High Average Removal Research Articles

Triggering Catalyst-Mediated Electron Transfer for Enhanced Ion Separation in Redox-Flow Battery Desalination System

Redox-flow battery desalination (FBD), an emerging electro-membrane separation technology, has garnered considerable attention due to its advantages such as continuous operation, low energy consumption, and relatively high average salt removal rate. FBD systems consist of current collectors, redox-flow electrolyte, and ion-exchange membranes (IEM) arranged in a 4-chamber structure. During operation, electron currents from the current collectors are converted into ion currents via the redox reaction of redox-active couples, such as Fe(CN)6 3− and Fe(CN)6 4−. Consequently, the ion current transported through the IEM leads to the production of diluted stream and concentrated stream in the dilute chamber and concentrate chamber, respectively.To optimize the performance of the FBD system, enhancing the efficiency of the redox reaction is crucial. The reaction mechanism involves three steps. Taking oxidation as an example, the first step entails the transfer of Fe(CN)6 4− from the bulk solution to the surface of the current collector. Subsequently, Fe(CN)6 4− undergoes electron transfer to the electrode, forming Fe(CN)6 3−. The third step is the diffusion of Fe(CN)6 3− into the bulk solution. To shorten the path of redox couple and enhance the transportation of electron current, studies have attempted to use conductive electrode in FBD system, such as graphite felt and electrospun carbon fiber. However, limited attention has been given to the electrochemical reaction kinetics between redox couples. Hence, there is an opportunity to focus on catalyzing the redox reaction within FBD systems.In this study, the FBD system performance were enhanced by incorporating an electrocatalyst. Nickel oxide (NiO) was chosen as the electrocatalyst and coated onto the graphite felt electrode (GF) through a hydrothermal method, resulting in the formation of the NiO-GF electrode. Electrochemical characterization conducted in Fe(CN)6 3−/4− electrolyte revealed that the NiO-GF electrode exhibited a smaller semicircle in EIS spectra and higher corresponding current in the CV loop, compared to the GF electrode. These results suggest that the NiO-GF electrode can effectively serve as a catalyst-mediated electrode in FBD process. Further investigations will be conducted to assess its performance in the FBD process, with a focus on its potential applications in high water recovery. Figure 1

Effect of monocultures and polycultures of Typha latifolia and Heliconia psittacorum on the treatment of river waters contaminated with landfill leachate/domestic wastewater in partially saturated vertical constructed wetlands

Partially Saturated Vertical Constructed Wetlands (PSV-CWs) are novel wastewater treatment systems that work through aerobic and anaerobic conditions that favor the removal of pollutants found in high concentrations, such as rivers contaminated with domestic wastewater and landfill leachate. The objective of the study was to evaluate the efficiency of PSV-CWs using monocultures and polycultures of Typha latifolia and Heliconia psittacorum to treat river waters contaminated with leachates from open dumps and domestic wastewater. Six experimental units of PSV-CWs were used; two were planted with Typha latifolia monoculture, two with Heliconia psittacorum monoculture and two with polycultures of both plants. The results indicated better organic matter and nitrogen removal efficiencies (p < 0.05) in systems with polycultures (TSS:95%, BOD5:83%, COD:89%, TN:82% and NH4+:99%). In general, the whole system showed high average removal efficiencies (TSS:93%, BOD5:79%, COD:85%, TN:79%, NH4+:98% and TP:85%). Regarding vegetation, both species developed better in units with monocultures, being Typha latifolia the one that reached a more remarkable development. However, both species showed high resistance to the contaminated environment. These results showed higher removals than those reported in the literature with conventional Free Flow Vertical Constructed Wetlands (FFV-CWs), so PSV-CWs could be a suitable option to treat this type of effluent.

Flexible construction of three-dimensional continuous conductive structure by hollow carbon sphere and CNT for promoted ions transport in flow-electrode capacitive deionization

Flow-electrode capacitive deionization (FCDI) emerges as a promising desalination technique, characterized by its unlimited desalination capacity, seamless operation, and easy scalability. However, challenges such as discontinuous electronic network, inadequate dispersion of suspended carbon particles, and hindered electron/ion transport pathways have impeded the full potential of FCDI. This study addresses the above issues by synergistically leveraging the advantage of hollow carbon sphere (HCS) and CNT to construct a flexible, continuous three-dimensional conductive network (HCS@CNT) as the flow-electrode for FCDI. The incorporation of HCS substantially improves the fluidity and effective collision of the flow-electrode slurry. Simultaneously, the bridging effect of CNT facilitates smooth ion transport routes and rapid electron/ion transfer. Moreover, the spherical structure of HCS as a node can effectively alleviate the agglomeration of CNT due to its inherent good fluidity. As a result, the meticulously designed HCS@CNT flow-electrode demonstrates outstanding rheological behavior with excellent hydrophilicity, a large specific capacitance, and low ion diffusion resistance. During desalination tests, the HCS@CNT flow-electrode exhibited a high average salt removal rate (0.56 µmol min−1 cm−2), appropriate energy-normalized removal salt (15 µmol J−1), and notable charge efficiency (89 %) in a 1 g L-1 NaCl solution. Impressively, it maintained good stability and continuity over a continuous 10-hour desalination process, showcasing substantial potential for treating highly concentrated saline water. In addition, density functional theory (DFT) calculations provided additional insights, confirming that the construction of HCS@CNT facilitated interfacial charge transfer and electron transport from HCS to CNT. This innovative approach sheds light on enhancing electron/ion transfer by harnessing the unique structural characteristics of the flow-electrode.

New insights into the performance analysis of flow-electrode capacitive deionization using ferri/ferrocyanide redox couples for continuous water desalination

Flow Electrode Capacitive Deionization (FCDI) is a promising technology that uses carbon materials as flow electrodes in aqueous conditions to enable continuous desalination. In this work, the parametric investigation of the FCDI cell was carried out for low and high surface area activated carbon. When 1 mM/1 mM ferri-/ferrocyanide redox couple in the 1 M NaCl supporting electrolyte containing the 5 wt% high surface area activated carbon and 0.5 wt% MWCNT is circulated as flow electrode at the flow rate of 8 mL/min in the electrode chamber and 0.1 mM NaCl feed water is circulated in single-pass mode at 8 mL/min, the FCDI system achieved a significant improvement in desalination performance up to 76.38 % of SRE, with a high average salt removal rate of 43.925 µg/cm2s @ 2 V, charge efficiency of 20.11 % and average energy consumption of 0.27 kWh/mol, through a thorough parametric investigation. When the FCDI cell was tested with tap water, the average salt removal rate, average energy consumption, and salt removal efficiency were calculated at 6.11 μg/cm2s, 2.46 kWh/mol, and 46.61 % respectively, resulting in the reduction of total dissolved solids of 600 mg/L at the inlet to 365 mg/L at the outlet. The combination of microporous high surface area carbon and ferro-ferri redox couple propelled the desalination performance in comparison with the macroporous low surface area carbon, maximizing the ion removal rate, which further reduced the energy consumption and operating voltage for the process.

Achieving an efficient redox-flow battery with high-conductivity electrospun carbon fiber for wastewater reclamation and seawater desalination

A redox-flow battery (RFB) has been established for continuous ion separation based on reversible redox reactions of the Fe(CN)63−/4− electrolyte. Herein, electrospun carbon fibers (CFs) with tailor-made properties were developed at different carbonization temperatures. With a carbonization temperature of 900°C, the CF (CF-900) showed a high degree of graphitization (Id/Ig = 0.92) and low electrode resistance. The cyclic voltammetry curve of CF-900 was composed of evident redox peaks with a high current level, revealing good electrochemical reversibility and high electrochemical activity of the redox reactions. With the CF-900 electrode, a high average salt removal rate (ASRR) of 97.5 μg/min/cm2 was achieved at 0.4 V while desalinating 10 mM NaCl, which was 1.4-fold higher than in the absence of the CF electrode. Moreover, the addition of the CF-900 electrode greatly improved the charge efficiency (96%) with a relatively low energy consumption of 0.0112 kWh/mol. The technical feasibility of RFB was assessed in terms of quantifying the ASRR for wastewater reclamation and seawater desalination. The application of high-conductivity CF-900 electrode demonstrated high ASRR (148.3 μg/min/cm2 for wastewater reclamation and 81.6 μg/min/cm2 for seawater desalination) with low energy consumption, making the strategy promising for achieving an efficient redox-flow battery process.

Study on the preparation and feasibility of a novel adding-type biological slow-release carbon source

The development of slow-release carbon sources is an effective biological treatment to remove nutrients from wastewater with low carbon-to-nitrogen ratio (C/N). Most filling-type slow-release carbon could not fulfil the needs of current wastewater treatment plants (WWTPs) process. And most adding-type slow-release carbon sources were prepared using some expensive chemical materials. In this study, combining the advantages of the aforementioned types, a novel adding-type wastepaper-flora (AT-WF) slow-release carbon source was proposed, aiming to realise wastepaper recycling in WWTPs. The screening and identification of the mixed flora, AT-WF carbon source release behaviour, and denitrification performance were investigated. The results showed that through the proposed screening method, a considerable proportion of cellulose-degradation-related genera was enriched, and the cellulose degradation ability and ratio of readily available carbon sources of flora T4, S4 and S5 were effectively strengthened. AT-WF had significant carbon release ability and stability, with an average total organic carbon (TOC) release of 8.82 ± 2.36 mg/g. Kinetic analysis showed that the entire carbon release process was more consistent with the first-order equation. Piecewise fitting with the Ritger-Peppas equation exhibited that the rapid-release (RR) stage was skeleton dissolution and the slow-release (SR) stage was Fick diffusion. Denitrification efficiency can achieve a high average removal efficiency of 94.17%, which could theoretically contribute 11.2% more to the total inorganic nitrogen (TIN) removal. Thus, this study indicated that AT-WF could be utilised as an alternative carbon source in WWTPs.

Biochemical treatment of coal mine drainage in constructed wetlands: Influence of electron donor, biotic–abiotic pathways and microbial diversity

The management and treatment of extremely acidic coal mine drainage (CMD) from Northeastern Coalfield (NEC), Assam, India, remains a perpetual environmental challenge. The present work proposes an effective passive bioremediation strategy for highly acidic (pH of 2.2) synthetic CMD simulated to represent mine discharge from the NEC (in mg L–1) (Fe: 100, Al: 25, Mn: 6, Zn: 5, Co: 1, Ni: 1, Cr: 1 and SO42-: 1000–1200), using a horizontal sub-surface flow constructed wetland (HSSF-CW). Gravel was used as the media in HSSF-CW and operated continuously for 218 days, including acclimatization (I–IV) and treatment (V–VI) phases at a hydraulic retention time of 7 days. COD/SO42- ratio was varied as 0.67 in phase I–V and 0.33 in phase VI. High average metal removal efficiency was achieved for Fe (73%), Al (79%), Zn (98%), Co (95%), Ni (99%) and Cr (100%), but Mn (21%) in the treatment phase. In phase V, high sulfate removal efficiency (74%) conforming sulfidogenesis pathway was observed. The prominence of acidophilic sulfate-reducing bacteria (SRB) (Desulfosporosinus meridiei) was revealed. Sulfate reduction by SRB generated alkalinity and increased pH to 5.1–6.8, which assisted in metal retention (as oxides, hydroxides and sulfides precipitates). At lower COD/SO42-, alkalinity decreased due to incomplete sulfate reduction (45%) as COD became the limiting factor, evident from the lower pH and subsequent remobilization of iron and other adsorbed metals in phase VI. This exploratory study recommends the optimization of COD/SO42- and provides an efficient sustainable solution to mitigate CMD pollution.

Modified pineapple peel extract coupled with electrokinetic techniques for remediation of chromium-contaminated soil

Remediation of chromium (Cr)-contaminated soil is a hot topic in environmental science and technology. In this field, one important issue is to develop a low-cost and effective electrolyte. This work investigated efficient remediation of Cr-contaminated soils by electrokinetic using pineapple-peel extract (PPE) as electrolyte. The main components of PPE were sugar and citric acid. The effects of these two components were investigated on remediation efficiency. The changes of soil properties, including pH, conductivity, electroosmotic flow, and Cr residue, were detailedly analyzed during electrokinetic remediation. After modification by H2O2, total sugar and organic acid contents in PPE changed from 64.5% and 0.115–42.5% and 0.304%, respectively. These changes further improved the Cr remediation. The highest average removal was 82.75% when 30% of H2O2 was used to modify PPE electrolyte. The main result of this work is in favor of developing and applying green electrolyte in electrokinetic technology. At the same time, pineapple residual is effectively recycled, which is devoted to green development.

Ameliorating effect of nitrate on nitrite inhibition for denitrifying P-accumulating organisms

Lowered air supply and organic carbon need are the key factors to reduce wastewater treatment costs and thereby, avoid eutrophication. Denitrifying PO43−- removal (DPR) process using nitrate instead of oxygen for PO43− uptake was started up in the sequencing batch reactor (SBR) at a nitrate dosing rate of 20–25 mg N L−1 d−1. Operation with a real municipal wastewater supplied with CH3COONa, K2HPO4 and KNO3 succeeded in the cultivation of biomass containing denitrifying polyphosphate accumulating organisms (DPAOs). The durations of SBR process anaerobic/anoxic/oxic cycles were 1.5 h, 3.5 h and 1 h, respectively. SBR operation resulted in a maximum PO43−-P uptake of 17 mg PO43−-P g−1 MLSS. The highest TN and PO43− removal efficiencies were observed during the first half of reactor operation at 77 (±10) % and 71 (±5) %, respectively. An average COD removal rate of 172 (±98) mg g−1 MLSS and a high average removal efficiency of 89 (±4) % were achieved.Nitrite effect with/without nitrate as DPR electron acceptor was investigated in batch-scale to show possibilities to use high nitrite and nitrate contents simultaneously as electron acceptors for the anoxic phosphate uptake. Nitrate attenuation against nitrite toxicity can be economically justified in full-scale treatment applications in which wastewater has a high nitrogen content. Nitrate attenuated nitrite toxicity (caused by nitrite content at 5–100 mg NO2−-N L−1) when using supplemental additions of nitrate (at concentrations of 45–200 mg NO3−-N L−1) in batch tests. Illumina sequencing emphasized that during biomass adaption microbial community changed by lowered aerobic cycle length and by lowered nitrate dosing towards representation of key DPAO/PAO- organisms, such as Candidatus Accumulibacter, Xanthomonadaceae, Comomonadaceae, Saprospiraceae and Rhodocyclaceae. This study showed that DPAO biomass adaption to nitrate maintained an efficient COD, nitrogen and phosphorus removal and the biomass can be applied for treatment of wastewater containing high nitrite and nitrate content.

Improving the performance of biotrickling filter microbial fuel cells in treating exhaust gas by adjusting the oxygen content of the anode tank

A biotrickling filter (BTF) was combined with a microbial fuel cell (MFC) to remove ethyl acetate from exhaust gas while generating electricity in the process. The results indicated that the use of carbide porous ceramic rings (CPCR) as auxiliary anodes produced more biomass and exhibited a high average removal efficiency (98%), making it a superior microorganism growth carrier compared with carbon coke. When CPCR was used as the cathode in the BTF-MFC, the maximum power density (PD) was 5.64–14.8% of that achieved when carbon cloth was used as the cathode, revealing that CPCR is not a suitable cathode. The maximum elimination capacity (EC) and output voltage of the two-stage BTF-MFC (tBTF-MFC) were only 69.4% and 68.4% of those of the single-stage BTF-MFC (sBTF-MFC), presumably because of voltage reversal. Although the output voltage and EC in the tBTF-MFC were less than those in the sBTF-MFC, the follow-up field application involves stacking multiple small MFCs to remove high-concentration pollutants and generate a high power output. Additionally, continuously adding sodium sulfite decreased the average dissolved oxygen; generated an averaged closed-circuit voltage of 477 mV; and produced a maximum PD of 71.7 mW/m3. These findings demonstrated that the aforementioned method can effectively improve the problem of oxygen and MFC anodes competing for electrons, thus delivering a method that enhances MFC performance through controlling the amount of oxygen in practical applications.

Reshaped structure of microbial community within a subsurface flow constructed wetland response to the increased water temperature: Improving low-temperature performance by coupling of water-source heat pump

To evaluate the pollutant removal mechanisms and pathways in traditional constructed wetlands (CWs), and remove its operation bottleneck under low temperature, a co-system was established by coupling a subsurface flow constructed wetland (SFCW) and the water-source heat pump (WSHP) units. Experimental consequence demonstrated that the water temperature had increased significantly, and the mean temperature of influent was 8 ± 3 °C while that of effluent was 15 ± 5 °C. High average removal efficiencies of COD (64.5%), NH3-N (89.5%), NO3-N (90.2%), TN (58%), and TP (93.5%) were achieved in the experimental co-system. Optimal removal efficiency was achieved when pH was 6–7.5 and hydraulic retention time (HRT) was 4 days. Nitrification led to the higher organic pollutants removal efficiency. Meanwhile, it was considered to be due to the significant variation of the microbial community structure after the application of the WSHP units, in which the species richness and community equitability significantly improved. The thermophilic communities grew and reproduced in large numbers. The results also showed the application of co-system was an effective and sustainable strategy for removing diverse pollutants in cold climate.

Hydroponic Farm Wastewater Treatment Using an Indigenous Consortium

Hydroponic farms produce wastewater that need to be treated before being released into the environment. A three-step screening process (microplate, batch, and semi-continuous flasks experiments) initially designed to select an efficient microalgae strain allowed the isolation of a consortium that naturally developed in the hydroponic farm wastewater. During the non-optimized semi-continuous experiments, the best performing microalgae strain, Scenedesmus obliquus UTEX393 and the wastewater-born consortium cultures achieved good average linear growth rate (0.186 and 0.198/d, respectively) and high average nitrogen removal rates (23.5 mgN/L/d and 21.9 mgN/L/d, respectively). Phosphorus removal was very high probably due to precipitation. An integrated process was designed to treat the hydroponic farm wastewater using the wastewater-born consortium. Despite relatively low coagulation efficiencies in the preliminary tests, when integrated in a continuous process, chitosan was efficient to harvest the naturally wastewater-born consortium. The process was also efficient for removing nitrate and phosphate in less than seven days (average removal of 98.2 and 87.1% for nitrate and phosphate, respectively). These very promising results will help to define a pre-industrial pilot process.

Pollutants removal, greenhouse gases emission and functional genes in wastewater ecological soil infiltration systems: influences of influent surface organic loading and aeration mode.

The influences of influent surface organic loading rate (SOLR) and aeration mode on matrix oxygen, organic matter, nitrogen, phosphorus removal, greenhouse gases emission and functional gene abundances in lab-scale wastewater ecological soil infiltration systems (WESISs) were investigated. In WESISs, intermittent or continuous aeration improved oxygen supply at 50 cm depth and hardly changed anaerobic condition below 80 cm depth, which enhanced chemical oxygen demand (COD), NH4+-N, total nitrogen (TN) removal, the abundances of bacterial 16S rRNA, amoA, nxrA, narG, napA, nirK, nirS, qnorB, nosZ genes and reduced CH4, N2O conversion efficiencies with SOLR of 16.9 and 27.6 g BOD/(m2 d) compared with non-aeration. Increased SOLR resulted in high TN removal, low N2O emission in aeration WESIS, which was different from non-aeration WESIS. High average COD removal efficiency of 90.7%, NH4+-N removal efficiency of 87.0%, TN removal efficiency of 84.6%, total phosphorus (TP) removal efficiency of 93.1% and low average N2O emission rate of 12.8 mg/(m2 d) were achieved with SOLR of 16.9 g BOD/(m2 d) in intermittent aeration WESIS. However, continuous aeration WESIS obtained high average removal efficiencies of 90.1% for COD, 87.5% for NH4+-N, 84.1% for TN, 92.9% for TP and low average emission rate of 13.1 mg/(m2 d) for N2O with SOLR of 27.6 g BOD/(m2 d). Aeration could be an optional strategy for WESISs to achieve high pollutants removal and low CH4, N2O emission when treating wastewater with high SOLR.

Impact of microbial activity on the performance of planted and unplanted wetland at laboratory scale

Abstract Three horizontal subsurface flow constructed wetland prototypes were set up to identify and understand the role of microflora in nutrient removal under diverse operating conditions. Out of three setups, one setup served as a control (without plants), and the rest were planted with Typha domingensis. The setups were operated at two different hydraulic loading rates (5 cm/day and 16 cm/day) for two months each. Among 27 bacteria species isolated, 80% of nitrate-reducing bacteria were observed in control, and 50–77% of nitrate-reducing bacteria were observed in the plant setups. Presence of diverse denitrifying bacteria and soil organic carbon contributed to high Nitrate-N removal in the control at both HLRs. Similar Ammonium-N (29%) and Ortho-P removal (30%) efficiency was observed at both HLRs in the control setup. Processes such as chemical sorption and adsorption dominated the Ammonium-N and Ortho-P removal in the control setup. High average Ammonium-N removal efficiency of 89% and 52% was observed in plant setups at 5 cm/day and 16 cm/day HLR. At low HLR, Ammonium-N removal in plant setups was dominated by nutrient uptake. In the plant setups, 35% and 15% Ortho-P removal efficiency was observed at low HLR (5 cm/day) and high HLR (16 cm/day) respectively. Hydraulic Retention Time (HRT) limited the uptake of ortho-P, thereby allowing mineralised phosphorus to escape the system without being absorbed by the plants.

Sulfonated nickel phthalocyanine redox flow cell for high-performance electrochemical water desalination

With clean water availability raising a great technological and social challenge, saltwater desalination has become a key strategic solution. Herein, we report a nickel phthalocyanine tetrasulfonic acid tetrasodium salt (NiPcTATS)-based redox flow desalination cell (RFDC) that allows safe, efficient and continuous water-salt separation. With the new, water-soluble NiPcTATS/NiPcTATS+ redox couple as electrolyte, the RFDC effectively desalinates saltwater and achieves a high average salt removal rate of 3.11 gNaCl/(molNiPcTATS·h) and a low energy consumption of 15.0 kJ/molNaCl at 0.5 V cell voltage. The cell exhibits excellent reversibility and durability for long-term operation, benefiting from the fast-redox kinetics and chemical stability of the redox couple. Efficient solar-driven RFDC for water desalination is demonstrated by powering the cell with a solar panel. This RFDC method provides a low-cost, efficient and safe strategy to purify saltwater, and the findings with NiPcTATS-based redox couple offer new opportunities of utilizing metal phthalocyanines and derivatives in water desalination research.

Acclimatization of microalgae Arthrospira platensis for treatment of heavy metals in Yamuna River

Bioaccumulation and biosorption in microalgae are effective approaches for the removal of heavy metals (HMs) from river water. The objective of this study was to investigate the potential for use of acclimatized microalgae in the removal of HMs from the Yamuna River water as an acclimatizing medium. An active culture of Arthrospira platensis (A. platensis) was acclimatized to HMs up to a concentration of 100 mg/L. It was gradually exposed to increasing concentrations of HMs in five subsequent batches with a step increase of 20 mg/L to acclimatize live cells in the simulated Yamuna River water. The presence of high levels of HMs in the Yamuna River water caused growth inhibition. An empirical growth inhibition model was developed, and it predicted high threshold concentrations of HMs (210.7–424.5 mg/L), producing a positive specific growth rate of A. platensis. A. platensis also showed high average removal efficiencies of HMs, including 74.0% for Cu, 77.0% for Cd, 50.5% for Ni, 76.0% for Cr, 76.5% for Pb, and 63.5% for Co, from HMs-enriched Yamuna River water. The findings demonstrated that the maximum specific removal amounts of Cu, Cd, Ni, Cr, Pb, and Co were 54.0, 58.0, 39.0, 62.8, 58.9, and 45.3 mg/g, respectively. The maximum yields of the value-added products chlorophyll and phycocyanin were 2.5 mg/g (in a batch of 40 mg/L for Cd) and 1 054 mg/g (in a batch of 20 mg/L for Cu), respectively. Therefore, acclimatized A. platensis was proven to be a potential microalga not only for sequestration of HMs but also for production of valuable pigments.

Converting treatment wetlands into “treatment gardens”: Use of ornamental plants for greywater treatment

Nowadays, the use of constructed wetlands for on-site greywater treatment is a very promising option. The successful application of this nature-based solution at full scale requires public acceptance, economic feasibility and the production of high-quality treated greywater. This work focuses on the use of ornamental plants as vertical flow constructed wetland (VFCW) vegetation for greywater treatment, aiming to improve aesthetic and acceptability of the system. The performance and economic feasibility of the proposed green technology were examined during a 2-years study. Results show that Pittosporum tobira and Hedera helix can grow in VFCW operating with greywater without any visible symptoms. These species tolerated both drought and flooding conditions, making them ideal for use not only in residential buildings but also in seasonal hotels and holiday homes. In contrast, partial defoliation of Polygala myrtifolia plants was observed during the winter period. High average removal efficiencies were observed for BOD (99%), COD (96%) and TSS (94%) in all examined VFCWs including unplanted beds. Phosphorus removal gradually decreased from 100% during first months of operation to 15% during second year of operation. In addition, total coliforms concentration reduced by 2.2 log units in the effluent of all planted systems, while lower removal efficiency was observed in the absence of plants. The mean concentration of BOD and TSS in the treated greywater met the standards for indoor reuse (<10 mg/L). Cost payback periods for the installation of the proposed technology in a multi-family building, a single house and a hotel in Greece were found 4.7, 16.6 and 2.5 years, respectively. Overall, the “treatment gardens” proposed in this study provide a technically and economically feasible solution for greywater treatment, with the additional benefit of improving the aesthetic of urban, semi-urban and touristic areas.

P1102EVALUATION THE EFFICACY OF MEDIUM CUT- OFF MEMBRANE DIALYZERS AND COMPARISON WITH HIGH FLUX DIALYZERS IN CONVENTIONAL HEMODIALYSIS

Abstract Background and Aims Hemodialysis (HD) is the most widely used modality of renal replacement therapy. The high-flux dialyzers in standard hemodialysis offer numerous benefits for ESRD patients, such as, increasing the uremic toxins removal and improving patients survival, reduced patients admission and morbidity. A new class of membranes, medium cut-off (MCO) membranes, has been designed to achieve better removal capacities for middle and large middle molecules, as well as to ensure the retention of albumin in hemodialysis (HD) treatments. We evaluated the removal efficacy of Theranova® in standard HD in comparison with standard high- flux HD. Method Four stable HD patients (M/F 1/4) were included in 12-weeks small observational pilot study in HD with Theranova® 400 (sup. 1.7 m2) and Theranova® 500 (sup. 2.0 m2) dialyzers. Each patient was assessed four times, T0 with standard high flux dialyzers, T1 at 1 month, T2 at second month and T3 at third month, by measuring pre and post-HD samples of: urea, creatinine, beta2-microglobilin (B2M), myoglobin, albumin and FLC-k, FLC-λ . Data are reported as mean ± standard deviation (SD). The removal rates of uremic toxins are expressed as percentages. Results The average removal rates for the uremic toxins with standard high-flux membranes were 18.4% for B2M, 14.3% for Myoglobin, 19.8 % for FLC-k and 17.4 % for FLC-λ. The data showed a higher average removal rate for all the uremic toxins with Theranova® dialyzers for B2M, Myoglobin, FLC-k and FLC-λ (62.7%, 56.9%, 63.5%, 54.6%, respectively) during the 3 months of follow up. The using of Theranova® dialyzers in standard HD was enough to significantly decrease the pre-dialysis value of Urea (17.72 ± 2.26 vs 13.75 ± 3.75, p=0.001), Creatinine (700.50 ± 315.07 vs 570.00 ± 206.64, p=0.021), B2M (40.90 ± 11.00 vs 29.00 ± 4.64, p=0.005), FLC-k (267.25 ± 113.28 vs 225.25 ± 100.62, p=0.018), FLC-λ (324.25 ± 116.12 vs 215.23 ± 64.44, p=0.011), Myoglobin ( 199.96 ± 124.41 vs 137.00 ± 83.14, p= 0.049). Finally, albumin retention was observed with Theranova® dialyzers, between T0 and T3 it increased significantly (40.50 ± 4.79 vs 42.25 ± 4.50, p=0.0001). Conclusion Compared to high-flux dialysis membranes, novel medium cut-off (MCO) membranes show greater permeability for larger middle molecules in mid -term report. But the long term analysis and larger number of patients is necessary to evaluate a clinical significance of this innovative therapy.

Does influent C/N ratio affect pollutant removal and greenhouse gas emission in wastewater ecological soil infiltration systems with/without intermittent aeration?

Wastewater ecological soil infiltration system (WESIS) is a land treatment technology for decentralized wastewater treatment that has been applied all over the world. In this study, the pollutant removal, emission of greenhouse gases (GHGs) and functional gene abundances with different influent C/N ratios were evaluated in WESISs with/without intermittent aeration. Intermittent aeration and influent C/N ratio affect pollutant removal and GHG emission. Increased influent C/N ratio led to high total nitrogen (TN) removal, low CH4 and N2O emission in the aerated WESIS, which was different from the non-aerated WESIS. High average removal efficiencies of chemical oxygen demand (COD) (94.8%), NH4 +-N (95.1%), TN (91.2%), total phosphorus (TP) (91.1%) and low emission rates for CH4 (27.2 mg/(m2 d)) and N2O (10.5 mg/(m2 d)) were achieved with an influent C/N ratio of 12:1 in the aerated WESIS. Intermittent aeration enhanced the abundances of bacterial 16S rRNA, amoA, nxrA, narG, napA, nirK, nirS, qnorB, nosZ genes and decreased the abundances of the mcrA gene, which are involved in pollutant removal and GHG emission. Intermittent aeration would be an effective alternative to achieving high pollutant removal and low CH4 and N2O emission in high influent C/N ratio wastewater treatment.

Microbial community composition in different carbon source types of biofilm A/O-MBR systems with complete sludge retention

ABSTRACT In this study, the three biofilm-anoxic-oxic-MBR systems were operated in parallel using different carbon source feed types. The three systems were operated with complete sludge retention to compare microbial community composition and system efficiency. High average removal of ammonia and COD was obtained in the three reactors. However, total nitrogen and total phosphorus removal efficiency were significantly higher in the VFAs feed systems when compared with the glucose feed system. The highest and most stable BNR efficiency was observed when acetate was used as a carbon source. The qPCR analysis revealed that ammonium oxidizing bacteria, denitrifiers and total bacteria were all highest in the acetate feed system followed by the propionate feed system. Moreover, among all carbon source types, the PUS-biofilm could maintain a higher degree of abundance of total bacteria than the sludge biomass. Meanwhile, ammonium oxidizing bacteria and denitrifiers were enriched in the sludge biomass rather than in the PUS-biofilm. The results of illumina sequencing revealed that acetate followed by propionate were favourable to the growth of microorganisms that were associated with the BNR process, which was the main reason for the high efficiency of nutrient removal in the acetate and propionate feed systems.