Micro and nano plastics release from a single absorbable suture into simulated body fluid.

Synthetic polymers are widely used in medical devices and implants where biocompatibility and mechanical strength are key enablers of emerging technologies. One concern that has not been widely studied is the potential of their microplastics (MPs) release. Here we studied the levels of MP debris released following 8-week in vitro tests on three typical polyglycolic acid (PGA) based absorbable sutures (PGA 100, PGA 90 and PGA 75) and two nonabsorbable sutures (polypropylene-PP and polyamide-PA) in simulated body fluid. The MP release levels ranked from PGA 100 > > PGA 90 > PGA 75 > > PP ∼ PA. A typical PGA 100 suture released 0.63 ± 0.087 million micro (MPs > 1 µm) and 1.96 ± 0.04 million nano (NPs, 200-1000 nm) plastic particles per centimeter. In contrast, no MPs were released from the nonabsorbable sutures under the same conditions. PGA that was co-blended with 10-25% L-lactide or epsilon-caprolactone resulted in a two orders of magnitude lower level of MP release. These results underscore the need to assess the release of nano- and microplastics from medical polymers while applied in the human body and to evaluate possible risks to human health.

Outcomes of revision surgery for idiopathic macular hole after failed primary vitrectomy.

Persistent idiopathic macular hole (PIMH), the occurrence of idiopathic macular holes that have failed to close after standard pars plana vitrectomy (PPV) with internal limiting membrane (ILM) peeling, has become a global health threat to the aging population. Because postoperative anatomic closure or restoration of visual acuity is more difficult to achieve in PIMH, surgical approaches that would yield the best outcomes remain to be elucidated. On paper, extended ILM peeling combined with silicone oil (SiO) tamponade is believed to be a feasible option for excellent macular hole closure. However, no studies on this combined treatment for PIMH is compared with simple air tamponade have been conducted. Thus, in this retrospective case series, we used spectral-domain optical coherence tomography (SD-OCT) and other technologies to investigate real-world evidence for the anatomical and functional outcomes of revisional PPV with either SiO or air tamponade for failed primary idiopathic macular hole surgery. We included the records of 76 patients with PIMH who had SD-OCT examinations and best-corrected visual acuity (BCVA). Regression analysis was performed to find factors affecting PIMH fracture closure. Seventy-six participants were allocated to a SiO group (n = 21, with an extended ILM peeling and SiO tamponade) or an air group (n = 55, with extended ILM peeling and air tamponade). Anatomical success was achieved in 18 (85.7%) and 40 (72.7%) eyes in the SiO and air groups, respectively (p = 0.37). BCVA was significantly improved in both subgroups of closed PIMH (SiO group: p = 0.041; air group: p < 0.001). Minimum linear diameter (MLD) was closely related to the closure rate (OR, 1.0; 95% CI (0.985-0.999); p = 0.03). MLD = 650 µm seemed like a cut-off point for closure rate (MLD ≤ 650 µm vs. MLD > 650 µm; 88.4% vs. 52%, p = 0.002). In conclusion, we demonstrated that extended ILM peeling combined with SiO or air tamponade is effective in PIMH treatment. Moreover, though not statistically significant herein, the anatomic closure rate was better for silicone-operated eyes than for air-operated eyes. MLD is the best predictor of PIMH closure; MLD ≤ 650 µm could achieve a significantly higher closure rate.

N,N-Dimethyl-3ß-hydroxycholenamide attenuates neuronal death and retinal inflammation in retinal ischemia/reperfusion injury by inhibiting Ninjurin 1.

BACKGROUND: Retinal ischemia-reperfusion (RIR) injury refers to an obstruction in the retinal blood supply followed by reperfusion. Although the molecular mechanism underlying the ischemic pathological cascade is not fully understood, neuroinflammation plays a crucial part in the mortality of retinal ganglion cells. METHODS: Single-cell RNA sequencing (scRNA-seq), molecular docking, and transfection assay were used to explore the effectiveness and pathogenesis of N,N-dimethyl-3ß-hydroxycholenamide (DMHCA)-treated mice with RIR injury and DMHCA-treated microglia after oxygen and glucose deprivation/reoxygenation (OGD/R). RESULTS: DMHCA could suppress inflammatory gene expression and attenuate neuronal lesions, restoring the retinal structure in vivo. Using scRNA-seq on the retina of DMHCA-treated mice, we provided novel insights into RIR immunity and demonstrated nerve injury-induced protein 1 (Ninjurin1/Ninj 1) as a promising treatment target for RIR. Moreover, the expression of Ninj1, which was increased in RIR injury and OGD/R-treated microglia, was downregulated in the DMHCA-treated group. DMHCA suppressed the activation of the nuclear factor kappa B (NF-κB) pathways induced by OGD/R, which was undermined by the NF-κB pathway agonist betulinic acid. Overexpressed Ninj1 reversed the anti-inflammatory and anti-apoptotic function of DMHCA. Molecular docking indicated that for Ninj1, DMHCA had a low binding energy of - 6.6 kcal/mol, suggesting highly stable binding. CONCLUSION: Ninj1 may play a pivotal role in microglia-mediated inflammation, while DMHCA could be a potential treatment strategy against RIR injury.

Application of 3D Printing Technology in Sensor Development for Water Quality Monitoring.

The development of sensors for water quality monitoring is crucial to protect water quality, aquatic biota and human health. Traditional sensor manufacturing methods have significant drawbacks, such as low fabrication freedom, limited material choice and expensive manufacturing cost. As a possible alternative method, 3D printing technologies are increasingly popular in sensor development due to their high versatility, fast fabrication/modification, powerful processing of different materials and ease of incorporation with other sensor systems. Surprisingly, a systematic review examining the application of 3D printing technology in water monitoring sensors has not yet been conducted. Here, we summarized the development history, market share and advantages/disadvantages of typical 3D printing techniques. Specifically focused on the 3D-printed sensor for water quality monitoring, we then reviewed the applications of 3D printing in the development of sensors' supporting platform, cell, sensing electrode as well as all-3D-printed sensors. The fabrication materials and processing, and the sensor's performances regarding detected parameters, response time and detection limit/sensitivity, were also compared and analyzed. Finally, the current drawbacks of 3D-printed water sensors and potential directions for future study were discussed. This review will substantially promote the understanding of 3D printing technology used in water sensor development and benefit the protection of water resources.

Deciphering Adult Neural Stem Cells with Single-Cell Sequencing.

Adult neural stem cells (NSCs) are restricted to the two neurogenic regions of the mammalian brain, where they self-renew and generate progenies of multiple lineages, including neurons, astrocytes, and oligodendrocytes. Single-cell RNA sequencing technology, which reconstructs high-resolution transcriptional landscapes, provides valuable insights into cellular heterogeneity and developmental dynamics. In this review, we overviewed recent progress in the single-cell analyses of both conventional and unconventional NSCs. We discussed the heterogeneity among the stem cell pool and characterized the transcriptional alterations in aging and brain tumors. A comprehensive understanding of NSCs in physiological and pathological settings will provide insights for the rejuvenation of the aged brain and restoration of normal brain function in multiple neurological disorders.

Recent Implementations of Hydrogel-Based Microbial Electrochemical Technologies (METs) in Sensing Applications.

Hydrogel materials have been used extensively in microbial electrochemical technology (MET) and sensor development due to their high biocompatibility and low toxicity. With an increasing demand for sensors across different sectors, it is crucial to understand the current state within the sectors of hydrogel METs and sensors. Surprisingly, a systematic review examining the application of hydrogel-based METs to sensor technologies has not yet been conducted. This review aimed to identify the current research progress surrounding the incorporation of hydrogels within METs and sensors development, with a specific focus on microbial fuel cells (MFCs) and microbial electrolysis cells (MECs). The manufacturing process/cost, operational performance, analysis accuracy and stability of typical hydrogel materials in METs and sensors were summarised and analysed. The current challenges facing the technology as well as potential direction for future research were also discussed. This review will substantially promote the understanding of hydrogel materials used in METs and benefit the development of electrochemical biosensors using hydrogel-based METs.

Structure evolution of air cathodes and their application in electrochemical sensor development and wastewater treatment.

Cathode structure and material are the most important factors to determine the performance and cost of single chamber air-cathode microbial fuel cell (MFC), which is the most promising type of MFC technology. Since the first air cathode was invented in 2004, five major structures (1-layer, 2-layer, 3-layer, 4-layer and separator-support) have been invented and modified to fit new material, improve power performance and lower MFC cost. This paper reviewed the structure evolution of air cathodes in past 18 years. The benefits and drawbacks of these structures, in terms of power generation, material cost, fabrication procedure and modification process are analyzed. The practical application cases (e.g., sensor development and wastewater treatment) employed with different cathode structures were also summarized and analyzed. Based on practical performance and long-term cost analysis, the 2-layer cathode demonstrated much greater potential over other structures. Compared with traditional activated-sludge technology, the cost of an MFC-based system is becoming competitive when employing with 2-layer structure. This review not only provides a detailed development history of air cathode but also reveals the advantages/disadvantages of air cathode with different structures, which will promote the research and application of air-cathode MFC technology.

Heterogeneity and Memory Effect in the Sluggish Dynamics of Vacancy Defects in Colloidal Disordered Crystals and Their Implications to High-Entropy Alloys.

Vacancy dynamics of high-density 2D colloidal crystals with a polydispersity in particle size are studied experimentally. Heterogeneity in vacancy dynamics is observed. Inert vacancies that hardly hop to other lattice sites and active vacancies that hop frequently between different lattice sites are found within the same samples. The vacancies show high probabilities of first hopping from one lattice site to another neighboring lattice site, then staying at the new site for some time, and later hopping back to the original site in the next hop. This back-returning hop probability increases monotonically with the increase in packing fraction, up to 83%. This memory effect makes the active vacancies diffuse sluggishly or even get trapped in local regions. Strain-induced vacancy motion on a distorted lattice is also observed. New glassy properties in the disordered crystals are discovered, including the dynamical heterogeneity, the presence of cooperative rearranging regions, memory effect, etc. Similarities between the colloidal disordered crystals and the high-entropy alloys (HEAs) are also discussed. Molecular dynamics simulations further support the experimental observations. These results help to understand the microscopic origin of the sluggish dynamics in materials with ordered structures but in random energy landscapes, such as high-entropy alloys.

Alcohol Pretreatment to Eliminate the Interference of Micro Additive Particles in the Identification of Microplastics Using Raman Spectroscopy.

Raman spectroscopy is an indispensable tool in the analysis of microplastics smaller than 20 µm. However, due to its limitation, Raman spectroscopy may be incapable of effectively distinguishing microplastics from micro additive particles. To validate this hypothesis, we characterized and compared the Raman spectra of six typical slip additives with polyethylene and found that their hit quality index values (0.93-0.96) are much higher than the accepted threshold value (0.70) used to identify microplastics. To prevent this interference, a new protocol involving an alcohol treatment step was introduced to successfully eliminate additive particles and accurately identify microplastics. Tests using the new protocol showed that three typical plastic products (polyethylene pellets, polyethylene bottle caps, and polypropylene food containers) can simultaneously release microplastic-like additive particles and microplastics regardless of the plastic type, daily-use scenario, or service duration. Micro additive particles can also adsorb onto and modify the surfaces of microplastics in a manner that may potentially increase their health risks. This study not only reveals the hidden problem associated with the substantial interference of additive particles in microplastic detection but also provides a cost-effective method to eliminate this interference and a rigorous basis to quantify the risks associated with microplastic exposure.

Microbe-Based Sensor for Long-Term Detection of Urine Glucose.

The development of a reusable and low-cost urine glucose sensor can benefit the screening and control of diabetes mellitus. This study focused on the feasibility of employing microbial fuel cells (MFC) as a selective glucose sensor for continuous monitoring of glucose levels in human urine. Using MFC technology, a novel cylinder sensor (CS) was developed. It had a quick response time (100 s), a large detection range (0.3-5 mM), and excellent accuracy. More importantly, the CS could last for up to 5 months. The selectivity of the CS was validated by both synthetic and actual diabetes-negative urine samples. It was found that the CS's selectivity could be significantly enhanced by adjusting the concentration of the culture's organic matter. The CS results were comparable to those of a commercial glucose meter (recovery ranged from 93.6% to 127.9%) when the diabetes-positive urine samples were tested. Due to the multiple advantages of high stability, low cost, and high sensitivity over urine test strips, the CS provides a novel and reliable approach for continuous monitoring of urine glucose, which will benefit diabetes assessment and control.

Multimode imaging characteristics and treatment of uveal schwannoma.

AIM: To delineate the different imaging characteristics of uveal schwannoma from melanoma and discuss the optimal treatment strategy for intraocular schwannoma. METHODS: Case series of three patients diagnosed with intraocular schwannoma was collected at Zhongshan Ophthalmic Center, Guangzhou, China from July 2014 to December 2020. All the study patients underwent ultrasonography and magnetic resonance imaging (MRI). The clinical features, therapeutic strategies, and prognoses of all patients were reviewed. RESULTS: Ultrasonography of all three patients (all females, mean age, 39y, age range, 23-54y) showed low to medium reflectivity with a homogeneous internal structure. MRI of all three patients demonstrated isointensity on T1-weighted imaging spin-echo (T1WI SE) images and hypointense on fast spin-echo T2-weighted images (FSE T2WI) images with respect to the brain. Minimally invasive pars plana vitrectomy (PPV) and local resection of the tumor was performed for all patients, and the diagnosis of schwannoma was confirmed by histopathological examination. CONCLUSION: The present study indicates that ultrasonography and MRI features of uveal schwannoma may contribute to the differentiation of uveal schwannoma from melanoma, and the optimal therapy for intraocular schwannoma is minimally invasive PPV and local resection.

The influence of drinking water constituents on the level of microplastic release from plastic kettles.

Microplastic (MP) release from household plastic products has become a global concern due to the high recorded levels of microplastic and the direct risk of human exposure. However, the most widely used MP measurement protocol, which involves the use of deionized (DI) water, fails to account for the ions and particles present in real drinking water. In this paper, the influence of typical ions (Ca2+/HCO3-, Fe3+, Cu2+) and particles (Fe2O3 particles) on MP release was systematically investigated by conducting a 100-day study using plastic kettles. Surprisingly, after 40 days, all ions resulted in a greater than 89.0% reduction in MP release while Fe2O3 particles showed no significant effect compared to the DI water control. The MP reduction efficiency ranking is Fe3+ ≈ Cu2+ > Ca2+/HCO3- > > Fe2O3 particles ≈ DI water. Physical and chemical characterization using SEM-EDX, AFM, XPS and Raman spectroscopy confirmed Ca2+/HCO3-, Cu2+ and Fe3+ ions are transformed into passivating films of CaCO3, CuO, and Fe2O3, respectively, which are barriers to MP release. In contrast, there was no film formed when the plastic was exposed to Fe2O3 particles. Studies also confirmed that films with different chemical compositions form naturally in kettles during real life due to the different ions present in local regional water supplies. All films identified in this study can substantially reduce the levels of MP release while withstanding the repeated adverse conditions associated with daily use. This study underscores the potential for regional variations in human MP exposure due to the substantial impact water constituents have on the formation of passivating film formation and the subsequent release of MPs.

Intraoperative choroidal detachment during small-gauge vitrectomy: analysis of causes, anatomic, and visual outcomes.

INTRODUCTION: To investigate the incidence and causes of intraoperative choroidal detachment (CD) during small-gauge vitrectomy, as well as the anatomic and visual outcomes. METHODS: We retrospectively reviewed the medical records of 1026 consecutive patients who underwent small-gauge vitrectomy from June 2017 to December 2018 at Zhongshan Ophthalmic Centre, Guangzhou, China. Data on the presence, location, and extent of intraoperative CD and its relationship to the infusion cannula were collected. Patient demographic characteristics and postoperative anatomic and visual outcomes were also assessed. RESULTS: A total of six cases were found to have intraoperative CD, including two with serous CD, three with limited haemorrhagic CD, and one with CD caused by inadvertent perfusion of gas during air/fluid exchange. Retraction of the infusion cannula and acute ocular hypotony were found to be the main causes of intraoperative CD in five out of the six cases. The best-corrected visual acuity of all cases significantly improved after the surgery. CONCLUSION: The incidence of intraoperative CD during small-gauge vitrectomy is low; the predominant causes are retraction of the infusion cannula and acute ocular hypotony. Immediate awareness and timely closure of the incision may contribute to a better surgical prognosis.

Sampling, Identification and Characterization of Microplastics Release from Polypropylene Baby Feeding Bottle during Daily Use.

Microplastics (MPs) are becoming a global concern due to the potential risk to human health. Case studies of plastic products (i.e., plastic single-use cups and kettles) indicate that MP release during daily use can be extremely high. Precisely determining the MP release level is a crucial step to identify and quantify the exposure source and assess/control the corresponding risks stemming from this exposure. Though protocols for measuring MP levels in marine or freshwater has been well developed, the conditions experienced by household plastic products can vary widely. Many plastic products are exposed to frequent high temperatures (up to 100 °C) and are cooled back to room temperature during daily use. It is therefore crucial to develop a sampling protocol that mimics the actual daily-use scenario for each particular product. This study focused on widely used polypropylene-based baby feeding bottles to develop a cost-effective protocol for MP release studies of many plastic products. The protocol developed here enables: 1) prevention of the potential contamination during sampling and detection; 2) realistic implementation of daily-use scenarios and accurate collection of the MPs released from baby feeding bottles based on WHO guidelines; and 3) cost-effective chemical determination and physical topography mapping of MPs released from baby feeding bottles. Based on this protocol, the recovery percentage using standard polystyrene MP (diameter of 2 µm) was 92.4-101.2% while the detected size was around 102.2% of the designed size. The protocol detailed here provides a reliable and cost-effective method for MP sample preparation and detection, which can substantially benefit future studies of MP release from plastic products.

Microbial physiology and interactions in anammox systems with the intermittent addition of organic carbons.

Organic carbon can affect nitrogen removal in the anaerobic ammonia oxidation (anammox) process. Two continuous up-flow anaerobic sludge blanket (UASB) reactors were operated under autotrophic (UASBN, without organic carbon) and mixotrophic (UASBCN, with the intermittent addition of acetate and propionate) conditions. Stable operation of anammox systems was achieved, with the nitrogen removal rate and percentage of 2.12 g/(L·d) and 86.4% in UASBN, and 2.09 g/(L·d) and 85.0% in UASBCN, respectively. The network of Candidatus Kuenenia, Thauera, and Nitrosomanas contributed to both nitrogen and carbon metabolisms, and the intermittent addition of acetate and propionate strengthened Ca. Kuenenia's ability to utilize several types of carbon sources. Anammox bacteria showed activity in the presence of organic carbon and without inorganic carbon, confirming the mixotrophic characteristic of Ca. Kuenenia. Cross-feeding of amino acids and vitamins existed among functional microorganisms, with extracellular polymeric substances acting as the media for microbial interactions.

The Morphological Relationship Between Dome-Shaped Macula and Myopic Retinoschisis: A Cross-sectional Study of 409 Highly Myopic Eyes.

Purpose: The purpose of this study was to analyze the clinical features of dome-shaped macula (DSM) in highly myopic eyes and its morphological relationship with myopic retinoschisis (MRS). Methods: In this cross-sectional study, 409 eyes of 409 patients with high myopia who had spectral-domain optical coherence tomography (OCT) examinations were included. The associations of DSM with the distribution of MRS and ocular biometry were evaluated. Results: Of 409 eyes, DSM was detected in 64 eyes (15.6%). The eyes with DSM were more myopic (-18.8 ± 3.9 vs. -13.4 ± 5.9; P < 0.001) and had longer axial length (31.7 ± 2.4 vs. 29.5 ± 2.5; P < 0.001) compared with those without DSM. A higher rate of extrafoveal retinoschisis (35.9% vs. 9.6%; P < 0.001) and a lower rate of foveoschisis (10.9% vs. 26.1%; P = 0.01) were detected in the eyes with DSM compared with those without DSM. In the eyes with DSM, MRS was detected in 30 eyes (46.9%). MRS predominantly affected the extrafoveal area (76.7%), especially the base of the dome (82.6%). The extrafoveal retinoschisis was most frequently distributed in the superior quadrant (52.2%). None of the eyes with DSM displayed fovea-only retinoschisis. The ratio of the height and width of the macular bulge was higher in eyes with MRS than those without MRS (0.05 vs. 0.04; P = 0.001). Conclusions: A DSM is found in highly myopic eyes with a longer axial length. MRS in eyes with DSM is more likely to affect the extrafoveal area, especially the base of the dome. A steeper macular bulge is associated with the occurrence of MRS.

Microplastic release from the degradation of polypropylene feeding bottles during infant formula preparation.

Polypropylene-based products are commonly used for food preparation and storage, but their capacity to release microplastics is poorly understood. We investigated the potential exposure of infants to microplastics from consuming formula prepared in polypropylene (PP) infant feeding bottles (IFBs). Here, we show that PP IFBs release microplastics with values as high as 16,200,000 particles per litre. Scenario studies showed that PP IFB sterilization and exposure to high-temperature water significantly increase microplastic release. A 21-d test of PP IFBs showed periodic fluctuations in microplastic release. To estimate the potential global exposure to infants up to 12 months old, we surveyed 48 regions, finding values ranging from 14,600-4,550,000 particles per capita per day, depending on the region. We demonstrate that infant exposure to microplastics is higher than was previously recognized due to the prevalence of PP-based products used in formula preparation and highlight an urgent need to assess whether exposure to microplastics at these levels poses a risk to infant health.

Enhanced shortcut nitrogen removal and metagenomic analysis of functional microbial communities in a double sludge system treating ammonium-rich wastewater.

Biological nitrogen removal processes based on partial nitrification are promising for ammonium-rich wastewater treatment. In this study, a partial nitrification-denitrification double sludge system was applied to treat synthetic ammonium-rich wastewater. Metagenomic analysis of functional genes and metabolic pathways was conducted, also with the evaluation of system performance and nitrous oxide (N2O) emission. In the nitrifying sequencing batch reactor (SBRPN), the removal percentage of ammonium nitrogen reached to 99.98% with a high nitritation efficiency of 93.24%, and the N2O emission factor was 0.88%. In the denitrifying sequencing batch reactor (SBRDN), there was almost no nitrate nitrogen and nitrite nitrogen in the effluent, and the maximum N2O emission was 0.078 mg N/L. The dominant ammonia oxidizing bacteria was Nitrosomonas in SBRPN (13.6%), and the main potential denitrifiers in SBRDN were Thauera (14.6%), an uncultured genus in the Comamonadaceae family (4.0%), an uncultured genus in Rhodocyclaceae family (2.4%) and Comamonas (1.1%). Metagenomic analysis revealed that amo mainly distributed in Nitrosomonas eutropha (38.3%), Nitrosomonas europaea (27.1%), Nitrosomonas sp. GH22 (20.5%) and Nitrosomonas sp. TK794 (15.0%), and Bacteroidetes had the N2O reduction potential in SBRPN.

Removal of nitrogen and phosphorus from the secondary effluent in tertiary denitrifying biofilters combined with micro-coagulation.

Effective control of nitrogen and phosphorus in secondary effluent can reduce or avoid the eutrophication of receiving water bodies. Two denitrifying biofilters (DNBFs) packed with different sizes of quartz sands combined with micro-coagulation were operated for simultaneous removal of nitrogen and phosphorus from the secondary effluent. The quartz sand size in one DNBF was 2-4 mm (DNBFS), and in the other was 4-6 mm (DNBFL). In both DNBFs, methanol was used as the electron donor and different organic carbon to nitrogen (C/N) ratios were applied. Under C/N ratios of 1.5, 1.25, and 0.75 g/g, the nitrate nitrogen (NO3(-)-N) removal percentages were 73%, 77%, and 50% in DNBFS, and 43%, 25%, and 21% in DNBFL; the effluent total phosphorus concentrations were 0.15, 0.14, and 0.18 mg/L in DNBFS, and 0.29, 0.35, and 0.24 mg/L in DNBFL. The performance of both biofilters was quite stable within a backwashing cycle. The NO3(-)-N reduction rates were 1.31, 1.10, and 0.48 mg/(L·min) in DNBFS, and 0.97, 0.27, and 0.10 mg/(L·min) in DNBFL. For biomass detached from both biofilters, their denitrifying activities were similar. Biofilm biomass in DNBFS was higher than that in DNBFL, inducing a high denitrification efficiency in DNBFS.

Denitrification and biofilm growth in a pilot-scale biofilter packed with suspended carriers for biological nitrogen removal from secondary effluent.

Tertiary denitrification is an effective method for nitrogen removal from wastewater. A pilot-scale biofilter packed with suspended carriers was operated for tertiary denitrification with ethanol as the organic carbon source. Long-term performance, biokinetics of denitrification and biofilm growth were evaluated under filtration velocities of 6, 10 and 14 m/hr. The pilot-scale biofilter removed nitrate from the secondary effluent effectively, and the nitrate nitrogen (NO3-N) removal percentage was 82%, 78% and 55% at the filtration velocities of 6, 10 and 14 m/hr, respectively. At the filtration velocities of 6 and 10 m/hr, the nitrate removal loading rate increased with increasing influent nitrate loading rates, while at the filtration velocity of 14 m/hr, the removal loading rate and the influent loading rate were uncorrelated. During denitrification, the ratio of consumed chemical oxygen demand to removed NO3-N was 3.99-4.52 mg/mg. Under the filtration velocities of 6, 10 and 14 m/hr, the maximum denitrification rate was 3.12, 4.86 and 4.42 g N/(m2·day), the half-saturation constant was 2.61, 1.05 and 1.17 mg/L, and the half-order coefficient was 0.22, 0.32 and 0.24(mg/L)1/2/min, respectively. The biofilm biomass increased with increasing filtration velocity and was 2845, 5124 and 7324 mg VSS/m2 at filtration velocities of 6, 10 and 14 m/hr, respectively. The highest biofilm density was 44 mg/cm3 at the filtration velocity of 14 m/hr. Due to the low influent loading rate, biofilm biomass and thickness were lowest at the filtration velocity of 6m/hr.