Selective inactivation of Gram-negative bacteria by carbon dots derived from natural biomass: Artemisia argyi leaves.

Infections caused by Gram-negative bacteria have been an increasing problem worldwide. Meanwhile, the overuse of traditional antibiotics has caused an emergence of drug resistance. The development of new antibacterial agents, which can cope with the threat from drug-resistant bacteria, is urgently needed. Herein, carbon dots (ACDs) derived from Artemisia argyi leaves were obtained via a smoking simulation method and exhibited selective antibacterial ability of targeting Gram-negative bacteria. The bactericidal efficiency of ACDs (150 µg mL-1) for Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, and Proteusbacillus vulgaris) can reach 100%, while for Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), ACDs have no significant antibacterial function, indicating that the particles can selectively target specific bacteria. The antibacterial mechanism for ACDs confirmed that ACDs could only damage the cell walls of Gram-negative bacteria but not that of Gram-positive bacteria. Moreover, ACDs can inhibit the activity of cell wall-related enzymes in Gram-negative bacteria by changing the enzymatic secondary structure. This work is of great significance for the development of new antibacterial nanomaterials derived from natural biomass as well as the treatment of infections caused by Gram-negative bacteria.

Decolorization and phytotoxicity reduction in an innovative anaerobic/aerobic photobioreactor treating textile wastewater.

The potential of a novel anaerobic/aerobic algal-bacterial photobioreactor for the treatment of synthetic textile wastewater (STWW) was here assessed. Algal-bacterial symbiosis supported total organic carbon, nitrogen and phosphorous removal efficiencies of 78 ±â€¯2%, 47 ±â€¯2% and 26 ±â€¯2%, respectively, at a hydraulic retention time (HRT) of 8 days. A decrease in the HRT from 8 to 4 and 2 days resulted in a slight decrease in organic carbon and phosphate removal, but a sharp decrease in nitrogen removal. Moreover, an efficient decolorization of 99 ±â€¯1% and 96 ±â€¯3% for disperse orange-3 and of disperse blue-1, respectively, was recorded. The effective STWW treatment supported by the anaerobic/aerobic algal-bacterial photobioreactor was confirmed by the reduction in wastewater toxicity towards Raphanus sativus seed germination and growth. These results highlighted the potential of this innovative algal-bacterial photobioreactor configuration for the treatment of textile wastewater and water reuse.

Comparison of monoculture and mixed culture (Scenedesmus obliquus and wild algae) for C, N, and P removal and lipid production.

This study compared the efficiency of nutrient removal and lipid accumulation by a monoculture of Scenedesmus obliquus and mixed cultures of microalgae. The highest removal efficiencies of ammonium (99.2%), phosphate (91.2%), and total organic carbon (83.6%) occurred in the monoculture. All the mixed cultures were dominated by S. quadricauda; in some mixed cultures, the proportions of Chlamydomonas reinhardtii and C. microsphaera reached > 20%. The lipid content and lipid production in the monoculture were 15.9% and 52.3 mg kg-1, respectively, significantly higher than those in all the mixed cultures of microalgae. In all the mixed cultures, the proportion of palmitic acid was > 50%. The results suggest that the monoculture had advantages over the mixed culture of microalgae in terms of nutrient removal and lipid production.

Hydrochars produced with by-products from the sucroenergetic industry: a study of extractor solutions on nutrient and organic carbon release.

Hydrothermal carbonization transforms biomass into value-added material called hydrochar. The release of nutrients (P, N, Ca, Mg, and K) and organic carbon (TOC) from hydrochar in different extractive solutions was investigated in this study. Two sets of hydrochar were produced: (i) hydrochar prepared from sugarcane bagasse and vinasse mixture (BV-HC) and (ii) hydrochar prepared by the addition of H3PO4 to this mixture (BVA-HC). Both hydrochar types released significative amounts of nutrient and organic carbon, mainly Ca (5.0 mg g-1) in the mixture (KCl, K2SO4, NaOH, 1:1:1) extractive solution and TOC (72.6 mg g-1) in the NaOH extractive solution, for BV-HC. Nutrient release was influenced by pH and ionic strength. The release of P, Ca, and Mg was affected by the presence of insoluble phosphate phases in BVA-HC. The release of nutrients P, N, Ca, Mg, and K and organic carbon demonstrated that hydrochar has potential for soil application purposes.

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.

Enhanced alure-type biological system (E-ATBS) for carbon, nitrogen and phosphorus removal from slaughterhouse wastewater: A case study.

Slaughterhouse wastewater is one of the most harmful agriculture and food industrial wastewaters. The emissions of not fully treated slaughtering wastewater would cause eutrophication of surface water and pollution of groundwater. This study investigated the nutrient removal performance for the enhanced alure-type biological system (E-ATBS) in the full-scale application. During the whole study period, COD, TN and TP removal efficiencies were higher than 97.1%, 90.8% and 90.1%, respectively. The effluent concentrations were lower than the newest effluent standard in China to avoid the discharged water pollution. Partial denitrification (PD)-ANAMMOX was considered as the main approach for anaerobic NH4+-N removal, which helped to guarantee the efficient N removal in the full-scale E-ATBS. Denitrifying P removal and aerobic P uptake ensured the efficient and stable P removal. E-ATBS is a promising technology especially for wastewater treatment in food processing facilities and should be widely popularized.

Adding maize cobs to vertical subsurface flow constructed wetlands treating marine recirculating aquaculture system effluents: Carbon releasing kinetics and intensified nitrogen removal.

This study aims to investigate the releasing behaviors of maize cobs with or without alkali (i.e. NaOH) pretreatment in seawater and distilled water, and to evaluate the effects of maize cobs addition (solid biomass and lixivium) on nitrogen removal in saline constructed wetland (CW) treating marine recirculating aquaculture system (RAS) effluents. Results revealed NaOH-treated maize cobs released carbon more efficiently, whether in seawater or in distilled water. Compared to distilled water, seawater conditions promoted carbon releasing. CW with maize cobs biomass and lixivium addition had high NO3-N removal efficiencies without significant difference, i.e. 94.9 ±â€¯6.0% and 87.1 ±â€¯13.2%, respectively. While CW with maize cobs biomass addition had higher effluent COD concentrations (16.3 ±â€¯3.6 mg L-1) compared with those adding lixivium (2.1 ±â€¯0.4 mg L-1). The study suggested adding maize cobs lixivium to be feasible and effective way to enhance nitrogen removal in saline CW.

Simultaneous nutrient and carbon removal and electricity generation in self-buffered biocathode microbial fuel cell for high-salinity mustard tuber wastewater treatment.

Mustard tuber wastewater (MTWW) was used as both anolyte and catholyte in biocathode microbial fuel cell (BMFC). The results showed simultaneous nutrient and carbon removal and electricity generation were realized in BMFC. Excellent Chemical Oxygen Demand (COD) removal occurred in both anode (>90%) and cathode (>91%). Concerning nutrient removal, it was mainly removed in cathode. The maximum total phosphorus (TP) removal could reach 80.8 ±â€¯1.0% by biological action. Simultaneous nitrification and denitrification (SND) was realized in cathode. The bacteria involved in nitrification were Nitrosomonas and SM1A02. Oceanimonas and Saprospiraceae_uncultured (anaerobic denitrifier), Thauera, Stenotrophomonas, Flavobacterium and Marinobacter (aerobic denitrifier), and Thioalkalispira (autotrophic denitrifier) were responsible for denitrification. Considering slight variation of anode and cathode pH, it could be concluded that MTWW was adequately self-buffered when used as electrolyte. Furthermore, electricity generation decreased with cathodic dissolved oxygen (DO) declining. These findings provide a novel method for MTWW resourceful treatment.

[Effect of Volume Loading Rate (VLR) on Denitrifying Phosphorus Removal by the ABR-MBR Process].

The effect of volume loading rate (VLR) on denitrifying phosphorus removal was investigated in a continuous-flow ABR-MBR combined process treating domestic wastewater to arrive at optimum process parameters. In the experiment, the VLR of the ABR was set at 0.76, 1.01, 1.51, and 2.27 kg·(m3·d)-1. The removal of carbon, nitrogen, and phosphorus in the system and the effect of the VLR in the MBR on nitrification performance were observed for each VLR of the ABR. The results showed that under the condition when the VLR of the ABR was 1.51 kg·(m3·d)-1, the amount of COD removal in the A2 chamber was the largest, and shortcut nitrification was achieved in the MBR when the VLR of the MBR was 1.51 kg·(m3·d)-1. Meanwhile, the removal efficiency of NH4+-N and TN reached more than 90% and 72%, respectively, the anaerobic P-release and anoxic P-uptake were 7.41 mg·L-1and 15.42 mg·L-1, respectively, and the concentration of PO43--P in effluent was lower than 0.5 mg·L-1, which indicated that the shortcut nitrification was more conducive to strengthening the performance of denitrifying phosphorus removal in the ABR-MBR system.

Carbon, nitrogen and phosphorus removal mechanisms of aerobic granules.

Aerobic granules are the potential tools to develop modern wastewater treatment technologies with improved nutrient removal efficiency. These granules have several promising advantages over conventional activated sludge-based wastewater treatment processes. This technology has the potential of reducing the infrastructure and operation costs of wastewater treatment by 25%, energy requirement by 30%, and space requirement by 75%. The nutrient removal mechanisms of aerobic granules are slightly different from that of the activated sludge. For instance, unlike activated sludge process, according to some reports, as high as 70% of the total phosphorus removed by aerobic granules were attributed to precipitation within the granules. Similarly, aerobic granule-based technology reduces the total amount of sludge produced during wastewater treatment. However, the reason behind this observation is unknown and it needs further explanations based on carbon and nitrogen removal mechanisms. Thus, as a part of the present review, a set of new hypotheses have been proposed to explain the peculiar nutrient removal mechanisms of the aerobic granules.

Extracellular enzymatic activity of two hydrolases in wastewater treatment for biological nutrient removal.

Due to the complex nature of the wastewater (both domestic and non-domestic) composition, biological processes are widely used to remove nutrients, such as carbon (C), nitrogen (N), and phosphorous (P), which cause instability and hence contribute to the damage of water bodies. Systems with different configurations have been developed (including anaerobic, anoxic, and aerobic conditions) for the joint removal of carbon, nitrogen, and phosphorus. The goal of this research is to evaluate the extracellular activity of ß-glucosidase and phosphatase enzymes in a University of Cape Town (UCT) system fed with two synthetic wastewaters of different molecular complexity. Both types of waters have medium strength characteristics similar to those of domestic wastewater with a mean C/N/P ratio of 100:13:1. The operation parameters were hydraulic retention time (HRT) of 10 h, solid retention time (SRT) of 12 days, mean concentration of the influent in terms of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), and total phosphorus (TP) of 600, 80, and 6 mg/L, respectively. According to the results obtained, statistically significant differences have been found in the extracellular enzyme activities with the evaluated wastewaters and in the units comprising the treatment system in some of the cases. An analysis of principal components showed that the extracellular enzymatic activity has been correlated to nutrient concentration in wastewater, biomass concentration in the system, and metabolic conditions of treatment phases. Additionally, this research has allowed determining an inverse relationship between wastewater biodegradability and the extracellular enzyme activity of ß-glucosidase and phosphatase. These results highlight the importance of including the analysis of biomass biochemical characteristics as control methods in wastewater treatment systems for the nutrient removal.

Microalgal bacterial flocs treating paper mill effluent: A sunlight-based approach for removing carbon, nitrogen, phosphorus, and calcium.

Treatment of upflow anaerobic sludge blanket (UASB) effluent from a paper mill in aerated activated sludge reactors involves high aeration costs. Moreover, this calcium-rich effluent leads to problematic scale formation. Therefore, a novel strategy for the aerobic treatment of paper mill UASB effluent in microalgal bacterial floc sequencing batch reactors (MaB-floc SBRs) is proposed, in which oxygen is provided via photosynthesis, and calcium is removed via bio-mineralization. Based on the results of batch experiments in the course of this study, a MaB-floc SBR was operated at an initial neutral pH. This SBR removed 58±21% organic carbon, 27±8% inorganic carbon, 77±5% nitrogen, 73±2% phosphorus, and 27±11% calcium. MaB-flocs contained 10±3% calcium, including biologically-influenced calcite crystals. The removal of calcium and inorganic carbon by MaB-flocs significantly decreased when inhibiting extracellular carbonic anhydrase (CA), an enzyme that catalyses the hydration and dehydration of CO2. This study demonstrates the potential of MaB-floc SBRs for the alternative treatment of calcium-rich paper mill effluent, and highlights the importance of extracellular CA in this treatment process.

Unraveling characteristics of simultaneous nitrification, denitrification and phosphorus removal (SNDPR) in an aerobic granular sequencing batch reactor.

An aerobic granular sequencing batch reactor (SBR) on an aerobic/oxic/anoxic (AOA) mode was operated for 50days with acetate sodium as the sole carbon source for simultaneous carbon, nitrogen and phosphorus removal. Excellent removal efficiencies for chemical oxygen demand (COD) (94.46±3.59%), nitrogen (96.56±3.44% for ammonia nitrogen (NH4(+)-N) and 93.88±6.78% for total inorganic nitrogen (TIN)) and phosphorus (97.71±3.63%) were obtained over operation. Mechanisms for simultaneous nutrients removal were explored and the results indicated that simultaneous nitrification, denitrification and phosphorus removal (SNDPR) under aerobic conditions was mainly responsible for most of nitrogen and phosphorus removal. Identification and quantification of the granular AOA SBR revealed that higher rates of nutrients removal and more potentials were to be exploited by optimizing the operating conditions including time durations for AOA mode and the feeding compositions.

A new activated primary tank developed for recovering carbon source and its application.

A novel activated primary tank process (APT) was developed for recovering carbon source by fermentation and elutriation of primary sludge. The effects of solids retention time (SRT), elutriation intensity (G) and return sludge ratio (RSR) on this recovery were evaluated in a pilot scale reactor. Results indicated that SRT significantly influenced carbon source recovery, and mechanical elutriation could promote soluble COD (SCOD) and VFA yields. The optimal conditions of APT were SRT=5d, G=152s(-1) and RSR=10%, SCOD and VFA production were 57.0mg/L and 21.7mg/L. Particulate organic matter in sludge was converted into SCOD and VFAs as fermentative bacteria were significantly enriched in APT. Moreover, the APT process was applied in a wastewater treatment plant to solve the problem of insufficient carbon source. The outcomes demonstrated that influent SCOD of biological tank increased by 31.1%, which improved the efficiency of removing nitrogen and phosphorus.

Nitrogen removal characteristics of enhanced in situ indigenous aerobic denitrification bacteria for micro-polluted reservoir source water.

Indigenous oligotrophic aerobic denitrifiers nitrogen removal characteristics, community metabolic activity and functional genes were analyzed in a micro-polluted reservoir. The results showed that the nitrate in the enhanced system decreased from 1.71±0.01 to 0.80±0.06mg/L, while the control system did little to remove and there was no nitrite accumulation. The total nitrogen (TN) removal rate of the enhanced system reached 38.33±1.50% and the TN removal rate of surface sediment in the enhanced system reached 23.85±2.52%. TN removal in the control system experienced an 85.48±2.37% increase. The densities of aerobic denitrifiers in the enhanced system ranged from 2.24×10(5) to 8.13×10(7)cfu/mL. The abundance of nirS and nirK genes in the enhanced system were higher than those of in the control system. These results suggest that the enhanced in situ indigenous aerobic denitrifiers have potential applications for the bioremediation of micro-polluted reservoir system.

[Water purification of four aquatic plant species with the presence of iron-carbon interior electrolytic substrates.] / 铁-ç¢³å† ç”µè§£è´¨ä¸‹4种水生植物的净水效果.

To compare water purification of common aquatic plants in wetland ecosystem, four common aquatic plant species (Eichhornia crassipes, Nymphaea tetragona, Acorus calamus and Phragmites australis) were used as study species. The effect of aquatic plants on the change of sewage ammonium nitrogen, COD, TP content during different experimental time (1-5 d) with the presence of iron-carbon interior electrolytic substrates were analyzed in small scale experimental apparatus. The results showed that single and combined aquatic plants could effectively remove ammonium nitrogen, COD, TP from the sewage compared with the no-plant control group, but the efficiencies were significantly different among the different species. Ammonium nitrogen removal up to 100% was achieved with E. crassipes in two days, and A. calamus in three days. Each plant combination performed well on ammonium nitrogen removal. Concentration of the sewage COD approached zero with E. crassipes in three days, A. calamus performed secondly. The concentration of COD in combination of E. crassipes and A. calamus water decreased by 85.1% to a minimum of 4.33 mg·L-1. The concentration of TP was the lowest with E. crassipes in four days, and second with P. australis. The lowest concentration of TP was found with the combination of E. crassipes and A. calamusin two days. The combination effect of interior electrolyte and plant was better than that of pure interior electrolyte on the purification of sewage. Plant configuration should be optimized according to the level of pollutants.

Simultaneous effective carbon and nitrogen removals and phosphorus recovery in an intermittently aerated membrane bioreactor integrated system.

Recovering nutrients, especially phosphate resource, from wastewater have attracted increasing interest recently. Herein, an intermittently aerated membrane bioreactor (MBR) with a mesh filter was developed for simultaneous chemical oxygen demand (COD), total nitrogen (TN) and phosphorous removal, followed by phosphorus recovery from the phosphorus-rich sludge. This integrated system showed enhanced performances in nitrification and denitrification and phosphorous removal without excess sludge discharged. The removal of COD, TN and total phosphorus (TP) in a modified MBR were averaged at 94.4 ± 2.5%, 94.2 ± 5.7% and 53.3 ± 29.7%, respectively. The removed TP was stored in biomass, and 68.7% of the stored phosphorous in the sludge could be recovered as concentrated phosphate solution with a concentration of phosphate above 350 mg/L. The sludge after phosphorus release could be returned back to the MBR for phosphorus uptake, and 83.8% of its capacity could be recovered.

A Multi-module Approach to Calculation of Oyster (Crassostrea virginica) Environmental Benefits.

Environmental benefits are one of the motivations for management restoration of depleted bivalve populations. We describe a series of linked modules for benefits calculation. The modules include: oyster (Crassostrea virginica) bioenergetics, materials transport via the tidal prism, and benefits quantification. Quantified benefits include carbon, nitrogen, and phosphorus removal and shell production. The modules are demonstrated through application to the Great Wicomico River, a tributary of Chesapeake Bay, USA. Oysters on seven reefs (total area 2.8 × 10(5) m(2)) are calculated to remove 15.2, 6.2, and 0.2 tons per annum of carbon, nitrogen, and phosphorus, respectively, from the Great Wicomico. Oyster mortality contributes 108 tons per annum dry weight shell to the reefs.

Cassava stillage and its anaerobic fermentation liquid as external carbon sources in biological nutrient removal.

The aim of this study was to investigate the effects of one kind of food industry effluent, cassava stillage and its anaerobic fermentation liquid, on biological nutrient removal (BNR) from municipal wastewater in anaerobic-anoxic-aerobic sequencing batch reactors (SBRs). Experiments were carried out with cassava stillage supernatant and its anaerobic fermentation liquid, and one pure compound (sodium acetate) served as an external carbon source. Cyclic studies indicated that the cassava by-products not only affected the transformation of nitrogen, phosphorus, poly-ß-hydroxyalkanoates (PHAs), and glycogen in the BNR process, but also resulted in higher removal efficiencies for phosphorus and nitrogen compared with sodium acetate. Furthermore, assays for phosphorus accumulating organisms (PAOs) and denitrifying phosphorus accumulating organisms (DPAOs) demonstrated that the proportion of DPAOs to PAOs reached 62.6% (Day 86) and 61.8% (Day 65) when using cassava stillage and its anaerobic fermentation liquid, respectively, as the external carbon source. In addition, the nitrate utilization rates (NURs) of the cassava by-products were in the range of 5.49-5.99 g N/(kg MLVSS⋅h) (MLVSS is mixed liquor volatile suspended solids) and 6.63-6.81 g N/(kg MLVSS⋅h), respectively. The improvement in BNR performance and the reduction in the amount of cassava stillage to be treated in-situ make cassava stillage and its anaerobic fermentation liquid attractive alternatives to sodium acetate as external carbon sources for BNR processes.