Simultaneous removal of nitrogen and pharmaceutical and personal care products from the effluent of waste water treatment plants using aerated solid-phase denitrification system

Mutual influence mechanism of nitrate and sulfamethoxazole on their biotransformation in poly (3-hydroxybutyrate-3-hydroxyvalerate) supported denitrification biofilter for a long-term operation

Nitrate and SMX both play a critical role in their biotransformation in biodegradable polymer-supported denitrification biofilters. However, the mutual influences of nitrate and SMX on their biotransformation for long-term operation remained obscure. Results showed SMX and nitrate had divergent effects on SMX removal. SMX removal rates was positively related with its loading rates, whereas they were negatively related to NLRs. The most abundant metabolite C10H14O3N3S (the reduced form of SMX moiety) from the N-O bond cleavage pathway by UHPLC-LTQ-Orbitrap-MS/MS and effluent TOC variations confirmed the presence of electron donor competition between nitrate and SMX. SMX less than 1000 μg/L had a negligible influence on denitrification performance. Denitrifiers such as Azospira and Denitratisoma were still enriched after chronic exposure, and nosZ/narG positively correlated with sul1/sul2 resistance genes, which were both responsible for the negligible influence of SMX. This work could guide the operational management of denitrification biofilters for simultaneous nitrate and antibiotics removal.

Acceleration of nitrogen removal performance in a biofilm reactor augmented with Pseudomonas sp. using polycaprolactone as carbon source for treating low carbon to nitrogen wastewater

Heterotrophic nitrification-aerobic denitrification (HN-AD) process was achieved in a moving bed biofilm reactor after 180-days acclimation using PCL as carbon source for low C/N wastewater treatment. A novel HN-AD strain, JQ-H3, with ability of PCL degradation was augmented to improve nitrogen removal. TN removal efficiencies of 82.31%, 90.05%, and 93.16% were achieved in the augmented reactor (R2), at different HRTs of 24 h, 20 h, and 16 h, while in the control reactor (R1), the TN removal efficiencies were 59.24%, 74.61%, and 76.68%. The effluent COD in R2 was 10.17 mg/L, much lower than that of 42.45 mg/L in R1. Microbial community analysis revealed that JQ-H3 has successfully proliferated with a relative abundance of 4.79%. Relative abundances of functional enzymes of nitrogen cycling remarkably increased due to bioaugmentation based on the analysis of PICRUSt2. This study provides a new approach for enhancing nitrogen removal in low C/N sewage treatment via the HN-AD process.

Effects of antibiotics on corncob supported solid-phase denitrification: Denitrification and antibiotics removal performance, mechanism, and antibiotic resistance genes

Solid-phase denitrification (SPD) has been used in wastewater treatment plant effluent to enhance nitrate removal, and antibiotics co-existing in the effluent is a common environmental problem. In this study, it was systematically investigated the effect of single trace sulfamethoxazole (SMX)/trimethoprim (TMP) and their mixture on microbial denitrification performance, the antibiotics removal, and antibiotics resistance genes (ARGs) in corncob supported SPD system. The average denitrification rate was improved by 46.90% or 61.09% with single 50 µg/L SMX or TMP, while there was no significant inhibition with mixed SMX and TMP. The abundance of dominant denitrifiers (Comamonadaceae family and Azospia) and fermentation bacteria (Ancalomicrobium) were consistent with the denitrification performance of different antibiotics groups. Single SMX and TMP achieved relatively higher denitrification gene and enzyme abundance. Mixed SMX and TMP improved the denitrification gene copies, but they reduced the key denitrification enzymes except for EC 1.7.7.2. Additionally, the removal efficiency of TMP (56.70% ± 3.18%) was higher than that of SMX (25.44% ± 2.62%) in single antibiotic group, and the existence of other antibiotics (i.e. SMX or TMP) had no significant impact on the TMP or SMX removal performance. Biodegradation was the main removal mechanism of SMX and TMP, while sludge and corncob adsorption contributed a little to their removal. SMX had the risk of sulfanilamide resistance genes (SRGs) dissemination. Furthermore, network analysis indicated that Niveibacterium and Bradyrhizobium were the potential hosts of SRGs, which promoted the horizontal transmission of ARGs.

Effects of hydraulic retention time and influent nitrate concentration on solid-phase denitrification system using wheat husk as carbon source

Solid-phase denitrification shows promise for removing nitrate (NO₃^--N) from water. Biological denitrification uses external carbon sources to remove nitrogen from wastewater, among which agriculture waste is considered the most promising source due to its economic and efficiency advantages. Hydraulic retention time (HRT) and influent nitrate concentration (INC) are the main factors influencing biological denitrification. This study explored the effects of HRT and INC on solid-phase denitrification using wheat husk (WH) as a carbon source. A solid-phase denitrification system with WH carbon source was constructed to explore denitrification performance with differing HRT and INC. The optimal HRT and INC of the wheat husk-denitrification reactor (WH-DR) were 32 h and 50 mg/L, respectively. Under these conditions, NO₃^--N and total nitrogen removal rates were 97.37 ± 2.68% and 94.08 ± 4.01%, respectively. High-throughput sequencing revealed that the dominant phyla in the WH-DR operation were Proteobacteria, Bacteroidetes, and Campilobacterota. Among the dominant genera, Diaphorobacter (0.85%), Ideonella (0.38%), Thiobacillus (4.22%), and Sulfurifustis (0.60%) have denitrification functions; Spirochaeta (0.47%) is mainly involved in the degradation of WH; and Acidovorax (0.37%) and Azospira (0.86%) can both denitrify and degrade WH. This study determined the optimal HRT and INC for WH-DR and provides a reference for the development and application of WH as a novel, slow-release carbon source in treating aquaculture wastewater.

Investigating the biodegradability of iodinated X-ray contrast media in simultaneous nitrification and denitrification system

The present study investigated the biodegradation of three iodinated X-ray contrast media (ICM), namely, iopamidol, iohexol, and iopromide, in simultaneous nitrification-denitrification (SND) system maintained in a sequencing batch reactor (SBR). The results showed that variable aeration patterns (anoxic-aerobic-anoxic) and micro-aerobic condition were most effective in the biotransformation of ICM while achieving organic carbon and nitrogen removal. The highest removal efficiencies of iopamidol, iohexol, and iopromide were 48.24%, 47.75%, and 57.46%, respectively, in micro-aerobic condition. Iopamidol was highly resistant to biodegradation and possessed the lowest K_bio value, followed by iohexol and iopromide, regardless of operating conditions. The removal of iopamidol and iopromide was affected by the inhibition of nitrifiers. The transformation products after hydroxylation, dehydrogenation, and deiodination of ICM were detected in the treated effluent. Due to the addition of ICM, the abundance of denitrifier genera Rhodobacter and Unclassified Comamonadaceae increased, and the abundance of class TM7-3 decreased. The presence of ICM affected the microbial dynamics, and the diversity of microbes in SND resulted in improving the biodegradability of the compounds.

Understanding the role of sorption and biodegradation in the removal of organic micropollutants by membrane aerated biofilm reactor (MABR) with different biofilm thickness

The role of sorption and biodegradation in a membrane aerated biofilm reactor (MABR) were investigated for the removal of 10 organic micropollutants (OMPs) including endocrine disruptors and pharmaceutical active compounds. The influence of the biofilm thickness on the mechanisms of removal was analyzed via kinetic test at three different stages. At all biofilm stages, biodegradation was demonstrated to dominate the removal of selected OMPs. Higher OMPs rates of removal via biodegradation (K_biol) were achieved when biofilm increased its thickness from (stage T1) 0.26 mm, to (stage T2) 0.58 mm and (stage T3) 1.03 mm. At stage T1 of biofilm, heterotrophs contribute predominantly to OMPs degradation. Hydrophilic compounds removal (i.e., acetaminophen) continue to be driven by heterotrophic bacteria at the next stages of biofilm thickness. However, for medium hydrophobic neutral and charged OMPs, the combined action of heterotrophic and enriched nitrifying activity at stages T2 and T3 enhanced the overall removal. A degradation pathway based on heterotrophic activity for acetaminophen and combined action of nitrifiers-heterotrophs for estrone was proposed based on identified metabolites. Although biodegradation dominated the removal of most OMPs, sorption was also observed to be essential in the removal of biologically recalcitrant and lipophilic compounds like triclosan. Furthermore, sorption capacity of apolar compound was enhanced as the biofilm thickness grew and increased in EPS protein fraction. Microbial analysis confirmed the higher abundance of nitrifying and denitrifying activity at stage T3 of biofilm, which not only facilitated near complete ammonium removal but also enhanced degradation of OMPs.

Recent advances in simultaneous nitrification and denitrification for nitrogen and micropollutant removal: a review

Simultaneous Nitrification and Denitrification (SND) is a promising process for biological nitrogen removal. Compared to conventional nitrogen removal processes, SND is cost-effective due to the decreased structural footprint and low oxygen and energy requirements. This critical review summarizes the current knowledge on SND related to fundamentals, mechanisms, and influence factors. The creation of stable aerobic and anoxic conditions within the flocs, as well as the optimization of dissolved oxygen (DO), are the most significant challenges in SND. Innovative reactor configurations coupled with diversified microbial communities have achieved significant carbon and nitrogen reduction from wastewater. In addition, the review also presents the recent advances in SND for removing micropollutants. The micropollutants are exposed to various enzymes due to the microaerobic and diverse redox conditions present in the SND system, which would eventually enhance biotransformation. This review presents SND as a potential biological treatment process for carbon, nitrogen, and micropollutant removal from wastewater.

Simultaneous nitrification and denitrification in a PCL-supported constructed wetland with limited aeration

Considerable advances have been made in the substrate design and operation strategies of constructed wetlands to facilitate nitrogen elimination. However, few studies examined the complicated interaction between solid organic substrates and limited aeration on nitrogen removal. A vertical flow constructed wetlands in gradient distribution of inorganic and solid organic substrates (polycaprolactone/PCL) (P-VFCW) and a controlled vertical flow constructed wetland without PCL (C-VFCW) were developed for the tertiary treatment of municipal tailwater. Results indicated that ammonia was nearly converted to nitrate, while the total nitrogen removal efficiencies (TNREs) in C-VFCW were negligible. In P-VFCW, however, optimal TNREs approached 95% with an aeration rate of 0.06 mL·min^-1 and hydraulic retention time (HRT) of 24 h, and simultaneous nitrification and denitrification process (SND) in aerobic conditions was confirmed. As for the spatial microbial community structure evolution, Comamonas, which is associated with heterotrophic nitrification and anoxic/aerobic denitrification, was enriched along the vertical profiles of P-VFCW. Autotrophic nitrifier (Nitrospira), aerobic denitrifier (Bradyrhizobium and Azospira), and anoxic denitrifier (Ignavibacterium and Methyloversatilis) were dominated in different depths of P-VFCW, respectively. Besides, Canna indica biomass in P-VFCW was significantly larger than that in C-VFCW, which was attributed to the plant adaption response to diverse nitrogen. The P-VFCW in gradient distribution of inorganic and solid carbon sources under limited aeration is a promising technology for advanced nitrogen removal.

The research progress, hotspots, challenges and outlooks of solid-phase denitrification process

Nitrogen pollution is one of the main reasons for water eutrophication. The difficulty of nitrogen removal in low-carbon wastewater poses a huge potential threat to the ecological environment and human health. As a clean biological nitrogen removal process, solid-phase denitrification (SPD) was proposed for long-term operation of low-carbon wastewater. In this paper, the progress, hotspots, and challenges of the SPD process based on different solid carbon sources (SCSs) are reviewed. Compared with synthetic SCS and natural SCS, blended SCSs have more application potential and have achieved pilot-scale application. Differences in SCSs will lead to changes in the enrichment of hydrolytic microorganisms and hydrolytic genes, which indirectly affect denitrification performance. Moreover, the denitrification performance of the SPD process is also affected by the physical and chemical properties of SCSs, pH of wastewater, hydraulic retention time, filling ratio, and temperature. In addition, the strengthening of the SPD process is an inevitable trend. The strengthening measures including SCSs modification and coupled electrochemical technology are regarded as the current research hotspots. It is worth noting that the outbreak of the COVID-19 epidemic has led to the increase of disinfection by-products and antibiotics in wastewater, which makes the SPD process face challenges. Finally, this review proposes prospects to provide a theoretical basis for promoting the efficient application of the SPD process and coping with the challenge of the COVID-19 epidemic.

Solid slow-release carbon sources improve the simultaneous nitrification and denitrification processes in low carbon resource wastewater

In this study, A Acinetobacter pittii sp. was isolated with high efficiency for heterotrophic nitrification and aerobic denitrification (HN-AD). The boundary conditions for total nitrogen (TN) removal were as follows: C/N ratios 8-14, temperature 25-35 °C, initial pH 7-9, and shaker speed 100-120 rpm. Addition of mixed carbon resources achieved 97.38 % ammonia-N and 91.50 % TN removal, which was higher than that of the group with sole carbon resources. The ammonia-N and TN removal profiles matched well with first-order kinetics in the rapid response period and zero-order kinetics in the slow reaction period. Meanwhile, enzyme activity related to nitrogen conversion would remarkably increase with mixed carbon resources. Furthermore, proposed a possible relationship between the solid carbon source, hydrolysis, soluble small molecule organic matter, microbial activity, and heterotrophic nitrification and aerobic denitrification (HN-AD). This study provides a new strategy for improving nitrogen removal in wastewater with low-carbon resources.

Simultaneous denitrification and antibiotic degradation of low-C/N-ratio wastewater by a three-dimensional biofilm-electrode reactor: Performance and microbial response

Three-dimensional biofilm-electrode reactors (3D-BERs) were fabricated and used to simultaneously remove nitrate and metronidazole (MNZ) from low-C/N-ratio wastewater. The results showed that 1 mg/L MNZ significantly promoted nitrate removal. After MNZ was added to the reactor, the removal efficiencies of total nitrogen (TN) and NO₃^--N increased significantly from 18.97% and 52.09% to 71.63% and 99.98% within 6 h, respectively. The MNZ-removal kinetics conformed to a pseudo-first-order model, and the removal rate constant reached a maximum value of 0.853 h^-1, which was 4.1 and 2.8 times higher than that of pure microorganisms and pure electrochemical reactors, respectively. This indicated that the 3D-BERs constructed in this study were capable of simultaneous MNZ degradation and denitrification. In the presence of nitrate, six MNZ-degradation intermediates were identified, and four MNZ transformation pathways were proposed, including cleavage of hydroxyethyl groups, reduction of nitro groups, N-denitration, and deprotonation of side-chain hydroxyl groups. High-throughput sequencing revealed that the reactor was rich in various MNZ-degraders and denitrifiers, such as Hydrogenophaga, Methylomonas, Crenohrix, Dechloromonas, and Methylophilus. A function prediction analysis of nitrogen metabolism showed that the 3D-BER reactor with MNZ had higher denitrification activity than the other reactors tested. It was speculated that the intermediates produced by MNZ could act as carbon sources allowing denitrifying bacteria to perform denitrification, which made a nonnegligible contribution to the removal of nitrogen.

Simultaneous biological removal of nitrogen and phosphorus from secondary effluent of wastewater treatment plants by advanced treatment: A review

With the advancement of water ecological protection and water control standard, it is the general trend to upgrade the wastewater treatment plants (WWTPs). The simultaneous removal of nitrogen and phosphorus is the key to improve the water quality of secondary effluent of WWTPs to prevent the eutrophication. Therefore, it is urgent to develop the applicable technologies for simultaneous biological removal of nitrogen and phosphorus from secondary effluent. In this review, the composition of secondary effluent from municipal WWTPs were briefly introduced firstly, then the three main treatment processes for simultaneous nitrogen and phosphorus removal, i.e., the enhanced denitrifying phosphorus removal filter, the pyrite-based autotrophic denitrification and the microalgae biological treatment system were summarized, their performances and mechanisms were analyzed. The influencing factors and microbial community structure were discussed. The advanced removal of nitrogen and phosphorus by different technologies were also compared and summarized in terms of performance, operational characteristics, disadvantage and cost. Finally, the challenges and future prospects of simultaneous removal of nitrogen and phosphorus technologies for secondary effluent were proposed. This review will deepen to understand the principles and applications of the advanced removal of nitrogen and phosphorus and provide some valuable information for upgrading the treatment process of WWTPs.

Bioaugmented removal of 17β-estradiol, nitrate and Mn(II) by polypyrrole@corn cob immobilized bioreactor: Performance optimization, mechanism, and microbial community response

The coexistence of nitrate and endocrine substances (EDCs) in groundwater is of global concern. Herein, an efficient and stable polypyrrole@corn cob (PPy@Corn cob) bioreactor immobilized with Zoogloea sp. was designed for the simultaneous removal of 17β-estradiol (E2), nitrate and Mn(II). After 225 days of continuous operation, the optimal operating parameters and enhanced removal mechanism were explored, also the long-term toxicity and microbial communities response mechanisms under E2 stress were comprehensively evaluated. The results showed that the removal efficiencies of E2, nitrate, and Mn(II) were 84.21, 82.96, and 47.91%, respectively, at the optimal operating conditions with hydraulic retention time (HRT) of 8 h, pH of 6.5 and Mn(II) concentration of 20 mg L^-1. Further increased of initial E2 (2 and 3 mg L^-1) resulted in the inhibiting effect of denitrification and manganese oxidation, but excellent E2 removal efficiencies maintained, which were associated with the formation and continuous accumulation of biomanganese oxides (BMO). Characterization analysis of biological precipitation demonstrated that adsorption and redox conversion on the BMO surface played key roles in the removal of E2. In addition, different levels of E2 exposure are decisive factors in community evolution, and bioaugmented bacterial communities with Zoogloea as the core group can dynamically adapt to E2 stress. This study offers the possibility to better utilize microbial metabolism and to advance opportunities that depend on microbial physiology and material characterization applications.

Co-degradation of ofloxacin and its impact on solid phase denitrification with polycaprolactone as carbon source

Solid-phase denitrification has been applied for advanced nitrogen removal from wastewater and can co-degrade emerging pollutants. Fluoroquinolones (FQs), broad-spectral antibiotic, are frequently detected in the effluent of conventional wastewater treatment plants. However, it remains unclear whether solid-phase denitrifying bacteria can remove FQs. Thus, this study investigated the removal capacity of ofloxacin (OFX) as a representative of FQs and the microbial community structures of denitrifying sludge acclimated to polycaprolactone and OFX. The Results indicate that OFX had a negative effect on denitrification performance. OFX was degraded, and a possible pathway was revealed based on ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry. The dominant genera in the acclimated denitrifying sludge were Microbacterium, Simplicispira, Alicycliphilus, Reyranella, Sediminibacterium, Acidovorax and Thermomonas. Moreover, ABC transporters and cytochrome P450, related to multi-drug resistance and drug metabolism, were highly expressed in the acclimated sludge. This study provides novel insights into antibiotics control.

Preparation of lightweight daisy-like magnetic molecularly imprinted polymers via etching synergized template immobilization for enhanced rapid detection of trace 17β-estradiol

17β-estradiol (E2), as one of the pharmaceutical and personal care product, frequently contaminates environmental water as estrogen pollutant and possesses great risk to human survival as well as the sustainable development of the ecosystem. Herein, to achieve an effective adsorbent system for the selective removal of E2 from the environmental water, Fe₃O₄ nanoparticles are subjected to chemical etching to reduce the overall mass and then employed as carriers to prepare a novel type of lightweight daisy-like magnetic molecularly imprinted polymers (LD-MMIPs) adopting template immobilization strategy. The LD-MMIPs based etched magnetic nanoparticles not only exhibit light mass but also have plentiful imprinted sites in the etched channels, which significantly increases the adsorption capacity for E2. The daisy-like LD-MMIPs own strong magnetic responsiveness, well crystallinity, fast binding kinetics, high adsorption amount, and excellent selectivity. Moreover, combining with HPLC, the LD-MMIPs as adsorbents have been successfully used to specifically recognize and detect trace E2 in environmental water. Thus, the proposed LD-MMIPs with high adsorption capacity hold great potential in monitoring water pollution. Additionally, this work also provides an alternative strategy for improving the adsorption capacity of magnetic molecularly imprinted polymers through a convenient chemical etching technology.

Efficiency and microbial diversity of aeration solid-phase denitrification process bioaugmented with HN-AD bacteria for the treatment of low C/N wastewater

To evaluate the simultaneous nitrification and denitrification (SND) performance of the aeration solid-phase denitrification (SPD) process and improve the operating efficiency, aeration SPD process using polybutanediol succinate as carbon source was optimized and the process was bioaugmented with heterotrophic nitrification-aerobic denitrification bacteria for the treatment of real wastewater. The results showed that after bioaugmentation, the total nitrogen removal efficiency of the aeration SPD process increased by 50.46 % under condition of dissolved oxygen (DO) 3 mg/L. According to Illumina MiSeq sequencing and correlation analyses, the microbial community can perform SND under the conditions of DO 5 mg and HRT 6 h, but is susceptible to DO. Bioaugmentation mainly affected the carbon source metabolic network with heterotrophic bacteria Methyloversatilis, Thiothrix, and norank_Lentimicrobiaceae as nodes to change the community structure, thereby improving the performance of the functional microbial community. Kyoto Encyclopedia of Genes and Genomes analysis suggested that narB, narG, narH, nirK and narI were the key genes involved in the response to bioaugmentation. This work provides new insights for the application of the SPD process in wastewater treatment.

Reductive potential from cathode electrode as an option for the achievement of short-cut nitrification in bioelectrochemical systems

Nitrogen removal based on short-cut nitrification (SCN) have attract more attentions, in which stable nitrite accumulation is prerequisite. In this study, different reductive potential was applied to inhibit nitrite oxidizing bacteria for achievement of SCN in aerobic cathode chamber of bioelectrochemical systems with dissolved oxygen concentration of 3.5 mg/L. The results demonstrated that the applied potential facilitated nitrite accumulation with high ammonia oxidation rates. The maximum nitrate accumulation rate of 87.61% was obtained at -800 mV. The abundance of Nitrosomonas and Thauera increased while Nitrospira abundance declined with more negative reductive potentials. The activity of nitric oxide reductase was also evidently inhibited. The above-mentioned three genera were the keystone taxa in co-occurrence network with high degree and closeness centrality. Interestingly, total nitrogen (TN) removal was enhanced simultaneously in the absence of external organic carbon. Reductive potential would be a promising approach for achieving SCN and simultaneously TN removal.

Research progress in solid carbon source-based denitrification technologies for different target water bodies

Nitrogen pollution in water bodies is a serious environmental issue which is commonly treated by various methods such as heterotrophic denitrification. In particular, solid carbon source (SCS)-based denitrification has attracted widespread research interest due to its gradual carbon release, ease of management, and long-term operation. This paper reviews the types and properties of SCSs for different target water bodies. While both natural (wheat straw, wood chips, and fruit shells) and synthetic (polybutylene succinate, polycaprolactone, polylactic acid, and polyhydroxyalkanoates) SCSs are commonly used, it is observed that the denitrification performance of the synthetic sources is generally superior. SCSs have been used in the treatment of wastewater (including aquaculture wastewater), agricultural subsurface drainage, surface water, and groundwater; however, the key research aspects related to SCSs differ markedly based on the target waterbody. These key research aspects include nitrogen pollutant removal rate and byproduct accumulation (ordinary wastewater); water quality parameters and aquatic product yield (recirculating aquaculture systems); temperature and hydraulic retention time (agricultural subsurface drainage); the influence of dissolved oxygen (surface waters); and nitrate-nitrogen load, HRT, and carbon source dosage on denitrification rate (groundwater). It is concluded that SCS-based denitrification is a promising technique for the effective elimination of nitrate-nitrogen pollution in water bodies.

Sulfur autotrophic denitrification filter and heterotrophic denitrification filter: Comparison on denitrification performance, hydrodynamic characteristics and operating cost

Sulfur autotrophic denitrification (SAD) process, as an alternative to heterotrophic denitrification (HD) filter, receives growing interest in polishing the effluent from secondary sewage treatment. Although individual studies have indicated several advantages of SAD over HD, rare study has compared these two systems under identical condition and by using real secondary effluent. In this study, two small pilot scale filters (SAD and HD) were designed with identical configuration and operated parallelly by feeding the real secondary effluent from a WWTP. The results showed SAD filter can be started up without the addition of soluble electron donor, although the time (14 days) was about 3 times longer than that of HD filter. The nitrate removal rate of SAD filter at HRT of 1.4 h was measured as 0.268 ± 0.047 kg N/(m³∙d). Similar value was observed in HD filter with supplementing 90 mg/L COD. The COD concentration of effluent always kept lower than that of influent in SAD filter but not in HD filter. In addition, SAD filter could maintain a stable denitrification performance without backwash for 15 days, while decline of nitrate removal rate was observed in HD filter just 2 days after stopping the backwash. This different behavior was further confirmed as the SAD filter had a better hydraulic flow pattern. Analysis according to high-throughput 16S rRNA gene-based Illumina MiSeq sequencing clearly showed the microbial community evolution and differentiation among the samples of seed sludge, SAD and HD filters. Finally, the economic assessment was carried out, showing the operation cost of SAD filter was over 50% lower than that of HD filter.

Degradation mechanism of Ibuprofen via a forward osmosis membrane bioreactor

Ibuprofen (IBU) is a non-steroidal drug that is classified as a trace organic compound (TrOC). A forward osmosis membrane bioreactor (FOMBR) has traditionally been a favored technology for wastewater treatment. In this study, the IBU degradation mechanism was clarified using an FOMBR. The results indicated that the average removal efficiencies of contaminants were greater than 96.32%. The ultra-performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOF-MS) results demonstrated that there were 10 intermediates and 5 possible pathways during the IBU degradation. Decarboxylation and hydroxylation may be the primary pathways of IBU degradation. The microbial results illustrated that Proteobacteria was dominant and of utmost importance in the degradation process. Thauera and Azoarcus were the dominant genera that participated in contaminant degradation.

Release Mechanism, Secondary Pollutants and Denitrification Performance Comparison of Six Kinds of Agricultural Wastes as Solid Carbon Sources for Nitrate Removal

Agricultural wastes used as denitrification carbon sources have some drawbacks such as excessive organic carbon release and unclear release characteristics of nitrogen, phosphorus, and chromatic substances, which can cause adverse effects on the effluent quality during the denitrification process. The composition and surface characteristics, carbon release mechanisms, and secondary pollutant release properties of six kinds of agricultural wastes, i.e., rice straw (RS), wheat straw (WS), corn stalk (CS), corncob (CC), soybean stalk (SS), and soybean hull (SH) were studied and analyzed in this research. The denitrification performance of these agricultural wastes was also investigated extensively by batch experiments. The results showed that the carbon release basically followed the second-order reaction kinetic equation and Ritger-Peppas equation in the 120 h reaction, and it was mainly controlled by the diffusion process. The kinetic equation fitting results and bioavailability test suggested that the potential risk of excessive effluent COD of CC was the lowest due to the appropriate amount and degradability of its released carbon. The NH₄⁺-N, TN, and TP in the leachate of RS were higher than those of the other five agriculture wastes, and the chroma in the leachate of WS and CS was heavier than that of the others. CC released the lowest pollutants, which resulted in slight fluctuations of effluent quality in the start-up period (1-11 d), and it had the best nitrogen removal capacity in the denitrification experiment. The average NO₃^--N removal of CC was 5.12 mg for each batch in the stable period (11-27 d), which was higher than that of others, and less NO₂^--N, NH₄⁺-N, and COD were accumulated in the CC effluent during the whole denitrification process.

Emerging nano-structured innovative materials as adsorbents in wastewater treatment

Water supply around the globe is struggling to meet the rapidly increasing demand by the population, drastic changes in climate and degrading water quality. Even though, many large-scale methods are employed for wastewater treatment they display several negative impacts owing to the presence of pollutants. Technological innovation is required for integrated water management with different groups of nanomaterials for the removal of toxic metal ions, microbial disease, organic and inorganic solutes. The method of manipulating atoms on a nanoscale is nanotechnology. Nanomembranes are used in nanotechnology to soften water and eliminate physical, chemical and biological pollutants. The present review concentrates on various nanotechnological approaches in wastewater remedy, mechanisms involved to promote implementation, benefits and limitations in comparison with current processes, properties, barriers and commercialization research needs. Also the review identifies opportunities for further exploiting the exclusive features for green water management by following the advances in nanotechnology.

Renovated filter filled with poly-3-hydroxybutyrateco-hydroxyvalerate and granular activated carbon for simultaneous removal of nitrate and PPCPs from the secondary effluent

Reclaimed water is in huge demand in water-deficient cities. However, nitrogen, pharmaceuticals and personal care products (PPCPs) are frequent contaminants in reclaimed water that are probable to bring environmental risks. To develop a technology for safe reclaimed water production, in this study, a renovated filter that integrates solid-phase denitrification (SPD) with biodegradable polymer poly-3-hydroxybutyrate-co-hydroxyvalerate (PHBV) and granular activated carbon (GAC) adsorption (SPD-GAC filter) was proposed and applied to remove nitrogen and target PPCPs (metoprolol and diclofenac) simultaneously. The influences of different ratio of the filled PHBV and GAC, and the hydraulic retention time (HRT) on the removal performances were investigated. The results showed that the filter with PHBV/GAC = 1 (25 cm PHBV/25 cm GAC) simultaneously achieved an average NO₃^--N removal efficiency of about 95% with no accumulation of ammonia and nitrite, and an average removal efficiency of PPCPs of about 80%. Compared with PHBV-based SPD system, the integrated SPD-GAC filter significantly improved the control of carbon release and the PPCP removals. SPD-GAC filter also exhibited a strong tolerance for the variation of influent NO₃^--N loading rate, achieving a highest denitrification rate of 0.76-0.82 g N·(L·d)^-1. The integrated SPD-GAC filter proves to be a promising technology for the simultaneous removal of nitrogen and PPCPs from the secondary effluent.

Comparison of the effects of salinity on microbial community structures and functions in sequencing batch reactors with and without carriers

This study investigated and compared the microbial communities between a sequencing batch reactor (SBR) without carriers and a hybrid SBR with addition of carriers for the treatment of saline wastewater. The two systems were operated over 292 days with alternating aerobic/anoxic mode (temperature: 28℃, salinity: 0.0-3.0%). High removal efficiency of chemical oxygen demand (COD) and total inorganic nitrogen (TIN) was achieved in both the SBR (above 86.7 and 95.4% respectively) and hybrid SBR (above 84.4 and 94.0%) at 0.0-2.5% salinity. Further increasing salinity to 3.0% decreased TIN removal efficiency to 78.4% in the hybrid SBR. Steep decline of biodiversity and relative abundance of ammonia-oxidizing bacteria (AOB) contributed to the worse performance. More genera related to sulfide-oxidizing and sulfate-reducing bacteria were detected in the hybrid SBR than the SBR at 3.0% salinity. The abundance of halotolerant bacteria increased with the salinity increase for both reactors, summing up to 25.5% in the suspended sludge (S-sludge) from the SBR, 28.9 and 22.9% in the S-sludge and biofilm taken from the hybrid SBR, respectively. Nitrification and denitrification via nitrate was the main nitrogen removal pathway in the SBR and hybrid SBR at 0.0 and 0.5% salinity, while partial nitrification and denitrification via nitrite became the key process for nitrogen removal in the two reactors when the salinity was increased to 1.0-3.0%. Higher abundance of anaerobic ammonium-oxidizing (ANAMMOX) and sulfide-oxidizing autotrophic denitrification (SOAD) bacteria were found in the hybrid SBR at 3.0% salinity.

Chemically Modified Biosorbents and Their Role in the Removal of Emerging Pharmaceutical Waste in the Water System

Presence of pharmaceutically active compounds (PACs) as emerging contaminants in water is a major concern. Recent reports have confirmed the presence of PACs in natural and wastewater systems, which have caused several problems indicating the urgent need for their removal. The current review evaluates the role of chemically modified biosorbents in the removal of PACs in water. Reported biosorbents include plant and animal solid waste, microorganisms and bio-composite. Bio-composites exhibited better prospects when compared with other biosorbents. Types of chemical treatment reported include acid, alkaline, solvent extraction, metal salt impregnation and surface grafting, with alkaline treatment exhibiting better results when compared with other treatments. The biosorption processes mostly obeyed the pseudo-second-order model and the Langmuir isotherm model in a process described mainly by ionic interaction. Desorption and regeneration capacity are very important in selecting an appropriate biosorbent for the biosorption process. Depending on the type of biosorbent, the cost of water treatment per million liters of water was estimated as US $10–US $200, which presents biosorption as a cheap process compared to other known water treatment processes. However, there is a need to conduct large-scale studies on the biosorption process for removing PACs in water.

Treatment technologies for pharmaceutical effluents-A scientometric study

Treatment of highly polluted pharmaceutical effluents is a major challenge all over the world for technical and economic considerations. In this study, scientometric study is performed on the application of various methods for the treatment of pharmaceutical effluents to explore further developments. In this regard, a total of 1964 documents were retrieved from the Web of Science (WoS) database using a set of relevant keywords to cover all published documents. The extracted documents were subjected to scientometric study including the contributed authors, publications, citations received, contributing countries and institutions as well as the subject categories. From the data retrieved, the status of scientific knowledge on the subject history and current trends were identified and scientific gaps were critically discussed. Publications in this area started to appear since the sixties and were considerably promoted around the beginning of 2000s. Scientific publications of years 1960-2018 followed sigmoidal trend. It was found that leading countries are China and the United States in terms of scientific output on treatment technologies for pharmaceutical effluents. Among the active journals published, "Water Research" has received the most citations. A detailed discussion on the science and developments in this field is provided including the potential applications of scientometry.

The configuration, purification effect and mechanism of intensified constructed wetland for wastewater treatment from the aspect of nitrogen removal: A review

Constructed wetland (CW) for wastewater treatment has attracted increasing attention. In this review, the system configuration optimization, purification effect and general mechanisms of nitrogen removal in CW are systematically summarized and discussed. Ammonia oxidation is a crucial and primary process for total nitrogen (TN) removal in domestic or livestock wastewater treatment. Aeration, waterdrop influent and tidal operation are three main methods to strengthen the oxygen supplement and nitrification process in CW. Aeration significantly increases the ammonia removal rate (almost 100%), followed by the removal of chemical oxygen demand (COD) and TN. Solid carbon source, iron and anode material can be filled as electron donor for the denitrification process. The co-adjustment of oxygen and carbon/electron donor can form different conditions for different nitrogen removal pathways (e.g. the simultaneous nitrification-denitrification, the partial nitrification-denitrification and the anammox process), and achieve the optimal removal of nitrogen.