Biological Phosphorus Removal Research Articles

Enhanced biological phosphorus removal by high concentration powder carrier bio-fluidized bed (HPB): Phosphorus distribution, cyclone separation, and metagenomics

This study provides a comparative investigation of phosphorus removal between anaerobic-anoxic-oxic (AAO) and high-concentration powder carrier bio-fluidized bed (HPB) in the same full-scale wastewater treatment plant. The results showed that the total phosphorus removal of HPB was 71.45%–96.71%. Compared with AAO, the total phosphorus removal of HPB can be increased by a maximum of 15.73%. The mechanisms of enhanced phosphorus removal by HPB include the followings. Biological phosphorus removal was significant. The anaerobic phosphorus release capacity of HPB was enhanced and polyphosphate (Poly-P) in the excess sludge of HPB was 1.5 times higher than that of AAO. The relative abundance of Candidatus Accumulibacter was 5 times higher than that of AAO, and oxidative phosphorylation and butanoate metabolism were enhanced. The analysis of phosphorus distribution showed that cyclone separation increased the chemical phosphorus precipitation (Chem-P) in the excess sludge by 16.96% to avoid accumulation in the biochemical tank. The phosphorus adsorbed by extracellular polymeric substance (EPS) in the recycled sludge was stripped, and the EPS bound-P in the excess sludge increased by 1.5 times. This study demonstrated the feasibility of HPB to improve the phosphorus removal efficiency for domestic wastewater.

Effect of return activated sludge diversion ratio on phosphorus removal performance in side-stream enhanced biological phosphorus removal (S2EBPR) process

In this study, a lab-scale continuous flow side-stream enhanced biological phosphorus (P) removal (S2EBPR) reactor was operated for 247 days treating synthetic wastewater with influent carbon to phosphorus (C/P) ratio of 25.0 g COD/g P and influent PO43–-P of 7.4 ± 0.3 mg P/L. The effect of the return activated sludge (RAS) diversion ratio on S2EBPR reactor was investigated by comparing P removal performance, microbial activity, and community structure. The results showed that the RAS diversion ratio of 8.0%, by yielding a side-stream sludge retention time (SRTSS) of ∼60 h, resulted in the lowest effluent PO43–-P concentration of 0.5 ± 0.3 mg P/L. The results of in situ process profiles and ex situ P release and uptake batch tests under different RAS diversion conditions showed that the more anaerobic P release was obtained in the side-stream reactor, the higher the P removal efficiency and EBPR activity were achieved. The stoichiometric ratios observed in EBPR activity tests indicated a polyphosphate accumulating organisms (PAOs) metabolism mainly dependent on the glycolysis pathway. The results of microbial ecology analysis revealed that the optimized SRTSS would give a competitive advantage to PAOs in the S2EBPR process. By obtaining statistically reliable results, this study would provide guidance for wastewater treatment plants to achieve optimal P removal performance in S2EBPR configuration.

Insights on biological phosphorus removal with partial nitrification in single sludge system via sidestream free ammonia and free nitrous acid dosing

The sidestream sludge treatment by free ammonium (FA)/free nitrous acid (FNA) dosing was frequently demonstrated to maintain the nitrite pathway for the partial nitrification (PN) process. Nevertheless, the inhibitory effect of FA and FNA would severely influence polyphosphate accumulating organisms (PAOs), destroying the microbe-based phosphorus (P) removal. Therefore, a strategic evaluation was proposed to successfully achieve biological P removal with a partial nitrification process in a single sludge system by sidestream FA and FNA dosing. Through the long-term operation of 500 days, excellent phosphorus, ammonium and total nitrogen removal performance were achieved at 97.5 ± 2.6 %, 99.1 ± 1.0 % and 75.5 ± 0.4 %, respectively. Stable partial nitrification with a nitrite accumulation ratio (NAR) of 94.1 ± 3.4 was attained. The batch tests also reported the robust aerobic phosphorus uptake based on FA and FNA adapted sludge after exposure of FA and FNA, respectively, suggesting the FA and FNA treatment strategy could potentially offer the opportunity for the selection of PAOs, which synchronously have the tolerance to FA and FNA. Microbial community analysis suggested that Accumulibacter, Tetrasphaera, and Comamonadaceae collectively contributed to the phosphorus removal in this system. Summarily, the proposed work presents a novel and feasible strategy to integrate enhanced biological phosphorus removal (EBPR) and short-cut nitrogen cycling and bring the combined mainstream phosphorus removal and partial nitrification process closer to practical application.

Reduction of SARS-CoV-2 by biological nutrient removal and disinfection processes in full-scale wastewater treatment plants

Detection of SARS-CoV-2 RNA in wastewater poses people's concerns regarding the potential risk in water bodies receiving wastewater treatment effluent, despite the infectious risk of SARS-CoV-2 in wastewater being speculated to be low. Unlike well-studied nonenveloped viruses, SARS-CoV-2 in wastewater is present abundantly in both solid and liquid fractions of wastewater. Reduction of SARS-CoV-2 in past studies were likely underestimated, as SARS-CoV-2 in influent wastewater were quantified in either solid or liquid fraction only. The objectives of this study were (i) to clarify the reduction in SARS-CoV-2 RNA during biological nutrient removal and disinfection processes in full-scale WWTPs, considering the SARS-CoV-2 present in both solid and liquid fractions of wastewater, and (ii) to evaluate applicability of pepper mild mottle virus (PMMoV) as a performance indicator for reduction of SARS-CoV-2 in WWTPs. Accordingly, large amount of SARS-CoV-2 RNA were partitioned in the solid fraction of influent wastewater for composite sampling than grab sampling. When SARS-CoV-2 RNA in the both solid and liquid fractions were considered, log reduction values (LRVs) of SARS-CoV-2 during step-feed multistage biological nitrogen removal (SM-BNR) and enhanced biological phosphorus removal (EBPR) processes ranged between>2.1–4.4 log and did not differ significantly from those in conventional activated sludge (CAS). The LRVs of SARS-CoV-2 RNA in disinfection processes by ozonation and chlorination did not differ significantly. PMMoV is a promising performance indicator to secure reduction of SARS-CoV-2 in WWTPs, because of its higher persistence in wastewater treatment processes and abundance at a detectable concentration even in the final effluent after disinfection.

Microbiome assembly mechanism and functional potential in enhanced biological phosphorus removal system enriched with Tetrasphaera-related polyphosphate accumulating organisms

Tetrasphaera-related polyphosphate accumulating organisms (PAOs) are the key functional guilds for enhanced biological phosphorus removal (EBPR) systems. Their biomass enrichment can be enhanced by the nitrification inhibitor allylthiourea (ATU). However, the underlying assembly mechanism and the functional potential of the EBPR microbiome regulated by ATU are unclear. This study investigates the effect of ATU on microbiome assembly and functional potential by closely following the microbiota dynamics in an EBPR system enriched with Tetrasphaera-related PAOs for 288-days before, during and after ATU addition. The results showed that ATU addition increased microbiota structural similarity and compositional convergence, and enhanced determinism in the assembly of EBPR microbiome. During exposure to ATU, Tetrasphaera-related PAOs were governed by homogeneous selection and the dominant species revealed by 16S rRNA gene-based phylogenetic analysis shifted from clade III to clade I. Meanwhile, ATU supply promoted significant enrichment of functional genes involved in phosphate transport (pit) and polyphosphate synthesis and degradation (ppk1 and ppk2), whereas both Nitrosomonas and ammonia monooxygenase-encoding genes (amoA/B/C) assignable to this group of nitrifying bacteria decreased. Moreover, ATU addition relieved the significant abundance correlation between filamentous bacteria Ca. Promineofilum and denitrifying Brevundimonas (FDR-adjusted P < 0.01), damaging their potential synergic or cooperative interactions, thus weakening their competitiveness against Tetrasphaera-related PAOs. Notably, ATU withdrawn created opportunistic conditions for the unexpected explosive growth and predominance of Thiothrix filaments, leading to a serious bulking event. Our study provides new insights into the microbial ecology of Tetrasphaera-related PAOs in EBPR system, which could guide the establishment of an efficient microbiota for EBPR.

Variations in the morphological phosphorus in a full‐scale A2O + MBR process with heavy chemical P removal addition dosing

AbstractThe removal of biological phosphorus (P) removal along with chemical P removal additions is significantly important role in removing P at full‐scale wastewater treatment plants (WWTPs). Few research groups have recently reported the use of P forms in these WWTPs. The current study mainly presents the varied forms of morphological phosphorus and the fate of chemical P removal agents in a full‐scale WWTP that has adopted the A2O + MBR process. With time, the TP concentration in the liquid phase and the solid phase reaches the minimum (0.27 mg/L) and maximum values (1.75 mg/g), respectively. At this point, the TP concentration at the end of the aerobic and membrane pool becomes nearly constant. This indicates the complete removal of effluent TP from in the system. The heavy chemical P removal and addition dosing result in Al–P being the predominant P form in the solid phase. The fate of the chemical P removal and agents was determined by investigating the valences of the surface elements in freeze‐dried MLSS at the membrane pool.

Pilot-scale aerobic granular sludge reactors with granular activated carbon for effective nitrogen and phosphorus removal from domestic wastewater

Aerobic granular sludge (AGS) is a breakthrough biotechnology of 21st century and an innovative alternative to activated sludge for treating wastewater. Concerns on long-start up periods for development of AGS and stability of granules are impeding its widespread implementation for treating low-strength domestic wastewater especially in tropical climate conditions. Addition of nucleating agents have been shown to improve development of AGS while treating low-strength wastewaters. There are no previous studies on AGS development and biological nutrient removal (BNR) in the presence of nucleating agents during treatment of real domestic wastewater. This study investigated AGS formation and BNR pathways while treating real domestic wastewater in a 2 m3 pilot-scale granular sequencing batch reactor (gSBR) operated without and with granular activated carbon (GAC) particles. The gSBRs were operated under tropical climate (T ≈ 30 °C) for >4-years to evaluate the effect of GAC addition on granulation, granular stability and BNR at pilot-scale. Formation of granules was observed within 3 months. MLSS values of 4 and 8 g/L were recorded within 6 months in gSBRs without and with GAC particles, respectively. The granules had an average size of 1.2 mm and SVI5 of 22 mL/g. Ammonium was mainly removed through nitrate formation in the gSBR without GAC. But, ammonium was removed by short-cut nitrification via nitrite due to washout of nitrite oxidizing bacteria in the presence of GAC. Phosphorus removal was much higher in gSBR with GAC due to the establishment of enhanced biological phosphorus removal (EBPR) pathway. After 3 months, the phosphorus removal efficiencies were at 15 % and 75 %, respectively, without and with GAC particles. The addition of GAC led to moderation in bacterial community and enrichment of polyphosphate-accumulating organisms. This is the first ever report on pilot-scale demonstration of AGS technology in the Indian sub-continent and GAC addition on BNR pathways.

Study on specific strategies of controlling or preventing sludge bulking in S2EBPR process

Side-stream enhanced biological phosphorus removal (S2EBPR) process was regarded as a promising innovative modification and emerging alternative to EBPR configurations, and more attention should also be paid to controlling and preventing sludge bulking. In this study, a pair of lab-scale continuous flow anaerobic-anoxic-aerobic (A²/O) and S2EBPR reactors were synchronously started and operated for 150 days. After 54 days of adjustment and maintenance, the reactors were successfully started. However, considering that the sludge bulking problem in the reactors occurred successively, the desired phosphorus removal performance were not secured. The causes of the sludge bulking in A²/O and S2EBPR reactors were investigated by comparing the performance and stability, ex situ EBPR metabolic activity, extracellular polymeric substances (EPS), sludge settling characteristics, and microbial community under different operating conditions. The results of the experiment indicated that, under the same conditions (including influent characteristics, environmental and operational conditions, etc.), the stability of the system in regards to sludge bulking was ranked in the following order: side-stream ratio of 6.7 % S2EBPR > side-stream ratio of 10.0 % S2EBPR > A²/O > side-stream ratio of 13.3 % S2EBPR. The study of sludge bulking in the continuous flow reactors demonstrated that the side-stream ratio adjustment of S2EBPR could be used as an effective strategy to control or prevent sludge bulking.

Chemical composition of organic acid digest from a municipal wastewater treatment plant and chemical modeling of nuisance struvite formation and phosphorus recovery as brushite

Modern municipal wastewater treatment often includes an anaerobic digestion step with a hydraulic retention time of ~1.5 days before the main anaerobic digestors. This step, often termed the organic acid digester or “acid digester” for short, produces a sludge characterized by lower pH, higher volatile fatty acid (VFA) concentrations, and high soluble phosphorus (P) concentrations, particularly if fed sludge from an enhanced biological phosphorus removal process. Here, the analysis of major ions, organic and inorganic, in the organic acid digest from a wastewater treatment plant (WWTP), Nine Springs, Madison, Wisconsin (USA), is reported for a period of 13 weeks. The bioengineered origin of this organic acid digest makes its composition unlike natural waters of any kind. From the chemical composition, the course of subsequent processes can be predicted by chemical modelling. Methanogenesis using VFAs as substrates is predicted to raise digest pH to the point where struvite is expected to form, and nuisance struvite is routinely observed at Nine Springs. Addition of calcium hydroxide to organic acid digest is expected to precipitate ~90% of soluble P from solution as the calcium phosphate mineral brushite at near neutral pH, confirmed by a pilot plant at Nine Springs. This study demonstrates the possible application of chemical analysis and chemical modelling in wastewater systems to predict and possibly adaptively manage waste streams to curb nuisance struvite formation and predict P recovery, and could be refined through broader testing and application at other wastewater treatment facilities.

Confronting Assumptions of Phosphorus-Accumulating Organisms and Glycogen-Accumulating Organisms: Peaceful Coexistence in a Carbon-Limited Sidestream EBPR Demonstration

Enhanced biological phosphorus removal (EBPR) is strongly influenced by the influent ratio of readily biodegradable carbon to soluble phosphorus due to the preferences of phosphorus-accumulating organisms (PAO). The sidestream EBPR (S2EBPR) process redirects a portion of return activated sludge (RAS) to a sidestream fermenter, increasing the availability of biodegradable carbon. In this study, we assessed the performance and microbial community structure of a full-scale S2EBPR demonstration supplemented with external carbon dosing. By the end of the 10 month study period, the demonstration achieved a median effluent orthophosphate of 0.3 mg/L. The microbial community consisted of a common core microbiome in the RAS fermenter, EBPR basin, and nitrification basin. The most abundant PAO detected were Ca. “Dechloromonas phosphorivorans”, while the canonical PAO Ca. “Accumulibacter” and Tetrasphaera were observed in lower relative abundance. In addition to non-canonical PAO enrichment, the glycogen-accumulating organism Ca. “Competibacter” proliferated throughout the study and at some points outnumbered PAO taxa by 30 to 1 with no tangible performance impacts. This study provides insights into successful S2EBPR implementation at a low-carbon facility and improves our understanding of microbial community structure and key PAO and GAO in S2EBPR systems.

Growing an Enhanced Culture of Polyphosphate-Accumulating Organisms to Optimize the Recovery of Phosphate from Wastewater

Having certain bacteria called phosphorus-accumulating organisms (PAOs) is important for getting rid of phosphorus (P) in wastewater from homes. This happens in a process called enhanced biological phosphorus removal (EBPR), where PAOs are active in activated sludge. To design and make EBPR processes work better, we need to have an in-depth understanding of how PAOs work. The best way to learn about them is by studying them in a laboratory. This study undertook to culture these microorganisms in the laboratory. A University of Cape Town membrane bioreactor (UCTMBR) activated sludge (AS) system was used to grow the microorganisms and see how well it worked. This paper looked at what type of substrate PAOs like best, either acetate or propionate, and how providing them with more of their preferred substrate affects how they grow. During the process, it was observed that P was not released or taken up significantly when acetate was added to the influent. The levels were consistently low at around 5.74 ± 4.47 mgP/L infl (release) and 19.9 ± 7.17 mgP/L infl (uptake). The signs become much better when propionate was used instead of acetate. When the amount of propionate in the influent was increased from 50% to 76% (as a percentage of influent total chemical oxygen demand), the amount of P released went up to 155 ± 17.7 mgP/L infl, and the amount of P taken up went up to 213.7 ± 11.4 mgP/L infl. The proof given indicated that propionate is preferred by PAOs. This study found that when more propionate was added to the wastewater, the concentration of PAO biomass went up. This was shown by certain signs that PAOs display when they are present. Results presented in this journal article emanate from an MSc Thesis (Thela, 2022) published in open-source UCT.

Total phosphorus contents currently found in the raw wastewater – Problems and technical solutions for its removal in full-scale wastewater treatment plants

The eutrophication of water bodies caused by the release of treated wastewater rich in total phosphorus (TP) is a worldwide problem. In this work a full-scale wastewater treatment plant (WWTP) was developed with an enhanced biological removal of phosphorus (EBPR) process for the TP removal in wastewater, despite high levels in raw effluent. The microbial community involved showed a low number of polyphosphates accumulating organisms (PAOs) and consequently a low TP level biological removal. The use of anaerobic, aerobic and anoxic zones in the WWTP, followed by the flocculation dropped the TP level in the treated wastewater to avoid the eutrophication was the water bodies. This study highlights strategies to improve the phosphorous removal in wastewaters, discussing that the low BOD/TP ratio is associated to the decreasing of PAOs abundance in the WWTPs, which in turn reduce the efficiency of the EBPR technology. Considering this, a complementary treatment was proposed to improve TP removal and avoid the harmful impacts on the receiving water bodies.

Benefits and drawbacks of integrating a side-stream sludge fermenter into an A2O system under limited COD conditions

The implementation of a side-stream sludge fermenter (SSSF) has been identified as a possible solution to improve the performance of an anaerobic/anoxic/aerobic (A2O) configuration when treating low COD wastewater. This study systematically evaluated the effects of incorporating a SSSF into an A2O configuration (side-stream enhanced biological phosphorus removal, S2EBPR) for P/N/COD removal under a limited influent COD (CODINF) condition. The performance of the S2EBPR (with the SSSF receiving 6% of the recycled activated sludge and operating with a hydraulic retention time (HRT) of 2.4 d) and A2O were compared under the same limited CODINF (350 mg/L) condition. S2EBPR improved the amount of P removed (26.6%) under a low influent COD/P of only 26.3 compared with A2O of 32.6, and enhanced denitrification (11%) without compromising full ammonium and COD removal. However, the PLOAD to the plant increased due to the P-release in SSSF, resulting in higher effluent P concentration. The methane and energy recovery indexes were around 45% lower than those of A2O. Sequencing analysis revealed a high abundance of PAO in accordance to its higher P removal. This study represents a comprehensive evaluation of the S2EBPR configuration and provides an assessment of its suitability.

Simultaneous phosphorus removal and sludge reduction in continuous-flow reactor with granules under long sludge retention time

The simultaneous phosphorus (P) removal and sludge reduction by extending the sludge retention time (SRT) in the continuous-flow reactor (CFR) with enhanced biological phosphorus removal (EBPR) granules were investigated in this study. While the system operated without sludge discharge for 60 days, the COD and P removal efficiencies and settling ability of granules deteriorated obviously. Meanwhile, the protein content increased and the sludge production reduced gradually during this period due to the decrease of PAOs activities. Then, some sludge was discharged every day during the day 61–180, and the performance of CFR and the settling ability of granules recovered gradually to an excellent level. The sludge production and sludge yield were 1.34 g day−1 and 0.11 gMLSS gCOD−1 during the recovery and stable operation period, respectively. Although about 60% sludge reduction was obtained, excellent P removal was demonstrated simultaneously. Hence, sludge minimization and excellent P removal were successfully coupled by extending SRT in CFR with EBPR granules. The results of Illumina MiSeq sequencing showed that the fermentative bacterium increased after extending the SRT, which played a key role in sludge reduction.

Improved Biological Phosphorus Removal under Low Solid Retention Time Regime in Full-Scale Sequencing Batch Reactor

Enhanced biological phosphorus removal (EBPR) is an obscure but economical and helpful technology for removing phosphorus biologically from wastewater. A 3-MLD capacity pre-anoxic selector-attached sequencing batch reactor (SBR) treated municipal wastewater from the residents of IIT Roorkee. The treatment in the plant satisfied the effluent discharge standards in all respects except phosphorus, observed during an intensive two-year study. An elaborated 80-day study was performed to enhance and improve the plant’s performance in terms of phosphorus removal specifically, with run 1: solid retention times (SRT) reduced from 56 to 20 days (t = 35 d), run 2: lowering the diffuser’s running time from 15 min to 10 min in anoxic cum anaerobic selector chambers (dissolved oxygen (DO) concentration reduced to &lt;0.15 mg/L) along with reducing SRT to 15 days (t = 25 d), and run 3:intensive reduction in SRT to ≤10 days (t = 20 d). During run 3, the increment in the enhanced biological phosphorus removal (EBPR) efficiency was three times that of the initial run (ηmax~65%) with a readily biodegradable chemical oxygen demand to total phosphorus ratio (rbCOD/TP) of 7.8. The 16SrRNA sequencing revealed the microbial community structure before and after the changes in SRT and EBPR efficiencies, to correlate the biochemical processes and functional organisms.

Optimization of Simultaneous Nutrients and Chemical Oxygen Demand Removal from Anaerobically Digested Liquid Dairy Manure in a Two-Step Fed Sequencing Batch Reactor System Using Taguchi Method and Grey Relational Analysis.

The technological development for efficient nutrient removal from liquid dairy manure is critical to a sustainable dairy industry. A nutrient removal process using a two-step fed sequencing batch reactor (SBR) system was developed in this study to achieve the applicability of simultaneous removal of phosphorus, nitrogen, and chemical oxygen demand from anaerobically digested liquid dairy manure (ADLDM). Three operating parameters, namely anaerobic time:aerobic time (min), anaerobic DO:aerobic DO (mg L-1), and hydraulic retention time (days), were systematically investigated and optimized using the Taguchi method and grey relational analysis for maximum removal efficiencies of total phosphorus (TP), ortho-phosphate (OP), ammonia-nitrogen (NH3-N), total nitrogen (TN), and chemical oxygen demand (COD) simultaneously. The results demonstrated that the optimal mean removal efficiencies of 91.21%, 92.63%, 91.82%, 88.61%, and 90.21% were achieved for TP, OP, NH3-N, TN, and COD at operating conditions, i.e., anaerobic:aerobic time of 90:90 min, anaerobic DO:aerobic DO of 0.4:2.4 mg L-1, and HRT of 3 days. Based on analysis of variance, the percentage contributions of these operating parameters towards the mean removal efficiencies of TP and COD were ranked in the order of anaerobic DO:aerobic DO > HRT > anaerobic time:aerobic time, while HRT was the most influential parameter for the mean removal efficiencies of OP, NH3-N, and TN followed by anaerobic time:aerobic time and anaerobic DO:aerobic DO. The optimal conditions obtained in this study are beneficial to the development of pilot and full-scale systems for simultaneous biological removal of phosphorus, nitrogen, and COD from ADLDM.

A comparative study of different iron minerals on phosphorus capture from municipal wastewater and subsequent recovery as vivianite through acidogenic fermentation

Exploiting phosphorus resources from waste streams such as municipal wastewater is essential for their recycling and utilization. However, common practice on phosphorus recovery via main-stream biological phosphorus removal and side-stream phosphorus precipitation still faces great challenges such as organic mineralization induced CO2 emission and aeration caused energy consumption. In this work, ferrihydrite and magnetite were respectively dosed into bioflocculation organic carbon capture system to comprehensively evaluate their potential improvements on phosphorus recovery from municipal wastewater. Results showed that ferrihydrite would outcompete magnetite on phosphorus capture, by increasing TP removal efficiency from 17.5% to 91.2% while maintaining a high organic carbon capture efficiency of about 50%. Although both iron minerals were favored for improving sludge settling performance, the potential toxicity of magnetite was higher than that of ferrihydrite. Chemical precipitation and adsorption are the main pathways for phosphorus removal by iron minerals. Subsequent anaerobic fermentation showed that ferrihydrite bounded phosphorus was mainly transformed to vivianite while magnetite captured phosphorus was released into the liquid. Surprisingly, ferrihydrite was favored for the volatile fatty acids rather than biogas production, with an average yield of 523.2 mg/g volatile suspended solids. This work might be valuable for exploring a more sustainable value-added resource recovery paradigm.

Aerobic granular sludge formation and stability in enhanced biological phosphorus removal system under antibiotics pressure: Performance, granulation mechanism, and microbial successions

Wastewater containing antibiotics can pose a significant threat to biological wastewater treatment processes. This study investigated the establishment and stable operation of enhanced biological phosphorus removal (EBPR) by aerobic granular sludge (AGS) under mixed stress conditions induced by tetracycline (TC), sulfamethoxazole (SMX), ofloxacin (OFL), and roxithromycin (ROX). The results show that the AGS system was efficient in removing TP (98.0%), COD (96.1%), and NH4+-N (99.6%). The average removal efficiencies of the four antibiotics were 79.17% (TC), 70.86% (SMX), 25.73% (OFL), and 88.93% (ROX), respectively. The microorganisms in the AGS system secreted more polysaccharides, which contributed to the reactor's tolerance to antibiotics and facilitated granulation by enhancing the production of protein, particularly loosely bound protein. Illumina MiSeq sequencing revealed that putative phosphate accumulating organisms (PAOs)-related genera (Pseudomonas and Flavobacterium) were enormously beneficial to the mature AGS for TP removal. Based on the analysis of extracellular polymeric substances, extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, and microbial community, a three-stage granulation mechanism was proposed including adaption to the stress environment, formation of early aggregates and maturation of PAOs enriched microbial granules. Overall, the study demonstrated the stability of EBPR-AGS under mixed antibiotics pressure, providing insight into the granulation mechanism and the potential use of AGS for wastewater treatment containing antibiotics.

Study on influencing parameters and long-term operation of electrocoagulation phosphorus removal from small rural domestic sewage.

Excessive discharge of phosphorus can produce eutrophication in aquatic environments, damaging public health, the living environment, and the economy. The conventional mechanical-biological phosphorus removal methods are not suitable for small rural domestic sewage due to the features of small scale, scattered distribution, intermittent emission, and large fluctuation. This work evaluated electrocoagulation (EC) with industrial steel as electrodes on small rural domestic sewage. Results showed that the best performance was achieved at a current density of 1 mA/cm2, electrode distance of 2 cm, electrode number of 2, pH of 7, and Hydraulic Retention Time of 30 min, respectively. Under optimum conditions, the EC process removed 93.91% phosphorus while consuming around 0.25 kWh/m3 of electricity. In addition, the electrode passivation of EC was further investigated; the long-term research found that the phosphorus removal efficiency only decreased by 4.34% after 10 days of continuous flow operation, and the operational energy consumption was 0.07 kWh/m3 at a Cl- concentration of 500 mg/L.

On-site performance evaluation of a 1,000-litre microbial fuel cell system using submergible multi-electrode modules with air-cathodes for sustainable municipal wastewater treatment and electricity generation.

The reliability of a microbial fuel cell (MFC) system was tested on an industrial scale by operating a 1,000-L single-chamber system under real conditions at a municipal wastewater treatment plant (WWTP) over a 6-month period. Submergible multi-electrode modules with large-scale grid-segmented gas diffusion cathodes with activated carbon as a catalyst were used. Maximum power densities normalised to the cathode area were above 100 mW m-2Cat. Fluctuating chemical and physical wastewater characteristics of the influent had reversible effects on MFC performance in terms of energetic efficiency. Thereby, the composition of the chemical oxygen demand (COD) fractions changes only insignificantly and the concentration of readily biodegradable (SS) required for the enhanced biological phosphorus removal (EBPR) process or upstream denitrification was reduced by 41 ± 10 mg L-1 (37 ± 2% of inflow SS).