Inadvertently enriched cyanobacteria prompted bacterial phosphorus uptake without aeration in a conventional anaerobic/oxic reactor.

The enhanced biological phosphorus removal (EBPR) process requires alternate anaerobic and aerobic conditions, which are regulated respectively by aeration off and on. Recently, in an ordinary EBPR reactor, an abnormal orthophosphate concentration (PO43--P) decline in the anaerobic stage (namely non-aerated phosphorus uptake) aroused attention. It was not occasionally but occurred in each cycle and lasted for 101 d and shared about 16.63 % in the total P uptake amount. After excluding bio-mineralization and surface re-aeration, indoor light conditions (180 to 260 lx) inducing non-aerated P uptake were confirmed. High-throughput sequencing analysis revealed that cyanobacteria could produce oxygen via photosynthesis and were inhabited inside wall biofilm. The cyanobacteria (Pantalinema and Leptolyngbya ANT.L52.2) were incubated in a feeding transparent silicone hose, entered the reactor along with influent, and outcompeted Chlorophyta, which existed in the inoculum. Eventually, this work deciphered the reason for non-aerated phosphorus uptake and indicated its potential application in reducing CO2 emissions and energy consumption via the cooperation of microalgal-bacterial and biofilm-sludge.

Towards low carbon demand and highly efficient nutrient removal: Establishing denitrifying phosphorus removal in a biofilm-based system.

The combined denitrifying phosphorus removal (DPR) and Anammox process is expected to achieve advanced nutrient removal with low carbon consumption. However, exchanging ammonia/nitrate between them is one limitation. This study investigated the feasibility of conducting DPR in a biofilm reactor to solve that problem. After 46-day anaerobic/aerobic operation, high phosphorus removal efficiency (PRE, 83.15 %) was obtained in the activated sludge (AS) and biofilm co-existed system, in which the AS performed better. Phosphate-accumulating organisms might quickly adapt to the anoxic introduced nitrate, but the following aerobic stage ensured a low effluent orthophosphate (<1.03 mg/L). Because of waste sludge discharging and AS transforming to biofilm, the suspended solids dropped below 60 mg/L on Day 100, resulting in PRE decline (17.17 %) and effluent orthophosphate rise (4.23 mg/L). Metagenomes analysis revealed that Pseudomonas and Thiothrix had genes for denitrification and encoding Pit phosphate transporter, and Candidatus_Competibacter was necessary for biofilm formation.

Response of performance, sludge characteristics, and microbial communities of biological phosphorus removal system to salinity.

The effects of salinity on highly enriched polyphosphate- or glycogen-accumulating organisms (PAOs or GAOs) have been revealed, which is meaningful but idealized. In this study, three salinity levels (0.5%, 1.0%, and 0.75%) were sequentially adopted in a PAOs and GAOs coexisted biological phosphorus removal (BPR) reactor within 150 days. Compared to a slight decrease of phosphorus removal efficiency (PRE) under 0.5% salinity (from 96.09% to 73.68%), doubled salinity (1.0%) resulted in a lengthy recovery period and a sharp PRE decline (13.89%), and the PRE was merely kept at 27.39% even through salinity was decreased to 0.75% hereafter. Salinity was also found to stimulate more extracellular protein secretion, resulting in sludge volume index reduction (<32.87 mL/g) and particle size enlargement (222.78 µm on average). Hyphomicrobium (0.96%-1.76%) and unclassified_f_Rhodobacteraceae (4.72%-13.33%) could resist certain salinity and conduct BPR, but better salt-tolerant Candidatus_Competibacter eventually became the predominant genus (>40%).

Efficient organics heterogeneous degradation by spinel CuFe2O4 supported porous carbon nitride catalyst: Multiple electron transfer pathways for reactive oxygen species generation.

Facilitating reactive oxygen species (ROS) generation is an effective way to promote the heterogeneous catalytic efficiency for organics removal. However, the metal leaching in metal-based catalysts and the low activity of non-metallic materials restrict ROS production. In this work, the purpose was achieved by loading a small amount of spinel CuFe2O4 onto porous carbon nitride substrate. The synthesized CuFe2O4@O-CN composite first to activate peroxymonosulfate (PMS), which produce a plenty of ROS (•OH, SO4•- and 1O2) for organics removal, leading to highly oxidation for diverse organics. Through the comparative analysis of the surface composition before and after reaction, we found that the interface multi-electron transfer routs, including surface Cu(II)/Cu(I), Fe(III)/Fe(II) and their cross interaction, participated in the redox cycle, giving rise to the rapid and massive production of ROS, so that DMPO and TEMP were instantly oxidized in electron paramagnetic resonance (ESR) detection. Importantly, the carrier of porous O-CN, which acted as the electron transfer mediator, not only favors PMS adsorption via surface -OH, but also facilitates the conversion between different metal species. As a result, the CuFe2O4@O-CN/PMS system can remove 99.1% BPA and achieve 52.6% mineralization under optimized conditions. Thus, this study not only sheds light on the tailored design of heterogeneous catalyst for organics removal and elucidates the interfacial catalytic mechanisms for PMS activation.

Unexpected phosphorous removal in a Candidatus_Competibacter and Defluviicoccus dominated reactor.

Competition between polyphosphate- and glycogen-accumulating organisms (PAOs and GAOs) is problematic in the enhanced biological phosphorus removal (EBPR) process. Aiming at a high phosphorus removal efficiency (PRE), the phosphorus release amount (PRA) is considered an essential evaluating indicator. However, the correlations between PRE and PRA and the abundance of PAOs are not clear. In this study, the EBPR was established and optimized via adjusting influent carbon to phosphorus ratio (C/P). After 110-day operation, 17.67 mg/L of PRA and 75.86% of PRE simultaneously achieved with influent C/P of 40 mgCOD/mgP. As for PAOs, Candidatus_Accumulibacter and Tetrasphaera were absent, while Hypomicrobium (3.69%), Pseudofulvimonas (1.02%), and unclassified_f_Rhodobacteraceae (2.41%) were found at a low level. On the contrary, Candidatus_Competibacter and Defluviicoccus were unexpectedly enriched with high abundance (24.94% and 16.04%, respectively). These results also suggested that it was difficult to distinguish whether PAOs were enriched merely based on the variations of PRA and PRE.

Molecular characterization of bacterial and archaeal communities in a full-scale anaerobic reactor treating corn straw.

A 16S rRNA gene-based method was used to characterize the structure of bacterial and archaeal communities in a full-scale, anaerobic reactor treating corn straw. Degradability experiment indicated biogas slurry had high microbial activity, the TS removal rate was 53% and the specific methanogenic activity was 86 mL CH4 g VSS(-1) d(-1). During anaerobic degradation of corn straw, volatile acids and aromatic compounds (p-cresol, phenylpropionate, phenol and benzoate) were detected as transient intermediates. Phylogenetic analysis revealed bacterial community exhibited high diversity, 69 bacterial phylotypes in 13 phyla were identified. Firmicutes (48.3%), Chloroflexi (20.1%), Actinobacteria (9.1%), Bacteroidetes (7.7%), and Proteobacteria (7.2%) represented the most abundant bacterial phyla. Hydrolytic and fermentative bacteria were major bacterial populations. Moreover, a relatively high proportion of syntrophic propionate and aromatic compounds degrading bacteria were detected. In the archaeal clone library, 11 archaeal phylotypes affiliated with two phyla of Crenarchaeota (10%) and Euryarchaeota (90%) were identified.