Fine-grained pyrites are difficult to be denitrified under natural environment due to chemical oxidation with O2. In this study, the pyrite/PHBV composites were synthesized through high-temperature melting and realized nitrogen and phosphate removal under natural aerobic conditions. Results showed that pyrite/PHBV-40 composites had the highest denitrification rate of 0.61 mg NO3–N /(LCh) with low SO42-production, and its removal efficiency of nitrogen and phosphorus was 98% and 41%, respectively. Microbial community structure analysis revealed that the enrich sulfate-reducing bacteria (SRB) on the pyrite/PHBV-40 composites demonstrated that the sulfate reduction driven by SRB enhanced denitrification process, and thereby the S cycle could underpin the potential self-sustainability of pyrite/PHBV-40 composites. Co-occurrence network analysis showed that Fe oxidizers/reducers (e.g., Ferruginibacter/Geobacter) and SRB (e.g., Desulfovibrio) were the keystone species in microbial community. Bugbase analysis showed that formed biofilms mainly consisted of aerobic and facultative anaerobic strains, which was corresponding to structure of biofilm including aerobic and anoxic layer. Partial mantel test revealed the total Fe and nutrients (e.g., N and P) are the drivers in OTU and phenotype composition, respectively. Metabolic pathway analysis suggested that pyrite/PHBV composites may not only accelerate glycolysis with rapid hydrolysis of PHBV, but also enhance the TCA cycle with high production of ATP and NADH. The final product of nitrate reduction is N2O or NO, and the cysJ gene play an important role in sulfate reduction in pyrite/PHBV systems. Overall, the novel synthesized pyrite/PHBV composites are an ideal functional material with high denitrification rate, no secondary pollution and long service life. Our study highlights pyrite/PHBV-induced strength in microbiota dynamics and C, N, S transformation, therein, the sulfate reduction process cannot be overlooked.

In this study, Mn-C composites using different MnO2 contents and solid carbon material were prepared to explore the synchronous removal performance of nutrients and SMX. Higher nitrate removal performance (97-98 %) with quickest nitrate removal rate (4.97 mg N L -1h- 1) was obtained in Mn\_20 systems. The increased Mn content and Mn-P compound were observed via surface characteristics, indicating the involvement of MnOx in pollutants removal, particularly for higher phosphorus removal (84-89 %) via Mn-P precipitation and BioMnOx adsorption. Nevertheless, compared to systems based on Mn\_0 composites (74 %), systems with Mn-C composites presented lower SMX reduction efficiency (34-51 %), which might be attributed to the large Mn(II) accumulation, impairing certain microbes and lower the MnOx function. Higher abundance of genera affiliated to Bacter-oidetes\_vadinHA17 and Rhodocyclaceae was observed in the Mn-C composites, as well as the gathering of Geo-bacter and Desulfovibrio as keystone taxa, responsible for the removal of nitrate and SMX and microbial interactions. Besides, the increase of sulfonamide ARGs was closely related to the predominant microbes in the Mn-C composites, which acted as the hosts of ARGs. This study broadens the knowledge of Mn-C composites in synergetic removal of nutrients and organics, and supports the potential application of manganese oxide in wastewater treatment.

In this study, an integrated treatment system was proposed and applied in situ, including detention tank, multistage constructed wetlands (CWs) and wastewater treatment plants (WWTPs), preventing nutrients flowing into Dianchi Lake, in which the treatment performance of multistage CWs were evaluated principally. Results skillfully realized the bypass purification of upstream river at dry reasons, as well as the effective management and treatment of the collected diffuse pollution at rainy reasons. The purified water flowing into water bodies could satisfy the Grade III of environmental quality standards for surface water in China with the average effluent concentrations of COD, NH4+-N, TN and TP decreased to 10 (51.2-72.7%), 0.5 (67.2-83.0%), 1.0 (71.2-79.6%) and 0.15 (72.3-89.4%) mg L-1, respectively. High-throughput sequencing results indicated that the application of poly-3-hydroxybutyrate-cohyroxyvelate-sawdust (PS) blends could enrich norank\_f\_Anaerolineaceae (7.95%) and Bradyrhizobium (10.2%), which were distinct from the dominant genera of Pleurocapsa (13.0%) in gravel -based CWs. Functional genes and metabolism analysis uncovered that the heterotrophic denitrification was the main pathway of nitrogen removal with the abundance of genes encoding TCA cycle, glycolysis and deni-trification process up-regulated. In addition, molecular ecological network (MEN) analysis suggested the deni-trification genes were positively correlated with the predominant microbes in PS-based CWs, favorable for denitrifiers to transfer and utilize electron donors during denitrification process. This study proved that the developed PS blends as carbon supplies in CWs and the proposed integrated treatment system are effective methods for watershed management, providing valuable reference to low-pollution wastewater treatment in practical engineering projects.

Manganese oxides (MnOx) are recognized as a strongest oxidant and adsorbent, of which composites have been proved to be effective in the removal of contaminants from wastewater. This review provides a comprehensive analysis of Mn biochemistry in water environment including Mn oxidation and Mn reduction. The recent research on the application of MnOx in the wastewater treatment was summarized, including the involvement of organic micropollutant degradation, the transformation of nitrogen and phosphorus, the fate of sulfur and the methane mitigation. In addition to the adsorption capacity, the Mn cycling mediated by Mn(II) oxidizing bacteria and Mn(IV) reducing bacteria is the driving force for the MnOx utilization. The common category, characteristics and functions of Mn microorganisms in recent studies were also reviewed. Finally, the discussion on the influence factors, microbial response, reaction mechanism and potential risk of MnOx application in pollutants’ transformation were proposed, which might be the promising opportunities for the future investigation of MnOx application in wastewater treatment.

The solid carbon source (poly-3-hydroxybutyrate co 3 hyroxyvalerate, PHBV) and manganese oxide mineral (Mn ore) were proposed firstly as co-substrates for eliminating nutrients and sulfamethoxazole (SMX) in this study. Results showed that high-rate nitrate and phosphate removal could be achieved in PHBV/Mn ore systems with the average efficiencies of 90% and 66.7%, respectively, although the addition of SMX decreased denitrification performance by 4.5-10.5%. SMX was removed mainly via biodegradation of enriched denitrifying microbes, with the average removal efficiency of 20-50% in PHBV/Mn ore systems, which was higher than that in PHBV systems. The existence of Mn ore markedly shaped the microbial community structure, leading to the dominant bacteria transforming from Microscillaceae to Sporomusaceae. The genera of Geobactor, Desulfovibrio and Anaerovorax were found to maintain the stability of microbial system as keystone species. Surprisingly, large amount of Mn(II) was accumulated, which not only verify the involvement of Mn cycling in decontamination process, but also might explain the propagation of ARGs (tnpA-04 and tnpA-05) in host microorganisms. Therefore, the optimized mixture proportion of PHBV and Mn ore should be further estimated avoiding Mn (II) accumulation in the effluent. On the whole, these results might shed light on new insight for advanced treatment of nutrients and emerging pollutants in biofilm reactors.

Effective control of nitrogen and phosphorus simultaneously is of great significance to satisfy the strict requirement of the ecological health of receiving waters. In this study, PHBV/ZVI composites made from solid carbon (poly-3-hydroxybutyrate-cohyroxyvelate, PHBV) and zero-valent iron (ZVI) were proposed to be functional fillers in biofilters for advanced wastewater treatment. Results showed that high-rate treatment performance was obtained with nitrate and phosphorus removal efficiencies of 79-97% and 97-98% in the biofilters packed with PHBV/ZVI composites. Lower N2O and CH4 emission (56.3-129.2 mu g m(-2) h(-1)) were also achieved simultaneously, further indicating the superiority of PHBV/ZVI composites applied in the wastewater treatment. High-throughput quantitative-PCR (HT-qPCR) results uncovered that the existence of ZVI could enrich carbon degradation genes (manA, gam and mxa) and facilitate denitrifier utilize organic matters more efficiently, as evidenced by up-regulations of genes involved in nitrate reduction (nirS and nosZ). Meanwhile, higher Fe concentration and less functional genes inducing lower activities of phosphate metabolism and in PHBV/ZVI systems indicated ZVI corrosion and coprecipitation were the main pathway of phosphorus removal. Network and redundancy analysis highlighted the role of ZVI in the removal of pollutants with keystone genes changed (pox and napA) and genes distribution remodeled compared to single PHBV fillers. Further, the activities of dehydrogenase (DHA) and nitrite reductase (Nir) enzymes also increased by the modulation of microbes, which explicitly interpreted the synergistic promotion of PHBV and ZVI on the denitrification process. These findings provided an alternative for the advanced treatment of wastewater and improve the understanding of C, N and P cycling in the co-occurrence of PHBV and ZVI.

In this study, a biofilter was developed with a ZVI/PHBV/sawdust (ZPS) composite for treating simulative secondary effluent from wastewater treatment plants. Results showed that effluent concentrations of NO3–N and TP in the ZPS biofilter were stable below 2.0 mg/L and 0.1 mg/L, corresponding to 95% NO3–N removal and 99% TP removal, respectively. Microbial community analysis revealed that the transformation of dominant taxa from Dechloromonas to Clostridium sensu stricto\_7 from 30 d to 120 d suggested that the ZVI-induced succession of dominant fermentation bacteria ensured the stable carbon supply for denitrification. Co-occurrence network analysis showed that the ZVI directly enhanced the interaction of microbial community. Fe-related bacteria occupied a key position in the rare species, which might maintain the function of iron-mediated organic matter decomposition and denitrification. These findings provide an alternative for advanced removal of nitrogen and phosphorus in biofilters packed with ZPS composites.

ABSTRACT: A higher denitrification rate was realized via controlling the mass ratio of pyrite and poly(3-hydroxybutyrate-hydroxyvalerate) (PHBV) under natural aerobic conditions. The results showed that the suitable mass ratio of PHBV and pyrite could be 1:2 with its removal efficiency of nitrogen and phosphorus of 99.7 and 53.4%, respectively. The PHBV/pyrite system has formed the spatial patterns of the biofilm community, such as Dechloromons attached to the pyrite surface, Rhodocyclaceae attached to the PHBV surface, and Acidovorax attached to the suppled sludge, which highlighted that the autotrophic??? heterotrophic synergy was achieved. The difference analysis among functional genes detected by high-throughput quantitative polymerase chain reaction indicated that the surface of pyrite in the pyrite/PHBV system is the hot area of methane production, the denitrifying process, and phosphorus removal. Network analysis indicated that there was a closer connection among functional genes on the pyrite surface, also supporting the speculation that pyrite was the hot area for the interaction of various genes in the pyrite/PHBV system. The key gene co-occurrence revealed that lig, nirS, and aspA are the keystone genes for cellulose degradation, denitrification, and S cycling, respectively. These results suggested that the pyrite surface was the hot area for denitrification, phosphorus removal in the blending system with pyrite and PHBV for nitrogen and phosphorus removal.

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.

In this study, batch experiments were conducted to investigate the immobilization of HMs (Cr and Pb) by DOM derived from biochar in the presence and absence of zero-valent iron (Fe) in nitrate and HMs co-contaminated groundwater. Both Cr and Pb were removed effectively in biochar-Fe aqueous systems, while only Pb could be mitigated in biochar systems. Excitation-emission spectrophotometry combined with parallel factor analysis (EEM-PARAFAC) revealed that DOM released from biochar mainly contained human-like and tryptophan-like substances. Moreover, the fluorescence of hemic-like components could be quenched differently by the complexation of HMs, which proved the different removal efficiencies of Cr and Pb in biochar aqueous phase. In biocharFe aqueous systems, Fe-C micro-electrolysis was formed in prior to the complexation of DOM-Fe hydroxides. Thus, the chemical reduction was the primary way to removal HMs in batch-Fe systems, which was corresponding with the less variation of DOM components when adding Cr and Pb into aqueous systems. Besides, the observed DOM components with higher aromaticity and humification after adding Cr and Pb, further indicated the complexation of DOM-HMs through the analysis of adsorption and fluorescence indices. These results will provide new insights into the HMs retention on biochar, particularly for the role of Fe on the complexation process. (c) 2021 Elsevier B.V. All rights reserved.

The pilot-scale solid-phase denitrification systems supporting with poly(3-hydroxybutyrateco-3-hydroxyvalerate) (PHBV) and PHBV-sawdust were constructed for advanced nitrogen removal from wastewater treatment plants (WWTPs) effluent, and the impacts of biomass blended carbon source on microbial community structure, functions and metabolic pathways were analyzed by metagenomic sequencing. PHBV-sawdust system achieved the optimal denitrification performance with higher NO3- - N removal efficiency (96.58%), less DOC release (9.00 +/- 4.16 mg L–(1)) and NH4+-N accumulation (0.37 +/- 0.32 mg L (- 1)) than PHBV system. Metagenomic analyses verified the significant differences in the structure of microbial community between systems and the presence of four anaerobic anammox bacteria. Compared with PHBV, the utilization of PHBV-sawdust declined the relative abundance of genes encoding enzymes for NH4+-N generation and increased the relative abundance of genes encoding enzymes involved in anammox, which contributed to the reduction of NH4+-N in effluent. What's more, the encoding gene for electrons generation in glycolysis metabolism obtained higher relative abundance in PHBV-sawdust system. A variety of lignocellulase encoding genes were significantly enriched in PHBV-sawdust system, which guaranteed the stable carbon supply and continuous operation of system. The results of this study are expected to provide theoretical basis and data support for the promotion of solid-phase denitrification. (C) 2021 Elsevier Ltd. All rights reserved.

Excessive discharge of nitrate and phosphate to aquatic environment can induce bad eutrophication phenomenon. Simultaneous removal of nitrate and phosphate is challenging for that the low C/N ratios and trace phosphate in wastewater concentration limit advanced nitrate and phosphate removal, respectively. In this study, a novel iron based solid carbon source composite namely solid carbon source/ zero-valent iron was prepared by solid carbon sources and zero-valent iron for advanced simultaneous removal of nitrate and phosphate. The novel composite with 30% zero-valent iron weight ratio presented best simultaneous removal performance with 1.1 +/- 0.1 mg NO3-N/(L.h) and 0.21 +/- 0.07 mg (PO4-P)-P-3/(L.h). The initial pH effects on the removal performance of the novel composite showed that initial pH = 7 remarkably enhanced the nitrate removal (1.1 +/- 0.1 mg NO3 -N/(L.h)) and phosphate concentration declined fastest (0.14 +/- 0.07 mg PO43–P/(L.h)) at initial pH = 5.5. Physical and chemical characterization of the composite confirmed the zero-valent iron oxidation and hydroxidation process after used and phosphate adsorption and precipitation were involved in this process. Microbial communities at genus level on the surface of the composite were identified to be capable of complex carbon hydrolysis and decomposition and denitrification, demonstrating the dominant role of microbial denitrification in nitrate removal. Interestingly, the observation of nitrate reducing Fe(II)-oxidizing bacteria suggested the synergistic effect of autotrophic and heterotrophic denitrification. The novel composite exhibited simultaneous removal of nitrate and phosphate effectively and can be applied in nutrients control in wastewater such as secondary effluent. (C) 2020 Published by Elsevier Ltd.

A two-stage multi-soil-layering system with blended carbon sources (MSL-BCS) was constructed at pilot scale for treatment of rural non-point source wastewater. Results showed the MSL-BCS system had effective removal efficiencies with 64% of TN and 60% of TP, respectively. The addition of BCS could result in higher (1.6-3.1 fold) denitrification gene abundances (nirS and nosZ) for enhancing denitrification. High-throughput sequencing approach revealed that the higher abundance (>50%) of Epsilonbacteraeotra (Genus: Sulfuricurvum, Family: Thiovulaceae, Class: Campylobacteria, Phylum: Epsilonbacteraeota) enriched in the surface of BCS, which suggested that Epsilonbacteraeotra are the keystone species in achieving nitrogen removal through enhancing denitrification at oligotrophic level. KEGG analysis indicated that BCS might release some signaling molecules for enhancing the energy metabolism process, as well as stimulate the enzyme activities of histidine kinase, glycogen phosphorylase and ATPase, and thereby the denitrification processes were strengthened in MSL-BCS system. Consequently, this study could provide some valuable information on the removal performance and mechanism of engineering MSL systems packed with BCS to govern the rural wastewater treatment. (C) 2021 Elsevier Ltd. All rights reserved.

Constructed wetlands (CWs) have been proved to be an alternative to the treatment of various wastewater. However, there are few studies focused on the removal performance and mechanisms of pollutants in pilot-scale CWs packed with novel solid carbon. In this study, we investigated the effect of poly-3-hydroxybutyrate-co-3hydroxyvalerate/polyacetic acid (PHBV/PLA) blends as carbon source on pollutant's transformation, microbial communities and functional genes in pilot-scale aeration-anoxic two-stage CWs for polishing rural runoff in southern China. Results showed a striking improvement of TN removal in CWs with PHBV/PLA blends (64.5%) compared to that in CWs with ceramsite (52.9%). NH4+-N (61.3-64.6%), COD (40.4-53.8%) and TP (43.6-47.1%) were also removed effectively in both two CWs. In addition, the strains of Rhodocyclaceae and Bacteroidetes were the primary denitrifiers on the surface of PHBV/PLA blends. Further, the aerobic stage induced gathering of 16 S and amoA genes and the anoxic zone with PHBV/PLA blends increased the nirS genes, which fundamentally explained the better denitrification performance in CW based on PHBV/PLA blends. Consequently, this study will provide straightforward guidance for the operation of engineering CWs packed with polymers to govern the low-C/N rural wastewater.

To explore an effective approach of simultaneous nitrification and denitrification in wastewater with low C/N ratios, integrated packed bed bioreactors based on poly(3-hydroxybutyrate-hydroxyvalerate) (PHBV) with different dosing methods were designed. The removal efficiency of NH4+-N in bioreactor with aeration was 88.62%, and higher NO3–N removal efficiency was observed in bioreactor filled with grainy PHBV (95.21%) than bioreactor filled with strip PHBV (93.34%). Microbial study indicated that microbes harboring amoA and nirS genes preferred to attach on the surface of ceramsite, and significant differences in microbial community compositions at phylum and genus levels were observed. To summarize, it is feasible to utilize grainy PHBV for simultaneous and efficient removal of NH4+-N and NO3–N from wastewater with low C/N ratios.

In this study, three pilot-scale solid-phase denitrification (SPD) systems filled with poly-3-hydroxybutyrate-co-hyroxyvelate (PHBV), PHBV-Rice hulls (PHBV-RH) and PHBV-Sawdust (PHBV-S) were operated to treat effluent of waste water treatment pangts (WWTPs). The fast start-up and intensified nitrogen removal performance were obtained in PHBV-RH and PHBV-S systems. Besides, the optimal total nitrogen (TN) removal efficiency was obtained in PHBV-S system (91.65 +/- 4.12%) with less ammonia accumulation and dissolved organic carbon (DOC) release. The significant enrichment of amx 16S rRNA and nirS genes in PHBV-RH and PHBV-S systems indicated the possible coexistence of anammox and denitrification. Miseq sequencing analysis exhibited more complex community diversity, more abundant denitrifying and fermenting bacteria in PHBV-RH and PHBV-S systems. The co-existence of denitrification and anammox might contribute to better control of nitrogen and dissolved organic carbon in PHBV-S system. The outcomes provide an economical and eco-friendly alternative to improve nitrogen removal of WWTPs effluent.

We propose a new technology to advanced treat overflow wastewater from a combined sewer system using a storage tank-wastewater treatment plant (STP)-constructed wetland (CW) system. The engineering demonstration (a 7,500 m(3)storage tank and a 3,436 m(2)CW) has been built to treat the combined sewer overflows (CSOs) at the largest combined rainwater/wastewater overflow outlet in the middle reaches of the Xinbaoxiang River, which is the second largest river in the Dianchi Lake Basin. During the rainfall period, CSOs enter the storage tank. After sedimentation purification, the higher concentration CSOs at the bottom enter the STP, and the upper low-concentration CSOs enter CWs, thereby linking the multiple means of treating CSOs and minimizing the impact of CSOs on the STP. During the dry season, CWs can also assist in purification of polluted river water. The supernatant (COD <80 mg/L) and the bottom part water (COD >200 mg/L) of the storage tank were sent to CWs and STP, respectively, for treatment. The project was stably operated over 6 months. The final effluent qualities were 12, 1.79, and 0.18 mg/L for COD, TN, and TP, respectively, which achieved the surface water class V standard. Practitioner points A combined system of storage tank-wastewater treatment plant-wetland was proposed to advanced treat overflow wastewater of rainy season. The SWMM could calculate the water quality and volume of overflow under different rainfall conditions in the runoff area. The effluent of the engineering demonstration reached the standard of surface water class V.

In the present study, simultaneous nitrification and denitrification of sewage treatment plant effluent was evaluated using an up-flow fixed-bed system packed with poly (3-hydroxybutyrate-hydroxyvalerate)/polylactide (PHBV/PLA) blends used in a dual role as carbon source and biofilms carrier. 98.1 +/- 2.9% and 87.2 +/- 6.8% of influent NH4+-N and NO3–N was removed from the synthetic wastewater. TN removal efficiency was 89.3 +/- 6.3% with the average effluent TN concentration of 1.6 +/- 0.9 mg/L during the stable period indicating that simultaneous nitrification and denitrification occurred. An initial high release of DOC in the effluent eventually stabilized at average of 9.0 +/- 3.4 mg/L. Simultaneous nitrification and denitrification occurred in the first 5 cm, and denitrification only in higher column sections. The PHBV/PLA supported system is a promising technology which could be applied for post-treatment of wastewater with low C/N ratios.

Nowadays, waste water treatment plants (WWTPs) are regarded as the pollution sources of nitrogen and pharmaceutical and personal care products (PPCPs). In the present study, the simultaneous removal of nitrogen and typical PPCPs, ibuprofen and triclosan, was evaluated in a poly-3-hydroxybutyrate-co-3- hydroxyvalerate (PHBV) based solid-phase denitrification (SPD) system. Results after 602 days showed that simultaneous nitrification and denitrification (SND) process occurred with average 83.85 +/- 13.09% NH4 (+) -N and 93.88 +/- 10.19% NO3- -N removals in the SPD system. Interestingly, the system achieved average 79.69 +/- 6.35% and 65.96 +/- 7.62% removals of ibuprofen and triclosan, respectively, under stable influent conditions of 50 mu g L-1. Cometabolic activities of heterotrophic denitrifying bacteria and ammonia oxidizing bacteria (AOB) probably played a role in the biodegradation of the two PPCPs. Illumina MiSeq sequencing results revealed that microbial composition enhanced the simultaneous removal of nitrogen and PPCPs in the SPD system.