Effect of influent pH on biological denitrification using biodegradable PHBV/PLA blends as electron donor

Effect of hydraulic retention time on denitrification performance and microbial communities of solid-phase denitrifying reactors using polycaprolactone/corncob composite

This study investigated the effect of hydraulic retention time (HRT) on the denitrification performance and microbial composition of reactors, packed with composite polycaprolactone and corncob carbon sources, during the treatment mariculture wastewater. The optimal HRT was 3 h, and average nitrogen removal efficiency was 99.00 %, 99.07 %, and 98.98 % in the HRT =3, 5, and 7 h groups, respectively. However, the 3 h group (DOC 2.91 mg/L) was the only group with a lower DOC concentration than that of the influent group (3.31 mg/L). Moreover, species richness was lower at HRT =3 h, with a greater proportion of denitrification-dominant phyla, such as Proteobacteria. The abundance of the NarG, NirK, and NirS functional genes suggested that the HRT =3 h group had a significant advantage in the nitrate and nitrite reduction phases. Under a short HRT, the composite carbon source achieved a good denitrification effect.

Ultrahigh carbon utilization in symbiotic Biofilm-Sludge denitrification systems using polymers as sole electron donors

The polymer-based denitrification system is an effective nitrate removal process for treating low carbon/nitrogen wastewater. However, in polymer denitrification systems, carbon used for the denitrification reaction is weakly targeted. Improving the efficiency of carbon utilization in denitrification is important to reduce carbon wastage. In this study, a symbiotic biofilm-sludge denitrification system was constructed using polycaprolactone as electron donors. Results show that the carbon release amount in 120 days was 85.32 ± 0.46 g, and the unit mass of polycaprolactone could remove 1.55 ± 0.01 g NO3--N. Meaningfully, the targeted carbon utilization efficiency for denitrification could achieve 79 %-85 %. The quantitative results showed that the release of electron donors can be well matched to the demand for electron acceptors in the biofilm-sludge denitrification system. Overall, the symbiotic system can improve the nitrate removal efficiency and reduce the waste of carbon source.

Rapid start-up and long-term stable operation of the anammox reactor based on biofilm process: Status, challenges, and perspectives

Anammox-biofilm processes have great potential for wastewater nitrogen removal, as it overcomes the slow growth and easy loss of AnAOB (anaerobic ammonium oxidation bacteria). Biofilm carrier is the core part of the Anammox-biofilm reactor and plays a key role in the start-up and long-term operation of the process. Therefore, the research on the biofilm carrier of Anammox-based process was summarized and discussed in terms of configurations and types. In the Anammox-biofilm process, fixed bed biofilm reactor is a relatively mature biofilm carrier configuration and has advantages in terms of nitrogen removal and long-term operational stability, while moving bed biofilm reactor has advantages in terms of start-up time. Although the long-term operational stability of fluidized bed biofilm reactor is good, its nitrogen removal performance needs to be improved. Among the different biofilm carrier categories, the inorganic biofilm carrier has an advantage in start-up time, due to the enhancement of the growth and metabolic of AnAOB by inorganic materials (such as carbon and iron). Anammox-based reactors using organic biofilm carriers, especially suspension carriers, are well-established and more stable in long-term operation. Composite biofilm carriers combine the advantages of several materials, but their complex preparation procedures lead to high costs. In addition, possible research directions for accelerating the start-up and keeping the long-term stable operation of Anammox reactor by biofilm process were highlighted. It is hoped to provide a possible pathway for the rapid start-up of Anammox-based process, and references for the optimization and promotion of process.

Recent updates to microbial production and recovery of polyhydroxyalkanoates

The increasing use of synthetic polymers and their disposal has raised concern due to their adverse effects on the environment. Thus, other sustainable alternatives to synthetic plastics have been sought, such as polyhydroxyalkanoates (PHAs), which are promising microbial polyesters, mainly due to their compostable nature, biocompatibility, thermostability, and resilience, making this biopolymer acceptable in several applications in the global market. The large-scale production of PHAs by microorganisms is still limited by the high cost of production compared to conventional plastics. This review reports some strategies mentioned in the literature aimed at production and recovery, paving the way for the bio-based economy. For this, some aspects of PHAs are addressed, such as synthesis, production systems, process control using by-products from industries, and advances and challenges in the downstream. The bioplastics properties made them a prime candidate for food, pharmaceutical, and chemical industrial applications. With this paper, it is possible to see that biodegradable polymers are promising materials, mainly for reducing the pollution produced by polymers derived from petroleum.

Nitrogen reduction by aerobic denitrifying fungi isolated from reservoirs using biodegradation materials for electron donor: Capability and adaptability in the lower C/N raw water treatment

Biological denitrification was considered an efficient and environmentally friendly way to remove the nitrogen in the water body. However, biological denitrification showed poor nitrogen removal performance due to the lack of electron donors in the low C/N water. In this study, three novel aerobic denitrifying fungi (Trichoderma sp., Penicillium sp., and Fusarium sp.) were isolated and enhanced the performance of aerobic denitrification of fungi in low C/N water bodies combined with polylactic acid/polybutylene adipate-co-terephthalate (PLA/PBAT). In this work, the aerobic denitrifying fungi seed were added to denitrifying liquid medium and mixed with PLA/PBAT. The result showed that Trichoderma sp., Penicillium sp., and Fusarium sp. could reduce 89.93 %, 89.20 %, and 87.76 % nitrate. Meanwhile, the nitrate removal efficiency adding PLA/PBAT exceeded 1.40, 1.68, and 1.46 times that of none. The results of material characterization suggested that aerobic denitrifying fungi have different abilities to secrete proteases or lipases to catalyze ester bonds in PLA/PBAT and utilize it as nutrients in denitrification, especially in Penicillium brasiliensis D6. Besides, the electron transport system activity and the intracellular ATP concentration were increased significantly after adding PLA/PBAT, especially in Penicillium brasiliensis D6. Finally, the highest removal efficiency of total nitrogen in landscape water by fungi combined with PLA/PBAT was >80 %. The findings of this work provide new insight into the possibility of nitrogen removal by fungi in low C/N and the recycling of degradable resources.

Effect of ferric iron (Fe(Ш)) on heterotrophic solid-phase denitrification: Denitrification performance and metabolic pathway

The effect of ferric iron (Fe(Ш)) on the performance of heterotrophic solid-phase denitrification (SPD) using biodegradable polymer composite as the electron donor was investigated. The results of continuous batch experiments showed that the addition of over 10 mg/L Fe(Ш) significantly inhibited nitrate removal and led to the accumulation of nitrite. The addition of Fe(Ш) reduced the microbial community diversity and shifted the community dominated by complete denitrifiers (e.g. Thauera) to that dominated by incomplete denitrifiers (e.g. Thermomonas, Stenotrophomonas and Sphingomonas). The predicted analysis of microbial function by PICRUSt2 indicated that the relative abundance of denitrifying genes, including napA/B, nirS and nosZ, were remarkably reduced in the Fe(Ш) groups comparing with the control group. In addition, Fe(Ш) inhibited the genes related to the generation of electron carriers, NADH and FADH₂, in TCA cycle and glycolysis processes, which could result in a lower carbon utilization efficiency for microbial denitrification.

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.

Response of nitrogen removal performance and microbial community to a wide range of pH in thermophilic denitrification system

Thermophilic biological nitrogen removal would be a promising alternative to conventional approaches for the treatment of high-temperature wastewater. In this study, the response of thermophilic denitrification system (50 °C) to a wide range of pH (3-11) was investigated. The results showed that thermophilic denitrification could adapt to pH 5-11, but suffered from obvious nitrite and ammonia accumulation at pH 3. Microbial insights indicated that the enrichment of specific functional thermophiles has contributed to the tolerance towards unfavorable pH. Besides, the potential selecting advantage of nitrate reducing bacteria over nitrite reducing bacteria and the enrichment of dissimilatory nitrate reduction to ammonium (DNRA) bacteria could be responsible for the nitrite and ammonia accumulation at pH 3. Moreover, the functional gene prediction denoted higher narG/(nirK + nirS) and nrfA at pH 3, which could facilitate partial denitrification and DNRA. These findings could provide new insight into the application of thermophilic biological nitrogen removal.

Denitrification performance and microbial community of bioreactor packed with PHBV/PLA/rice hulls composite

In this study, a novel biodegradable PHBV/PLA/rice hulls (PPRH) composite was applied and tested as biofilm attachment carrier and carbon source in two bioreactors for biological denitrification process. The denitrification performance, effect of operational conditions and microbial community structure of PPRH biofilm were evaluated. The batch experiment results showed that PPRH-packed bioreactor could completely remove 50 mg L^-1 of NO₃^--N at natural pH (ca. 7.5) and room temperature. The continuous flow experiments indicated that high NO₃^--N removal efficiency (77%-99%) was achieved with low nitrite (<0.48 mg L^-1) and ammonia (<0.81 mg L^-1) accumulation, when influent NO₃^--N concentration was 30 mg L^-1 and hydraulic retention time was 2-6 h. Furthermore, the microbial community analysis indicated that bacteria belonging to genus Diaphorobacter in phylum Proteobacteria were the most dominant and major denitrifiers in denitrification. In summary, PPRH composite was a promising carbon source for biological nitrate removal from water and wastewater.

Efficacy of heated tourmaline in reducing biomass clogging within woodchip bioreactors

Woodchip bioreactors can effectively remove waterborne nitrates from subsurface agricultural drainage and prevent the eutrophication of receiving water, but rapid biofilm growth can severely reduce water flux and denitrification efficiency of this practice within a few years. Tourmaline minerals with thermal excitation could generate reactive oxygen species which would inhibit bacterial growth. In this study, laboratory scale woodchip bioreactors were set up to test the anti-clogging and denitrification efficiency of heated woodchips with tourmaline, heated woodchips without tourmaline, and unheated woodchips. The results showed that the heated tourmaline treatment could reduce the clogging and optimize the nitrate removal rate (47.6 g N/m³/day) under all three hydrologic retention times tested (1, 4, and 8 h). Dissolved oxygen and pH values fluctuated with the removal rate and temperature change, while temperature was identified as the key factor impacting the tourmaline treatment. The heated tourmaline treatment had the lowest biofilm growth (lowest DNA concentration), while the 16S rRNA and a higher abundance of nirS-, nirK-, and nosZ-encoding denitrifying bacteria (based on qPCR) confirmed the higher denitrification efficiency of the heated tourmaline treatment.

Research on efficient denitrification system based on banana peel waste in sequencing batch reactors: Performance, microbial behavior and dissolved organic matter evolution

Nitrate pollution presents a serious threat to the environment and public health. As an excellent heterotrophic denitrification carbon source, banana peel (a kind of agricultural waste) provides a feasible alternative to deal with the persistent high concentrations of nitrate pollution. Although the feasibility and economy of banana peel for denitrification have already been reported, the long-term stability and mechanism were still unclear. The coupling mechanism of organic matters and microorganism in the denitrification process was systematically investigated through a 17-cycle experiment. The results showed that significant NO₃^--N removal load and rate of 164.42 mg/g and 4.69 mg/(L·h) after long-term tests could be obtained. Organic matter analysis and 16S rRNA sequencing showed that the evolution of organic matter was dominated by Anaerolineaceae (fermenting bacteria), and, in the final step, the humification of organic matter was realized. Moreover, the presence of Lentimicrobium (denitrifying bacteria) was indispensable for the continuous removal of high concentrations of nitrate. The main functional gene of nitrogen transformation in this reaction system was NirS (haem-containing). This lab-scale heterotrophic denitrification process could contribute to a better understanding of the carbon and nitrogen cycles in the biogeochemical cycles to some extent, and it also provides a reference for the construction of highly efficient nitrate degradation reactors, based on agricultural wastes.

The impact of biodegradable carbon sources on nutrients removal in post-denitrification biofilm reactors

Wastewater from households wastewater treatment plants (HWWTP) is discharged to the ground or to the surface waters. Special consideration should be given to the improvement of HWWTP effectiveness, particularly in relation to nutrients. The addition of biodegradable carbon sources to biofilm reactor, can enhance microbial activity but may also lead to filling clogging. The study aimed to compare 3 different organic substrates: acetic acid (commonly applied)and two untypical - citric acid and waste beer, under the same operational conditions in a post-denitrification biofilm reactor. The study investigated the impact of a type of organic substrate, low pH and time on: (1) biofilm growth, (2) the characteristics of extracellular polymeric substances (EPS), (3) the kinetics of nutrients removal and (4) reactor clogging. Results were referred to (5) the effectiveness of nutrients removal. The study demonstrated that low pH assured the development of a thinbiofilm. Citric acid ensured the lowest biomass volume, being by 53% lower than in the reactor with acetic acid and by as much as 61% lower than in the reactor with waste beer. The soluble EPS fraction prevailed in the total EPS in all reactors. The content of the tightly bound EPS fraction ranged from 26.93% (citric acid) to 36.32% (waste beer). Investigations showed also a high ratio of exoproteins to polysaccharide in all fractions, which indicated a significant role of proteins in developing a highly-proliferating biofilm. The treated wastewater met requirements of Polish regulations concerning COD and nitrogen concentrations.

Technologies for biological removal and recovery of nitrogen from wastewater

Water contamination is a growing environmental issue. Several harmful effects on human health and the environment are attributed to nitrogen contamination of water sources. Consequently, many countries have strict regulations on nitrogen compound concentrations in wastewater effluents. Wastewater treatment is carried out using energy- and cost-intensive biological processes, which convert nitrogen compounds into innocuous dinitrogen gas. On the other hand, nitrogen is also an essential nutrient. Artificial fertilizers are produced by fixing dinitrogen gas from the atmosphere, in an energy-intensive chemical process. Ideally, we should be able to spend less energy and chemicals to remove nitrogen from wastewater and instead recover a fraction of it for use in fertilizers and similar applications. In this review, we present an overview of various technologies of biological nitrogen removal including nitrification, denitrification, anaerobic ammonium oxidation (anammox), as well as bioelectrochemical systems and microalgal growth for nitrogen recovery. We highlighted the nitrogen removal efficiency of these systems at different temperatures and operating conditions. The advantages, practical challenges, and potential for nitrogen recovery of different treatment methods are discussed.

Denitrification performance and microbial communities of solid-phase denitrifying reactors using poly (butylene succinate)/bamboo powder composite

This study explored the denitrification performance of solid-phase denitrification (SPD) systems packed with poly (butylene succinate)/bamboo powder composite to treat synthetic aquaculture wastewater under different salinity conditions (0‰ Vs. 25‰). The results showed composite could achieve the maximum denitrification rates of 0.22 kg (salinity, 0‰) and 0.34 kg NO3--N m-3 d-1 (salinity, 25‰) over 200-day operation. No significant nitrite accumulation and less dissolved organic carbon (DOC) release (<15 mg/L) were found. The morphological and spectroscopic analyses demonstrated the mixture composites degradation. Microbial community analysis showed that Acidovorax, Simplicispira, Denitromonas, SM1A02, Marinicella and Formosa were the dominant genera for denitrifying bacteria, while Aspergillus was the major genus for denitrifying fungus. The co-network analysis also indicated the interactions between bacterial and fungal community played an important role in composite degradation and denitrification. The outcomes provided a potential strategy of DOC control and cost reduction for aquaculture nitrate removal by SPD.

Effects of Hydraulic Retention Time and Influent Nitrate-N Concentration on Nitrogen Removal and the Microbial Community of an Aerobic Denitrification Reactor Treating Recirculating Marine Aquaculture System Effluent

The effects of hydraulic retention time (HRT) and influent nitrate-N concentration on nitrogen removal and the microbial community composition of an aerobic denitrification reactor treating recirculating marine aquaculture system effluent were evaluated. Results showed that over 98% of nitrogen was removed and ammonia-N and nitrite-N levels were below 1 mg/L when influent nitrate-N was below 150 mg/L and HRT over 5 h. The maximum nitrogen removal efficiency and nitrogen removal rate were observed at HRT of 6 or 7 h when influent nitrate-N was 150 mg/L. High-throughput DNA sequencing analysis revealed that the microbial phyla Proteobacteria and Bacteroidetes were predominant in the reactor, with an average relative total abundance above 70%. The relative abundance of denitrifying bacteria of genera Halomonas and Denitratisoma within the reactor decreased with increasing influent nitrate-N concentrations. Our results show the presence of an aerobically denitrifying microbial consortium with both expected and unexpected members, many of them relatively new to science. Our findings provide insights into the biological workings and inform the design and operation of denitrifying reactors for marine aquaculture systems.

Effect of potassium on nitrate removal from groundwater in agricultural waste-based heterotrophic denitrification system

Heterotrophic denitrification based on solid carbon sources has been widely investigated for nitrogen removal in recent years. In this study, the response of the heterotrophic denitrification process under different K⁺ concentrations was clarified. Additionally, the denitrification enhancement mechanism was revealed and resource utilization of agricultural waste was achieved. A series of batch tests were conducted to study the effect of different K⁺ concentrations on the denitrification performance, dissolved organic matter (DOM) dissolution and microbial community structure. Results demonstrate that the threshold of K⁺ concentration for the NO₃^--N and NO₂^--N reduction rates were 229.78 ± 25.80 and 159.10 ± 24.60 mg-K/L, respectively. Excitation-emission matrix (EEM) analysis identified the main DOM components associated with tyrosine-like, tryptophan-like and humic-like substances, as well as illustrated the evolutionary behavior and utilization of DOM. High throughput 16S rRNA gene sequencing indicates that a K⁺ concentration of 229.78 ± 25.80 mg-K/L exhibited the highest diversity of functional species associated with fermentation and denitrification. The genera Pseudomonas and Thiobacillus were the unique denitrifiers at this K⁺ concentration. The correlation of K⁺ concentration, DOM dissolution of different regions and microorganism structure were analyzed using correlation matrix and PCA, and the appropriate K⁺ concentration of different functional microorganisms survival was optimized by this analysis method.

Effect of temperature on tertiary nitrogen removal from municipal wastewater in a PHBV/PLA-supported denitrification system

In this study, a poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/poly(lactic acid) (PHBV/PLA)-supported denitrification system was built to remove nitrogen from municipal wastewater treatment plant secondary effluent, and the influence of operating temperature on nitrogen removal was further investigated. Results indicated that a PHBV/PLA-supported denitrification system could effectively fulfill the tertiary nitrogen removal. The nitrogen removal efficiency gradually declined with the operating temperature decreasing, and the denitrification rate at 30 °C was 5 times higher than that at 10 °C. Meanwhile, it was found that a slight TOC accumulation only occurred at 30 °C (with an average of 2.03 mg/L) and was avoided at 10~20 °C. The reason for effluent TOC variation was further explained through the consumption and generation pathways of TOC in this system. Furthermore, the temperature coefficient was about 0.02919, indicating that the PHBV/PLA-supported denitrification system was a little sensitive to temperature. A better knowledge of the effect of operating temperature will be significant for the practical application of the solid-phase denitrification system.

Selective production of volatile fatty acids at different pH in an anaerobic membrane bioreactor

This study investigated the production of major volatile fatty acid (VFA) components in an anaerobic membrane bioreactor (AnMBR) to treat low-strength synthetic wastewater. No selective inhibition was applied for methane production and solvent-extraction method was used for VFA extraction. The results showed acetic and propionic acid were the predominant VFA components at pH 7.0 and 6.0 with concentrations of 1.444 ± 0.051 and 0.516 ± 0.032 mili-mol/l respectively. At pH 12.0 isobutyric acid was the major VFA component with a highest concentration of 0.712 ± 0.008 mili-mol/l. The highest VFA yield was 48.74 ± 1.5 mg VFA/100 mg COD_feed at pH 7.0. At different pH, AnMBR performance was evaluated in terms of COD, nutrient removal and membrane fouling rate. It was observed that the membrane fouled at a faster rate in both acidic and alkaline pH conditions, the slowest rate in membrane fouling was observed at pH 7.0.

Recent developments in bioreactor scale production of bacterial polyhydroxyalkanoates

Polyhydroxyalkanoates (PHAs) are biological plastics that are sustainable alternative to synthetic ones. Numerous microorganisms have been identified as PHAs producers. They store PHAs as cellular inclusions to use as an energy source backup. They can be produced in shake flasks and in bioreactors under defined fermentation and physiological culture conditions using suitable nutrients. Their production at bioreactor scale depends on various factors such as carbon source, nutrients supply, temperature, dissolved oxygen level, pH, and production modes. Once produced, PHAs find diverse applications in multiple fields of science and technology particularly in the medical sector. The present review covers some recent developments in sustainable bioreactor scale production of PHAs and identifies some areas in which future research in this field might be focused.

Enhancing denitrification efficiency for nitrogen removal using waste sludge alkaline fermentation liquid as external carbon source

External carbon source was usually added to enhance denitrification efficiency for nitrogen removal in wastewater treatment. In this study, waster sludge alkaline fermentation liquid was successfully employed as an alternative carbon source for biological denitrification. The denitrification performance was studied at different C/Ns (carbon-to-nitrogen ratios) and HRTs (hydraulic retention times). A C/N of 7 and an HRT of 8 h were the optimal conditions for denitrification. The nitrate removal efficiency of 96.4% and no obvious nitrite accumulation in the effluent were achieved under the optimal conditions with a low soluble chemical oxygen demand (SCOD) level. The sludge carbon source utilization was analyzed and showed that the volatile fatty acids (VFAs) were prior utilized than proteins and carbohydrates. The excitation-emission matrix (EEM) spectroscopy with fluorescence regional integration (FRI) was adopted to analyze the compositional and variations of dissolved organic matters (DOM). Moreover, a high denitrification rate (V_DN) and potential (P_DN) with low heterotroph anoxic yield (Y_H) was exhibited at the optimal C/N and HRT condition, indicating the better denitrification ability and organic matter utilization efficiencies.

Effect of different carbon sources on denitrification performance, microbial community structure and denitrification genes

Solid and liquid organic substances as carbon sources for denitrification process were deeply explored. In this study, the effect of three carbon sources, referred to as poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/poly (lactic acid) (PHBV/PLA) polymer, glucose and CH₃COONa, on denitrification performance, microbial community and functional genes were investigated. It was found that maximum denitrification rates of 0.37, 0.46 and 0.39gN/(L·d) were achieved in PHBV/PLA, glucose and CH₃COONa supported denitrification systems, respectively. Meanwhile, Illumina MiSeq sequencing revealed that three carbon sources led to different microbial community structures. It can be seen that Brevinema/Thauera/Dechloromonas, Tolumonas/Thauera/Dechloromonas, Thauera dominated in the PHBV/PLA, glucose and CH₃COONa supported denitrification systems, respectively. Transcriptome-based analysis further indicated that the glucose supported denitrification system showed the highest FPKM values (the fragments per kilobase per million mapped reads) of the genes participating in the dissimilatory nitrate reduction process, corresponding to the greatest effluent NH₄⁺-N concentration. A better knowledge of effect of different carbon sources on denitrification process will be significant for nitrate removal in practice.