Combined effects of volume ratio and nitrate recycling ratio on nutrient removal, sludge characteristic and microbial evolution for DPR optimization.

The optimization of volume ratio (VAn/VA/VO) and nitrate recycling ratio (R) in a two-sludge denitrifying phosphorus removal (DPR) process of Anaerobic Anoxic Oxic-Moving Bed Biofilm Reactor (A2/O-MBBR) was investigated. The results showed that prolonged anaerobic retention time (HRTAn: 1.25→3.75 hr) exerted favorable effect on chemical oxygen demand (COD) removal (57.26%→73.54%), poly-ß-hydroxyalkanoates (PHA) synthesis (105.70→138.12 mgCOD/L) and PO43- release (22.3→38.9 mg/L). However, anoxic retention time (HRTA) and R exhibited positive correlation with PHA utilization (43.87%-81.34%) and denitrifying phosphorus removal (DPR) potential (ΔNO3-/ΔPO43-: 0.57-1.34 mg/mg), leading to dramatical TN removal variations from 68.86% to 81.28%. Under the VAn/VA/VO ratio of 2:6:0, sludge loss deteriorated nutrient removals but the sludge bioactivity quickly recovered when the oxic zone was recovered. The sludge characteristic and microstructure gradually transformed under the dissolved oxygen (DO) control (1.0-1.5→1.5-2.0 mg/L), in terms of sludge volume index (SVI: 194→57 mL/gVSS), median-particle-size (D50: 99.6→300.5 µm), extracellular polymeric substances (EPS) (105.62→226.18 mg/g VSS) and proteins/polysaccharides (PN/PS) ratio (1.52→3.46). Fluorescence in situ hybridization (FISH) results showed that phosphorus accumulation organisms (PAOs) (mainly Cluster I of Accumulibacter, contribution ratio: 91.79%-94.10%) dominated the superior DPR performance, while glycogen accumulating organisms (GAOs) (mainly Competibacter, contribution ratio: 82.61%-86.89%) was responsible for deteriorative TN and PO43- removals. The optimal HRTA and R assembled around 5-6.5 hr and 300%-400% based on the PHA utilization and DRP performance, and the oxic zones also contributed to PO43- removal although it showed low dependence on DO concentration and oxic retention time (HRTO).

Elucidating sludge characteristic, substrate transformation and microbial evolution in a two-sludge denitrifying phosphorus removal system under the impact of HRT.

Granule formation has been recognized as a promising biotechnology in denitrifying phosphorus removal (DPR) systems by facilitating phosphorus accumulation organisms (PAOs) especially denitrifying PAOs (DPAOs), and hydraulic selection made this a more difficult task in continuous operation. This study aimed at exploring the microscopic mechanism and putting forward an effective strategy for DPR granulation under the impact of hydraulic retention time (HRT) (12 h, 10 h, 8 h) in a novel Anaerobic Anoxic Oxic - Moving Bed Biofilm Reactor (A2/O - MBBR) system. With the reduction of intracellular carbon storage (CODintra) efficiency (88.58%-78.53%), nitrogen (N) (85.45%-79.11%) and phosphorus (P) (96.55%-92.47%) removals both dropped, but it exhibited a growth of anoxic phosphorus uptake rate (PURA) (3.79-5.68 mg P/(gMLVSS·h)). The batch tests associating with substrate transformation of poly-ß-hydroxyalkanoates (PHA), glycogen (Gly) agreed well with the corresponding stoichiometry of phosphorus release rate (PRR) (4.83-7.53 mg P/(gMLVSS·h)), PURA (3.55-5.43 mg P/(gMLVSS·h)), oxic phosphorus uptake rate (PURO) (6.08-6.21 mg P/(gMLVSS·h)), and DPAOs/PAOs ratios (57.17%-89.31%), indicating a shift of microbial community. DPR granules gradually stabilized with low sludge volume index (SVI5/SVI30 ratio = 1.1-1.2), dense and compact structure, higher P content (11.63%), more extracted extracellular polymeric substances (EPS) (111.40-160.31 mg/gMLVSS) as proteins/polysaccharides (PN/PS) ratios (1.70-3.47) increased, leading to better sludge settleability and cell hydrophobicity. Fluorescence in situ hybridization (FISH) results showed that PAOs (mainly Cluster I: 20.20%) were the dominant bacteria in the A2/O reactor although a small amount of Defluviicoccus (3.18-3.48%) was responsible for nitrite accumulation, while ammonium-oxidizing bacteria (AOB) (mainly Nitrosomonas: 10.75%) and nitrite-oxidizing bacteria (NOB) (mainly Nitrospira: 15.06%) were enriched in the MBBR.

Development and evaluation of MTLSER and QSAR models for predicting polyethylene-water partition coefficients.

Current study was aimed to make further improvements in measuring low density polyethylene (LDPE) -water partition coefficient (KPE-w) for organic chemicals. Modified theoretical linear solvation energy relationship (MTLSER) model and quantitative structure activity relationship (QSAR) model were developed for predicting KPE-w values from chemical descriptors. With the MTLSER model, α (average molecular polarizability), µ (dipole moment) and q- (net charge of the most negative atoms) as significant variables were screened. With the QSAR model, main control factors of KPE-w values, such as CrippenLogP (Crippen octanol-water partition coefficient), CIC0 (neighborhood symmetry of 0-order) and GATS2p (Geary autocorrelation-lag2/weighted by polarizabilities) were studied. As per our best knowledge, this is the first attempt to predict polymer-water partition coefficient using the MTLSER model. Statistical parameters, correlation coefficient (R2) and cross-validation coefficients (Q2) were ranging from 0.811 to 0.951 and 0.761 to 0.949, respectively, which indicated that the models appropriately fit the results, and also showed robustness and predictive capacity. Mechanism interpretation suggested that the main factors governing the partition process between LDPE and water were the molecular polarizability and hydrophobicity. The results of this study provide an excellent tool for predicting log KPE-w values of most common hydrophobic organic compounds, within the applicability domains to reduce experimental cost and time for innovation.

Long-Term Trends in Acid Neutralizing Capacity under Increasing Acidic Deposition: A Special Example of Eutrophic Taihu Lake, China.

While North America and Europe have been recovering from acidification, China is experiencing impacts of acid deposition. The Taihu region is a seriously impacted area by acid rain in China, with the average rainfall pH < 5. However, the acid neutralizing capacity (ANC) and pH of Taihu Lake have significantly increased over the past 60 years (p < 0.05). Analyses showed that watershed neutralization by carbonates and in-lake alkalinization by algae activities were the two major reactions responsible for the increase. In the Taihu basin, the dominant carbonate bedrocks are the major source of base cations (particularly Ca2+ and Mg2+) and act as the acidification buffer. In addition, our field measurements across the lake showed that the pH values were significantly higher in algal bloom waters than in areas without blooms. This observation was further supported by our statistical analysis showing that the Taihu ANC and pH were significantly correlated with the chlorophyll increase (p < 0.05; 1985-2015). However, our regression analysis indicated that the base cations in the watershed would be depleted by the early 2040s if the acid deposition continues at the current rate. Our results suggest that interactions between human accelerated weathering, watershed geochemistry, and in-lake algae activities significantly impact the water chemistry of the lake. We urgently recommend an "integrated and balanced" recovery plan for the lake ecosystem.

[Characterization and spectral analysis of the stable mineral phases alpha, beta-FeOOH included in iron oxyhydroxides].

In the present work, based on the stable phase of alpha-FeOOH and beta-FeOOH easily formed in ferric solutions of Fe (NO3)3 and FeCl3 at the appropriate pH values, respectively, the phase and crystallizability, morphologies and sizes for the particles of FeOOH minerals prepared under the conditions of heating at 40 and 70 degreeC, and magnetic stirring at 25 degreeC were identified and examined by X-ray diffraction (XRD), transmission/scanning electron microscopy (TEM/SEM) and laser scattering particle analyzer. Meanwhile the surface chemistry properties were also detected and analyzed by Fourier transform infrared spectrometer (FTIR). Investigation results showed that the prepared minerals Gth-T70 (alpha-FeOOH), Aka-T40 and Aka-T70 (beta-FeOOH) have good properties of nanocrystallity, homogeneous particles and higher specific surface areas, which induced that the above alpha, beta-FeOOH are potentially excellent adsorbent materials for removal of some contaminants in circumstances.

Elucidating nitrifying performance, nitrite accumulation and microbial community in a three-stage plug flow moving bed biofilm reactor (PF - MBBR).

A three-stage plug flow moving bed biofilm reactor (PF - MBBR, consisting of three identical chambers of N1, N2 and N3) was proposed for nitrifier enrichment using synthetic wastewater. During the stable operation, the average NH4+-N effluent was 0.67 mg/L and NH4+-N removal was as high as 97.19% with the nitrite accumulation ratio (NAR) of 54.23%, although the biofilm thickness and biomass both presented downward trends from N1 (296 µm, 2280 mg/L), N2 (248 µm, 1850 mg/L) to N3 (198 µm, 1545 mg/L). Particularly, the comparative results of three stages revealed that N2 showed the optimum NH4+-N removal (77.27%) and NAR (75.21%) in the continuous-flow, while NAR of N3 unexpectedly maintained a high level of 65.83% in the batch test, suggesting that ammonia oxidizing bacteria (AOB) accounted for absolute advantage over nitrite oxidizing bacteria (NOB). High-throughput sequencing initially verified different distribution of bacterial community structure, where N2 was far away from N1 and N3 with the lowest community richness and community diversity (operational taxonomic units (OTUs): 454(N2)<527(N3)<621(N1)). Proteobacteria (77.60%-83.09%), Bacteroidetes (1.66%-3.66%), Acidobacteria (2.28%-4.67%), and Planctomycetes (1.19%-6.63%) were the major phyla. At the genus level, AOB (mainly Nitrosomonas) accounted for 5.08% (N1), 20.74% (N2) and 14.24% (N3) while NOB (mainly Nitrospira) increased from 0.14% (N1), 7.06% (N2) to 4.91% (N3) with the total percentages of 5.22%, 27.80% and 19.15%. Finally, the application feasibility of MBBR optimization linked with nitrite (NO2--N) accumulation for deep-level nutrient removal was discussed.

Efficient purification of toluene gas by anoxic denitrification.

As a part of volatile organic compounds (VOCs), toluene does harm to human health. This paper reported the purification of toluene waste gas by liquid-phase absorption and anoxic denitrification. In this work, two same biofilm reactors were set to treat toluene waste gas, one of which was added into nitrate as an electron acceptor. Then, the purification properties of toluene waste gas treated by anoxic denitrification and biological methods were compared. The results indicate that with the increase of toluene mass concentration, the toluene removal rate of the denitrifying reactor decreased slightly. When the inlet concentration increased from 50 mg m-3 to 3440 mg m-3, the removal efficiency of the denitrifying reactor remained over 94.1% while the removal efficiency of the traditional bioreactor decreased to 82.9%. The highest removal capacity of the denitrifying reactor was 127.2 g m-3 h-1, which was 11.8% higher than that of the traditional bioreactor. Toluene was degraded by denitrification inside the biofilm microenvironment hypoxia; the denitrification rate increased along with the increase of inlet concentration within certain limits and reached a maximum of 2.4 mg NO3--N L-1 h-1. Nitrate can act as an electron acceptor, and denitrification can promote aerobic degradation and intensify the concentration gradient inside the biofilm to strengthen the toluene transfer process.

Nitrite accumulation and microbial behavior by seeding denitrifying phosphorus removal sludge for partial denitrification (PD): The effect of COD/NO3- ratio.

Effect of influent COD/NO3- ratios (2.0-5.0) on partial denitrification (PD, NO3- to NO2-) was investigated by seeding denitrifying phosphorus removal (DPR) sludge at ambient temperature (16 ± 2℃). At COD/NO3- ratio of 2.5, the optimal NO2- effluent and nitrate-to-nitrite transformation ratio (NTR) reached up to 27.18 mg/L and 82.18%, respectively, and nitrate removal efficiency (NRE) (59.34 â†’ 97.98%) showed positive relationship with increasing COD/NO3- ratios. The variations were further illustrated by denitrification kinetics, where faster COD degradation (1.55 g COD/(gVSS·d)), more NO3- consumption (0.55 gN/(gVSS·d)) and higher NO2- production (0.52 gN/(gVSS·d)) were observed although the NO2- peaks happened at anoxic 30 min. Microbial analysis showed lower community diversity and more concentrated composition with dominated genera Thauera (14.10%), Terrimonas (9.40%), Saprospiraceae (13.50%) and Flavobacterium (28.23%) at COD/NO3- ratio of 2.5. Based on the achievement of PD, the application feasibility of integrated PD-DPR-Anammox in a two-sludge DPR system for deep-level nutrient removal was discussed.

Comparisons of nitrite accumulation, microbial behavior and nitrification kinetic in continuous stirred tank (ST) and plug flow (PF) moving bed biofilm reactors.

Two types of continuous stirred tank moving bed biofilm reactors (ST-MBBR) and plug flow MBBR (PF-MBBR) were compared for nitrification. PF-MBBR showed strong shock resistance to temperature, and ammonium oxidation ratio (AOR) was 9.63% higher than that in the ST-MBBR, although the average biomass and biofilm thickness of ST-MBBR were 7.32-18.59%, 9.44-14.06% higher than those in the PF-MBBR. Meanwhile, a lower nitrite accumulation ratio (NAR) was observed (54.88%) in the PF-MBBR than the ST-MBBR (78.92%) due to different operation modes, and the divergence was demonstrated by the microbial quantitative analysis. Nitrification kinetics revealed that the temperature coefficient (θ) in the ST-MBBR (1.068) was much higher than that in the PF-MBBR (1.006-1.015), proving the contrasting nitrification performances caused by temperature shock. According to the Monod equation, the half-saturation coefficient (KN) in the ST-MBBR was 0.19 mg/L while it varied around 0.12-0.24 mg/L in the PF-MBBR, revealing various NH4+ affinity owing to different biofilm thickness and microbial composition. Finally, MBBR optimization related to operation mode, temperature, and free ammonium (FA) inhibition for nitrite accumulation was discussed.

Deep-level nutrient removal and denitrifying phosphorus removal (DPR) potential assessment in a continuous two-sludge system treating low-strength wastewater: The transition from nitration to nitritation.

In a continuous two-sludge denitrifying phosphorus removal (DPR) process of anaerobic anoxic oxic - moving bed biofilm reactor (AAO - MBBR), nitritation was practicable through the combined regulation of high temperature (T: 30-32 °C), short hydraulic retention time (HRT: 8 h) and low dissolved oxygen (DO: 1.0-1.5 mg/L). The system lasted for 90 days with stable nitrite accumulation ratio (NAR > 60%), and the total inorganic nitrogen (TIN) removal was 7% higher than complete nitrification. Ammonia oxidizing bacteria ((AOB) 6.18-9.41%) responsible for nitritation showed a clear relationship with NAR, but Nitrospira (2.11% â†’ 2.35%) gradually outcompeted Nitrobacter (1.19% â†’ 0.31%) under higher temperature. During the transition from nitration to nitritation, the DPR potential (characterized by ΔPO43-/ΔNOx-) increased by 11.90% while the energy requirement of poly-ß-hydroxyalkanoates (PHA) and glycogen (Gly) decreased by 12.58% and 14.50%, respectively, contributing to higher TIN (84.83%) and TP (97.45%) removals. DPR batch tests using different electron acceptors (NO3- .vs. NO3- + NO2-) revealed that removing 1 mg PO43- only consumed 7.12 ± 0.25 mg PHA via NO3- + NO2- (.vs. 8.50 ± 0.12 mg PHA via NO3-) and 16% carbon source was saved although the DPR capability was suppressed as NO2- concentration exceeded 15 mg/L. Based on the achievement of nitritation, the feasibility of integrated DPR - Anammox in the AAO - MBBR system for deep-level nutrient removal was discussed.

A combination method for multicriteria uncertainty analysis and parameter estimation: a case study of Chaohu Lake in Eastern China.

Eutrophication models are of great importance and are valuable tools for the development of policy and legislation. However, the parameter uncertainty and substantial computational cost lead to difficulties in decision-making, especially for complex models with multiple indicators. A multicriteria uncertainty analysis and parameter estimation (MUAPE) method, which selected behavioral parameters combined with Pareto domination and simultaneously obtained acceptable values for modeling by the maximum likelihood concept and kernel density estimation, was shown. This method, which did not assign thresholds and weights, was applied to analyze the uncertainty of the Chaohu Lake eutrophication model and estimate parameters. The results of the behavioral parameters were compared using different criterion sets, the relative error (RE) and the root mean square error (RMSE), and the results showed little discrepancy in terms of the effects on parameter uncertainty represented by the marginal probability density. The uncertainties of the parameters related to algal kinetics (i.e., BMR, PM, and KESS) were smaller than those of nutrient- and temperature-related parameters (i.e., KDN, Nitm, KTB, and KTHDR) for both sets of criteria. However, the reduction in the joint uncertainty of the two parameters was greater when RE was used than when RMSE was used. The acceptable values for the key parameters of the Chaohu Lake eutrophication model were also obtained by the RE criterion. The results strongly agreed with the observed values, and parameters could be applied for model prediction. This result indicated that the combination method was not only practical for reducing parameter uncertainty but also useful for determining parameter values. This method provides a basis for multicriteria uncertainty analysis and parameter estimation in eutrophication modeling.

Nutrient metabolism, mass balance, and microbial structure community in a novel denitrifying phosphorus removal system based on the utilizing rules of acetate and propionate.

The effect of acetate (HAc) and propionate (HPr) on denitrifying phosphorus removal (DPR) was evaluated in a novel two-sludge A2/O - MBBR (anaerobic/anoxic/oxic - moving bed biofilm reactor) system. Results showed that it was the carbon source transformation and utilization especially the composition of poly-ß-hydroxyalkanoates (PHA) (mainly poly-ß-hydroxybutyrate (PHB) and poly-bhydroxyvalerate (PHV)) decided DPR performance, where the co-exist of HAc and HPr promoted the optimal nitrogen (85.77%) and phosphorus (91.37%) removals. It facilitated the balance of PHB and PHV and removing 1 mg NO3- (PO43-) consumed 3.04-4.25 (6.84-9.82) mgPHA, where approximately 40-45% carbon source was saved. Mass balance revealed the main metabolic pathways of carbon (MAn,C (consumed amount in anaerobic stage) and MA-O,C (consumed amount in anoxic and oxic stages): 66.38-76.19%), nitrogen (MDPR,N (consumed amount in DPR): 57.01-65.75%), and phosphorus (MWS,P (discharged amount in waste sludge): 81.05-85.82%). Furthermore, the relative abundance and microbial distribution were assessed to elucidate DPR mechanism (e.g. Accumulibacter, Acinetobacter, Dechloromonas, Competibacter, and Defluviicoccus) in the A2/O reactor and nitrification performance (e.g. Nitrosomonas, Nitrosomonadaceae and Nitrospira) in the MBBR. Carbon source was demonstrated as the key point to stimulate the biodiversity and bioactivity related to DPR potential, and the operational strategy of carbon source addition was proposed based on the utilizing rules of HAc and HPr.

Operational optimization of a three-stage nitrification moving bed biofilm reactor (NMBBR) by obtaining enriched nitrifying bacteria: Nitrifying performance, microbial community, and kinetic parameters.

A two-sludge system consisting of A2/O (Anaerobic Anoxic Oxic) and NMBBR (Nitrification Moving Bed Biofilm Reactor) was developed. Stable and efficient denitrifying phosphorus removal can be realized by high-efficiency utilization of carbon sources in A2/O reactor with the electron acceptors of NOx--N in a three-stage NMBBR (consisting of N1, N2, N3). The three-stage NMBBR was successfully started within 18 days without additional inoculation sludge. Then a long-term operation (22-120 d) for the optimization of nitrifying performance, microbial community, and kinetic parameters was investigated. The biofilm characteristics (MLSS and biofilm thickness) and real-time control parameters (DO and pH) initially revealed the differences of three stages, while FISH results confirmed the optimizing nitrifying bacteria populations including AOB, Nitrobacteria and Nitrospira (N1: 5.94 ±â€¯0.12%; N2: 8.26 ±â€¯0.42%; N3: 10.06 ±â€¯0.27% on day 50), basically consisting with the qPCR results (N1: 4.05%; N2: 8.04%; N3: 14.14%). The specific ammonium oxidation rate (SAOR: 3.24-10.02 mg/(gMLSS·h)) and temperature coefficient (θ: 1.008-1.011) based on temperature variation (15-35 °C) exhibited a strong resistant ability to low temperature operation. Moreover, half-saturation constants (KN,AOB, KN,NOB, KO,AOB and KO,NOB) fitted by Monod equation proved that DO diffusion played a significant role than substrate utilization (NH4+-N and NO2--N), but the diffusion resistance was negligible for flocs size smaller than 70 µm. Additionally, the dominant NOB (mainly Nitrospira) due to a higher KN,NOB and KO,NOB was more sensitive to mass transfer and diffusion resistance, which was helpful to understand the microbial competition for short-cut nitrification between AOB and NOB. Based on the above mechanism analysis, the MBBR optimization for the design and operation was put forward.

Bioaugmentation of low C/N ratio wastewater: Effect of acetate and propionate on nutrient removal, substrate transformation, and microbial community behavior.

The effect of various acetate/propionate ratios (1:0, 2:1, 1:1, 1:2, and 0:1) in a two-sludge A2/O - MBBR process was investigated. Results showed that the increased propionic/acetic ratios exerted indistinctive impact on COD (91.21-93.44%) and P (92.23-93.87%) removals, but high P content (7.42%) accelerated sludge granulation proved by SEM and EDS. Acetate favored N removal (79.52%-82.92%) with higher PURA (3.53-4.06 mgP/(gVSS·h)), while the removal declined (75.14%) due to lower PHB/PHA ratio (52.3-57.8%) with propionate as sole carbon source. Based on the stoichiometry-based quantifications, PAOs were the major contributors to nutrient removal although certain GAOs and OHO participated. The mixture ratio of 1:1 facilitated microbial diversity (995 OTUs), Rhodobacteraceae (25.63%) was responsible for high-efficient denitrifying phosphorus removal, while Defluviicoccus (15.23%) contributed to nitrite accumulation was the main competitiveness with PAOs. Nitrospira, Nitrosomonas, and Nitrosomonadaceae responsible for nitrification accounted for 7.73%, 27.11%, and 38.76% in MBBR, but the biodiversity decreased owing to the enrichment and purification.

[Temporal and Spatial Variations in the Conductivity in Different Media in Taihu Lake, China].

Conductivity is an important parameter for characterizing dissolved solids and salinity in water, and is also one of the routinely measured parameters in water quality monitoring. To reveal temporal and spatial variations in conductivity in different media in Taihu Lake, historical data (1980-2009) were collected and field monitoring data (2009-2018) were analyzed. The results indicated that water conductivity in Taihu Lake has shown a significant increasing trend over the past 40 years and diverged in 1996-1997. Conductivity values increased from (239.43±70.60)µS·cm-1 in the period 1980-1996 to(477.31±23.47)µS·cm-1 in the present day, with an average annual increase of 10.40 µS·(cm·a)-1. Spatially, the conductivity of water in the northwest part of the lake was significantly higher than the southeast part. These changes in conductivity are dominated by changes in major ions, and the contribution of nitrogen was essentially negligible. Human activities in the basin have been the main factors causing changes in water conductivity. In addition, conductivity is significantly affected by seasonal runoff. Compared with the water, the conductivity of the surface sediments and pore water (0-10 cm) in the northwest part of the lake were lower than in the southeast part, while this trend was opposite in the deeper sediments (>10 cm). The conductivity of the sediment and pore water were no different between surface (0-10 cm) and deeper (>10 cm) sediments in the northwest lake, while these were higher in the surface sediments in the southeast part of the lake. Sediment conductivity was positively correlated with organic matter (P<0.01) and was negatively correlated with pH (P<0.05). This indicated that organic matter promotes the activation and migration of metal ions, which are more activated under acidic conditions. We found that conductivity in the surface sediments and pore water (0-10 cm) were significantly positively correlated with conductivity in the overlying water (P<0.01). In contrast, the conductivity of overlying water was not correlated with the conductivity of deeper sediments and pore water (>10 cm). These patterns indicated that surface sediments and pore water have a significant effect on the conductivity of overlying waters. In addition, there was a significant positive correlation between the conductivity of sediment and pore water (P<0.01) within the entire sedimentary section (0-50 cm), indicating efficiency ion-exchange between the two. The interaction between sediment and pore water was generally stronger than their interaction with the overlying water.

Disolved organic matter (DOM) removal from bio-treated coking wastewate using a new polymeric adsorbent modified with dimethylamino groups.

In the current study a new recyclable aminated hyper-cross-linked polymeric adsorbent (A-HPA) was prepared for effective removal of DOM from BTCW. Possibly benefited from its unique structure of polystyrene matrix, sufficient aminated groups and high specific surface area, A-HPA could remove DOM from BTCW through the synergetic effect of π-π interactions, acid-base interactions and micropore filling, and exhibited the highest removal efficiency than the other adsorbents. Moreover, the exhausted A-HPA was amenable to effective regeneration by using acid and alkaline solution, allowing for repeated use with a constant removal efficiency. Field application of continuous 3-year fixed-bed runs demonstrated that A-HPA is capable of effectively removing DOM from BTCW with no significant capacity loss, and the treated effluent can be partially used as recycled water in production. All the above results demonstrated that A-HPA adsoption could serve as a good choice for the advanced treatment of bio-treated sewage effluent.

Effect of cyclic aeration on fouling in submerged membrane bioreactor for wastewater treatment.

Due to the inefficiency of aeration measures in preventing fouling by soluble and colloidal particles. The effect of alternating high/low cyclic aeration mode on the membrane fouling in the submerged membrane bioreactor was studied by comparing to fouling in a constant aeration mode. Results indicated a higher overall fouling rate in the cyclic aeration mode than in the constant aeration. However, a higher percentage of reversible fouling was observed for the cyclic aeration mode. The membrane permeability can be more easily recovered from physical cleaning such as backwashing in the cyclic aeration mode. The activated sludge floc size distribution analysis revealed a floc destruction and re-flocculation processes caused by the alternating high/low aeration. The short high aeration period could prevent the destruction of strong strength bonds within activated sludge flocs. Therefore, less soluble and colloidal material was observed in the supernatant due to the preservation of the strong strength bonds. The weak strength bonds damaged in the high aeration period could be recovered in the re-flocculation process in the low aeration period. The floc destruction and re-flocculation processes were suggested to be the main reason for the low irreversible fouling in the cyclic aeration mode.