (< 2 to >5.5). Digital PCR further confirmed that these bacterial groups included pathogenic species, in several instances at LRVs different than those for their respective genera. These results were used to evaluate the potential risks associated both with the reuse of the MBR effluents for irrigation purposes and with land application of the activated sludge from the full-scale MBR system.
Project description:Membrane biofilm development was evaluated to improve psychrophilic (15°C) anaerobic membrane bioreactor (AnMBR) treatment of domestic wastewater. An AnMBR containing three replicate submerged membrane housings with separate permeate collection was operated at three levels of membrane fouling by independently controlling biogas sparging for each membrane unit. High membrane fouling significantly improved permeate quality, but resulted in dissolved methane in the permeate at a concentration two to three times the equilibrium concentration predicted by Henry's law. Illumina sequencing of 16S rRNA targeting Bacteria and Archaea and reverse transcription-quantitative polymerase chain reaction targeting the methyl coenzyme-M reductase (mcrA) gene in methanogens indicated that the membrane biofilm was enriched in highly active methanogens and syntrophic bacteria. Restoring fouled membranes to a transmembrane pressure (TMP) near zero by increasing biogas sparging did not disrupt the biofilm's treatment performance, suggesting that microbes in the foulant layer were tightly adhered and did not significantly contribute to TMP. Dissolved methane oversaturation persisted without high TMP, implying that methanogenesis in the biofilm, rather than high TMP, was the primary driving force in methane oversaturation. The results describe an attractive operational strategy to improve treatment performance in low-temperature AnMBR by supporting syntrophy and methanogenesis in the membrane biofilm through controlled membrane fouling.
Project description:The effects of solid retention times (SRTs) (100 days, 50 days, 25 days) on the performance, microbial community, and membrane fouling of a lab-scale anaerobic yttria-based ceramic membrane bioreactor (AnCMBR) treating synthetic domestic wastewater at ambient temperature (31.2 ± 2.7 °C) were examined. The soluble chemical oxygen demand (SCOD) removal was higher (89.6%) at 25 days SRT compared with 50 days (39.61%) and 100 days (34.3%) SRT. At 100 days SRT, more Bacteroidetes, Firmicutes, and Proteobacteria were present in the microbial community. At 25 days SRT, more Chloroflexi, Synergistetes, and Pastescibacteria emerged, contributing to the stable performance. The SRT of 25 days has resulted in a more stable microbial community compared with 50 days and 100 days SRT. Both bacterial and archaeal community diversities were higher at 25 days SRT, and the specific production of soluble microbial by-products (SMPs) and extracellular polymeric substances (EPSs) were higher at 25 days SRT as well. Consequently, the membrane flux was lower at 25 days SRT with the increased particle size and the enhanced SMPs and EPSs production. Fourier transform infrared spectroscopy analysis (FTIR) and three-dimensional excitation and emission matrix (3D-EEM) analysis showed that protein and SMPs were the major membrane foulants at all SRT stages. In this study, SRT at 25 days was favorable for the stable operation of an AnCMBR treating domestic wastewater at ambient temperature.
Project description:Municipal wastewater effluent can impact its receiving environment. In the St. Lawrence River, male fish living downstream from Montreal exhibit increased hepatic vitellogenin, intersex, delayed spermatogenesis and altered immune function. Few studies have examined genome-wide effects associated with municipal effluent exposure in fish to decipher the mechanisms of toxicity. The present objective was to identify hepatic cellular signaling pathways in fathead minnows following exposure to municipal wastewater effluent. Immature minnows were exposed for 21 days to either 0% (Control) or 20% municipal effluent, the highest concentration in the St. Lawrence River. Hepatic RNA was extracted and used to hybridize a fathead minnow oligonucleotide microarray containing approximately 15K gene sequences. Sixteen samples were examined, 8 control samples and 8 exposed samples.