Project description:This study explores the use of short settling times as a strategy to enhance microbial selection and prevent bulking induced by nutrient shortage in an aerobic dynamic feeding (ADF) process using mixed microbial cultures (MMCs) for polyhydroxyalkanoate (PHA) production from fermentation digestate. A 5.0-L aerobic reactor was operated under three conditions: Long Settling (LS, 30 minutes), Short Settling (SS, 10 minutes), and Short Settling under Nutrient Shortage (SS-NS, 10 minutes with reduced nutrient load). Short settling significantly improved biomass settleability, reducing the Sludge Volume Index (SVI) from 126 to 25 mL g⁻¹, and promoted the formation of dense flocs enriched in PHA-accumulating bacteria, as confirmed by transmission electron microscopy. Process kinetics revealed enhanced substrate uptake rates and improved storage yields under SS conditions, despite an elevated C/P ratio. Notably, nutrient shortage conditions were inadvertently reached by the proliferation of Polytoma mirum in the feeding tank. Although Polytoma mirum did not affect VFA composition, its presence significantly reduced nitrogen and phosphorus concentrations. These nutrient shortage conditions were maintained for at least 30 days until the system began to exhibit stress, as demonstrated by an increased SVI (178.6 mL g⁻¹). Microbial community analyses indicated marked shifts: the eukaryotic assemblage transitioned from sessile to motile ciliates under SS, while bacterial diversity within the PHA‐accumulating fraction remained high, with key taxa such as Sphaerotilus and Neomegalonema becoming more prevalent under phosphorus-limited conditions. Overall, short settling not only improved microbial selection but also prevented bulking by retaining well-aggregated biomass, thereby mitigating nutrient shortage conditions.
Project description:This study explores the use of short settling times as a strategy to enhance microbial selection and prevent bulking induced by nutrient shortage in an aerobic dynamic feeding (ADF) process using mixed microbial cultures (MMCs) for polyhydroxyalkanoate (PHA) production from fermentation digestate. A 5.0-L aerobic reactor was operated under three conditions: Long Settling (LS, 30 minutes), Short Settling (SS, 10 minutes), and Short Settling under Nutrient Shortage (SS-NS, 10 minutes with reduced nutrient load). Short settling significantly improved biomass settleability, reducing the Sludge Volume Index (SVI) from 126 to 25 mL g⁻¹, and promoted the formation of dense flocs enriched in PHA-accumulating bacteria, as confirmed by transmission electron microscopy. Process kinetics revealed enhanced substrate uptake rates and improved storage yields under SS conditions, despite an elevated C/P ratio. Notably, nutrient shortage conditions were inadvertently reached by the proliferation of Polytoma mirum in the feeding tank. Although Polytoma mirum did not affect VFA composition, its presence significantly reduced nitrogen and phosphorus concentrations. These nutrient shortage conditions were maintained for at least 30 days until the system began to exhibit stress, as demonstrated by an increased SVI (178.6 mL g⁻¹). Microbial community analyses indicated marked shifts: the eukaryotic assemblage transitioned from sessile to motile ciliates under SS, while bacterial diversity within the PHA‐accumulating fraction remained high, with key taxa such as Sphaerotilus and Neomegalonema becoming more prevalent under phosphorus-limited conditions. Overall, short settling not only improved microbial selection but also prevented bulking by retaining well-aggregated biomass, thereby mitigating nutrient shortage conditions.
Project description:This study explores the use of short settling times as a strategy to enhance microbial selection and prevent bulking induced by nutrient shortage in an aerobic dynamic feeding (ADF) process using mixed microbial cultures (MMCs) for polyhydroxyalkanoate (PHA) production from fermentation digestate. A 5.0-L aerobic reactor was operated under three conditions: Long Settling (LS, 30 minutes), Short Settling (SS, 10 minutes), and Short Settling under Nutrient Shortage (SS-NS, 10 minutes with reduced nutrient load). Short settling significantly improved biomass settleability, reducing the Sludge Volume Index (SVI) from 126 to 25 mL g⁻¹, and promoted the formation of dense flocs enriched in PHA-accumulating bacteria, as confirmed by transmission electron microscopy. Process kinetics revealed enhanced substrate uptake rates and improved storage yields under SS conditions, despite an elevated C/P ratio. Notably, nutrient shortage conditions were inadvertently reached by the proliferation of Polytoma mirum in the feeding tank. Although Polytoma mirum did not affect VFA composition, its presence significantly reduced nitrogen and phosphorus concentrations. These nutrient shortage conditions were maintained for at least 30 days until the system began to exhibit stress, as demonstrated by an increased SVI (178.6 mL g⁻¹). Microbial community analyses indicated marked shifts: the eukaryotic assemblage transitioned from sessile to motile ciliates under SS, while bacterial diversity within the PHA‐accumulating fraction remained high, with key taxa such as Sphaerotilus and Neomegalonema becoming more prevalent under phosphorus-limited conditions. Overall, short settling not only improved microbial selection but also prevented bulking by retaining well-aggregated biomass, thereby mitigating nutrient shortage conditions.
Project description:Phosphorus (P) limitation will play a key role in the productivity of agriculture in the coming decades. Struvite is an ammonium magnesium phosphate mineral that can be recovered from wastewater-treatment plants and can be considered as an alternative source of P. However, the impact of struvite on the plant yield and, particularly, on the soil microbial community is barely known. Here, we tested the impacts of struvite, sewage sludge, and their combination on the barley yield, soil macro and micronutrients, and biochemical and microbiological soil properties. Amendment with struvite alone and its combination with sludge increased the availability of P in soil, the plant uptake of P and Mg, and the barley yield. The analysis of phospholipid fatty acids (PLFAs) and metaproteomics approaches revealed significant effects of struvite on the biomass of Gram-positive bacteria and, particularly, on actinobacterial populations in soil.
Project description:Wastewater treatment plants use a variety of bioreactor types and configurations to remove organic matter and nutrients. Little is known regarding the effects of different configurations and within-plant immigration on microbial community dynamics. Previously, we found that the structure of ammonia-oxidizing bacterial (AOB) communities in a full-scale dispersed growth activated sludge bioreactor correlated strongly with levels of NO2- entering the reactor from an upstream trickling filter (Wells et al 2009). Here, to further examine this puzzling association, we profile within-plant microbial biogeography (spatial variation) and test the hypothesis that substantial microbial immigration occurs along a transect (raw influent, trickling filter biofilm, trickling filter effluent, and activated sludge) at the same full-scale wastewater treatment plant. AOB amoA gene abundance increased >30-fold between influent and trickling filter effluent concomitant with NO2- production, indicating unexpected growth and activity of AOB within the trickling filter. Nitrosomonas europaea was the dominant AOB phylotype in trickling filter biofilm and effluent, while a distinct ‘Nitrosomonas-like’ lineage dominated in activated sludge. Prior time series indicated that this ‘Nitrosomonas-like’ lineage was dominant when NO2- levels in the trickling filter effluent (i.e., activated sludge influent) were low, while N. europaea became dominant in the activated sludge when NO2- levels were high. This is consistent with the hypothesis that NO2- production may co-occur with biofilm sloughing, releasing N. europaea from the trickling filter into the activated sludge bioreactor. Phylogenetic microarray (PhyloChip) analyses revealed significant spatial variation in taxonomic diversity, including a large excess of methanogens in the trickling filter relative to activated sludge and attenuation of Enterobacteriaceae across the transect, and demonstrated transport of a highly diverse microbial community via the trickling filter effluent to the activated sludge bioreactor. Our results provide compelling evidence that substantial immigration between coupled process units occurs and may exert significant influence over microbial community dynamics within staged bioreactors.
2015-11-03 | GSE52079 | GEO
Project description:Microbiological analysis of excess sludge