Domestic wastewater treatment with purple phototrophic bacteria using a novel continuous photo anaerobic membrane bioreactor

Abstract

A key future challenge of domestic wastewater treatment is nutrient recovery while still achieving acceptable discharge limits. Nutrient partitioning using purple phototrophic bacteria (PPB) has the potential to biologically concentrate nutrients through growth. This study evaluates the use of PPB in a continuous photo-anaerobic membrane bioreactor (PAnMBR) for simultaneous organics and nutrient removal from domestic wastewater. This process could continuously treat domestic wastewater to discharge limits (<50 mgCOD L(-1), 5 mgN L(-1), 1.0 mgP L(-1)). Approximately 6.4 ± 1.3 gNH4-N and 1.1 ± 0.2 gPO4-P for every 100 gSCOD were removed at a hydraulic retention time of 8-24 h and volumetric loading rates of 0.8-2.5 COD kg m(3) d(-1). Thus, a minimum of 200 mg L(-1) of ethanol (to provide soluble COD) was required to achieve these discharge limits. Microbial community through sequencing indicated dominance of >60% of PPB, though the PPB community was highly variable. The outcomes from the current work demonstrate the potential of PPB for continuous domestic (and possibly industrial) wastewater treatment and nutrient recovery. Technical challenges include the in situ COD supply in a continuous reactor system, as well as efficient light delivery. Addition of external (agricultural or fossil) derived organics is not financially nor environmentally justified, and carbon needs to be sourced internally from the biomass itself to enable this technology. Reduced energy consumption for lighting is technically feasible, and needs to be addressed as a key objective in scaleup.

Resource Recovery from Wastewater by Biological Technologies: Opportunities, Challenges, and Prospects

“…This has been demonstrated as a domestic treatment option in the laboratory (Hülsen et al, 2014, 2016b). Technology readiness level (TRL) has to be upgraded before real application of the technology to achieve at least TRL 7.…”

“…A more efficient use of fertilizer-nitrogen but also a more efficient recovery of nitrogen from waste sources, e.g., via microbial resynthesis has the potential to enable a biobased circular economy (Matassa et al, 2015). Used nitrogen can be recovered and harvested as microbial protein from waste streams (close to 100% recovery) (Shi et al, 2007; Hülsen et al, 2016b) and used directly as organic fertilizer or food for animals (Kobayashi and Tchan, 1973) as well as humans (Becker, 2007). This would at least partly rectify the current inefficiencies whereby the revival of SCP promises alternative proteinaceous food and fertilizer sources for the future.…”

“…In this context, the anaerobic growth of PPB as SCP in a closed photobioreactor seems promising as nitrogen removal is non-destructive and losses were reported to be less than 10% with 90% being incorporated into biomass (Hülsen et al, 2016b). Complete assimilation of nutrients by PPB depends on the available organics which have to be added for domestic wastewater but are abundant in industrial sources.…”

Control tools to selectively produce purple bacteria for microbial protein in raceway reactors

“…To achieve selectivity with PNSB (i.e. uneven microbial community and high abundance of one species), current research has focused on closed PBR such as anaerobic membrane bioreactors, 16 anaerobic tubular PBR 13,17 and illuminated anaerobic sequencing batch reactors 18 . These closed PBR only allow the growth of phototrophs and anaerobic chemotrophs.…”

Enriching and aggregating purple non-sulfur bacteria in an anaerobic sequencing-batch photobioreactor for nutrient capture from wastewater

“…512513In the PNSB mixed culture, the HRT was initially set high to 48 h (i.e., 1 cycle d -1 at a volume 514 exchange ratio of 50%) to maintain biomass during start-up, prior to decreasing it to 16 h (3 515 cycles d -1 ) from SBR2 onward. This value was in the range of the HRTs of 8-24 h that have 516 been used in the operation of continuous photo anaerobic membrane bioreactor (PAnMBR) to 517 enrich for purple phototrophic bacteria (PPB) at bench(Hülsen et al, 2016). It was also in the 518 range of traditional SBRs operated with conventional activated sludge(Mace and Mata- 519 Alvarez, 2002).…”