Genome-centric metagenomics provides new insights into metabolic pathways of polyhydroxyalkanoates biosynthesis and functional microorganisms subsisting on municipal organic wastes.

The microbial community of a sequencing batch reactor operated under feast and famine conditions for production of polyhydroxyalkanoates (PHAs) was characterized through high-throughput sequencing and metagenomic analysis. The fermented food waste and chemically-enhanced primary sludge was fed in this bioreactor. After acclimation, the PHA yield achieved as high as 0.60-0.69 g CODPHA/g CODS. The complete changes of microbial community structure were found during shifts of feedstock. A synthesis of SCL/MCL-PHAs pathway was established for PHA-producing bioreactor in this mixed-culture system. The structure-performance relationship of PHA-producing microbial community and feedstock composition was investigated. The results showed that microbial community tends to be decentralized and prefer team work for PHA synthesis to consume the multiple substrates and digest inevitable non-VFA contents in fermented liquor. This study also discovered unreported potential PHA producers (e.g., genera Tabrizicola, Nannocystis, Ga0077539, Ga0077559, JOSHI-001, SNC69-320 and UBA2334) subsisting on municipal organic wastes and expands the current knowledge about mixed-culture system that the PHA synthesis pathway is widely existed in activated sludge.

Transformation of Fe-P Complexes in Bioreactors and P Recovery from Sludge: Investigation by XANES Spectroscopy.

The transformation of Fe-P complexes in bioreactors can be important for phosphorus (P) recovery from sludge. In this research, X-ray absorption near-edge structure analysis was conducted to quantify the transformation of Fe and P species in the sludge of different aging periods and in the subsequent acidogenic cofermentation for P recovery. P was readily removed from wastewater by Fe-facilitated coprecipitation and adsorption and could be extracted and recovered from sludge via acidogenic cofermentation and microbial iron reduction with food waste. The fresh Fe-based sludge mainly contained fresh ferrihydrite and amorphous FePO4 with sufficient accessible surface area, which was favorable for Fe-P mobilization and dissolution via microbial reaction. Ferric iron dosed into wastewater underwent rapid hydrolysis, clustering, aggregation, and slow crystallization to form hydrous iron oxides (HFO) with various complicated structures. With the aging of sludge in bioreactors, the HFO densified into phases with much reduced surface area and reactivity (e.g., goethite), which greatly increased the difficulty of P release and recovery. Thus, aging of P-containing sludge should be minimized in wastewater treatment systems for the purpose of P recovery.

Characterization and mitigation of the fouling of flat-sheet ceramic membranes for direct filtration of the coagulated domestic wastewater.

Ceramic membranes allow a high filtration flux with a low fouling propensity. Direct filtration of municipal wastewater using flat-sheet ceramic membranes (FSCM) is an attractive and promising technology for wastewater treatment and resource recovery. Urgent need is to determine the fouling behavior of FSCM and its optimal cleaning strategy in direct filtration applications. This study was conducted on pre-coagulation of sewage with FeCl3 (20 mg Fe/L) or polyaluminum chloride (15 mg Al/L), followed by FSCM filtration at around 1.0 m/d (as high as 41.7 L/m2-h in flux). The results showed that the coagulation-FSCM filtration removed chemical oxygen demand and total phosphorus by up to 90.0% and 99.9%, respectively. The pollutants (organics and nutrients) in the sewage influent were concentrated into the sludge for potential resource recovery. Without pre-coagulation, foulants easily entered the membrane pores, causing rapid membrane fouling. Chemically enhanced coagulation greatly decreased the membrane fouling rate by aggregating various foulants into flocs. Fouled membranes were effectively renewed by physical means, such as water flushing and sonication, or a short period of chemical backwashing with NaOH, HCl or oxidizing agents. The study revealed the fouling mechanisms of FSCM in sewage filtration and developed effective cleaning strategies for its long-term operation.

Performance and bacterial community of moving bed biofilm reactors with various biocarriers treating primary wastewater effluent with a low organic strength and low C/N ratio.

A laboratory-scale sequencing batch reactor (SBR) and two moving bed biofilm reactors (MBBRs) with different types of biocarriers were operated to treat the effluent of chemically enhanced primary sedimentation (CEPS). Due to the low organic strength and low carbon/nitrogen ratio of the CEPS effluent, COD and NH4+-N were effectively removed by the MBBRs but not by the SBR. Of the two MBBRs, MBBR2 filled with LEVAPOR biocarrier cubes performed even better than MBBR1 filled with K3 polystyrene biocarriers. The continuous decline of the sludge concentration in the SBR and the high and stable biomass content in MBBR2 contributed to their performances. High-throughput sequencing analysis showed that the reactors had selective effects on the bacterial community structure. Principal coordinate analysis indicated the different dynamic successions in the three reactors. Network analysis showed different community composition and diversity that were highly suggestive of different bacterial interactions among the three bioreactors.

Direct filtration for the treatment of the coagulated domestic sewage using flat-sheet ceramic membranes.

Direct membrane filtration (DMF) is considered as a promising technology for municipal wastewater treatment. We utilized an innovative application of flat-sheet ceramic membranes (FSCM) for DMF for the rapid treatment of domestic sewage. Coagulation was applied before FSCM filtration to increase the pollutant removal and to mitigate membrane fouling. This coagulation-FSCM filtration can significantly reduce the pollutant load on the downstream treatment and concentrate organics and nutrients into sludge to facilitate resource recovery. Using polyaluminum chloride (PACl) based FSCM filtration, approximately 90.0% of the chemical oxygen demand (COD) and 99.0% of the phosphorus (P) were removed from the sewage influent and retained in the concentrated sludge, with less than 25.0 mg/L COD left in the effluent. Long-term operation of the PACl-based FSCM filtration stably maintained a high flux of 41.7 L/m2-h (LMH, or 1.0 m/d). The fouled membranes were cleaned chemically every 3-5 d, and the membrane permeability could almost be completely recovered using chemical backwash for only 10 min with a diluted acidic, alkaline, chlorine or H2O2 solution. The novel FSCM process will fundamentally advance wastewater treatment technology. It can be readily modularized and installed as simple add-on units to upgrade and retrofit existing wastewater treatment systems.

Acidogenic phosphorus recovery from the wastewater sludge of the membrane bioreactor systems with different iron-dosing modes.

A novel acidogenic phosphorus recovery (APR) process was developed in combination with Fe(III)-based chemical phosphorus removal and a membrane bioreactor (MBR) for enhanced wastewater treatment and effective P recovery. Two different system configurations were evaluated: Fe-dosing MBR (Fe-MBR), with the Fe-dosing into the MBR, and Fe-enhanced primary sedimentation followed by the MBR (FeP-MBR). The results show that both systems performed well for enhanced nutrient (N and P) removals and P recovery, with approximately 50% of the total P recovered from the municipal wastewater in the form of vivianite. Compared to the Fe-MBR system, FeP-MBR achieved more efficient P recovery under low food-waste loading conditions, maintained a higher ratio of biomass in activated sludge and experienced a slower rate of membrane fouling. Important functional bacteria were identified, including Prevotella and Selenomonas, which are active in hydrolysis and acidogenesis of sludge, and Aeromonas and Sulfurospirillum, which are involved in dissimilatory iron reduction.

Phosphorus Removal and Recovery from Wastewater using Fe-Dosing Bioreactor and Cofermentation: Investigation by X-ray Absorption Near-Edge Structure Spectroscopy.

A new phosphorus (P) removal and recovery process that integrates an FeCl3-dosing, membrane bioreactor (MBR), and side-stream cofermentation was developed for wastewater treatment. The Fe and P species and their transformation mechanisms via aerobic and anaerobic conditions were investigated with X-ray absorption near edge structure (XANES) spectroscopy. In the new treatment system, 98.4% of the total P in domestic wastewater was removed and retained in activated sludge in the MBR. During the subsequent acidogenic cofermentation with food waste, P in the MBR sludge was released and eventually recovered as vivianite, achieving an overall P recovery efficiency of 61.9% from wastewater. The main pathways for P removal and recovery with iron dosing and acidogenic fermentation were determined by XANES analysis. The results showed that Fe-enhanced P removal with the MBR was mainly achieved by precipitation as ferric phosphate (24.2%) and adsorption onto hydrous iron oxides (60.3%). During anaerobic fermentation, transition from Fe(III)-P to Fe(II)-P complex occurred in the sludge, leading to Fe(II) dissolution and P release. The pH decrease and microbial Fe reduction were crucial conditions for effective P extraction from the MBR sludge. The efficiency of P recovery increased with an increase in the fermentation time and organic load and a decrease of pH in the solution.

An integrated membrane bioreactor system with iron-dosing and side-stream co-fermentation for enhanced nutrient removal and recovery: System performance and microbial community analysis.

An integrated membrane bioreactor (MBR) system was developed for enhanced nutrient (N and P) removal and effective P recovery in wastewater treatment. The system consisted of an iron-dosing MBR and side-stream fermentation for P removal and recovery and side-stream denitrification for N removal. Around 98.1% of the total phosphorus (TP) in wastewater was removed by ferric iron-induced precipitation and membrane filtration in the aerobic MBR, and nearly 53.4% of the TP could be recovered via anaerobic fermentation from the MBR sludge. In addition, the fermenter that allowed acidogenic co-fermentation with food waste provided sufficient soluble organics for biological denitrification, and an overall 91.8% total N removal was achieved through the side-stream denitrification. High-throughput sequencing was applied to analyse the microbial communities in the integrated system, and important functional bacteria were identified for nitrification, denitrification, acidogenic fermentation and dissimilatory iron reduction through the different components of the system.

A membrane bioreactor with iron dosing and acidogenic co-fermentation for enhanced phosphorus removal and recovery in wastewater treatment.

A novel phosphorous (P) removal and recovery process using a membrane bioreactor (MBR) with ferric iron dosing and acidogenic co-fermentation was developed for municipal wastewater treatment. The very different solubility of Fe(III)-P and Fe(II)-P complex and the microbial transformation of Fe(III) to Fe(II) were utilized for P removal and recovery. By means of Fe-induced precipitation, chemical P removal was effectively achieved by an MBR with a flat-plate ceramic membrane; however, the Fe(III)-P solids accumulated in the MBR that constituted a significant fraction of the activated sludge. Anaerobic co-fermentation of the MBR sludge and food waste in a side-stream allowed the extraction of P and Fe from the sludge into the supernatant. The P in the supernatant was recovered as a fertilizer resource, while the sludge was returned to the MBR tank. The experimental results show that by adding FeCl3 at 20 mg Fe/L into the influent of domestic wastewater, about 95.6% of total P could be removed by the MBR. One fifth (20%) of the sludge in the MBR was circulated daily through the side-stream fermenters for co-fermentation with cooked rice as the model food waste. The sludge underwent acidogenesis and dissimilatory iron reduction, resulting in a drop of the pH to below 5.0 and reduction of Fe(III) to Fe(II). Owing to the high solubility of the Fe(II)-P complex, P and Fe were then dissolved and released from the sludge into the supernatant. By simply adjusting the solution pH to 8.0, the P and Fe(II) in the supernatant readily re-precipitated to form vivianite for the P recovery. Using the iron dosing MBR and side-stream sludge fermentation, an overall P recovery efficiency of 62.1% from wastewater influent can be achieved, and the problem of inorganic build-up in the MBR is effectively alleviated.

Recovery of phosphorus and volatile fatty acids from wastewater and food waste with an iron-flocculation sequencing batch reactor and acidogenic co-fermentation.

A sequencing batch reactor-based system was developed for enhanced phosphorus (P) removal and recovery from municipal wastewater. The system consists of an iron-dosing SBR for P precipitation and a side-stream anaerobic reactor for sludge co-fermentation with food waste. During co-fermentation, sludge and food waste undergo acidogenesis, releasing phosphates under acidic conditions and producing volatile fatty acids (VFAs) into the supernatant. A few types of typical food waste were investigated for their effectiveness in acidogenesis and related enzymatic activities. The results show that approximately 96.4% of total P in wastewater was retained in activated sludge. Food waste with a high starch content favoured acidogenic fermentation. Around 55.7% of P from wastewater was recovered as vivianite, and around 66% of food waste loading was converted into VFAs. The new integration formed an effective system for wastewater treatment, food waste processing and simultaneous recovery of P and VFAs.

Inhibition of the NEDD8 conjugation pathway by shRNA to UBA3, the subunit of the NEDD8-activating enzyme, suppresses the growth of melanoma cells.

Neural precursor cell-expressed developmentally down-regulated 8 (NEDD8), a ubiquitin-like protein, mainly functions through covalent ligation to cullin proteins. Conjugation of NEDD8 with cullins can promote ubiquitination, which plays a critical role in the degradation of many proteins. UBA3 is the subunit of NEDD8- activating enzyme which is one of the keys for NEDD8 linkage to cullin proteins. Previous research showed NEDD8 conjugation to be up-regulated in highly proliferative cell lines. In the present study, up-regulated NEDD8 conjugation was observed in melanoma cell lines by Western blot analysis. After down-regulation with a RNAi to UBA3, proliferation of M14 was suppressed in vitro and in vivo. In conclusion, up-regulated NEDD8 conjugation may be involved in the development of melanoma. Interference in this pathway might offera promising method for melanoma therapy.