Agricultural runoff treatment by constructed wetlands filled with iron-carbon composites in winter: Performance augmentation by organic solids and denitrifying bacteria addition.

Iron-carbon composite-filled constructed wetlands (Fe-C CWs) were employed to treat agricultural runoff in the winter season in this study, and organic substrates and phosphate-accumulating denitrifying bacteria were supplemented to improve the treatment performance. Fe-C CWs performed significantly better in pollutant removal than the control system filled with only gravel by effectively driving autotrophic denitrification, Fe-based dephosphorization and organic degradation. Organic substrate and functional bacteria addition further augmented the performance, and immobilized bacterial cells were more effective than free cells. Fe-C and organic substrates decreased the greenhouse gas emission fluxes of the CWs, and denitrifier inoculation alleviated N2O emission. The microbial community in the Fe-C substrates showed a very distinct distribution pattern compared to that in the gravel, with notably higher proportions of Trichococcus, Thauera and Dechloromonas. Bioaugmented Fe-C-based CWs are highly promising for agricultural runoff treatment, especially at low temperatures.

Effect of mariculture wastewater concentrations on high-value production and pollutants removal with bacterial-algal coupling reactor (BACR).

To achieve the goal of cost-effective mariculture wastewater treatment, a novel Bacteria-Algae Coupling Reactor (BACR) integrating acidogenic fermentation with microalgae cultivation was applied for the mariculture wastewater treatment. Currently, there is limited research on the impact of different concentrations of mariculture wastewater on the pollutant removal and the high-value products recovery. In this study, different concentrations (4, 6, 8, and 10 g/L) of mariculture wastewater were treated with BACR. The results showed thatoptimalMW concentrations of 8 g/L improved the growth viability and biochemical components synthetic of Chlorella vulgaris, which increased the potential for high-value products recovery. The BACR exhibited the excellent removal efficiency of chemical oxygen demand, ammonia-nitrogen and total phosphorus with 82.30%, 81.12% and 96.40%, respectively. This study offers an ecological and economic approach to improve the MW treatment through the utilization of a novel bacterial-algal coupling system.

Chromoionophoric probe-anchored mesoporous silica nanospheres for rapid and reliable naked-eye detection of Ni(II) ions in petroleum products and removal from electroplating wastewater.

This paper presents the expansion of an optical, chemical sensor that can rapidly and reliably detect, quantify, and remove Ni(II) ions in oil products and electroplating wastewater sources. The sensor is based on mesoporous silica nanospheres (MSNs) that have an extraordinary surface area, uniform surface morphology, and capacious porosity, making them an excellent substrate for the anchoring of the chromoionophoic probe,3'-{(1E,1' E)-[(4-chloro-1,2 phenylene)bis (azaneylylidene)]-bis(methaneylylidene)}bis(2-hydroxybenzoic acid) (CPAMHP). The CPAMHP probe is highly selective and sensitive to Ni(II), enabling it to be used in naked-eye colorimetric recognition of Ni(II) ions. The MSNs provide several accessible exhibited sites for uniform anchoring of CPAMHP probe molecules, making it a viable chemical sensor even with the use of naked-eye sensing. The surface characters and structural analysis of the MSNs and CPAMHP sensor samples were examined using various techniques. The CPAMHP probe-anchored MSNs exhibit a clear and vivid color shift from pale yellow to green upon exposure to various concentrations of Ni(II) ions, with a reaction time down to approximately 1 minute. Furthermore, the MSNs can serve as a base to retrieve extremely trace amounts of Ni(II) ions, making the CPAMHP sensor a dual-functional device. The calculated limit of recognition for Ni(II) ions using the fabricated CPAMHP sensor samples is 0.318 ppb (5.43 × 10-9 M). The results suggest that the proposed sensor is a promising tool for the sensitive and reliable detection of Ni(II) ions in petroleum products and for removing Ni(II) ions in electroplating wastewater; the data indicate an excellent removal of Ni (II) up to 96.8%, highlighting the high accuracy and precision of our CPAMHP sensor.

Microalgae systems - environmental agents for wastewater treatment and further potential biomass valorisation.

Water is the most valuable resource on the planet. However, massive anthropogenic activities generate threatening levels of biological, organic, and inorganic pollutants that are not efficiently removed in conventional wastewater treatment systems. High levels of conventional pollutants (carbon, nitrogen, and phosphorus), emerging chemical contaminants such as antibiotics, and pathogens (namely antibiotic-resistant ones and related genes) jeopardize ecosystems and human health. Conventional wastewater treatment systems entail several environmental issues: (i) high energy consumption; (ii) high CO2 emissions; and (iii) the use of chemicals or the generation of harmful by-products. Hence, the use of microalgal systems (entailing one or several microalgae species, and in consortium with bacteria) as environmental agents towards wastewater treatment has been seen as an environmentally friendly solution to remove conventional pollutants, antibiotics, coliforms and antibiotic resistance genes. In recent years, several authors have evaluated the use of microalgal systems for the treatment of different types of wastewater, such as agricultural, municipal, and industrial. Generally, microalgal systems can provide high removal efficiencies of: (i) conventional pollutants, up to 99%, 99%, and 90% of total nitrogen, total phosphorus, and/or organic carbon, respectively, through uptake mechanisms, and (ii) antibiotics frequently found in wastewaters, such as sulfamethoxazole, ciprofloxacin, trimethoprim and azithromycin at 86%, 65%, 42% and 93%, respectively, through the most desirable microalgal mechanism, biodegradation. Although pathogens removal by microalgal species is complex and very strain-specific, it is also possible to attain total coliform and Escherichia coli removal of 99.4% and 98.6%, respectively. However, microalgal systems' effectiveness strongly relies on biotic and abiotic conditions, thus the selection of operational conditions is critical. While the combination of selected species (microalgae and bacteria), ratios and inoculum concentration allow the efficient removal of conventional pollutants and generation of high amounts of biomass (that can be further converted into valuable products such as biofuels and biofertilisers), abiotic factors such as pH, hydraulic retention time, light intensity and CO2/O2 supply also have a crucial role in conventional pollutants and antibiotics removal, and wastewater disinfection. However, some rationale must be considered according to the purpose. While alkaline pH induces the hydrolysis of some antibiotics and the removal of faecal coliforms, it also decreases phosphates solubility and induces the formation of ammonium from ammonia. Also, while CO2 supply increases the removal of E. coli and Pseudomonas aeruginosa, as well as the microalgal growth (and thus the conventional pollutants uptake), it decreases Enterococcus faecalis removal. Therefore, this review aims to provide a critical review of recent studies towards the application of microalgal systems for the efficient removal of conventional pollutants, antibiotics, and pathogens; discussing the feasibility, highlighting the advantages and challenges of the implementation of such process, and presenting current case-studies of different applications of microalgal systems.

Organic media-based two-stage traditional and electrode-integrated tidal flow wetlands to treat landfill leachate: Influence of aeration strategy and plants.

Landfill leachate treatment employing normal and electrode-integrated constructed wetlands is difficult due to the presence of significant amounts of organic compounds, which frequently impede the progression of microbial-based aerobic pollutant removal pathways. As a result, this study examines the effect of supplementary air availability via intermittent and continuous aeration strategies in improving organic, nutrient, and coliform removals of the unplanted, planted (normal and electrode-integrated) two-stage tidal flow constructed wetlands designed to treat landfill leachate. The constructed wetlands were filled with coal and biochar media and planted with Canna indica. Mean chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), and coliform removal percentages of the externally aerated two-stage unplanted, only planted, planted-microbial fuel cell integrated constructed wetland systems ranged between 96 and 99%, 82 and 93%, 91 and 98%, 86 and 96%, respectively, throughout the experimental campaign. External aeration inhibited the development of a dominant anaerobic environment within the media of the wetland systems and improved overall pollutant removal. The electrode-integrated planted tidal flow wetlands produced better effluent quality than the unplanted or only planted tidal flow systems without electrode assistance. The first stages of the three wetland systems achieved an additional 5-7% COD, 7-12% TN, and 15-22% coliform removal during the continuous aeration period compared to the corresponding performance of the intermittent aeration phase. The pollutant removal performance of the second-stage wetlands decreased during the continuous aeration phase. The media composition supported electrochemically active and inactive microbial-based pollutant removal routes and the chemical adsorption of pollutants. Nitrogen and phosphorus accumulation percentage in plant tissues was low, i.e., 0.4-2.2% and 0.04-0.8%, respectively. During the continuous aeration period, the electrode-integrated tidal flow constructed wetlands achieved higher power density production, i.e., between 859 and 1432 mW (mW)/meter3(m3). This study demonstrates that external aeration might improve pollutant removal performance of the normal, electrodes integrated tidal flow-based constructed wetlands when employed for high organic-strength wastewater treatment such as landfill leachate.

A review of compaction effect on subsurface processes in soil: Implications on stormwater treatment in roadside compacted soil.

Sustainable cities require spacious infrastructures such as roadways to serve multiple functions, including transportation and water treatment. This can be achieved by installing stormwater control measures (SCM) such as biofilters and swales on the roadside compacted soil, but compacted soil limits infiltration and other functions of SCM. Understanding the effect of compaction on subsurface processes could help design SCM that could alleviate the negative impacts of compaction. Therefore, we synthesize reported data on compaction effects on subsurface processes, including infiltration rate, plant health, root microbiome, and biochemical processes. The results show that compaction could reduce runoff infiltration rate, but adding sand to roadside soil could alleviate the negative impact of compaction. Compaction could decrease the oxygen diffusion rate in the root zone, thereby affecting plant root activities, vegetation establishment, and microbial functions in SCM. The impacts of compaction on carbon mineralization rate and root biomass vary widely based on soil type, aeration status, plant species, and inherent soil compaction level. As these processes are critical in maintaining the long-term functions of SCM, the analysis would help develop strategies to alleviate the negative impacts of compaction and turn road infrastructure into a water solution in sustainable cities.

Effect of transient organic load and aeration changes to pollutant removal and extracellular polymeric substances.

Transient organic load shocks have an important influence on the removal of pollutants and the content and composition of extracellular polymeric substances (EPS). This study was based on a micro-pressure reactor (MPR) with the influent COD concentration as the variable, while different operating conditions were controlled by adjusting the aeration rate. The effect of single-cycle transient organic loading shocks on EPS and pollutant removal and the correlation between their changes were investigated. The results showed that COD removal was unaffected under the shock, and the effect of nitrogen and phosphorus removal decreased. As the incoming carbon source increased, the EPS content at shock increased, with the polysaccharide (PS) content being the most affected. As aeration increased, the effect of organic load shock on EPS and pollutant removal decreased. Under different aeration conditions, PS contributed to denitrification and anaerobic phosphorus release during transient organic load shocks, and protein (PN) contributed to aerobic phosphorus uptake. The reduction in PS and PN relative to the pre-shock caused by the shock resulted in the EPS exhibiting a favourable effect on COD removal and an inhibitory effect on the effectiveness of nitrogen and phosphorus removal.

Enhancement of nutrients removal and biomass accumulation of algal-bacterial symbiosis system by optimizing the concentration and type of carbon source in the treatment of swine digestion effluent.

The algae-bacteria symbiosis system (ABS) is used to effectively solve the problems of low carbon/nitrogen (C/N) ratio, low biodegradability and high ammonia toxicity in swine digestion effluent. This study examined the effects of the concentration and type of carbon source on ABS in the pollutants removal especially ammonia. When C/N ratio was 30:1 and carbon source was sodium acetate, the ABS was most conducive to the removal of nitrogen, phosphorus and COD, and to the accumulation of biomass and lipids. To make the wastewater discharge meet the relevant standard, the ABS + mono-cultivation of algae reprocessing system (MAS), was applied to actual swine digestion effluent. Through adjusting the C/N ratio in ABS to 30:1, the biomass concentration was 2.06 times higher than that of raw wastewater, and the removal efficiencies of NH4+-N, TN, TP and COD increased by 1.43, 1.46, 1.95 and 1.28 times, respectively. The final concentrations of NH4+-N, TN, TP and COD after the treatment of ABS (C/N ratio of 30:1) + MAS, were 16.98 ± 1.07 mg L-1, 18.72 ± 1.81 mg L-1, 0.48 ± 0.01 mg L-1 and 263.49 ± 11.89 mg L-1, respectively, reached the Chinese discharge standards for livestock and poultry wastewater. Bacterial community analysis showed that the dominant species of the ABS (C/N ratio of 30:1) was Corynebacterium (genus level). This study revealed that adjusting the concentration and type of carbon source was helpful to the nutrient cycling and resource utilization of ABS, indicating a feasible technique for treating high ammonia nitrogen digestate.

Assessment of plants radial oxygen loss for nutrients and organic matter removal in full-scale constructed wetlands treating municipal effluents.

Bidirectional cross flow wetlands with different plant species were set to investigate seasonal variation in radial oxygen loss (ROL) and its effects on COD and NH4+-N removal. Findings demonstrated a strong seasonal effect on the rate of ROL, with Arundo donax var.versicolor showing the highest ROL of 2.99 µmol·h-1·g-1. Additionally, ROL showed strong positive correlations with plant total biomass (P < 0.01), aboveground biomass (P < 0.01), height, maximum root length (P < 0.01), root porosity (P < 0.01), and removal efficiency of COD and NH4+-N (P < 0.01). Furthermore, high-throughput sequencing analysis of substrate samples from three wetland units planted with Thalia dealbata, Canna indica and Arundo donax var. versicolor revealedProteobacteria as the predominant rhizospheric phylum. Relative abundance of Alpha- and Gamma-Proteobacteria were higher in the Arundo donax var.versicolor samples due to its higher oxygen transport capacity. These results demonstrate that root properties are important determinants for selecting appropriate plants for constructed wetland.

Iris pseudacorus as precursor affecting ecological transformation of graphene oxide and performance of constructed wetland.

The role of plants is largely unknown in constructed wetlands (CWs) exposed to phytotoxic nanomaterials. Present study investigated transformation of graphene oxide (GO) and performance of CWs with Iris pseudacorus as precursor. GO was trapped by CWs without dependence on plants. GO could move to lower substrate layer and present increases on defects/disorders with stronger effects in planted CW. Before adding GO, planted CW achieved better removal both of phosphorus and nitrogen. After adding GO, phosphorus removal in planted CW was 93.23-95.71% higher than 82.55-90.07% in unplanted CW. However, total nitrogen removal was not improved, showing 48.20-56.66% and 53.44-56.04% in planted and unplanted CWs. Plant improved urease, phosphatase, and arylsulfatase, but it decreased ß-glucosidase and had less effects on dehydrogenase and catalase. Pearson correlation matrix revealed that plant enhanced microbial interaction with high degree of positive correlation. Moreover, there were obvious shifts in microbial community at phylum and genus level, which presented closely positive action on substrate enzyme activities. The functional profile was less affected due to functional redundancy in microbial system, but time effects were obvious in CWs, especially in planted CW. These findings could provide the basis on understanding role of plants in CWs for treating nanoparticles wastewater.

Periodic oxygen supplementation drives efficient metabolism for enhancing valuable bioresource production in photosynthetic bacteria wastewater treatment.

Periodic oxygen supplementation (A-O) strategy was proposed to improve pollutant removal and enhance bioresource production of photosynthetic bacteria (PSB). The A-O strategy obtained higher COD (91.4%) and NH4+-N (78.6%) removal compared with the non-oxygen supplementation (N-O) strategy, which was similar to the continuous oxygen supplementation (C-O) strategy. A-O strategy achieved the highest biomass concentration of 1338.5 mg/L. Bacteriochlorophyll and carotenoids concentration in the A-O strategy were 24.9-31.1% and 15.1-23.7% higher than those in the other two strategies; coenzyme Q10 concentration and content were 52.5% and 21.3% higher than that in the N-O strategy. The metabolomic analysis showed that the A-O strategy enhanced the tricarboxylic acid cycle after fumaric acid formation and ß-alanine metabolism, then caused higher biomass accumulation. The A-O strategy reduced the inhibition of photophosphorylation by oxidative-phosphorylation and maintained both characteristics. Hence, A-O might be an economic strategy for enhancing pollutant removal and bioresource production in PSB-based wastewater treatment.

P=O Functionalized Black Phosphorus/1T-WS2 Nanocomposite High Efficiency Hybrid Photocatalyst for Air/Water Pollutant Degradation.

Research on layered two-dimensional (2D) materials is at the forefront of material science. Because 2D materialshave variousplate shapes, there is a great deal of research on the layer-by-layer-type junction structure. In this study, we designed a composite catalyst with a dimension lower than two dimensions and with catalysts that canbe combined so that the band structures can be designed to suit various applications and cover for each other's disadvantages. Among transition metal dichalcogenides, 1T-WS2 can be a promising catalytic material because of its unique electrical properties. Black phosphorus with properly controlled surface oxidation can act as a redox functional group. We synthesized black phosphorus that was properly surface oxidized by oxygen plasma treatment and made a catalyst for water quality improvement through composite with 1T-WS2. This photocatalytic activity was highly efficient such that the reaction rate constant k was 10.31 × 10-2 min-1. In addition, a high-concentration methylene blue solution (20 ppm) was rapidly decomposed after more than 10 cycles and showed photo stability. Designing and fabricating bandgap energy-matching nanocomposite photocatalysts could provide a fundamental direction in solving the future's clean energy problem.

Haloarchaea, excellent candidates for removing pollutants from hypersaline wastewater.

Hypersaline wastewater is difficult to treat due to the inhibition of salt stress on microbes' viability and metabolic capabilities. Haloarchaea, native microorganisms that thrive in hypersaline habitats, overcome this key obstacle naturally. This review provides a comprehensive overview of the metabolic versatility of Haloarchaea in hypersaline wastewater treatment, including carbon, nitrogen, phosphorus, sulfur, and heavy metal metabolism. It also analyzes factors affecting pollutant removal and addresses metabolic mechanisms. Additionally, haloarchaea microbial characteristics and strategies to cope with salt stress are highlighted. Finally, the biotechnological potential of biomolecules produced from haloarchaea is investigated. To get better insight into the potential of haloarchaea, a deeper investigation of basic metabolism and more in-depth studies of their genomics and applications in actual wastewater are also necessary.

Do mycorrhizae increase plant growth and pollutant removal in stormwater biofilters?

Mycorrhizae can improve plant growth and drought tolerance by enhancing plant uptake of nutrients and water, which are important targets for biofilters, a common stormwater treatment system. This study evaluated the role of mycorrhizal inoculation on plant growth, photosynthetic efficiency and pollutant removal in two Australian plant species grown in stormwater biofilters. During the establishment period and column study, Ficinia nodosa showed over 80% mycorrhizal colonization, leading to a doubling of shoot and root biomass compared to the control, while Carex appressa showed less than 26% mycorrhizal colonization and no effect on shoot and root biomass. Columns planted with mycorrhizal-inoculated F. nodosa had 5% higher removal of total phosphorus and 10% higher removal of total nitrogen (Figure 5), phosphate (Figure 6), and cadmium (Table 3). Mycorrhizal colonization did not appear to affect plant stress during drought as indicated by similar photosynthetic efficiencies within species. Our results indicate that mycorrhizal inoculation can be highly successful in biofilters while increasing plant growth and nutrient removal, opening opportunities to further study the role of mycorrhizae in enhancing plant drought tolerance and pollutant removal in existing biofiltration systems.

Effect of Fe3+ on the sludge properties and microbial community structure in a lab-scale A2O process.

During biological wastewater treatment, ferric salt (Fe3+) usually serves as an inorganic flocculant to improve the agglomeration and sedimentation of suspended solids, and thus the removal efficiency of pollutants to meet the increasing strictly regulated wastewater discharge standards. In this study, we investigated the effects of Fe3+ on the removal efficiencies of pollutants, sludge properties, dominant flora and metabolic pathways of bacterial community in a classical anaerobic-anoxic-oxic (A2O) process. The results showed that a Fe3+ concentration lower than 10 mg·L-1 could improve the removal efficiencies of chemical oxygen demand (COD) and total nitrogen (TN), while an inhibition effect was exerted at concentration higher than 10 mg·L-1. The maximum removal efficiencies of COD and TN were 97% and 89%, respectively, under the critical Fe3+ concentration of 10 mg·L-1. Total phosphorous (TP) removal was constantly positively correlated with Fe3+ concentration, due to the enhanced adsorption of phosphorus on activated sludge with the increase of surface roughness. Thauera displayed the highest relative abundance, and certain bacteria in Proteobacteria, Dehloromonas and Candidatus-Competibacter exhibited good adaptability to high concentration of Fe3+. In the context of metabolic collaterals, the most abundant functional gene families were identified to be Carbohydrate Metabolism, Amino Acid Metabolism, Cell Motility, Membrane Transport, and Replication and Repair. This study provides an extensive mechanistic insight into the impact of Fe3+ on the A2O process, which is of fundamental significance to exploit the contributions of inorganic salts to biological wastewater treatment.

Performance of permeable pavement systems on stormwater permeability and pollutant removal.

Permeable pavement is an effective means for stormwater runoff control and pollutant removal. However, relatively few studies have examined the characteristics of permeable brick and corresponding permeable pavement system (PPS). In this work, the permeable pavement systems consisted of surface permeable brick layer (concrete or ceramic) with structural layer (including a cement mortar layer, a permeable concrete layer, and a gravel layers) were selected as typical cases to assess their permeability and runoff pollutant removal performance by laboratory experiments. The results indicated that PPS had obvious outflow hysteresis effect. The PPS with ceramic brick layer reached the saturation flow rate earlier and showed larger outflow rate than that with concrete brick layer. Both types of PPSs had a relatively high efficiency (83.8-95.2%) in removing suspended solids (SS) in stormwater runoff mainly due to the interception and filtration of the surface brick layer, whereas the structural layer of the PPS played a vital role in the removal of total phosphorus (TP). The percentage of total nitrogen (TN) removal efficiency via ceramic brick layer accounted for via corresponding PPS was obviously larger than that of concrete brick layer. The PPS also displayed a certain chemical oxygen demand (COD) removal ability: around 14.0-27.0% for concrete type and 20.9-28.9% for ceramic type. Subsequently, a multi-objective evaluation model was implemented based on the analytic hierarchy process (AHP) method to identify the optimal scheme in relation to four indices: permeability, environmental benefit, compressive strength, and comprehensive economic cost. The results showed, insofar, the ceramic PPS is preferred with a better economic performance. Our study attempts to select optimal designs of PPS and provides insight into the permeable capacity and the efficiency of pollutant removal in PPS.

Effect of influent salinity on the selection of macrophyte species in floating constructed wetlands.

Pilot-scale floating constructed wetlands (FCWs) under varying influent salinities were implemented, and the effects of influent salinity on pollutant removal efficiency (RE) and macrophyte species selection were identified. The results suggest that a salinity increase generally decreased pollutant REs, while some macrophytes, such as Iris pseudacorus, could effectively resist this decrease. The average coefficients of variation between macrophyte species in REs of chemical oxygen demand, ammonium nitrogen, nitrate nitrogen and total phosphorus increased from 28.6% at low salinity to 91.3% at high salinity, which suggests the greater importance of macrophyte selection under high salinity. With an increase in salinity, the rhizosphere bacterial community showed convergent evolution or convergence followed by slight divergent evolution between macrophyte species, while the importance of macrophyte parameter selection in characterizing pollutant REs decreased. Therefore, influent salinity is a key factor to consider in macrophyte selection and application, especially in FCWs without soil.

Investigation on the treatment effect of slope wetland on pollutants under different hydraulic retention times.

This work was aimed at investigating the feasibility of the slope wetland system (SWs) for improving the polluted river water. According to the characteristics of polluted river water with different hydraulic retention time (HRT) changes, a field simulation device was set up. In this experiment, a SWs simulation device was set up to study pollutant removal of SWs under different hydraulic conditions. It was found that the effect of mixed fillers (zeolite and ceramsite) as the bed was better than that of the gravel fillers as the bed. The improvement of each treatment index was about 5% (P < 0.05). When HRT = 5 days, the removal rate of chemical oxygen demand (COD) was 28.02%, total nitrogen (TN) was 32.99%, ammonia nitrogen (NH3-N) was 32.49%, and total phosphorus (TP) was 38.15%. At the same time, it was found that the characteristic moderate extension of HRT is conducive to the removal of pollutants in SWs. The growth of plants in the environment of the gravel matrix was worse than that of mixed fillers (zeolite and ceramsite). It was found that physical adsorption was the main form of pollution removal on the SWs fillers by Fourier infrared spectrum (FTIR) analysis. Based on the analysis of the microbial community in the packing of the device, it is indicated that the enrichment of microorganisms appeared during the experiment, forming the dominant bacteria against the polluted river water.

Nitric oxide and nitrous oxide production in anaerobic/anoxic nitrite-denitrifying phosphorus removal process: effect of phosphorus concentration.

Nitric oxide (NO) and nitrous oxide (N2O) production in biological nutrient removal has been studied widely due to the strong negative effects on the environment. Nitrite-denitrifying phosphorus removal (N-DPR), as a significant source of NO and N2O production, has received great attention. However, the mechanism of NO and N2O production at different phosphorus concentrations is not well understood. Therefore, this study was conducted to investigate the effect of phosphorus concentration on pollutant removal, as well as NO and N2O production during the N-DPR process. The results showed that the phosphorus removal efficiency was improved with the increase of phosphorus concentration, which is caused by the enrichment of denitrifying phosphorus accumulating organisms (DPAOs) at high phosphorus concentration. High NO production was observed at phosphorus concentration of 0.5 mg L-1, which is mainly attributed to the slow recovery of reductase activity and low abundance of DPAOs. The maximal N2O accumulation of 31.45 mg L-1 was also achieved at phosphorus concentration of 0.5 mg L-1. The possible reason is that fewer poly-ß-hydroxyalkanoates (PHAs) were synthesized by glycogen accumulating organisms (GAOs) at low phosphorus concentration, which could intensify the electron competition among different reductases. In addition, free nitrous acid (FNA) inhibition was another significant reason for high N2O production.

Effects of di-n-butyl phthalate and di-2-ethylhexyl phthalate on pollutant removal and microbial community during wastewater treatment.

Due to the wide use of plastic products and the releasability of plasticizer into surrounding environment, the hazards, residues and effects of phthalic acid esters (PAEs) in ecosystems have been paid more and more attention. Little information is available about the effects of PAEs on the normal wastewater treatment, although the distribution of PAEs in soil and other ecosystems is closely related to the discharge of sewage. In this study, the effects of high concentrations of di-n-butyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) on pollutant removal and the microbial community during landfill leachate treatment was investigated. After domestication, the activated sludge was used in the co-treatment of landfill leachate and simulated domestic wastewater. We verified that this process reduced the toxicity of landfill leachate. However, high concentrations of added DBP and DEHP were removed first, while the removal of these pollutants from raw landfill leachate was limited. The results of high-throughput sequencing revealed that the bacterial diversity was diminished and the microbial community structure was significantly affected by the addition of DBP and DEHP. The DBP and DEHP samples had 79.05% and 82.25% operational taxonomic units (OTU), respectively, in common with the raw activated sludge. Many genera of PAE-degrading bacteria that had no significant evolutionary relationship were found in the raw activated sludge. And the widespread presence of PAE-degrading bacteria could effectively keep the concentrations of PAEs low during the wastewater treatment.