Removal Efficiencies Of NH3-N Research Articles

Sustainable control of microplastics in wastewater using the electrochemically enhanced living membrane bioreactor

Wastewater treatment plant (WWTP) discharges are major contributors to the release of microplastics (MPs) into the environment. This research work aimed to assess the performance of the novel living membrane bioreactor (LMBR), which utilizes a biological layer as a membrane filter for the removal of polyethylene (PE) MPs from wastewater. The impact of an intermittently applied low current density (0.5 mA/cm2) on the reduction of MPs in the electrochemically enhanced LMBR (e-LMBR) has also been examined. The reactors were also compared to a conventional membrane bioreactor (MBR) and an electro-MBR (e-MBR). 1H nuclear magnetic resonance spectroscopy (1H NMR) was implemented for the MPs detection and quantification in terms of mass per volume of sample.The LMBR and MBR achieved comparable mean PE MPs reduction at 95% and 96%, respectively. The MPs mass reduction in the e-LMBR slightly decreased by 2% compared to that achieved in the LMBR. This potentially indicated the partial breakdown of the MPs due to electrochemical processes. Decreasing and inconsistent NH4-N and PO4-P removal efficiencies were observed over time due to the addition of PE MPs in the MBR and LMBR. In contrast, the integration of electric field in the e-MBR and e-LMBR resulted in consistently high values of conventional contaminant removals of COD (99.72–99.77 %), NH4-N (97.96–98.67%), and PO4-P (98.44–100.00%), despite the MPs accumulation.Integrating electrochemical processes in the e-LMBR led to the development of a stable living membrane (LM) layer, as manifested in the consistently low effluent turbidity 0.49 ± 0.33 NTU. Despite the increasing MPs concentration in the mixed liquor, applying electrochemical processes reduced the fouling rates in the e-LMBR. The e-LMBR achieved comparable efficiencies in contaminant reductions as those observed in the e-MBR, while using a low-cost membrane material.

Manufacture and performance assessment of PVDF-La@TiO2 Photocatalyst implanted membrane for efficient produced water treatment via ozonation-adsorption process under visible-light exposure

This research aims to develop a visible light-activated photocatalytic membranes for produced water treatment system by employing the phase inversion technique for implantation of La@TiO2 photocatalytic nanoparticles into PVDF membrane at concentrations varying from 0 % to 2 % wt. The results demonstrated significant amplification of COD and NH3-N removal efficiency. Implantation of the photocatalyst into PVDF membranes via bulk mixing, coupled with elemental doping and combination with La@TiO2 appreciably reduces band gap energy and increases visible light absorption thereby improves membrane's optical properties. SEM-EDX analysis confirms uniform distribution of La@TiO2 nanoparticles on the membrane surface, which leads to amplify membrane's hydrophilicity and water absorption. The modified membrane facilitated concurrent photocatalytic degradation and filtration processes that lead to remarkable reductions in TDS, COD, and NH3-N pollutants, with the highest flux was achieved when 1.5 % wt. La@TiO2 was incorporated into the membrane matrix. Obviously, adsorption and ozonation processes promote synergistic effect and amplify pollutant flux and efficiency to a greater extent. Furthermore, the modified membrane exhibited extraordinary antifouling properties and stability, providing excellent reusability with a 96.22 % fouling reduction rate after five consecutive cycle tests.

Assessing the nutrient removal performance from rice-crayfish paddy fields by an ecological ditch-wetland system

Agricultural drainage from catchments significantly impacts aquatic ecosystems due to high nitrogen and phosphorus concentrations in runoff. While original ecological ditches and wetlands have demonstrated effectiveness in nutrient load removal, the overall impact of an ecological ditch-wetland system (EDWS) on agricultural nutrient removal has received limited attention. This study conducted a field experiment to investigate the physicochemical conditions and nutrient removal efficiency of an EDWS for purifying nutrient discharge from rice-crayfish paddy fields. Variations in water temperature (WT), dissolved oxygen (DO), pH, and total suspended solids (TSS) within the EDWS were assessed. Nutrient concentrations—including total nitrogen (TN), ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), total phosphorus (TP), and soluble reactive phosphorus (SRP)—were monitored from the tillering to the ripening stage of the rice growth cycle. The evaluation of nutrient removal efficiencies in the EDWS revealed that ecological ditches exhibited higher removal efficiencies compared to wetlands. The average total removal efficiencies for TN, NH4-N, NO3-N, TP, and SRP were 37.50 %, 39.38 %, 38.62 %, 37.94 %, and 39.51 %, respectively, with peak removal efficiencies observed at specific growth stages of the rice crop. Furthermore, the study explored the influence of hydraulic retention time on nutrient removal efficiency in the EDWS, indicating higher nutrient discharge removal efficiencies under low water discharge rates. Linear regression analysis identified water discharge, influent nutrient loads, and TSS as significant factors affecting nutrient removal efficiency in the EDWS. This study provides valuable insights into the effectiveness of EDWS in purifying nutrient discharge from rice-crayfish paddy fields, highlighting their potential as sustainable solutions for nutrient management in agricultural landscapes.

Efficiency of Canna indica, Phragmites australis and Eichhornia crassipes in Remediation of Leachate Through a Vertical Flow Constructed Wetland

Leachate treatment and disposal from landfills is one of major environment concern. Leachate contains various pollutants which may cause various environmental and health problem to terrestrial and aquatic living bodies. In the Present study, Landfill leachate was collected from Okhla landfill, New Delhi and treatment of leachate was done by using laboratory scale vertical flow treatment grown with Canna indica, Phragmites australis and Eichhornia crassipes, respectively. The experimental plots were obtained by set up of four different flow rates by balancing the inflow manipulations to obtain detention times of 1,7,14 for 21 days. The reduction of COD, BOD, NH4-N, TSS and heavy metals (Cd, Cu, Co, Cr, As, Pb, Ni, Fe, Zn and V) were investigated for 21 days. Average removal efficiency (%) for VCW (W1) planted with Canna indica showed 77.7%, 78.7%, 63.6%, and 76.7% for COD, BOD, NH4-N and TSS, respectively. Heavy metal removal (%) efficiencies of W1 planted with Canna indica was 60%, 82.5%, 100%, 29.37%, 27.9%, 62.67%, 13.33%, 44.5%, 75.2% and 78.85% for As, Cr, Cd, Cu, Co, Fe, Mn, Pb, Zn and V, in given order. VCW(W2) planted with Eicchornia crassipes species has shown reduction efficiency (%) of COD (68.5%), BOD (52%), NH4-N (45.4%), TSS (92.75%), respectively and in case of heavy metal 89.9% Cr, 100% Cd, 53.49% Cu, 62.7% Co, 85.2% Fe, 67.9% Ni, 76.2% Pb, 83.08% Zn, 65% As and 61.15% V, respectively. VCW (W3) planted with Phragmites australis exhibited removal efficiency (%) of COD (68.5%), BOD (52%), NH4-N (45.4%) and TSS (92.7%), respectively. Phragmites australis was able to remove As (100%), Cd (100%), Cr (89.9%), Cu (53.49%), Co (62.7%), Fe (85.82%), Ni (67.9%), Pb (76.2%), V (61.15%) and Zn (83.08%), respectively. All the three species were able to remove Cd (100 %). However, Canna indica (W1) has highest removal efficiencies (%) of COD (77.7%), BOD (78.7%) and NH4-N (63.6 %), respectively. Eicchornia crassipes has highest reduction efficiency (%) of TSS (92.75%), Cr (89.9%), Cd (100%), Cu (53.49%), Co (62.7%), Fe (85.2%), Ni (67.9%), Pb (76.2%) and Zn (83.08%), respectively. Phragmites australis was found good for removal of As (100 %) and Cd (100%). The result highlighted that these plant species can be used as single in lab scale Constructed wetland for the treatment Organic pollutants and heavy metals from landfill leachate.

Application of Cu@Cu foam and RuO2@Ti for removal of nitrogen compounds and organic matters from non-standard treated municipal wastewater by continuous electrochemical process: Optimization and mechanism

Public health, potable water supplies, and ecosystems are endangered by the disposal or reuse of non-standard effluents of wastewater treatment plants. To achieve the Sustainable Development Goals (SDG 6) and USEPA quality standards, this work utilized an innovative electrochemical technique with continuous flow. Cu@Cu foam and RuO2@Ti were prepared for NO3 reduction and NH4 and COD oxidation, respectively. The characterization of electrodes was performed by XRD, EDS, FTIR, FE-SEM, and CV analysis. The effects of parameters including NH4 concentration (10–30 mg N/L), NO3 concentration (4–12 mg N/L), current (0.5–1.5 A), and Cl- concentration (100–400 mg/L) were examined for the removal of NH4, NO3, and COD. Characterization results confirmed that Cu and RuO2 were successfully coated on the surface of electrodes. Operating parameters were optimized using response surface methodology. The ideal conditions for current, Cl- concentration, and HRT were 1.5 A, 347.7 mg/L, and 120 min, respectively for concentrations of 9 mg /L NO3-N, 30 mg/L NH4-N, and 30 mg/L COD. Under these conditions, NO3-N, NH4-N, and COD removal efficiencies were 78 %, 97.8 %, and 61.2 %, respectively. The proposed electrochemical process was a sustainable technology for the concurrently removal nitrogen and carbon with advantages including environmental compatibility, versatility merits, and simplicity.

Removal of ammoniacal nitrogen from Malaysian palm oil mill effluent (POME) using optimized operating parameters of peat soil as natural adsorbent

Nowadays, the use of natural absorbents to remove pollutants from POME has gained remarkable attention. The main objective of this study is to investigate the suitability and performance of modified peat soil as an adsorbent for the removal of NH3-N from POME. The chemical activation method was performed using readily available NaOH for the first time to improve the adsorption performance of naturally available low-cost peat soil. The physical properties of raw and modified peat soil were determined using water-holding capacity, moisture content, bulk density, porosity, and BET surface area. The adsorbents were also characterized by SEM and FTIR to investigate surface morphology and chemical composition. To optimize the experimental parameters namely adsorbent dosage, agitation rate, and contact time for removal of NH3-N from POME, response surface methodology (RSM) was employed in this study with two different activation ratios. Substantial improvement of physical properties was attained after the modification of raw peat soil. The SEM images of modified peat soil showed a more porous space structure with larger voids while the FT-IR demonstrated the distinctive functional groups in the raw and modified peat soil. At optimized conditions of 5.71 g/L adsorbent dosage, 50 rpm agitation rate, and 38.96 min contact time predicted removal efficiency of NH3-N has been revealed 64.06 and 58.74 % at 1:20 and 1:30 activation ratios, respectively. The experimental investigation using optimized parameters showed 69.12 ± 2.5 and 61.57 ± 4.3 % removal of NH3-N. The experimental and predicted results showed good agreement. The rapid removal of NH3-N (69.1 % within 39 min) was achieved by chemically modified peat soil in this study compared to previously reported studies. Nevertheless, the raw and modified peat soil showed good stability up to three cycles of reusability.

Removal of NH3-N from wastewater by novel zeolite X: adsorption behavior and removal mechanism

This study utilized a straightforward method to fabricate zeolite X, demonstrating high adsorption performance for the removal of NH3-N from wastewater. The adsorption behavior of zeolite X towards NH3-N was investigated through various methods including adsorption kinetics, isothermal adsorption, and thermodynamic models. The mechanism of zeolite X for removing NH3-N were analyzed using techniques such as SEM, EDS, XRD, BET, and XPS. The results indicated that when t = 30 min, pH = 6, zeolite dosage was 20 g/L and initial NH3-N concentration was 100 mg/L, the removal efficiency of NH3-N could reach 95.5%. The adsorption process followed Freundlich model and were endothermic. The enthalpy change (ΔH), entropy change (ΔS) and Gibbs function (ΔG(308.15 K)) were 10.66 kJ/mol, 28.81 J/(mol･K), and 1.78 kJ/mol, respectively. SEM and XRD analysis show that the crystal shape of zeolite X is octahedral, which is a typical morphology of FAU-type zeolite. The specific surface area of zeolite X was as high as 643 m2/g. The results of XPS analysis show that after Na+ exchange with NH4+, hydrogen bonds were formed between ammonia nitrogen and oxygen in zeolite X. This study introduces a novel adsorbent, offering a fresh approach to tackling ammonia nitrogen pollution in wastewater.

Straw Biochar and Graphite Oxide Enhanced External Pressure Ultrafiltration for Leaded Wastewater Treatment.

In order to solve the problem of the low treatment efficiency of wastewater containing heavy metals in mining areas, straw biochar and graphene oxide enhanced external pressure ultrafiltration (SGU) was used to treat wastewater containing high concentrations of Pb2+. The operation parameters such as pH and temperature were optimized, and the removal efficiency of CODCr, NH3-N, turbidity and Pb2+ via SGU, straw biochar ultrafiltration (SU), ultrafiltration (UF), and conventional treatment (CT) were systematically investigated. The results showed that the pH and temperature of polluted water were 4.8-5.2 and 21-30 °C, respectively, the average removal rates of CODCr, NH3-N, turbidity and Pb2+ by SGU reached 91%, 97%, 98% and 95%, respectively, and the removal effect was better than that of other processes. In addition, under the backwash conditions of clean water, weak acid, and weak alkali, the membrane flux recovered 65%, 88%, and 89% of the new membrane, respectively. This study provides scientific and theoretical support for the advanced treatment of polluted water in mining areas.

Pontederia crassipes utilization for dual phytoremediation and adsorption in greywater treatment: a techno-economic and sustainable approach

While phytoremediation has been widely employed for greywater treatment, this system suffers from the transfer of considerable amounts of surfactants to the aquatic environment through partially treated effluent and/or exhausted plant disposal. Hence, this study focuses on greywater phytoremediation followed by recycling the spent plant for preparing an adsorbent material used as post-treatment. P. crassipes was used to operate a phytoremediation unit under 23 °C, 60% relative humidity, plant density (5–30 g/L), dilution (0–50%), pH (4–10), and retention time (3–15 days). The optimum condition was 12.7 g/L density, 34.0% dilution, pH 8.4, and 13 days, giving chemical oxygen demand (COD), surfactant, and NH4-N removal efficiencies of 94.62%, 90.45%, and 88.09%, respectively. The exhausted plant was then thermally treated at 550 °C and 40 min to obtain biochar used as adsorbent to treat the phytoremediation effluent. The optimum adsorption process was biochar dosage of 1.51 g/L, pH of 2.1, and 137 min, providing a surfactant removal efficiency of 92.56%. The final discharge of this phytoremediation/adsorption combined process contained 8.30 mg/L COD, 0.23 mg/L surfactant, and 0.94 mg/L NH4 +-N. Interestingly, this approach could be economically feasible with a payback period of 6.5 years, 14 USD net present value, and 8.6% internal rate of return.

Enhancing Rubber Industry Wastewater Treatment through an Integrated AnMBR and A/O MBR System: Performance, Membrane Fouling Analysis, and Microbial Community Evolution.

This study explores the effectiveness of an integrated anaerobic membrane bioreactor (AnMBR) coupled with an anoxic/oxic membrane bioreactor (A/O MBR) for the treatment of natural rubber industry wastewater with high sulfate, ammonia, and complex organic contents. This study was conducted at the lab-scale over a duration of 225 days to thoroughly investigate the efficiency and sustainability of the proposed treatment method. With a hydraulic retention time of 6 days for the total system, COD reductions were over 98%, which reduced the influent from 22,158 ± 2859 mg/L to 118 ± 74 mg/L of the effluent. The system demonstrates average NH3-N, TN, and total phosphorus (TP) removal efficiencies of 72.9 ± 5.7, 72.8 ± 5.6, and 71.3 ± 9.9, respectively. Despite an average whole biological system removal of 50.6%, the anaerobic reactor eliminated 44.9% of the raw WW sulfate. Analyses of membrane fouling revealed that organic fouling was more pronounced in the anaerobic membrane, whereas aerobic membrane fouling displayed varied profiles due to differential microbial and oxidative activities. Key bacterial genera, such as Desulfobacterota in the anaerobic stage and nitrifiers in the aerobic stage, are identified as instrumental in the biological processes. The microbial profile reveals a shift from methanogenesis to sulfide-driven autotrophic denitrification and sulfammox, with evidence of an active denitrification pathway in anaerobic/anoxic conditions. The system showcases its potential for industrial application, underpinning environmental sustainability through improved wastewater management.

Optimization of Ammonia Nitrogen Removal and Recovery from Raw Liquid Dairy Manure Using Vacuum Thermal Stripping and Acid Absorption Process: A Modeling Approach Using Response Surface Methodology

Dairy manure adds a substantial amount of nitrogen to wastewater due to its high levels of associated nutrients. Removal and recovery of ammonia nitrogen (NH3-N) from raw liquid dairy manure (RLDM) is greatly valued. This study was focused on the vacuum thermal stripping–acid absorption (VTS-AA) process for NH3-N from RLDM, followed by modeling and optimization. Using the response surface methodology (RSM)-based central composite design (CCD) approach, the critical operational parameters of the vacuum thermal stripping process, including temperature (50–70 °C), pH (9–11), vacuum pressure (35–55 kPa), and treatment time (60–90 min), were optimized. With the specified parameters set at temperature 69.9 °C, pH 10.5, vacuum pressure 53.5 kPa, and treatment time 64.2 min, the NH3-N removal efficiency attained was 98.58 ± 1.05%, aligning closely with the model prediction. Furthermore, the recovered ammonium sulfate ((NH4)2SO4) closely matched their commercial counterparts, confirming the effectiveness of the VTS-AA process in recovering NH3-N from RLDM. The distinct advantage of the employed technology lies in the concurrent energy demand reduction achieved by introducing a vacuum system. These findings contribute valuable insights into the practical implementation of the VTS-AA process for treating raw dairy manure, particularly in large-scale operational contexts.

High capacities of carbon capture and photosynthesis of a novel organic carbon-fixing microalgae in municipal wastewater: From mutagenesis, screening, ability evaluation to mechanism analysis

The development of wastewater treatment processes capable of reducing and fixing carbon is currently a hot topic in the wastewater treatment field. Microalgae possess a natural carbon-fixing advantage, and microalgae that can symbiotically coexist with indigenous bacteria in actual wastewater attract more significant attention. Ultraviolet (UV) mutagenesis and dissolved organic carbon (DOC) acclimation were applied to strengthen the carbon-fixing performance of microalgae in this study. The mechanisms associated with microalgal water purification ability, gene regulation at the molecular level and photosynthetic potential under different trophic modes resulting from carbon fixation and transformation were disclosed. The superior performance of Chlorella sp. MHQ2 was eventually screened out among a large number of mutants generated from 3 wild-type Chlorella strains. Results indicated that the dry cell weight of the optimal species Chlorella sp. HQ mutant MHQ2 was 1.91 times that of the wild strain in the pure algal system, more carbon from municipal wastewater (MW) were transferred to the microalgae and re-entered into the biological cycle through resource utilization. In addition, COD, NH3-N and TP removal efficiencies of MW by Chlorella sp. MHQ2 were found to increase to 95.8% (1.1-times), 96.4% (1.4-times), and 92.9% (1.2-times), respectively, under the extra DOC supply and the assistance of indigenous bacteria in the MW. In the transcriptome analysis of the logarithmic phase, the glycolytic pathway was inhibited, and the pentose phosphate pathway was mainly carried out for microalgal life activities, further promoting efficient energy utilization. Upon analysis of carbon capture capacity and photosynthetic potential in trophic mode, the addition of NaHCO3 increased the photosynthetic rate of Chlorella sp. MHQ2 in mixotrophy whereas it was attenuated in autotrophy. This study could provide a new perspective for the study of resource utilization and microalgae carbon- fixing mechanisms in the actual wastewater treatment process.

Optimization of pollutants removal from anaerobically digested dairy wastewater by electro-oxidation process: a response surface methodology modeling and validation

The release of anaerobically digested dairy wastewater (ANDDW) without a treatment can lead to severe environmental pollution, prompting the exploration of effective and sustainable treatment methods. Amidst various wastewater treatment approaches, the electro-oxidation (EO) process is considered as a promising, clean, and adaptable solution. In this study, the major operational parameters viz. current density, electrolyte concentration, treatment time, and mixing speed of an EO comprising Ti/PbO2 anode and stainless-steel cathode, were optimized using response surface methodology (RSM) for efficient removal of chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total phosphorus (TP), orthophosphate (OP), total nitrogen (TN), and total Kjeldahl nitrogen (TKN) from ANDDW. Optimal conditions were identified as a current density of 90 mA cm−2, 0.08% electrolyte concentration, 180 min treatment time, and 400 rpm mixing speed. Under the optimum conditions, the COD, NH3-N, TP, OP, TN, and TKN removal efficiencies were 78.36, 63.93, 87.41, 92.39, 67.01, and 81.42%, respectively. Furthermore, the reaction rate followed the first-order kinetic model for the pollutants removal with correlation coefficients (R2) close to 1. The findings highlight the potential of using the EO process to treat high pollutant-laden ANDDW and encourage further studies to confirm the corresponding outcomes on a pilot scale.Graphical abstract

Performance assessment of up-flow anaerobic multi-staged reactor followed by auto-aerated immobilized biomass unit for treating polyester wastewater, with biogas production

Polyester manufacturing industries produce highly polluted effluents, containing organics, nutrients, trace metals, and 1,4-dioxane, requiring a high degree of treatment before being discharged into the water bodies. This study focused on removing complex pollutants from a diluted polyester industrial effluent (DPIE) via a cost-efficient anaerobic/aerobic combined system, with biogas recovery. The integrated pilot-scale system was composed of an up-flow anaerobic multi-staged reactor (UASR; V = 41 L) followed by an auto-aerated immobilized biomass (AIB; Vsponge = 9.54 L) unit and operated at a total organic loading rate (OLR) of 0.75 ± 0.16 g COD/L/d and pH of 7.14 ± 0.14 at 25 °C. The UASR achieved removal efficiencies of 17.82 ± 3.14% and 15.90 ± 3.08% for chemical oxygen demand (COD, total and soluble) and 15.83 ± 4.68% for total Kjeldahl nitrogen (TKN), with bio-CH4 yield of 263.24 ± 31.98 mL/g COD. Adding the AIB unit improved the overall CODtotal, CODsoluble, and TKN to 93.94 ± 2.39%, 94.84 ± 2.23%, and 75.81 ± 3.66%, respectively. The NH4-N removal efficiency was 85.66 ± 2.90% due to the oxic/nitrification condition on the sponge’s outer surface. The entire system also achieved 73.26 ± 2.68%, 77.48 ± 5.74%, and 81.26 ± 6.17% removals for Fe (3.93 ± 0.95 ppm), Zn (5.92 ± 2.32 ppm), and 1,4 dioxane (2.50 ± 0.61 ppm). Moreover, the UASR-AIB maintained removal efficiencies of 76.53 ± 8.47% and 77.51 ± 7.38% for total suspended solids (TSS: 335.95 ± 42.84 mg/L) and volatile suspended solids (VSS: 263.50 ± 36.94 mg/L). Regarding the DPIE toxicity level, the EC50 value increased from 12.9 to 39.4% after UASR/AIB application. The UASR’s microbial community at the genus level demonstrated that the synergistic cooperation of solubilization, hydrolysis, acidogenesis, acetogenesis, and methanogenesis was responsible for the degradation of DPIE components.

Application of different aquatic plants in an alternated fill and drain wetland system of Phetchaburi municipal wastewater treatment in Thailand

This study evaluated the treatment efficiency of municipal wastewater from Phetchaburi in Thailand in an alternated 5-day flooding and 2-day drying wetland system with two plants species, namely, Canna indica and Heliconia psittacorum. The efficiencies of biochemical oxygen demand (BOD5) treatment were in the ranges of 90.5% ± 4.8% and 86.9% ± 7.3% for Canna and Heliconia, respectively. Those of chemical oxygen demand (COD) treatment were in the ranges of 75.5% ± 7.9% and 75.3% ± 9.0% for Canna and Heliconia, respectively. Both plants’ removal efficiencies of TN, NH4-N, and TP were greater than 40%. Lead and cadmium accumulation in both plants significantly differed between the upper and lower parts of the plants. However, the lead and cadmium accumulation in Heliconia were greater than their accumulation in Canna. Although Canna had a higher nutrient removal efficiency than Heliconia, there are many varieties of Canna in Thailand. These results indicate that the variety of Canna does not affect the nutrient removal efficiency. In conclusion, a wetland system with alternated flooding and drying conditions can be applied in communities where BOD5 and COD are the dominant wastewater pollution characteristics. Both ornamental plants are suitable absorbents for lead and cadmium, and although the accumulation is lower in Canna than in Heliconia for both heavy metals, the difference was not significant.

Full-scale integrated skid-mounted plug flow photocatalytic reactor: Treatment of hospital wastewater

A full scale treatment of hospital wastewater (60 m3/day), was newly developed, combining many processes including activated sludge, coagulation-flocculation, and skid-mounted photocatalysis. The tested raw hospital wastewater had the following characteristics: biochemical oxygen demand (BOD): 250–400 mg/L, chemical oxygen demand (COD): 800–1000 mg/L, ammonia nitrogen (NH3-N): 70–100 mg/L, total phosphorus (TP): 3.0–5.0 mg/L, suspended solids (SS): 200–300 mg/L and fecal coliform (FC): 9.2 × 104–1 × 105 MON/L. During more than 3 years the in-situ operation of the average removal efficiency of COD was 90–95% with an effluent value in the range of 35–48 mg/L. The average removal efficiency of BOD, FC, TP, NH3-N, SS, color, and turbidity was in the range of 85–90%, 95–97%, 75–80%, 50–55%, 89–92%, and 95–97%, respectively. The overall operating cost was determined as 3.5 RMB /m3. This innovative technology was evaluated at a full-scale plant, demonstrating that its application was feasible and addressed many environmental concerns. This reactor has the following advantages: modular design, low infrastructure investment and simple operation. More importantly, this could be one of the first commercial photocatalytic reactors.

A novel photo-assisted activated persulfate strategy for selective oxidation of ammonia nitrogen to dinitrogen using sodium silicate and sodium sulfite as regulators

Persulfate (PS)-based advanced oxidation processes (SR-AOPs) is a promising approach for the removal of ammonia nitrogen (NH3-N) from wastewater, but it suffered from the low removal efficiency and the excessive oxidation of NH3-N to nitrate (NO3−) or nitrite (NO2−) in the absence of in-situ generated chlorine radicals. Therefore, it is still a challenge to improve the efficiency of NH3-N removal and the selectivity of NH3-N oxidation products towards dinitrogen (N2) by SR-AOPs without chlorine radicals. Herein, a novel photo-assisted activation of SR-AOPs involving sodium silicate (Na2SiO3) and sodium sulfite (Na2SO3) was developed for NH3-N removal from wastewater. In this system, Na2SiO3 was acted as a green buffer to maintain NH3-N in the form of un-ionized ammonia (NH3) with strong reducibility, promoting the efficiency of NH3-N removal as well as ensuring the neutral effluent by receiving the H+ from PS activation. Na2SO3 could inhibit the excessive oxidation of NH3-N by regulating the redox potential of the solution and generating hydrated electrons (eaq−) under light (hv) irradiation, enhancing the selectivity of NH3-N oxidation products towards N2. 100 % of NH3-N removal efficiency and more than 98 % of N2 selectivity were obtained after 30 min at the initial pH of 3–9 and the initial NH3-N concentration of 30 mg N/L. Based on the quenching experiment, EPR test and probe experiment, the HO and SO4− were the main reactive oxygen species (ROS) to be responsible for NH3-N oxidation. This study proposed a new approach for treatment of wastewater containing NH3-N by SR-AOPs.

Effects of antibiotic exposure on bioreactor treatment efficiency and dynamic migration of resistance genes in landfill leachate

Different concentrations of tetracycline (TC) (10 and 30 mg/L) were added to the anaerobic-anoxic-aerobic reactor to investigate the changes in effluent quality, sludge performance and the dynamic migration of antibiotic resistance genes (ARGs) in simulated landfill leachate. The maximum removal rates of COD, TN, and TP occurred at a TC concentration of 10 mg/L, reaching 75.99 %, 50.46 %, and 60.26 %, while the removal efficiency of NH3-N continued to decline. Microorganisms secreted abundant extracellular polymeric substance (EPS) and combined with antibiotic to form a stable and dense EPS antibiotic complex to resist adverse stress. The concentration of heavy metals showed a trend of first increasing and then decreasing, especially Mn and Zn. At a concentration of 10 mg/L TC, aerobic condition weakened ARGs, while anaerobic facilitated the proliferation of ARGs. The tetA and tetM in leachate were positively correlated with TC, TP, TN, NH3-N, and COD (P < 0.05), while the diffusion and transmission of ARGs in sludge were under the superimposed pressure of TC, various heavy metals, and EPS. Moreover, changes in bacterial communities drove the release of ARGs. To analyze the potential risks of ARGs in landfill leachate under antibiotic exposure, providing clues for the management and risk assessment of sewage biological treatment facilities.

Applying a microbial electrolysis cell to promote imidacloprid removal in the adsorption biological coupling system at low temperature via accelerating coke regeneration and bioaugmentation

In this study, imidacloprid (IMI) wastewater was treated by adsorption biological coupling (ABC) and microbial electrolysis cell (MEC)-ABC technologies at low temperature (15 °C). Meanwhile, the degradation mechanism of IMI and the expression of functional genes were revealed. Results showed that under MEC enhanced treatment, the removal efficiency of COD, NH3-N, total-phosphorous (TP), and IMI reached 90.37 %, 92.03 %, 77.12 %, and 100 %, respectively, which were 9.71 %, 6.30 %, 9.48 % and 30.40 % higher than those of ABC treatment, respectively. Aestuariivirga sp. YIM B02566 became the dominant bacterium in ABC and MEC-ABC reactors under low-temperature conditions. MEC increased the relative abundance of Sphingomonadales, Hyphomicrobiales, and Aestuariivirga sp. YIM B02566 by 8.87 %, 16.15 %, and 5.29 %, respectively. Moreover, it up-regulated the abundance of key genes related to carbon and phosphorus metabolism, such as PGK (10.91 %), ENO (15.61 %), pstS (2.40 %), phnP (0.45 %) and phoD (0.97 %). Finally, MEC facilitated the conversion of C9H9ClN4 (m/z 209.0581), C9H11ClN4 (m/z 211.0729), C9H10ClN3O (m/z 212.0584), C9H11N5O2 (m/z 222.0964), C9H11ClN4O (m/z 227.0685) to C9H10ClN3O (m/z 212.0600), C9H11N5O2 (m/z 222.0964). The stability of MEC-ABC reactor operation at low temperature not only minimized the formation of IMI degradation products, but also provided an theoretical foundation for expanding the practical application of MEC-ABC technology in the treatment of IMI neonicotinoid insecticide wastewater.

Effect of floating plant growth rate on water quality performance of wetland in treating domestic sewage

A man-made system that mimics the function and structures of natural wetlands is called constructed wetlands. It is able to treat sewage water with low technology, low energy requirements, affordable and easy to maintain. However, how it works in tropical climates is still unknown and there is a need to figure out the sustainability of floating plants in treating domestic sewage. This study aims to investigate the pollutant removal efficiency of two selected floating plant species, water hyacinth and water lettuce, in treating domestic sewage. The growth rate of both plants will be examined for the best-recommended plants in the constructed wetland systems for domestic sewage treatment. The data was collected through a pilot-constructed wetland in the USM, Engineering Campus that is integrated with two species of floating plants: water hyacinth and water lettuce. The parameters studied were chemical oxygen demand (COD), total suspended solids (TSS), and ammoniacal nitrogen (AN). The findings reveal that the removal efficiency of water hyacinth is higher for COD and TSS at 40.96 % and 43.94 % respectively compared to Water Lettuce with 26.86 % for COD and 17.79 % for TSS. However, Water Lettuce has a slightly higher removal efficiency of NH3-N at 26.52 % compared to Water Hyacinth at 24.35 %. In terms of growth rate, Water Hyacinth is lost to water lettuce, but they have higher biomass to uptake nutrients with just a small increment of area coverage. Therefore, water hyacinth is favourable to implement in floating plant-constructed wetlands as it needs less maintenance than water lettuce to achieve discharge with standard A for TSS and COD and standard B for NH3-N based on Malaysia Wastewater Effluent Discharge Standards.