Micro-polluted Water Treatment Research Articles

Ammonium nitrogen and phosphorus removal by bacterial-algal symbiotic dynamic sponge bioremediation system in micropolluted water: Operational mechanism and transformation pathways

Construct a bacteria-algae symbiotic dynamic sponge bioremediation system to simultaneously remove multiple pollutants under micro-pollution conditions. The average removal efficiencies of NH4+-N, PO43−-P, total nitrogen (TN), and Ca2+ were 98.35, 78.74, 95.64, and 84.92 %, respectively. Comparative studies with Auxenochlorella sp. sponge and bacterial sponge bioremediation system confirmed that NH4+-N and TN were mainly removed by bacterial heterotrophic nitrification - aerobic denitrification (HN-AD). PO43−-P was removed by algal assimilation and the generation of Ca3(PO4)2 and Ca5(PO4)3OH, and Ca2+ was removed by algal electron transfer formation of precipitates and microbially induced calcium precipitation (MICP) by bacteria. Algae provided an aerobic environment for the bacterial HN-AD process through photosynthesis, while respiration produced CO2 and adsorbed Ca2+ to promote the formation of calcium precipitates. Immobilization of Ca2+ with microalgae via bacterial MICP helped to lift microalgal photoinhibition. The bioremediation system provides theoretical support for research on micropolluted water treatment while increasing phosphorus recovery pathways.

Three-Dimensional Biofilm Electrode Reactors with a Triple-Layer Particle Electrode for Highly Efficient Treatment of Micro-Polluted Water Sources

Micro-polluted water, which is widespread in rural areas, poses a serious health risk. To address this issue, we propose a three-dimensional biofilm electrode reactor with triple-layer particle electrodes (TL-BERs) for the decentralized and small-scale treatment of micro-polluted water. The first and second layers of the electrode, granular activated carbon (GAC) and biological ceramsite (BC), respectively, are responsible for electric field oxidation and microbial degradation, respectively, while the third, quartz sand (QS), is responsible for further improving turbidity and pollutant removal. Our tests indicated that the TL-BER-treated effluent met the drinking water quality standards of China. At 10 V, the average turbidity, CODMn, NH4+-N, and UV254 removal rates of the TL-BERs system were 97.66%, 61.11%, 91.67%, and 72.94%, respectively. Furthermore, the intensities of the main fluorescence peaks, A, B, C, and D, of the raw water sample, decreased by 36.67%, 66.22%, 67.08%, and 69.76%, respectively, after treatment, indicating that tryptophan-like proteins, fulvic acid, and humic acid were also effectively removed. High-throughput sequencing analysis showed the enrichment of microorganisms, such as Proteobacteria, Bacteroidota, and Actinobacteriota, which play important roles in the removal of various pollutants. Therefore, the application of this strategy will enable the practical treatment of micro-polluted water.

Aerobic Denitrification Enhanced by Immobilized Slow-Released Iron/Activated Carbon Aquagel Treatment of Low C/N Micropolluted Water: Denitrification Performance, Denitrifying Bacterial Community Co-occurrence, and Implications.

The key limiting factors in the treatment of low C/N micropolluted water bodies are deficient essential electron donors for nitrogen removal processes. An iron/activated carbon aquagel (IACA) was synthesized as a slowly released inorganic electron donor to enhance aerobic denitrification performance in low C/N micropolluted water treatment. The denitrification efficiency in IACA reactors was enhanced by more than 56.72% and the highest of 94.12% was accomplished compared with those of the control reactors. Moreover, the CODMn removal efficiency improved by more than 34.32% in IACA reactors. The Illumina MiSeq sequencing consequence explained that the denitrifying bacteria with facultative denitrification, iron oxidation, and iron reduction function were located in the dominant species niches in the IACA reactors (e.g., Pseudomonas, Leptothrix, and Comamonas). The diversity and richness of the denitrifying bacterial communities were enhanced in the IACA reactors. Network analysis indicated that aerobic denitrifying bacterial consortia in IACA reactors presented a more complicated co-occurrence structure. The IACA reactors presented the potential for long-term denitrification operation. This study affords a pathway to utilize IACA, promoting aerobic denitrification during low C/N micropolluted water body treatment.

Treatment of micro-polluted water with low C/N ratio by immobilized bioreactor using PVA/sintered ores@sponge cube: Performance effects and potential removal pathways

The widespread use of industrial products containing lead (Pb2+) and tetracycline (TC) medications led to the combined pollution of nitrate, Pb2+, and TC in water. A novel biomaterial containing polyvinyl alcohol (PVA) and sponge cube with sintered ores (PVA/sintered ores@sponge cube) was prepared to ensure the maximum NO3−-N removal efficiency (96.21 %) of the bioreactor under the hydraulic retention time (HRT) of 7.0 h, pH of 6.0, and the carbon to nitrogen (C/N) of 1.5 that had the ability to remove TC and Pb2+ synergistically. Composite pollutants slightly decreased denitrification performance in the combined pollution system on account of the addition of sintered ores. Results of scanning electron microscopy (SEM) showed that the sintered ores in the biocarrier induced denitrification and the adsorption of bio‑iron oxides were involved in the removal of TC and Pb2+. The simultaneous removal of composite pollutants during denitrification was facilitated by extracellular polymeric substances (EPS) as revealed by Fourier transform infrared spectroscopy (FTIR) and fluorescence excitation-emission matrix (EEM). In addition, high-throughput sequencing results showed that Zoogloea had the highest proportion in the bioreactor.

Integration of a pure moving bed biofilm reactor process into a large micro-polluted water treatment plant.

The pure-MBBR process was applied to remove ammonia in a full-scale micro-polluted-water treatment plant with a daily treatment capacity of 260 × 104 m3/d, Guangdong, China. The relationship between treatment efficiency, physical and chemical properties and microbial diversity in the process of biofilm growth was explored, and the oxygen transfer model of biofilm was established. The results show that the effluent of two-stage pure MBBR process is stable and up to standard after 10 days' incubation. The nitrification loads of two-stage biofilm was stable on the 14th day. The biomass and biofilm thickness lagged behind the nitrification load, and reached a relatively stable level on the 28th day. The species richness of biofilm basically reached a stable level on the 21st day, and the microbial diversity of primary biofilm was higher. In the primary and secondary stage at different periods, the relative abundance of dominant nitrifying bacteria Nitrospira reaches 8.48-13.60%, 6.48-9.27%, and Nitrosomonas reaches 2.89-5.64%, 0.00-3.48%. The pure MBBR system mainly adopts perforated aeration. Through the cutting and blocking of bubbles by suspended carriers, the oxygen transfer rate of the system was greatly improved.

Reactivity of nitrogen species with inorganic and organic compounds in water.

Many studies on the reactive nitrogen species (RNS, ●NO2, ●NO and ●NH2) with pollutants in water have been performed to understand the abatement of inorganic and organic compounds by these species, and the mechanisms of the formation of oxidative transformation products, especially nitrogenous oxidized byproducts. In this review, approaches to generate RNS in aqueous solution is first presented, followed by a summary of their reactivity with a wide range of compounds. The second-order rate constants (k, M-1 s-1) for the reactivity of ●NO2 and ●NO with a wide range of inorganic radical and nonradical species were correlated with thermodynamic one-electron oxidation potentials (E0). The positive correlation between log(k) versus E0 suggests one-electron transfer reactions. The Hammett-type correlations were developed for the reactions of ●NO2 and ●NH2 with organic compounds, using the unsubstituted benzene as a reference molecule (i.e., Σσo,p,m=0) to calculate Σσo,p,m=σo+σp+σm for each organic molecule. Linear negative correlations of log(k) with Σσo,p,m were obtained for both ●NO2 and ●NH2, suggesting electrophilic substitution mechanism. The correlations presented herein may assist in eliminating organic micropollutants in water treatment and reuse processes.

Nitrogen and Phosphorus Removal Efficiency and Denitrification Kinetics of Different Substrates in Constructed Wetland

Constructed wetlands (CWs) are generally used for wastewater treatment and removing nitrogen and phosphorus. However, the treatment efficiency of CWs is limited due to the poor performance of various substrates. To find appropriate substrates of CWs for micro-polluted water treatment, zeolite, quartz sand, bio-ceramsite, porous filter, and palygorskite self-assembled composite material (PSM) were used as filtering media to treat slightly polluted water with the aid of autotrophic denitrifying bacteria. PSM exhibited the most remarkable nitrogen and phosphorus removal performance among these substrates. The average removal efficiencies of ammonia nitrogen, total nitrogen, and total phosphorus of PSM were 66.4%, 58.1%, and 85%, respectively. First-order continuous stirred-tank reactor (first-order-CSTR) and Monod continuous stirred-tank reactor (Monod-CSTR) models were established to investigate the kinetic behavior of denitrification nitrogen removal processes using different substrates. Monod-CSTR model was proven to be an accurate model that could simulate nitrate nitrogen removal performance in vertical flow constructed wetland (VFCWs). Moreover, PSM demonstrated significant pollutant removal capacity with the kinetics coefficient of 2.0021 g/m2 d. Hence, PSM can be considered as a promising new type of substrate for micro-polluted wastewater treatment, and Monod-CSTR model can be employed to simulate denitrification processes.

Electroactive algae-bacteria wetlands for the treatment of micro-polluted aquaculture wastewater: Pilot-scale verification

The treatment of micro-polluted water via a constructed wetland (CW), such as fishpond aquaculture wastewater, encounters problems such as low effectiveness and poor stability. In this study, an emerging algae-bacteria microbial fuel cell (AB-MFC) was coupled with CW to strengthen the treatment of fishpond aquaculture wastewater. Compared with those in the control group (without AB-MFC), the average removal efficiencies of chemical oxygen demand, total phosphorus, total nitrogen, NH4+-N, NO3—N, and NO2—N in AB-MFC-CW were enhanced by 23.84%, 21.44%, 15.07%, 16.91%, 15.02%, and 9.83%, respectively. High-throughput sequencing revealed that Acinetobacter, Cyanobium, Pseudomonas, and Ottowia were relatively abundant on the electroactive AB biofilm. Geobacter, Aminicenantales and Clostridium grew well in the MFC Anode. The economic evaluation indicated that energy consumption per ton of sewage treatment was 0.0045 kWh/m3. These results confirm that the AB-MFC-CW is feasible for enhancing the treatment of aquaculture wastewater at both technical and economic levels through pilot-scale verification.

Influence of Particle Size of River Sand on the Decontamination Process in the Slow Sand Filter Treatment of Micro-Polluted Water

Slow sand filters (SSFs) have been widely used in the construction of water plants in rural areas. It is necessary to find river sand of suitable particle size to improve SSF treatment of micro-polluted water so as to ensure the effective and long-term operation of these plants. In this study, SSF1# (particle size of 0.1–0.5 mm), SSF2# (particle size of 0.5–1 mm), and SSF3# (particle size of 1–1.5 mm) were selected. The physical absorption, CODMn and NH4+-N removal effect, and microbial community were analyzed. According to Langmuir and Freundlich adsorption model fitting, the smaller the particle size of the river sand, the more pollutants are adsorbed under the same conditions. SSF1# has the shortest membrane-forming time, highest CODMn and NH4+-N removal rate, and highest Shannon estimator, indicating that there are more abundant microbial species in the biofilm. Mesorhizobium, Pannonibacter, Pseudoxanthomonas, Aquabacterium, Devosia, and other bacteria have different proportions in each system, each forming its own stable biological chain system. The effluent quality of the three SSFs can meet drinking water standards. However, river sand with a particle size range of 0.1–0.5 mm is easily blocked, and thus the recommended size range for SSF is 0.5–1 mm.

Distribution coefficients of nitrogen pollutants between water and sediment and their environmental risks in Lingang hybrid constructed wetland fed by industrial tailwater, Tianjin, China.

Exploring the fate of nitrogen pollutants in constructed wetlands (CWs) fed by industrial tailwater is significant to strengthen its pollution control and promoting the development of CWs in the field of micro-polluted water treatment. In this study, the distribution coefficients and the environmental risks of nitrogen pollutants between water and sediment of the hybrid CW in Tianjin were systematically investigated. From a spatial perspective, the nitrogen pollutants could be removed in this hybrid CW, and subsurface flow wetland played a key role in nitrogen pollutant removal. From a temporal perspective, the concentration of nitrogen pollutants was largely affected by the dissolved oxygen (DO) and temperature. The distribution coefficient of nitrogen pollutants between water and sediment was further clarified, suggesting that NH4+-N was more likely to be enriched in sediments due to microbial process. The overall level of pollution in hybrid CW was moderate according to the nutritional pollution index (NPI) analysis. The risk assessment indicated that timely dredging control measures should be considered to maintain the performance of hybrid CW.

Evaluation of an ozone diffusion process using a hollow fiber membrane contactor

Conventional ozonation processes efficiently remove micropollutants in water treatment, but uncontrolled ozone dosing can produce problematic by-products. Bubbleless operation could help overcome this hurdle. To evaluate this alternative, ozonation was carried out using a polytetrafluoroethylene (PTFE) hollow fiber membrane contactor. The objective was to conduct an extensive characterization of the ozone transfer in an in/out configuration. The overall mass transfer coefficient KLa was determined and was higher than in bubble columns. The transfer resistance due to the membrane was estimated to be lower than 1%. The impact of several variables (liquid flowrate, gas flowrate, and ozone concentration) on the ozone transfer was studied. Ozone concentration was the variable that most increased ozone transfer, followed by the liquid flowrate and then to a lesser extent the gas flowrate. The impact of the presence of a reaction in the water was also evaluated using an organic dye (Acid Orange 7). The Hatta number and the acceleration factor were calculated, corresponding to a reaction that took place partially in the liquid film and in the liquid bulk. Finally, the impact of ozone on membrane material over time was evaluated.

Combined Nanofiltration and Thermocatalysis for the Simultaneous Degradation of Micropollutants, Fouling Mitigation and Water Purification.

Due to progressive limitation of access to clean drinkable water, it is nowadays a priority to find an effective method of water purification from those emerging organic contaminants, which might have potentially harmful and irreversible effects on living organisms and environment. This manuscript reports the development of a new strategy for water purification, which combines a novel and recently developed Al2O3-doped silica nanofiltration membrane with a thermocatalytic perovskite, namely cerium-doped strontium ferrate (CSF). The thermocatalytic activity of CSF offers the opportunity to degrade organic pollutants with no light and without input of chemical oxidants, providing simplicity of operation. Moreover, our studies on real samples of secondary effluent from wastewater treatment showed that the thermocatalyst has the ability to degrade also part of the non-toxic organic matter, which allows for reducing the chemical oxygen demand of the retentate and mitigating membrane fouling during filtration. Therefore, the new technology is effective in the production of clean feed and permeate and has a potential to be used in degradation of micropollutants in water treatment.

Mix-cultured aerobic denitrifying bacterial communities reduce nitrate: Novel insights in micro-polluted water treatment at lower temperature

Three mix-cultured aerobic denitrifiers were screened from a source water reservoir and named HE1, HE3 and SU4. Approximately 72.9%, 68.6% and 66.2% of nitrate were effectively removed from basal medium, respectively, after 120 h of cultivation at 8 °C. The nitrogen balance analysis revealed about one-fifth of the initial nitrogen was converted into gaseous denitrification products. According to the results of Biolog, the three microfloras had high metabolic capacity to carbon sources. The dominant genera were Pseudomonas and Paracoccus in these bacterial communities based on nirS gene sequencing. Response surface methodology elucidated that the denitrification rates of identified bacteria reached the maximum under the following optimal parameters: C/N ratio of 7.51–8.34, pH of 8.03–8.09, temperature of 18.03–20.19 °C, and shaking speed of 67.04–120 rpm. All results suggested that screened aerobic denitrifiers could potentially be applied to improve the source water quality at low temperature.

Activated carbon-gravity driven biomimetic membrane (AC-GDBM) for organic micro-polluted water treatment

Gravity-driven biomimetic membrane (GDBM) has been developed as a promising membrane separation technology regarding ecological water treatment. Given its catalytic function on micro-pollutant removal and fouling control, detailed mechanism for fabrication material influence, organic micro-pollutants (OMPs) degradation, and operation strategy optimization have not been clear so far. In this work, the GDBM performance with various activated carbon (AC) materials (wood, coal, column and powder AC), and hydrostatic heights were investigated and verified. The activated carbon-gravity driven biomimetic membrane (AC-GDBM) fabrication tests demonstrated that AC-GDBM with powdered wooden AC had better filtration performance (up to 55 LMH flux and 97.5% removal rate) than AC-GDBM with other ACs. Furthermore, the effects of operation strategies (AC dosage, lacasse dosage, carbamazepine (CBZ) concentration, hydraulic height and rotating speed) on the filtration performance of AC-GDBM were conducted. At 25 g m−2 AC dosage, 30 g m−2 lacasse dosage, 10 mg L−1 CBZ concentration, and 5 cm hydraulic height, the optimized flux and removal rate were obtained. Further investigation revealed the surface morphology and property of AC-GDBM, displaying that powdered wooden AC and laccase formed the even biomimetic layer on base membrane. Additionally, for treating various OMPs (CBZ, tetracycline hydrochloride (TET), quinolones (norfloxacin (NFX)), and sulfonamides (sulfamethoxazole (SMZ))), with the optimized conditions, the removal rate and flux of AC-GBDM could maintain at high levels. This study demonstrates an example of a niche application, where GDBM is expected to offer a highly efficient and cost-effective ecological water treatment technology.

Photocatalytic ZnO Foams for Micropollutant Degradation

AbstractPhotocatalytic foams can concomitantly overcome the disadvantages of slurry and immobilized photocatalysts in water treatment. However, foams have, so far, been restricted to nanoparticles grafting onto inert foam substrates, with the consequent risk of nanoparticle release into the environment. In this work, self‐supporting, highly porous photocatalytic zinc oxide (ZnO) foams are produced using a combination of liquid templating and sintering for the first time. Systematic changes in sintering times and temperature affect the foams’ morphology and structure, in turn controlling their photocatalytic activity and stability. Sintering at 900 °C and decreasing sintering times from 20 to 6 h lead to a doubling in surface‐area‐to‐volume ratio and a 30% increase in pore diameter, resulting in a near doubling of the overall quantum yield and degradation kinetics. However, photocorrosion and Zn leaching increase markedly for the shortest sintering time. Optimal sintering conditions at 900 °C for 12 h yield foams capable of effectively degrading the model micropollutant carbamazepine under UV irradiation with high stability, showing no performance decrease over five irradiation cycles corresponding to 20 h of use. This study paves the way to producing self‐supporting, highly stable photocatalytic foams for the removal of organic micropollutants in water treatment.

Nitrate reduction by the aerobic denitrifying actinomycete Streptomyces sp. XD-11-6-2: Performance, metabolic activity, and micro-polluted water treatment

Aerobic denitrifying bacteria were widely reported in different nitrogen polluted aquatic ecosystem. However, the aerobic denitrification characteristics of actinomycete were not well understood. Here, the actinomycete strain XD-11-6-2 was isolated from reservoir and identified as Streptomyces sp. XD-11-6-2 by DNA sequencing. Strain XD-11-6-2 removed 90.34% of total organic carbon and 93.66% of total nitrogen under aerobic condition. A total of 77.87% of nitrogen was removed as a gaseous product, and 15.67% of nitrogen was converted into biomass. Biolog combined with network model indicated that strain XD-11-6-2 could use six types of carbon sources, and exhibit outstanding capacity to metabolize diverse carbon sources. Moreover, the highest nitrate and total nitrogen removal efficiencies of raw water were 72.29% and 74.86%, respectively. In general, these results provide new insights to understand the potential of actinomycetes in treating micro-polluted water.

Dynamics and Model Research on the Electrosorption by Activated Carbon Fiber Electrodes

Electrosorption is a new emerging technology for micro-polluted water treatment. To gain a more accurate understanding of the mass and charge transfer process of electrosorption, the electrosorption performance of activated carbon fiber (ACF) electrodes with various concentrations was studied. In this paper, quasi-first-order and quasi-second-order dynamic equations, and an intra-particle diffusion equation were used to describe the electrosorption behaviors. It is believed that the electrosorption process is dominated by physical adsorption for ACF material, and the most important rate control steps in this process are intra-diffusion and electromigration steps. Based on the experimental results and modified Donnan model theory, a considerable electrosorption dynamic model which considered the influence of physical adsorption and the intra-diffusion resistance was proposed. This model quantitatively described the salt adsorption and charge storage in the ACF electrode and can fit the experimental data well.

Enhanced transformation of phenolic compounds by manganese(IV) oxide, manganese(II) and permanganate in the presence of ligands: The determination and role of Mn(III)

In this study, colorimetric methods using diethyl phenylene diamine (DPD), 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulfonate (ABTS), and potassium iodide (KI) were adopted to determine manganese(III)-pyrophosphate complex (Mn(III)-PP) in trace levels (10 µM). An ozonation method was developed to measure the concentration of dissolved Mn including Mn(II) and Mn(III) via quantifying permanganate (Mn(VII)) generation during ozonation of dissolved Mn with PP. The ozonation method combined with DPD method were applied to determine MnO2 dissolution kinetics in the presence of oxalic acid through monitoring MnO2 decay and Mn(III)/Mn(II) formation. PP and oxalic acid could enhance the oxidation of bisphenol A (BPA) by MnO2 at acidic pH, while no promoting effects were found at neutral pH. EDTA had enhancing effect on the oxidation of BPA by MnO2 at neutral pH but inhibiting effect at acidic pH. This result indicated high activities of Mn(III)-PP at acidic pH, Mn(III)-oxalic acid at acidic pH, and Mn(III)-EDTA at neutral pH, respectively. Enhancing effect of low concentration of humic acid (HA) on the oxidation of BPA by MnO2 at acidic pH, however inhibiting effect was found with high dosage of HA due to the occupation of HA on the active sites of MnO2. Furthermore, desferrioxamine B (DFO) was observed to accelerate the transformation of hydroquinone (HQ) with Mn(II) at alkaline pH, ascribed to the formation of Mn(III)-DFO from the reaction of oxygen with Mn(II) rapidly. Finally, a Mn(VII)-reducer-PP system for the transformation of phenolic compounds was evaluated. Two effective reducers (i.e., Mn(III) inducers), Mn(II) and bisulfite, could accelerate Mn(III)-PP formation in the initial step, and then promote the oxidation of phenolic compounds by Mn(VII). Transformation of phenolic compounds were enhanced by MnO2(IV), Mn(II) and Mn(VII) in the presence of ligands due to the generation of Mn(III), which reflected the potential application value of Mn(III) in micro-polluted water treatment.

Effect of powdered activated carbon deposited ultrafiltration membrane for enhanced micro-polluted water treatment

Effect of powdered activated carbon deposited ultrafiltration membrane for enhanced micro-polluted water treatment

Membrane fouling in a powdered activated carbon – membrane bioreactor (PAC-MBR) for micro-polluted water purification: Fouling characteristics and the roles of PAC

To identify the characteristics of fouling in the powdered activated carbon – membrane bioreactor (PAC-MBR) for micro-polluted water treatment, a pilot-scale PAC-MBR was continuously operated for 4 months without chemical cleaning. The membrane autopsy suggested that physically recoverable and irrecoverable fouling accounted for 56.6 and 43.4% of the total fouling, respectively, and intermediate blocking model showed the best fitting for fouling evolution. Colloidal matter, which had a large proportion of protein and polysaccharide, was the major contributor to the physically recoverable fouling resistance, while polysaccharide and humic substances were the major contributors to the physically irrecoverable fouling resistance. By comparing the MBRs with and without PAC, it was found that PAC increased fouling rate because it exerted a marginal effect on foulants reduction and membrane scouring, but a synergistic effect on cake layer formation. These fouling characteristics in PAC-MBR were different from those in the MBRs for municipal wastewater treatment, which could be ascribed to the poor-nutrient of the micro-polluted water.