Water-lifting and aeration system improves water quality of drinking water reservoirs: Biological mechanism and field application.

Reservoirs have been served as the major source of drinking water for dozens of years. The water quality safety of large and medium reservoirs increasingly becomes the focus of public concern. Field test has proved that water-lifting and aeration system (WLAS) is a piece of effective equipment for in situ control and improvement of water quality. However, its intrinsic bioremediation mechanism, especially for nitrogen removal, still lacks in-depth investigation. Hence, the dynamic changes in water quality parameters, carbon source metabolism, species compositions and co-occurrence patterns of microbial communities were systematically studied in Jinpen Reservoir within a whole WLAS running cycle. The WLAS operation could efficiently reduce organic carbon (19.77%), nitrogen (21.55%) and phosphorus (65.60%), respectively. Biolog analysis revealed that the microbial metabolic capacities were enhanced via WLAS operation, especially in bottom water. High-throughput sequencing demonstrated that WLAS operation altered the diversity and distributions of microbial communities in the source water. The most dominant genus accountable for aerobic denitrification was identified as Dechloromonas. Furthermore, network analysis revealed that microorganisms interacted more closely through WLAS operation. Oxidation-reduction potential (ORP) and total nitrogen (TN) were regarded as the two main physicochemical parameters influencing microbial community structures, as confirmed by redundancy analysis (RDA) and Mantel test. Overall, the results will provide a scientific basis and an effective way for strengthening the in-situ bioremediation of micro-polluted source water.

Evaluation of activated carbon fiber supported nanoscale zero-valent iron for chromium (VI) removal from groundwater in a permeable reactive column.

An activated carbon fiber supported nanoscale zero-valent iron (ACF-nZVI) composite for Cr(VI) removal from groundwater was synthesized according to the liquid phase reduction method. The techniques of N2 adsorption/desorption, FESEM, EDX, XRD and XPS were used to characterize the ACF-nZVI composite and the interaction between the ACF-nZVI composite and Cr(VI) ions. Batch experiments were conducted to evaluate the effects of several factors, including the amount of nZVI on activated carbon fiber (ACF), pH value, initial Cr(VI) concentration, and co-existing ions on Cr(VI) removal. The results indicate that presence of ACF can inhibit the aggregation of nanoscale zero-valent iron (nZVI) particles and increase its reactivity, and the Cr(VI) removal efficiency increases with increasing amounts of nZVI on ACF and a decrease in the initial Cr(VI) concentration. In acidic conditions, almost 100% of Cr(VI) in solution can be removed after 60 min of reaction, and the removal efficiency decreases with increasing initial pH values. The Cr(VI) removal is also dependent on the co-existing ions. Reusability experiments on ACF-nZVI demonstrate that the ACF-nZVI composite can keep a high reactivity after five successive reduction cycles. The removal mechanisms are proposed as a two-step interaction including the physical adsorption of Cr(VI) on the surface or inner layers of the ACF-nZVI composite and the subsequent reduction of Cr(VI) to Cr(III) by nZVI.

Aerobic denitrifying bacterial community with low C/N ratio remove nitrate from micro-polluted water: Metagenomics unravels denitrification pathways.

The efficient nitrogen removal from micro-polluted source water is an international challenge to be solved urgently. However, the inner denitrification mechanism of native aerobic denitrifying bacterial communities in response to carbon scarcity remains relatively unclear. Here, the bacterial community XT6, screened from an oligotrophic reservoir, exhibited aerobic denitrifying capacity under low-carbon environments. Up to 76.79-81.64 % of total organic carbon (TOC) and 51.48-67.60 % of NO3--N were removed by XT6 within 48 h at C/N ratios of 2.0-3.0. Additionally, the nitrogen balance experiments further manifested that 26.27-38.13 % of NO3--N was lost in gaseous form. As the C/N ratio decreased, XT6 tended to generate more extracellular polymeric substances (EPS), with the tightly bound EPS showing the largest increase. Pseudomonas and Variovorax were quite abundant in XT6, constituting 59.69 % and 28.65 % of the total sequences, respectively. Furthermore, metagenomics analysis evidenced that XT6 removed TOC and nitrate mainly through the tricarboxylic acid cycle and aerobic denitrification. Overall, the abovementioned results provide a deeper understanding of the nitrogen metabolic pathways of indigenous aerobic denitrifying bacterial communities with low C/N ratios and offer useful guidance for controlling nitrogen pollution in oligotrophic ecosystems.

Mix-cultured aerobic denitrifying bacterial communities reduce nitrate: Novel insights in micro-polluted water treatment at lower temperature.

Three mix-cultured aerobic denitrifiers were screened from a source water reservoir and named HE1, HE3 and SU4. Approximately 72.9%, 68.6% and 66.2% of nitrate were effectively removed from basal medium, respectively, after 120 h of cultivation at 8 °C. The nitrogen balance analysis revealed about one-fifth of the initial nitrogen was converted into gaseous denitrification products. According to the results of Biolog, the three microfloras had high metabolic capacity to carbon sources. The dominant genera were Pseudomonas and Paracoccus in these bacterial communities based on nirS gene sequencing. Response surface methodology elucidated that the denitrification rates of identified bacteria reached the maximum under the following optimal parameters: C/N ratio of 7.51-8.34, pH of 8.03-8.09, temperature of 18.03-20.19 °C, and shaking speed of 67.04-120 rpm. All results suggested that screened aerobic denitrifiers could potentially be applied to improve the source water quality at low temperature.

Excess sludge disintegration by discharge plasma oxidation: Efficiency and underlying mechanisms.

A huge amount of excess sludge is inevitably produced in wastewater treatment, and it is becoming more and more urgent to realize efficient sludge reduction. Discharge plasma oxidation was used to efficiently disintegrate excess sludge for sludge reduction in this study. Approximately 18.22% sludge disintegration and 27.8% reduction of total suspended solids (TSS) were achieved by discharge plasma treatment. The water content of the filter cake decreased from 81.9% to 76.0% and the bound water content decreased from 2.66 g/g dry solid to 0.73 g/g dry solid after treatment. The large quantities of reactive oxygen species (ROS) generated by discharge plasma played important roles in sludge disintegration by destroying flocs and promoting the transformation of organic substances. Concurrent cell lysis induced by ROS oxidation released intracellular organics and water into the liquid phase. The fraction of soluble extracellular polymer substances (S-EPS) was enhanced from 16.10% to 58.51%, whereas the tightly bound fraction was reduced from 70.62% to 28.91%. Migration and decomposition of EPS were the main processes for EPS changing at a low oxidation capacity, whereas cell lysis became important at a high oxidation capacity. In summary, the plasma treatment effectively improved sludge disintegration.

[Nitrogen Removal Performance and Nitrogen/Carbon Balance of Oligotrophic Aerobic Denitrifiers].

Due to the problems of low nitrogen removal efficiency and unclear electron transfer during biological denitrification treatment of an oligotrophic drinking water reservoir, the nitrogen removal characteristics, environmental adaptability, and electron transfer during denitrification were systematically studied using the aerobic denitrifier Acinetobacter junii ZMF5, which has efficient nitrogen removal ability. The results showed that:① Strain ZMF5 exhibited efficient heterotrophic nitrification and aerobic denitrification ability, with an ammonia removal rate of 0.211 mg·(L·h)-1 and a nitrate removal rate of 0.236 mg·(L·h)-1, and the nitrification intermediates were not accumulated during the treatment process. ② According to analysis of the nitrogen removal efficiency and growth kinetics of strain ZMF5, the strain can effectively utilize different types of carbon source, and show efficient nitrogen removal efficiency under the conditions of low C/N, low pH, and low temperature. ③ Analysis of nitrogen balance showed that carboxylate compound, compared with carbohydrate, could promote the process of aerobic denitrification and change the nitrogen removal pathway of strain ZMF5, i.e., 38.81% of nitrogen was transformed into gas, higher than the 29.81% for assimilation. ④ Analysis of carbon balance indicated that most carbon sources were used as electron donors in the denitrification process, but fewer electrons were used for nitrate reduction, and with respect to different carbon sources, electron transfer to the nitrate respiratory chain was regulated by different reduction potentials, electron donor abundance, and molecular weight. Acinetobacter junii ZMF5 could be used to control nitrogen pollution in drinking water reservoirs.

Nitrogen Removal in Oligotrophic Reservoir Water by a Mixed Aerobic Denitrifying Consortium: Influencing Factors and Immobilization Effects.

Nitrogen pollution in reservoirs has received increasing attention in recent years. Although a number of aerobic denitrifying strains have been isolated to remove nitrogen from eutrophic waters, the situation in oligotrophic water environments has not received significant attention. In this study, a mixed aerobic denitrifying consortium screened from reservoir samples was used to remove nitrogen in an oligotrophic denitrification medium and actual oligotrophic source water. The results showed that the consortium removed 75.32% of nitrate (NO3--N) and 63.11% of the total nitrogen (TN) in oligotrophic reservoir water during a 24-h aerobic cultivation. More initial carbon source was helpful for simultaneous removal of carbon and nitrogen in the reservoir source water. NO3--N and TN were still reduced by 60.93% and 46.56% at a lower temperature (10 °C), respectively, though the rates were reduced. Moreover, adding phosphorus promoted bacterial growth and increased TN removal efficiency by around 20%. The performance of the immobilized consortium in source water was also explored. After 6 days of immobilization, approximately 25% of TN in the source water could be removed by the carriers, and the effects could last for at least 9 cycles of reuse. These results provide a good reference for the use of aerobic denitrifiers in oligotrophic reservoirs.

Inhibition of P2X4 suppresses joint inflammation and damage in collagen-induced arthritis.

Recent data have shown that the purinergic receptor P2X4 plays key roles in inflammatory responses. We evaluated whether P2X4 inhibition could affect the development of arthritis and autoimmunity in collagen-induced arthritis (CIA) model. P2X4 antisense oligonucleotide (asODN) was injected intravenously via tail vein into the CIA mice to selectively inhibit P2X4 expression daily for 14 days. P2X4 asODN treatment reduced the clinical score of CIA in mice. P2X4 asODN also decreased the levels of serum IL-1ß, TNF-α, IL-6, and IL-17. P2X4 asODN treatment significantly inhibited synovial inflammation and joint destruction. P2X4 asODN treatment also suppressed the NLR family, pyrin domain containing 1 (NLRP1) inflammasome activation in CIA mice and synovial cells of human rheumatoid arthritis. These data show that P2X4 asODN confers a therapeutic benefit on CIA. Inhibition of the NLRP1 inflammasome signaling pathway is the underlying mechanism of action.

SUMO-conjugating enzyme UBC9 promotes proliferation and migration of fibroblast-like synoviocytes in rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune disease with high morbidity and mortality. Fibroblast-like synoviocytes (FLS) in the synovial tissues play critical roles in joint destruction. Recent studies implicate the sumoylation in the regulation of the inflammation and arthritis. Thus, we explored whether SUMO-conjugating enzyme UBC9 is involved in the progression of RA using a mouse collagen-induced arthritis (CIA) model. The effects of UBC9 siRNA on cell invasion and migration in human RA-FLS were also assessed in vitro. Treatment with siRNA against UBC9 for 3 weeks reduced the arthritis score and joint destruction. The expression of SUMO-1 and UBC9 protein in CIA joints was inhibited by UBC9 knockdown. Serum levels of anti-collagen (CII) antibodies, vascular endothelial growth factor A (VEGF-A), matrix metalloproteinases (MMP)-3, and MMP-9 were also decreased in CIA mice. In vitro, UBC9 silencing inhibited the secretion of VEGF-A, MMP-3, and MMP-9 from TNF-α-stimulated human RA-FLS. TNF-α-induced RA-FLS proliferation and migration were significantly attenuated by UBC9 knockdown. These findings indicate that SUMO-conjugating enzyme UBC9 promotes proliferation and migration of fibroblast-like synoviocytes in rheumatoid arthritis. Inhibition of UBC9 activity may be a viable therapeutic target in amelioration of disease progression in RA by attenuating FLS proliferation, migration, and invasion.