Differences in microbial communities and performance between suspended and attached growth anaerobic membrane bioreactors treating synthetic municipal wastewater

Abstract

Anaerobic membrane bioreactors (AnMBRs) have recently gained consideration as an alternative technology for the treatment of municipal wastewater. Despite that, the effect of reactor configurations on their performance and sustainability remains understudied.This work aims to evaluate two different AnMBR types at low organic-loading conditions. Results show that the microbial consortium developed in each reactor can potentially have a significant impact on both biogas production and the microbial products that affect biofouling. Abstract 1Two lab-scale anaerobic membrane bioreactors (AnMBRs), one up-flow attached-growth 2 (UA) and another continuously stirred (CSTR), were operated under mesophilic 3 conditions (35 °C) while treating synthetic municipal wastewater (800 mg/L COD). Each 4 reactor was attached to both polyvinylidene fluoride (PVDF) and polyethersulfone (PES) 5 microfiltration (MF) membranes in an external cross-flow configuration. Both reactors 6were started-up and run under the same operating conditions for multiple steady-state 7 experiments. Chemical oxygen demand (COD) removal rates were similar for both 8 reactors (90-96%), but captured methane was found to be 11-18% higher for the CSTR 9 than the UA reactor. Ion Torrent sequencing targeting 16S rRNA genes showed that 10 several operational taxonomic units (OTUs) most closely related to fermentative bacteria 11 (e.g., Microbacter margulisiae) were dominant in the suspended biomass of the CSTR, 12 accounting for 30% of the microbial community. Conversely, methanogenic archaea 13 (e.g., Methanosaeta) and syntrophic bacteria (e.g., Smithella propionica) were found in 14 significantly higher relative abundances in the UA AnMBR as compared to the CSTR, 15 due to their affinity for surface attachment. Of the methanogens that were present in the 16 CSTR sludge, hydrogenotrophic methanogens dominated (e.g., Methanobacterium). 17 Measured EPS (both proteins and carbohydrates) -which has been broadly linked to 18fouling -was determined to be consistently lower in the UA AnMBR membrane samples 19 than in CSTR AnMBR membrane samples. Principal component analysis (PCA) based 20 on HPLC profiles of soluble microbial products (SMPs) further demonstrated these 21 differences between reactor types in replicate runs. The results of this study showed that 22 reactor configuration can significantly impact the development of the microbial 23

Design of anaerobic membrane bioreactors for the valorization of dilute organic carbon waste streams

“…The two reactor types considered in this study were CSTRs 25,31,38,39,41 and AF reactors. 4,5,28,41,47 For CSTRs, the volume of the reactor was dictated by HRT whereas AF sizing was determined by the organic loading rate (OLR; Table 2 lists values used for reactor design).…”

“…The three membrane types considered in this study were hollow fiber (HF), 24,31,35,37,40 flat sheet (FS), 25,36,38,41 and multi-tube (MT). 47,67 While FS membranes can be used in either configuration, in full-scale systems HF or MT membranes are generally restricted to submerged or cross-flow configurations, respectively.…”

“…4,5,28,41,47 For CSTRs, the volume of the reactor was dictated by HRT whereas AF sizing was determined by the organic loading rate (OLR; Table 2 lists values used for reactor design). The impact of including a down-flow aerobic sponge filter (AeF) 63 downstream of the AF was also evaluated, where AeF sizing was also dictated by OLR.…”

“…Within plastic, four types were considered: polyethersulfone (PES), polyvinylidenefluoride (PVDF), polyethylene terephthalate (PET), and polytetrafluoroethylene (PTFE). 25,32,34,35,38,39,41 Plastic was assumed to be usable for any membrane type, but sintered steel and ceramic were limited to FS and HF membranes, respectively. While these materials incur different environmental impacts due to their respective production methods, differences in costs were assumed to be negligible.…”

Application of hierarchical oligonucleotide primer extension (HOPE) to assess relative abundances of ammonia- and nitrite-oxidizing bacteria

“…The components per L of basal substrate were modified from a previous study [19] and include: 153 mg NH 4 Cl, 480 mg NaHCO 3 , 24 mg MgSO 4 .7H 2 O, 20 mg K 2 HPO 4 , 11.3 mg CaSO 4 .2H 2 O and 7.1 mg FeCl 3 .6H 2 O, 100 μL of trace elements that contained 0.274 g/L Na 2 MoO 4 .2H 2 O, 2.74 g/L ZnSO 4 .7H 2 O, 0.036 g/L CuSO 4 .5H 2 O, 0.03 g/L CoCl 2 .6H 2 O, 7 g/L FeSO 4 .7H 2 O and 1.55 g/L MnCl 2 .2H 2 O. Upon reaching stabilization and from day 40 onwards, the basal substrate was prepared by diluting the anaerobic effluent that was high in ammonium content [20]. The anaerobic effluent contained on average 160 mg/L NH 4 + -N and 40 mg/L of chemical oxygen demand (COD), and the ammonium content in the basal feed was diluted accordingly to provide 80 mg/L NH 4 + -N from day 40 to 83 (Phase B), 110 mg/L NH 4 + -N from day 84 to 120 (Phase C), and 150 mg/L NH 4 + -N from day 121 to 150 (Phase D1).…”