Effect Of Phosphorus Removal Research Articles

The Performance and Mechanism of Solvothermal Synthesis of a Ca-Fe-La Composite for Enhanced Removal of Phosphate from Aqueous Solutions

Since it is a limiting nutrient element in rivers and lakes, the effective removal of phosphorus is key to alleviating eutrophication. In this study, the one-pot solvothermal method was adopted to prepare an environmentally friendly Ca-Fe-La composite. This is an amorphous material with a large specific surface area of 278.41 m2 g−1. The effects of coexisting anions and pH on the phosphate removal performance were explored. Phosphate adsorption mechanisms were revealed by various characterization techniques. The phosphate adsorption obeyed the fractal-like pseudo-second-order (PSO) kinetic model, implying that the overall adsorption system was highly heterogeneous. In this work, the maximum adsorption capacity predicted by the Langmuir model was 93.0 mg g−1 (as PO43−-P). The phosphate-loaded Ca-Fe-La composite could be used as a slow-release fertilizer, achieving waste management and resource utilization. The presence of SO42−, CO32− and HCO3− anions inhibited the phosphate adsorption significantly. It was unfavorable for phosphate removal at a high pH value. Inner-sphere complexation and electrostatic attraction were mainly responsible for phosphate adsorption onto the Ca-Fe-La composite.

Simultaneous enhanced phosphorus removal and hydration reaction: Utilisation of polyaluminium chloride and polyaluminium ferric chloride to modify phosphogypsum-based excess-sulphate slag cement

This study employed polyaluminium chloride (PAC) and polyaluminium ferric chloride (PAFC) for the phosphorus removal released during the hydration of phosphogypsum-based excess-sulphate slag cement (PESSC), as well as microstructure modification. The results indicated that the PESSC samples presented shorter setting times and bleeding rates with further modifier addition due to the effective phosphorus removal and rapid establishment of the flocculated structure. Compressive and flexural strengths were also significantly enhanced in modified samples at each age, where they exceeded 58 MPa and 13 MPa at 180 d, respectively, when PAC and PAFC supplements were within 1.0%. Furthermore, the distinctions in the effect mechanism of two functional compositions (Keggin-Al13 and iron phase) in modifiers have also been studied. In contrast to affecting the microstructure of C-(A)-S-H gel, the released Al(OH)4‐ and Fe(OH)4‐ during hydrolysis often acted with sulphate and portlandite, leading to a higher level of ettringite formation, as well as hydration degree. Comparatively, the introduction of the iron phase adversely impacted pH value development of pore solution and retarded the activation process of slag at early age, while also promoting continuous hydration at later age. The optimisation in the microstructure of PESSC also contributed to impurities solidification, presenting the lower leaching concentration in an acid environment. Overall observations suggested that adding 0.5%–1.0% PAC or PAFC in the PESSC are capable of enhancing not only its engineering properties but also promoting its sustainability.

Understanding Partial Denitrification-hydroxyapatite (PD-HAP) coupled granules to enhance process stability and phosphorus removal by investigating the size effect of granules

The innovative Partial Denitrification-hydroxyapatite (PD-HAP) coupled granule offers a promising biotechnology for supplying nitrite to Anammox while simultaneously removing phosphorus. This study systematically examined the characteristics, biomass activity, and microbial community of PD-HAP granules of various sizes to enhance system stability and phosphorus removal efficiency. The results showed that larger granules had higher inorganic mineral and extracellular polymeric substances (EPS) content. These factors contributed to their denser structure, smoother surfaces, and better settling velocities compared to smaller granules. In contrast, smaller granules exhibited higher denitrification activity due to their greater biomass content and more efficient mass transfer. Calcium and phosphorus were identified as the primary inorganic constituents, mainly in the form of HAP, and were especially abundant in larger granules. Granules larger than 3.0 mm demonstrated a higher capacity for phosphorus removal. This was due to their significantly greater tightly bound EPS (T-EPS) content, which led to increased HAP and phosphorus levels. All granule sizes maintained a nitrate-to-nitrite transformation ratio (NTR) above 80 %, primarily due to the dominance of Flavobacterium (65.8 %-74.9 %). Although larger granules had lower denitrification activity, they still achieved an excellent NTR (above 85 %). They also showed superior settling velocity (174.9 m/h) and stronger phosphorus removal capacity (54.1 mg/g SS) compared to smaller granules. Maintaining a dominant proportion of granules larger than 3.0 mm could be an effective strategy to enhance both system stability and phosphorus removal. This study provides valuable insights into the PD-HAP coupled granular process, promoting efficient nitrite production and effective phosphorus removal.

Effectiveness of cyclic treatment of municipal wastewater by Tetradesmus obliquus – Loofah biofilm, its internal community changes and potential for resource utilization

Microalgae biofilm has garnered significant attention from researchers in the field of sewage treatment due to its advantages such as ease of collection and stable sewage treatment capabilities. Using agricultural waste as biofilm carriers has become a hotspot in reducing costs for this method. This study first combined Tetradesmus obliquus with loofah to form a microalgae biofilm for the study of periodic nitrogen and phosphorus removal from municipal wastewater. The biofilm could stably treat 7 batches of wastewater within one month. The removal rate of TP almost reached 100 %, while the removal rates of NH4+ and TN both reached or exceeded 80 %. The average biomass yield over 25 days was 102.04 mg/L/day. The polysaccharide content increased from 8.61 % to 16.98 % during the cyclic cultivation. The lipid content gradually decreased from 40.91 to 26.1 %. The protein content increased from 32.93 % in the initial stage to 41.18 % and then decreased to 36.31 % in the later stage. During the mid-stage of culturing, the richness of anaerobic bacteria decreased, while the richness of aerobic and facultative bacteria increased, which was conducive to the construction of the microalgae-bacteria symbiotic system and steadily improved the effect of nitrogen and phosphorus removal. As the culturing progressed, the Rotifers that emerged during the mid-stage gradually damaged the biofilm over time, leading to a decline in the effectiveness of sewage treatment in the later stages. This study offers technical support for carrier selection in microalgae biofilm methods and for the periodic removal of nitrogen and phosphorus from wastewater.

Effects of Phosphorus Removal and pH Changes in the Culture Medium of Spirulina sp. on the Production Rate of Polyhydroxybutyrate

Effects of Phosphorus Removal and pH Changes in the Culture Medium of Spirulina sp. on the Production Rate of Polyhydroxybutyrate

Lanthanum-Integrated Porous Adsorbent for Effective Phosphorus Removal.

In pursuit of accessing clean water, the phosphate removal is of great importance for preventing eutrophication toward sustainable ecology. However, effective adsorbents with high capacity, selectivity, and long-term stability for treating phosphate in water still remain desired, which requires further development. Herein, a type of porous La-based adsorbents, which are composed of highly dispersed La(OH)3 on amino-functionalized Caragana korshinskii (CK) nanowires, are designed and fabricated through simple amination and decoration of lemon bars. Specifically, the adsorption to phosphate can be quickly completed within 50 min, and an ultrahigh adsorption capacity of 173.3 mg of P g-1 is realized. Moreover, these composite adsorbents display excellent selectivity and anti-interference ability to phosphate in the presence of common anions (CO3 2-, NO3-, Cl-, and SO4 2-). After four regenerations, there is still a removal rate of 85%. This study underscores an integrated material model for designing advanced structures toward efficient wastewater treatment.

Synergistic Removal of Nitrogen and Phosphorus in Constructed Wetlands Enhanced by Sponge Iron

Insufficient denitrification and limited phosphorus uptake hinder nitrogen and phosphorus removal in constructed wetlands (CWs). Sponge iron is a promising material for the removal of phosphorus and nitrogen because of its strong reducing power, high electronegativity, and inexpensive cost. The influence of factors including initial solution pH, dosage, and the Fe/C ratio was investigated. A vertical flow CW with sponge iron (CW-I) was established, and a traditional gravel bed (CW-G) was used as a control group. The kinetic analysis demonstrated that for both nitrogen and phosphorus, pseudo-second-order kinetics were superior. The theoretical adsorption capacities of sponge iron for nitrate (NO3−-N) and phosphate (PO43−-P) were 1294.5 mg/kg and 583.6 mg/kg, respectively. Under different hydraulic retention times (HRT), CW-I had better total nitrogen (TN) and total phosphorus (TP) removal efficiencies (6.08–15.18% and 5.00–20.67%, respectively) than CW-G. The enhancing effect of sponge iron on nitrogen and phosphorus removal was best when HRT was 48 h. The increase in HRT improved not only the nitrogen and phosphorus removal effects of CWs but also the reduction capacity of iron and the phosphorus removal effect. The main mechanisms of synergistic nitrogen and phosphorus removal were chemical reduction, ion exchange, electrostatic adsorption, and precipitation formation.

Molecular insight into the allocation of organic carbon to heterotrophic bacteria: Carbon metabolism and the involvement in nitrogen and phosphorus removal

Carbon metabolism and nutrient removal are crucial for biological wastewater treatment. This study focuses on analyzing carbon allocation and utilization by heterotrophic bacteria in response to increasing COD concentration in the influent. The study also assesses the effect of denitrification and biological phosphorus removal, particularly in combination with anaerobic ammonia oxidation (anammox). The experiment was conducted in a SBR operating under anaerobic/anoxic/oxic conditions. As COD concentration in the influent increased from 100 to 275 mg/L, intracellular COD accounted for 95.72 % of the COD removed. By regulating the NO3− concentration in the anoxic stage from 10 to 30 mg/L, the nitrite accumulation rate reached 69.46 %, which could serve as an electron acceptor for anammox. Most genes related to the tricarboxylic acid (TCA) cycle declined, while the genes involved in the glyoxylate cycle, gluconeogenesis, PHA synthesis increased. This suggests that glycogen accumulation and carbon storage, rather than direct carbon oxidation, was the dominant pathway for carbon metabolism. However, the genes responsible for the reduction of NO2−-N (nirK) and NO (nosB) decreased, contributing to NO2− accumulation. The study also employed metagenomic analysis to reveal microbial interactions. The enrichment of specific bacterial species, including Dechloromonas sp. (D2.bin.10), Ca. Competibacteraceae bacterium (D9.bin.8), Ca. Desulfobacillus denitrificans (D6.bin.17), and Ignavibacteriae bacterium (D3.bin.9), played a collaborative role in facilitating nutrient removal and promoting the combination with anammox.

Structural design of La2(CO3)3 loaded magnetic biochar for selective removal of phosphorus from wastewater

High levels of phosphorus released into the environment can cause eutrophication issues in wastewater, therefore discharge concentrations of such element are regulated in many countries. This study addresses the pressing need for effective phosphorus removal methods by developing a novel La2(CO3)3 and MnFe2O4 loaded biochar composite (LMB). A remarkable adsorption capacity towards the three forms of phosphorus from wastewater, including phosphate, phosphite, and etidronic acid monohydrate (as a representative of organic phosphorus), was exhibited by LMB (88.20, 16.35, and 15.95 mg g−1, respectively). The high saturation magnetization value (50.17 emu g−1) highlighted the easy separability and recyclability of the adsorbent. The adsorption process was well described by the Langmuir isotherm model and the pseudo-second-order kinetic model, which mainly involved chemisorption. Characterization results confirm the effective loading of La2(CO3)3 with ligand exchange and electrostatic attraction identified as the primary mechanisms. Importantly, the LMB demonstrated exceptional selectivity for phosphorus in wastewater samples containing various substances, exhibiting minimal interference from competing ions (Cl−, NO3−, SO42−, and CO32−). These findings enhance the understanding of LMB's application in efficient wastewater phosphorus removal. Holding significant promise in wastewater remediation, the LMB acts as an effective adsorbent, contributing substantially to the prevention and control of various types of phosphorus pollutants, thereby mitigating wastewater eutrophication.

Side-Stream Enhanced Biological Phosphorus Removal (S2EBPR) enables effective phosphorus removal in a pilot-scale A-B stage shortcut nitrogen removal system for mainstream municipal wastewater treatment

While the adsorption/bio-oxidation (A/B) process has been widely studied for carbon capture and shortcut nitrogen (N) removal, its integration with enhanced biological phosphorus (P) removal (EBPR) has been considered challenging and thus unexplored. Here, full-scale pilot testing with an integrated system combining A-stage high-rate activated sludge with B-stage partial (de)nitrification/anammox and side-stream EBPR (HRAS-P(D)N/A-S2EBPR) was conducted treating real municipal wastewater. The results demonstrated that, despite the relatively low influent carbon load, the B-stage P(D)N-S2EBPR system could achieve effective P removal performance, with the carbon supplement and redirection of the A-stage sludge fermentate to the S2EBPR. The novel process configuration design enabled a system shift in carbon flux and distribution for efficient EBPR, and provided unique selective factors for ecological niche partitioning among different key functionally relevant microorganisms including polyphosphate accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs). The combined nitrite from B-stage to S2EBPR and aerobic-anoxic conditions in our HRAS-P(D)N/A-S2EBPR system promoted DPAOs for simultaneous internal carbon-driven denitrification via nitrite and P removal. 16S rRNA gene-based oligotyping analysis revealed high phylogenetic microdiversity within the Accumulibacter population and discovered coexistence of certain oligotypes of Accumulibacter and Competibacter correlated with efficient P removal. Single-cell Raman micro-spectroscopy-based phenotypic profiling showed high phenotypic microdiversity in the active PAO community and the involvement of unidentified PAOs and internal carbon-accumulating organisms that potentially played an important role in system performance. This is the first pilot study to demonstrate that the P(D)N-S2EBPR system could achieve shortcut N removal and influent carbon-independent EBPR simultaneously, and the results provided insights into the effects of incorporating S2EBPR into A/B process on metabolic activities, microbial ecology, and resulted system performance.

Changes in microbial community during hydrolyzed sludge reduction.

In this study, the effects of different enzymes (lysozyme, α-amylase and neutral protease) on sludge hydrolysis efficiency and microbial community in sequencing batch reactor (SBR) were introduced. The results showed that the hydrolysis efficiencies of the three enzymes were 48.5, 22.5 and 31%, respectively, compared with the accumulated sludge discharge of the blank control group. However, it has varying degrees of impact on the effluent quality, and the denitrification and phosphorus removal effect of the system deteriorates. The lysozyme that achieves the optimal sludge hydrolysis effect of 48.5% has the greatest impact on the chemical oxygen demand (COD), total nitrogen (TN), and nitrate nitrogen (NO3--N) of the effluent. The sludge samples of the control group and the groups supplemented with different enzyme preparations were subjected to high-throughput sequencing. It was found that the number of OTUs (Operational Taxonomic Units) of the samples was lysozyme > α-amylase > blank control > neutral protease. Moreover, the abundance grade curve of the sludge samples supplemented with lysozyme and α-amylase was smoother, and the community richness and diversity were improved by lysozyme and α-amylase. The species diversity of the sludge supplemented with lysozyme and neutral protease was great, and the community succession was obvious. The introduction of enzymes did not change the main microbial communities of the sludge, which were mainly Proteobacteria, Actinobacteria and Bacteroidetes. The effects of three enzyme preparations on sludge reduction and microbial diversity during pilot operation were analyzed, the gap in microbial research was filled, which provided theoretical value for the practical operation of enzymatic sludge reduction.

Isolation and Identification of a Carbon-Fixing Bacteria Strain and Its Efficiency for Nitrogen and Phosphorus Removal from Viaduct Rainwater

In order to explore bacteria resources that are applicable for purification of viaduct rainwater, a carbon-fixing bacteria strain numbered 1C-1 was isolated from the sediment of a viaduct rainwater tank. The strain was identified through morphological characteristics and 16S rDNA sequences. The effects of three main factors (the simulated viaduct rainwater concentration, the carbon source dosage, and the inoculation amount) on the nitrogen and phosphorus removal rate of the strain were tested using simulated viaduct rainwater. Based on this, the nitrogen and phosphorus removal efficiencies for the actual viaduct rainwater were verified. The results showed that the strain belonged to Streptomyces sp. Under different simulated viaduct rainwater concentrations, the strain exhibited relatively high efficiency for nitrogen and phosphorus removal at the original concentration of simulated viaduct rainwater; other conditions remaining unchanged, the purification efficiency was relatively high when the glucose dosage was 800 mg, and the removal rates of ammonia nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) were 71.48%, 47.86%, and 10.43%, respectively; other conditions remaining unchanged, the purification efficiency was relatively high when the inoculation amount was 1%, and the removal rates of NH4+-N, TN, and TP reached 58.62%, 58.35%, and 27.32%, respectively. Under the above optimal process conditions of an original concentration of viaduct rainwater, a carbon source dosage of 800 mg, and an inoculation amount of 1%, the strain removed 92.62%, 6.98%, and 6.16% of NH4+-N, TN, and TP, respectively from the actual viaduct rainwater; more interestingly, the removal rates of NH4+-N and TN were 43.26% and 78.02%, respectively, even without carbon source addition. It seems that there is no need for carbon source addition to remove nitrogen from the actual viaduct rainwater for the strain. To sum up, the carbon-fixing bacteria 1C-1 presents an obvious nitrogen and phosphorus removal effect (especially for nitrogen) for viaduct rainwater treatment and has application potential.

Atomic-Level Structural Differences between Fe(III) Coprecipitates Generated by the Addition of Fe(III) Coagulants and by the Oxidation of Fe(II) Coagulants Determine Their Coagulation Behavior in Phosphate and DOM Removal.

In situ Fe(III) coprecipitation from Fe2+ oxidation is a widespread phenomenon in natural environments and water treatment processes. Studies have shown the superiority of in situ Fe(III) (formed by in situ oxidation of a Fe(II) coagulant) over ex situ Fe(III) (using a Fe(III) coagulant directly) in coagulation, but the reasons remain unclear due to the uncertain nature of amorphous structures. Here, we utilized an in situ Fe(III) coagulation process, oxidizing the Fe(II) coagulant by potassium permanganate (KMnO4), to treat phosphate-containing surface water and analyzed differences between in situ and ex situ Fe(III) coagulation in phosphate removal, dissolved organic matter (DOM) removal, and floc growth. Compared to ex situ Fe(III), flocs formed by the natural oxidizing Fe2+ coagulant exhibited more effective phosphate removal. Furthermore, in situ Fe(III) formed through accelerated oxidation by KMnO4 demonstrated improved flocculation behavior and enhanced removal of specific types of DOM by forming a more stable structure while still maintaining effective phosphate removal. Fe K-edge extended X-ray absorption fine structure spectra (EXAFS) of the flocs explained their differences. A short-range ordered strengite-like structure (corner-linked PO4 tetrahedra to FeO6 octahedra) was the key to more effective phosphorus removal of in situ Fe(III) than ex situ Fe(III) and was well preserved when KMnO4 accelerated in situ Fe(III) formation. Conversely, KMnO4 significantly inhibited the edge and corner coordination between FeO6 octahedra and altered the floc-chain-forming behavior by accelerating hydrolysis, resulting in a more dispersed monomeric structure than ex situ Fe(III). This research provides an explanation for the superiority of in situ Fe(III) in phosphorus removal and highlights the importance of atomic-level structural differences between ex situ and in situ Fe(III) coprecipitates in water treatment.

Selective removal of phosphate by magnetic NaCe(CO3)2/Fe3O4 nanocomposites: Performance and mechanism

Phosphorus (P) contamination has become a worldwideissuedue to its adverse impacts on water security and human health. Additional research is required because the selectivity and adsorption capacity of P adsorbents continue to impede their practical application. Herein, a novel NaCe(CO3)2/Fe3O4 nanocomposite (NCF) with good magnetic properties were synthesized through a modified hydrothermal method for P removal from water. With an adsorption capacity of 86.69 mg P g−1, the NCF demonstrates outstanding phosphate uptake efficiency. At low P concentrations, the removal rate exceeded 90.0%, and the residual P concentration was below 0.1 mg P L−1. Notably, NCF demonstrated exceptional P selectivity in actual water containing multiple substances, with negligible interference from competing ions and humic acid (HA). The adsorption processes of NCF were well described by the pseudo-second-order kinetic model (PSO) and Langmuir isotherm model, corresponding to its kinetics and thermodynamics, respectively. The exhausted NCF can be regenerated and retain an effective phosphorus removal capability even after regeneration. Characterization results demonstrated that electrostatic attraction and ligand exchange were responsible for P adsorption, forming stable CePO4 crystals with low solubility. Moreover, the NCF demonstrated some efficacy in removing typical organic and inorganic phosphorus.

Effect of different enrichment methods on the independent biological phosphorus removal performance after nitrogen removal using immobilized fillers

In order to find a biological phosphorus removal enrichment method with high performance and low energy consumption, two enrichment methods were used in this study, namely gradient carbon source addition (S1) and fixed carbon source addition (S2). The two enrichment methods were applied to the enrichment of phosphorus removing bacteria in an independent biological phosphorus removal system based on nitrogen removal by immobilized fillers. The phosphorus removal performance, stoichiometry and microbial structure were compared for the two enrichment methods. It was found that PO43--P remained 0.15–0.2 mg/L at the end of enrichment in S1, while PO43--P increased from 0.27 to 0.38 mg/L at the end of enrichment in S2. Stoichiometric analysis showed that S1 used more PHAs (1.47 molC/L) for phosphorus absorption, while S2 used nearly half of the PHAs (0.87 molC/L) for glycogen synthesis. Moreover, the absorbed phosphorus content in S2 was significantly less than S1 (5.67 < 8.65 mg/L). As a result, denitrifying phosphorus-removing bacteria predominated S1, while phosphate-accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs) both played a role in S2. Dechloromonas, the dominant denitrifying PAO in both S1 and S2 increased from 0.26 % to 3.34 % and 1.04 %, respectively, while Defluviicoccus, a typical GAO, changed from 0.24 % to 0.2 % and 2.01 %, respectively. As a result, gradient carbon source enrichment demonstrated a better phosphorus removal effect and dominant bacteria, whereas the fixed carbon source enrichment increased the abundance of GAOs while negatively impacting the phosphorus removal effect.

Facile fabrication of microstructure-tunable aluminum-based metal–organic frameworks for exceptional phosphorus recovery from water

The recovery of phosphorus from phosphorus-contaminated water is of great significance to prevent the eutrophication of natural water and overcome the shortage of phosphorus resources. To increase the effectiveness of phosphorus removal from water, aluminum metal–organic frameworks (Al-MOFs) with different microstructures were synthesized in this study by varying the ratio of metal centers (Al) to organic ligands (terephthalic acid, BDC) in the precursor solution. For the precursor solution of a 10:1 M ratio of Al3+ to BDC, the synthesized Al-MOF exhibited the maximum phosphorus adsorption capacity (100.37 mg P/g). The pseudo-second-order kinetic model indicated a better fit for the experimental data obtained from the adsorption of phosphorus onto the synthesized Al-MOFs. The synthesized Al-MOFs appeared highly effective in removing phosphorus from water at an initial pH of 3.0 to 9.0. In addition, phosphorus adsorption onto Al-MOFs is not seriously affected by the presence of coexisting ions in water such as Ca2+, Mg2+, CO32–, HCO3–, NO3–, and Cl-. After five cycles of adsorption–desorption, the phosphorus recovery efficiency of the synthesized Al-MOFs decreased by only 15%. The phosphorus adsorption onto synthesized Al-MOFs is mainly governed by electrostatic interaction, complexation, and ligand exchange mechanisms.

Phosphorus Removal in VFCWs with Lightweight Aggregates Made of Fly Ash from Sewage-Sludge Thermal Treatment (FASSTT LWA)

This study analyzed the effect of lightweight aggregates made of fly ash from sewage-sludge thermal treatment (FASSTT LWA) on the effectiveness of phosphorus removal from wastewater in vertical constructed wetlands (CWs), depending on FASSTT LWA content in the CW filling and hydraulic loading rate. It was performed over 13 weeks using 15 lysimeters prepared as double-layer systems. An upper layer was made of FASSTT LWA above the gravel layer with different thicknesses of FASSTT LWA (CW 0 cm: only gravel; CW 12 cm, CW 25 cm; CW 50 cm, and CW 100 cm: only FASSTT LWA). Each filling variant was repeated three times. Wastewater with a mean phosphorus concentration of 7.43 mgP/L was fed to the lysimeters once a day. The hydraulic loading rates tested were 3.0, 5.0, and 7.0 mm/d. Both the increased FASSTT LWA content in the CW filling and the decreasing hydraulic loading rate were found to boost the effectiveness of phosphorus removal in the treated wastewater. Constructed wetland filled in 100 % with FASSTT LWA ensured a reduction in phosphorus concentration below 2.0 mg P/L at all hydraulic loading rates tested.

Decomposition of Phosphorus Pollution and Microorganism Analysis Using Novel CW-MFCs under Different Influence Factors

A constructed wetland (CW)-coupled microbial fuel cell (MFC) system was constructed to treat wastewater and generate electricity. The total phosphorus in the simulated domestic sewage was used as the treatment target, and the optimal phosphorus removal effect and electricity generation were determined by comparing the changes in substrates, hydraulic retention times, and microorganisms. The mechanism underlying phosphorus removal was also analyzed. By using magnesia and garnet as substrates, the best removal efficiencies of two CW-MFC systems reached 80.3% and 92.4%. Phosphorus removal by the garnet matrix mainly depends on a complex adsorption process, whereas the magnesia system relies on ion exchange reactions. The maximum output voltage and stabilization voltage of the garnet system were higher than those of the magnesia system. Microorganisms in the wetland sediments and electrode also changed considerably. It indicates that the mechanism of phosphorus removal by the substrate in the CW-MFC system is adsorption and chemical reaction between ions to generate precipitation. The population structure of proteobacteria and other microorganisms has an impact on both power generation and phosphorus removal. Combining the advantages of constructed wetlands and microbial fuel cells also improved phosphorus removal in coupled system. Therefore, when studying a CW-MFC system, the selection of electrode materials, matrix, and system structure should be taken into account to find a method that will improve the power generation capacity of the system and remove phosphorus.

The effectiveness of sediment and phosphorus removal by a small constructed wetland in Norway: 18 years of monitoring and perspectives for the future

Constructed wetlands (CWs) are a widely recognised measure for reducing pollution loads and improving the quality of surface waters. The removal efficiency of CWs varies considerably depending on system type and design as well as residence time, hydraulic load, particles and nutrient loading rates. Therefore, there is a need to closely monitor the efficiency of existing measures, look at their efficiency in practice and be able to foresee potential implications for their efficiency in light of climate change and land management intensification.This study presents 18 years of data from a typical Norwegian small CW established in the Skuterud catchment. The main objective of this study was to look at the impact of hydraulic load, particles and nutrient loads (depending on climatic factors such as temperature and precipitation) on CW effectiveness. The results showed an average of 39 % and 22 % annual removal efficiency for sediment and phosphorus, respectively. It appears that good CW effectiveness coincides with a combination of high sediment or phosphorus loads to the CW and a stable runoff of low to moderate intensity.At the seasonal level, the highest sediment and phosphorus removal efficiency is observed in the summer seasons (47% for sediment and 29% for phosphorus), when the sediment and phosphorus loads and runoff are at their lowest, and the lowest in autumn (23% for sediment) and in winter (4% for phosphorus). The relationship between removal efficiency and loads to the CW is not that straightforward, as other seasonal differences, such as erosion patterns, vegetation development, also become important.The conclusion based on the results presented is that establishing CWs can be a good supplement to best management practice in erosion-prone catchments with sensitive recipients.

Optimal Operation and Effect Research of Enhanced Denitrification AAO Process for Treating Rural Domestic Sewage

In view of the low concentration of organic matter in rural domestic sewage and the lack of carbon source in the biochemical denitrification process, resulting in excessive total nitrogen in the effluent, the traditional AAO process was improved to enhance the system's biochemical denitrification capacity. Through engineering demonstration, an improved process based on enhanced denitrification AAO process was constructed and applied to a village in Zhejiang Province. This process can ensure the complete separation of mixed liquid denitrification and sludge denitrification. While ensuring the denitrification efficiency, it can further reduce nitrate entering the anaerobic zone, so as to ensure a stable denitrification and phosphorus removal effect. The removal rates of the system for COD, NH3-N, TN, TP and SS are 95.6%, 99.5%, 75.1%, 97.6%, 91.6% respectively, in line with Zhejiang Province's "Water Pollution Discharge Requirements for Rural Domestic Sewage Centralized Treatment Facilities" (DB33 973-2021) Table 1 Level 1 Standard. In addition, the system energy consumption is 0.28 kwh/m³, which meets the requirements of low energy consumption system. This case can provide technical reference for the technical selection of rural domestic sewage treatment in my country.