Phosphorus Removal Process Research Articles

Enhanced tetracycline removal in sequencing batch reactors by bioaugmentation using tetX-carrying strains: Efficiency and mechanisms

Tetracyclines antibiotics (TCs) pose notable environmental challenges due to their persistence in the effluent of wastewater treatment systems. Bioaugmentation offers a promising strategy for their removal, yet information is still very limited. This study aimed to assess the efficacy of bioaugmentation using wild-type (Sphingobacterium sp. WM1) and engineered tetX-carrying (PUC-tetX) strains for enhancing tetracycline (TC) removal in sequencing batch reactors (SBRs). Bioaugmentation mitigated TC's inhibitory effects on denitrification and phosphorus removal processes within SBR systems. Specifically, strain WM1 outperformed strain PUC-tetX in removing TC from sludge and maintained a longer viability. TC addition (500 μg/L, at an environmentally relevant concentration) and bioaugmentation did not significantly impact overall microbial community diversity. Notably, the introduction of these exogenous bacteria markedly increased the abundance of the tetX gene, correlating with the increase in TC degradation. Interestingly, MAGs associated with the Chloroflexi phylum in bioaugmented reactors showed the transfer of the tetX gene to autochthonous bacterial species, promoting TC removal capability. These findings underscored the potential of bioaugmentation to enhance antibiotic removal and provided insights into the dynamics of ARGs and tetX gene within activated sludge systems.

Unveiling the potential role of virus-encoded polyphosphate kinases in enhancing phosphorus removal in activated sludge systems

While microbial phosphate removal in activated sludge (AS) systems has been extensively studied, the role of viruses in this process remains largely unexplored. In this study, we identified 149 viral auxiliary metabolic genes associated with phosphorus cycling from 2,510 viral contigs (VCs) derived from AS systems. Notably, polyphosphate kinase 1 (ppk1) and polyphosphate kinase 2 (ppk2) genes, which are primarily responsible for phosphate removal, were found in five unclassified VCs. These genes exhibited conserved protein structures and active catalytic sites, indicating a pivotal role of viruses in enhancing phosphorus removal. Phylogenetic analysis demonstrated a close relationship between viral ppk genes and their bacterial counterparts, suggesting the occurrence of horizontal gene transfer. Furthermore, experimental assays validated that viral ppk genes enhanced host phosphate removal capabilities. VCs carrying ppk genes were observed across diverse ecological and geographical contexts, suggesting their potential to bolster host functions in varied environmental and nutrient settings, spanning natural and engineered systems. These findings uncover a previously underappreciated mechanism by which viruses enhance phosphate removal in wastewater treatment plants. Overall, our study highlights the potential for leveraging virus-encoded genes to improve the efficiency of biological phosphorus removal processes, offering new insights into the microbial ecology of AS systems and the role of viruses in biogeochemical cycling.

Synergistic phosphorus removal mechanism of Tetrasphaera enrichment in a micro-pressure swirl reactor

To investigate the effect of Tetrasphaera’s enrichment on phosphorus removal mechanism, three micro-pressure swirl reactor (MPSR) groups were used to experiment on sewage treatment under different SRT (17.2, 50.8, and 68.2 d). Results showed that Tetrasphaera enrichment in the MPSR system was promoted by extending the SRT. After extending the SRT from 17.2 to 68.2 d, the relative abundance of Tetrasphaera increased from 3.1% to 12.1%, and the TP removal efficiency maintained above 92%. The internal circulation results indicated that after extending the SRT, glycogen and polyhydroxybutyrate were co-synthesized during the anaerobic stage, which enhanced the driving force of nutrient removal. Analysis of the microbial composition and functional gene prediction indicated that efficient phosphorus removal can be attributed to the enrichment of Tetrasphaera at long SRT. Overall, the synergistic mechanisms of Tetrasphaera in the organic matter degradation and phosphorus removal processes were integrated into the MPSR.

Electrochemical Approaches for Enhanced Phosphorus Recovery from Synthetic Animal Wastewater: A Comparative Analysis of Response Surface Methodology and Artificial Neural Networks

Electrochemical recovery from animal wastewater is a novel and comprehensive strategy needed in the effort to develop sustainable technology and nutrient delivery solutions, with an emphasis on nitrogen (N) and phosphorus (P) components. This research study addresses critical global environmental sustainability challenges associated with waste by contributing to the evolving conversation on nutrient recovery by using synthetic animal wastewater (SAW) as a substrate. This approach presents a viable solution for wastewater treatment and aligns with the sustainable management of water and energy resources.This research utilized a Box-Behnken experimental design framework formulated with the aid of Minitab Statistical Software. The constructed design laid out a series of experimental runs (comprising 12 distinct conditions, each replicated twice, along with five central points) to explore the influence of three different variables (Mg:Ca molar ratio, N:P molar ratio, and temperature), each at three distinct levels, on phosphorus removal efficiency. The relationship between these three variables and the removal efficiency was then investigated using two distinct modeling methods: Artificial Neural Networks (ANN) and Response Surface Methodology (RSM). ANN, part of machine learning, involves developing a model that learns from experimental data using a network of neurons for training and validation. This allows the ANN to address complex, nonlinear relationships between variables effectively. Conversely, based on statistical analysis, RSM focused on understanding the interactions between the multiple factors, using designed experiments to build a model. Employing both methods leveraged ANN's prowess in handling nonlinearity and RSM's strength in experimental design and optimization, offering a comprehensive approach to enhance P removal efficiency from SAW. The combination of these approaches provided a deep insight into the dynamics of the process, aiding in the effective optimization of the removal response.However, at optimal conditions, the ANN model predicted a higher P removal efficiency (66%) than RSM (45%). The precision of the ANN predictions was reflected in the minimal error margins with Root Mean Squared Error (RMSE) of 2.4, suggesting the robustness of this model in predicting the optimal conditions for P removal compared to the RSM, with an RMSE of 4.7. These findings underscore the potential of employing ANN and RSM to enhance the phosphorus removal process in wastewater treatment applications and show how ANN gives better predictions than RSM. Additional details will be presented at the meeting, including experimental data, regression models, and neural networks.

A novel three-dimensional biofilm-electrode/anoxic-oxic process for nitrogen and phosphorus removal: Performance, mechanism and microbial community

Traditional anoxic-oxic (AO) process cannot meet increasingly high pollutants emission standards in China. In order to improve removal efficiencies of the pollutants and the electron transfer rate, graphite-graphite electrodes and iron carbon fillers were added into AO reactor to form three-dimensional biofilm electrode/anoxic aerobic reactor (3DBER/AO). Removal efficiencies of the pollutants, sludge properties and microbial community structure were investigated under different current intensities. The results showed that microbial activity and removal efficiencies of the pollutants were the maximum, and mass percentage of Fe reached the highest value of 5.11 % under the current of 40 mA. Excessive or insufficient current intensity could lead to a decrease in sludge activity and removal efficiencies of the pollutants. The removal of nitrogen mainly depended on the nitrification and denitrification of microorganisms, and dissolved phosphorus was removed through chemical precipitation. Current intensity affected microbial communities and biosynthesis. AKYH767 and Saccharmonadales were dominant microorganisms in the cathode and anode sludge, respectively, under the current of 40 mA. However, Azospira and Dechlorobacter were dominant microorganisms in the cathode sludge, and Hydrogenophaga was dominant microorganisms in the anode sludge under the current of 60 mA. These microorganisms were closely related to the removal of organic matter, nitrogen and phosphorus. Therefore, microbial community structure and removal efficiencies of the pollutants could be regulated by controlling the current intensity in the 3DBER/AO process.

Optimization of a Novel Engineered Ecosystem Integrating Carbon, Nitrogen, Phosphorus, and Sulfur Biotransformation for Saline Wastewater Treatment Using an Interpretable Machine Learning Approach.

The denitrifying sulfur (S) conversion-associated enhanced biological phosphorus removal (DS-EBPR) process for treating saline wastewater is characterized by its unique microbial ecology that integrates carbon (C), nitrogen (N), phosphorus (P), and S biotransformation. However, operational instability arises due to the numerous parameters and intricates bacterial interactions. This study introduces a two-stage interpretable machine learning approach to predict S conversion-driven P removal efficiency and optimize DS-EBPR process. Stage one utilized the XGBoost regression model, achieving an R2 value of 0.948 for predicting sulfate reduction (SR) intensity from anaerobic parameters with feature engineering. Stage two involved the CatBoost classification and regression model integrating anoxic parameters with the predicted SR values for predicting P removal, reaching an accuracy of 94% and an R2 value of 0.93, respectively. This study identified key environmental factors, including SR intensity (20-45 mg S/L), influent P concentration (<9.0 mg P/L), mixed liquor volatile suspended solids (MLVSS)/mixed liquor suspended solids (MLSS) ratio (0.55-0.72), influent C/S ratio (0.5-1.0), anoxic reaction time (5-6 h), and MLSS concentration (>6.50 g/L). A user-friendly graphic interface was developed to facilitate easier optimization and control. This approach streamlines the determination of optimal conditions for enhancing P removal in the DS-EBPR process.

Nitrate and nitrite utilization during denitrifying phosphorus removal: Electron acceptor preference and feasible process combinations

Denitrifying phosphorus removal (DPR), which is dominated by denitrifying polyphosphate-accumulating organisms (DPAOs), is a promising process for nitrogen and phosphorus removal. Denitrifying glycogen-accumulating organisms (DGAOs) and DPAOs typically coexist in the DPR sludge, complicating the study of DPAOs’ denitrification capacity. In this study, two reactors were fed with nitrate and nitrite during the anoxic phase to cultivate nitrate-DPR and nitrite-DPR sludge. Both reactors yielded high and low DGAO abundance sludges, enabling the evaluation of the denitrification capacity of DPAOs. For the nitrate-DPR sludge, the nitrite reduction rate was 1.63 times higher than the nitrate reduction rate when DPAOs were the primary denitrifiers. For the nitrite-DPR sludge, the reduction rate of nitrite was more than three times that of nitrate, irrespective of DGAO abundance. These findings indicated that DPAOs preferred nitrite to nitrate and were well suited to reduce nitrite rather than reduce nitrate to supply nitrite.

Inhibition of phosphorus removal performance in activated sludge by Fe(III) exposure: transitions in dominant metabolic pathways.

Simultaneous chemical phosphorus removal process using iron salts (Fe(III)) has been widely utilized in wastewater treatment to meet increasingly stringent discharge standards. However, the inhibitory effect of Fe(III) on the biological phosphorus removal system remains a topic of debate, with its precise mechanism yet to be fully understood. Batch and long-term exposure experiments were conducted in six sequencing batch reactors (SBRs) operating for 155 days. Synthetic wastewater containing various Fe/P ratios (i.e., Fe/P = 1, 1.2, 1.5, 1.8, and 2) was slowly poured into the SBRs during the experimental period to assess the effects of acute and chronic Fe(III) exposure on polyphosphate-accumulating organism (PAO) growth and phosphorus metabolism. Experimental results revealed that prolonged Fe(III) exposure induced a transition in the dominant phosphorus removal mechanism within activated sludge, resulting in a diminished availability of phosphorus for bio-metabolism. In Fe(III)-treated groups, intracellular phosphorus storage ranged from 3.11 to 7.67 mg/g VSS, representing only 26.01 to 64.13% of the control. Although the abundance of widely reported PAOs (Candidatus Accumulibacter) was 30.15% in the experimental group, phosphorus release and uptake were strongly inhibited by high dosage of Fe(III). Furthermore, the abundance of functional genes associated with key enzymes in the glycogen metabolism pathway increased while those related to the polyphosphate metabolism pathway decreased under chronic Fe(III) stress. These findings collectively suggest that the energy generated from polyhydroxyalkanoates oxidation in PAOs primarily facilitated glycogen metabolism rather than promoting phosphorus uptake. Consequently, the dominant metabolic pathway of communities shifted from polyphosphate-accumulating metabolism to glycogen-accumulating metabolism as the major contributor to the decreased biological phosphorus removal performance.

Distinguished denitrifying phosphorus removal in the high-rate anoxic/microaerobic system for sewage treatment

This study re-evaluated the role of anoxic and anaerobic zones during the enhanced biological phosphorus (P) removal process by investigating the potential effect of introducing an anoxic zone into a high-rate microaerobic activated sludge (MAS) system (1.60–1.70 kg chemical oxygen demand (COD) m−3 d−1), i.e., a high-rate anoxic/microaerobic (A/M) system for sewage treatment. In the absence of a pre-anaerobic zone, introducing an anoxic zone considerably reduced effluent NOx−-N concentrations (7.2 vs. 1.5 mg L−1) and remarkably enhanced total nitrogen (75% vs. 89%) and total P (18% vs. 60%) removal and sludge P content (1.48% vs. 1.77% (dry weight)) due to further anoxic denitrifying P removal in the anoxic zone (besides simultaneous nitrification and denitrification in the microaerobic zone). High-throughput pyrosequencing demonstrated the niche differentiation of different polyphosphate accumulating organism (PAO) clades (including denitrifying PAO [DPAO] and non-DPAO) in both systems. Introducing an anoxic zone considerably reduced the total PAO abundance in sludge samples by 42% and modified the PAO community structure, including 17–19 detected genera. The change was solely confined to non-DPAOs, as no obvious change in total abundance or community structure of DPAOs including 7 detected genera was observed. Additionally, introducing an anoxic zone increased the abundance of ammonia-oxidizing bacteria by 39%. The high-rate A/M process provided less aeration, higher treatment capacity, a lower COD requirement, and a 75% decrease in the production of waste sludge than the conventional biological nutrient removal process.

Forming densified activated sludge in a modified simultaneous nitrification–denitrification and phosphorus removal (SNDPR) system by introducing shift work mode

Forming granular-like sludge in the Simultaneous Nitrification-Denitrification and Phosphorus Removal (SNDPR) process would promote nutrient removal and improve the sludge settleability. This study introduced the “shift work mode” into an SNDPR system, which featured that 50 % of sludge was temporarily transferred into and “rested” in a side-stream reactor a cyclic time rather than let it keep “working” in the mainstream SNDPR reactor. Results showed that 77.6 % of inorganic nitrogen and 80.6 % of orthophosphate were removed well even after the combination, which attributed to the co-work of Candidatus_Competibacter (10.1 %–29.0 %), nitrifiers, and phosphate accumulating organisms. The 30-min settled sludge volume and sludge volume index were 8 % and 45.8 mL/g, respectively, the sludge density was 1.045 g/mL, and cumulative 90 % of the particle diameter was less than 80 µm; these indicated the densified activated sludge was formed. After analyses, the increase in the food-to-microorganisms ratio and temporary enrichment of filamentous bacteria Thiothrix might be the causes. Such shift work mode promisingly serves as a simple and practical way to improve settleability and promote granulation.

Turning alkalinity deficiency-induced metabolic disorder into an opportunity for promoting granulation and enhancing heat generation

Shortage of alkalinity is a common problem in treating low carbon/nitrogen (C/N) wastewater and industrial influents. It negatively affects system stability and efficiency, but its positive effects remain unclear. To address this issue, insufficient (R1: 400 mg CaCO3/L) and sufficient alkalinity (R2: 750 mg CaCO3/L) levels were established in our study, where R1 served as the experimental group and R2 as the control group. In the experimental group, alkalinity deficiency deteriorated the nitrification and phosphorus removal process by reducing the abundance of functional microbes (Nitrosomonas, genus ammonia-oxidizing bacteria, AOB, and Dechloromonas, genus polyphosphate-accumulating organisms, PAOs) and genes (hao). At the same time, the alkalinity deficiency enriched slow-growing functional microbes (Candidatus_Competibacter, genus glycogen-accumulating organisms, GAOs) and key genes (nirK, norB, nosZ, acnB, fumA, fumB) increased the content of extracellular polymeric substances (EPS) and the ratio of protein to polysaccharide (PN/PS). By day 113, over 87 % of the particles were larger than 200 μm, and complete granulation was achieved. Microbial energy metabolism further indicated that alkalinity deficiency diverted some energy to non-growth metabolism, thereby enhancing microbial heat generation. Our results highlight an innovative approach, using the setting of insufficient alkalinity conditions to improve heat recovery and address the challenges of WWTPs. These research findings are in favor of wastewater treatment plants seeking to meet multiple sustainable objectives, including improving water quality, saving footprint, and maximizing energy recovery.

Effects of microorganisms on nitrogen and phosphorus removal from wastewater

Nitrogen and phosphorus are key to plant growth. The balance of nitrogen and phosphorus is crucial in nature. Excessive nitrogen and phosphorus content in wastewater has caused great harm to the environment. Traditional nitrogen and phosphorus removal methods can no longer meet the treatment standards for nitrogen and phosphorus. This article introduces the hazards of nitrogen and phosphorus, and points out the harm to nature and human beings if they are not up to standard in wastewater treatment plants. Through the analysis and discussion of several methods, the advantages of microbial nitrogen and phosphorus removal are explained. This article further summarizes several representative new microorganisms and microbial processes through the types and mechanisms of microbial nitrogen and phosphorus removal. Anammox bacteria can accept other electron pools to increase nitrogen removal efficiency. Denitrifying phosphorus-removing bacteria can achieve energy saving and carbon reducing effects through endogenous denitrification. Besides, the enhanced biological phosphorus removal process can allow denitrifying phosphorus accumulating bacteria to absorb phosphorus in an anaerobic, anoxic, aerobic alternating environment. The moving bed biofilm reactor (MBBR) abandons the disadvantages of the traditional biofilm method, while retaining the advantages of the traditional biofilm method such as shock load resistance and low sludge production. These new microorganisms and new microbial processes have become important applications in future nitrogen and phosphorus removal processes due to their advantages of high efficiency, low energy, and no secondary pollution. This article is conducive to the promotion of microbial-based wastewater treatment and can provide suggestions for the sustainable development of wastewater treatment.

Insights into the mechanism of phosphorus enrichment and stripping in side-stream enhanced biological phosphorus removal and enrichment process

In-depth research on the side-stream enhanced biological phosphorus removal (S2EBPR) process holds promise for addressing the challenge of low phosphorus (P) enrichment concentration. This study developed a side-stream enhanced biological phosphorus enrichment/removal (S2EBPE/R) reactor by improving a S2EBPR process. The P removal, enrichment, and mass balance were used to evaluate polyphosphate-accumulating organisms (PAOs) activity. Microbial community structures were investigated to reveal the mechanism of P enrichment and stripping. The results showed that the P removal efficiency reached up to 93% in the S2EBPE/R process. Approximately 13% of P-rich liquid could be stably obtained from the side-stream system, with a concentration of 108.85 ± 4.53 mg P/L. Apart from responses to EBPR activity (P/HAc) of up to 0.41 P-mol/C-mol, enrichment of typical PAOs of up to 12.0% enhanced the P enrichment and removal performance. The abundance of functional microorganisms (PAOs and glycogen accumulating organisms (GAOs)) related to P was as high as 13.4%. These findings highlighted the outstanding advantages of the S2EBPE/R process in P enrichment and removal, thereby making significant contributions to P recovery from wastewater.

Microplastics shaped performance, microbial ecology and community assembly in simultaneous nitrification, denitrification and phosphorus removal process

The widespread use of microplastics (MPs) has led to an increase in their discharge to wastewater treatment plants. However, the knowledge of impact of MPs on macro-performance and micro-ecology in simultaneous nitrification, denitrification, and phosphorus removal (SNDPR) systems is limited, hampering the understanding of potential risks posed by MPs. This study firstly comprehensively investigated the performance, species interactions, and community assembly under polystyrene (PS) and polyvinyl chloride (PVC) exposure in SNDPR systems. The results showed under PS (1, 10 mg/L) and PVC (1, 10 mg/L) exposure, total nitrogen removal was reduced by 3.38–10.15 %. PS and PVC restrained the specific rates of nitrite and nitrate reduction (SNIRR, SNRR), as well as the activities of nitrite and nitrate reductase enzymes (NIR, NR). The specific ammonia oxidation rate (SAOR) and activity of ammonia oxidase enzyme (AMO) were reduced only at 10 mg/L PVC. PS and PVC enhanced the size of co-occurrence networks, niche breadth, and number of key species while decreasing microbial cooperation by 5.85–13.48 %. Heterogeneous selection dominated microbial community assembly, and PS and PVC strengthened the contribution of stochastic processes. PICRUSt prediction further revealed some important pathways were blocked by PS and PVC. Together, the reduced TN removal under PS and PVC exposure can be attributed to the inhibition of SAOR, SNRR, and SNIRR, the restrained activities of NIR, NR, and AMO, the changes in species interactions and community assembly mechanisms, and the suppression of some essential metabolic pathways. This paper offers a new perspective on comprehending the effects of MPs on SNDPR systems.

Modeling and Forecasting the Removal of Biogenic Elements from Agricultural Lands Depending on the Soil Agrophysical Properties

Introduction. Environmental pollution prevention, including prevention of water bodies, with nutrients (nitrogen and phosphorus) when they are removed from agricultural lands with possible runoff is a topical problem that requires a timely solution. The studies have found that the removal of nutrients is a result of geochemical processes, fertilization, and other factors. In this regard, mathematical modeling of the process of removal of nutrients from agricultural lands and their possible entry into water bodies is an urgent task. Aim of the Study. The study is aimed at modeling and predicting the process of possible removal of nutrients from agricultural lands to water bodies. Materials and Methods. When conducting the study, there were used well-known modeling methods. They are the methods for calculating the removal of nutrients from agricultural objects into water bodies, based on the minimum amount of initial information for predicting the eutrophication of water bodies and agrochemical methods taking into account the structure and size of field and agricultural areas, crop yields, and removal nutrients with the harvest. Results. Based on an analysis of the literature and expert judgment, a list of the most significant indicators influencing the process of nitrogen and phosphorus removal was justified. There have been developed mathematical models to determine and predict the input of nutrients from agricultural lands to water bodies. There have been found significant indicators influencing the amount of input of nutrients, such as the amount of applied fertilizers, the volume of moisture, soil water capacity, field area, depth of cultivation, etc. There is given an example of calculating the amount of input of nutrients into water bodies with a rainfall intensity of 50 mm per hour. Discussion and Conclusion. The essence of the proposed mathematical models comes down to the synthesis of numerous indicators in the complex process of removal of nutrients and their impact on water quality. The proposed mathematical models make it possible to predict the removal of nutrients from agricultural lands and to develop and implement technical and technological solutions to prevent environmental pollution.

Enhanced the simultaneous removal and recovery of phosphorus in induced crystallization coupled biological phosphorus removal process

Remove and recovery of phosphorus from wastewater is expected to be a promising strategy to solve the shortage of phosphorus resources and control the water environment pollution. In this study, induced crystallization coupled biological phosphorus removal (IC-BPR) process was established to achieve simultaneous removal and recovery of phosphorus in wastewater. The effects of side stream ratio (SSR) on the removal and recovery efficiency of phosphorus and the microbial community structure were explored. The results indicated that the SSR of 40% was optimal to phosphorus removal and recovery in the IC-BPR. The total phosphorus removal efficiency was 94.23% under the SSR of 40%, of which the phosphorus removal efficiency by IC accounted for 74.87%. And the total phosphorus recovery efficiency was 67.29%. The particle size and crystal structure analysis of the crystallized products indicated that the increase of SSR was conductive to heterogeneous crystallization. Furthermore, typical polyphosphate accumulation organisms (PAOs), including Rhodocyclaceae, Acinetobacter, and Dechloromonasin, were enriched under the side stream ratio of 40%. And functional genes related to amino acid transport and metabolism, energy production and conversion were activated. The above results indicated that the IC could significantly enhance the removal and recovery of phosphorus under a suitable SSR condition. It will provide important reference for wastewater treatment coupled phosphorus resource recovery technology.

Effect of internal and external recycle ratios on the nutrient removal efficiency of anaerobic/anoxic/oxic (VIP) wastewater treatment plant

Abstract Due to the disposal of different wastewater into the water bodies, the rate of surface water pollution is increasing. The virginia initiative plant (VIP), one of the most efficient and economical wastewater treatment systems, was assessed. The experiments were carried out by a laboratory-scale VIP system used for this study, with a flow rate of 100 L/day and a solid retention time rate estimated at 10 days. The system works on three different ratios for internal rotation (100, 150, and 200%) and three for external rotation (80, 90, and 100%), and the effective volumes were 20, 40, and 60 L for anaerobic, anoxic, and oxic reactors, respectively. The results showed that the VIP system achieved the best removal efficiency of organic matter represented by COD, phosphorous, and ammonia (86, 94, and 93%, respectively). The impact of internal and external rotation ratios was tested by removing COD, phosphorous, and ammonia. The percentages of internal rotation significantly affect the biological removal of nitrates. The relationship between them is inverse, while the percentages of external rotation significantly impact the biological removal process of phosphorus. The relationship between them is positive, whereas the internal and external rotation percentages did not considerably affect the efficiency of removing both ammonia and COD. According to the research results, internal and external rotation ratios enhanced the removal efficiency of phosphorus and nitrates. The VIP system proved to be an effective method for domestic wastewater treatment with a flow conforming to Iraqi standards for draining wastewater with all organic matter, phosphorous, and nitrogenous compounds to rivers.

FePO4 activated sulfite autoxidation for simultaneous pollutant degradation and phosphorus release

FePO4 (FP) as a precursor of lithium iron phosphate batteries has been mass-produced in recent years and may face the problem of overproduction. Also, the phosphorus removal process in wastewater treatment plants produces large amounts of sludge containing FP. It is a huge waste of both iron and phosphorus resources if such FP cannot be utilized. This work explores a new strategy for utilizing FP to activate sulfite (S(IV)) autoxidation for simultaneous pollutant degradation and phosphorus release in water. Acid orange 7 (AO7) and several pharmaceutical and personal care products (PPCPs) were chosen as the target pollutants for the FP‒S(IV) system and the influence of pH, FP and S(IV) dosage were investigated. Typically, up to 89.5% AO7 (10 mg L−1) and above 60% PPCPs (10 μM) were oxidized within 90 min by adding 1 g L−1 FP and 2 mM S(IV) into the water at the initial pH 4.0. Results of quenching experiments and electron spin resonance analysis confirmed SO5•− as the dominant reactive species for AO7 oxidation. Meanwhile, two stages of phosphorus release from FP were observed along with the AO7 oxidation and their linear correlation over the pH range 3.0–8.0 was proven. The first stage (0–5 min) was thought to be dependent on the initial pH and was obviously faster than the second stage (10–45 min), whose rate increased linearly with S(IV) dosage. Phosphorus released high up to 24.3 μM at 90 min with 4 mM S(IV). Moreover, the mechanisms of FP activated sulfite autoxidation as well as phosphorus release were proposed, and the AO7 degradation pathway was investigated. This study provides a novel possibility for FP waste utilization and potential recovery of phosphorus resources.

Partial denitrifying phosphorus removal coupling with anammox (PDPRA) enables synergistic removal of C, N, and P nutrients from municipal wastewater: A year-round pilot-scale evaluation

Applying anaerobic ammonium oxidation (anammox) in municipal wastewater treatment plants (MWWTPs) can unlock significant energy and resource savings. However, its practical implementation encounters significant challenges, particularly due to its limited compatibility with carbon and phosphorus removal processes. This study established a pilot-scale plant featuring a modified anaerobic-anoxic-oxic (A2O) process and operated continuously for 385 days, treating municipal wastewater of 50 m3/d. For the first time, we propose a novel concept of partial denitrifying phosphorus removal coupling with anammox (PDPRA), leveraging denitrifying phosphorus-accumulating organisms (DPAOs) as NO2− suppliers for anammox. 15N stable isotope tracing revealed that the PDPRA enabled an anammox reaction rate of 6.14 ± 0.18 μmol-N/(L·h), contributing 57.4 % to total inorganic nitrogen (TIN) removal. Metagenomic sequencing and 16S rRNA amplicon sequencing unveiled the co-existence and co-prosperity of anammox bacteria and DPAOs, with Candidatus Brocadia being highly enriched in the anoxic biofilms at a relative abundance of 2.46 ± 0.52 %. Finally, the PDPRA facilitated the synergistic conversion and removal of carbon, nitrogen, and phosphorus nutrients, achieving remarkable removal efficiencies of chemical oxygen demand (COD, 83.5 ± 5.3 %), NH4+ (99.8 ± 0.7 %), TIN (77.1 ± 3.6 %), and PO43− (99.3 ± 1.6 %), even under challenging operational conditions such as low temperature of 11.7 °C. The PDPRA offers a promising solution for reconciling the mainstream anammox and the carbon and phosphorus removal, shedding fresh light on the paradigm shift of MWWTPs in the near future.

Phosphorus removal of coal-based bottom ash: Performance evaluation and mechanism exploration

In this paper, the phosphorus removal efficiency and capability and pore structure and composition of coal-based bottom ash before and after phosphorus removal are studied to reveal the phosphorus removal mechanism. The results show that the phosphorus removal rate of bottom ash increases with the increase of pH value; When the pH value is 8, the phosphorus removal rate can reach more than 95%. The highest desorption rate is only 2.42% and the pseudo-second order model can be better fitted with the phosphorus removal process of bottom ash, indicating chemical adsorption is the control mechanism. The maximum phosphorus removal capacity is 5.54 mg/g. After phosphorus removal the fractal dimension and porosity decrease, and the specific surface area increases, indicating that the complexity of the pore structure decreases, and the roughness of the pore wall increases. The characteristic peak of brushite (CaHPO4·2H2O) in the XRD spectrum and HPO42− at 2362 cm−1, 985 cm−1 and 800-650 cm−1 appear, respectively. In the XRF results, P2O5/SiO2 ratio increases from 0.008 to 0.089, but SO3/SiO2 ratio decreases from 0.047 to 0.027. The phosphorus removal mechanism of coal-based bottom ash lies in its complex pore structure and the precipitation reaction between soluble Ca2+ and HPO4− in the sewage.