The rapid development of modern industries is accompanied with the aggravating water heavy metal pollution, which poses a potential threat to the aquatic environment and the health of local populations. As an efficient and economical adsorbent, biochar demonstrates the adsorption capacity for heavy metal ions and its adsorption capacity is significantly enhanced after modification. Therefore, biochar can effectively mitigate environmental pollution. By reviewing the existing studies, we summarize the modification methods of biochar, compare the advantages and disadvantages of physical, biological, and chemical modification methods, analyze the effects of modification on the adsorption capacity of biochar for heavy metal ions, and expound the modification mechanism of biochar. On this basis, this article puts forward the future research directions of the application of biochar in treating coexisting pollutants, aiming to provide a reference for the application of biochar in the purification of heavy metal-containing wastewater.
Charcoal/chemistry* ; Metals, Heavy ; Adsorption ; Wastewater/chemistry* ; Water Pollutants, Chemical/chemistry* ; Water Purification/methods* ; Heavy Ions ; Waste Disposal, Fluid/methods*

The effects of two different external carbon sources (acetate and ethanol) and electron acceptors (dissolved oxygen, nitrate, and nitrite) were investigated under aerobic and anoxic conditions with non-acclimated process biomass from a full-scale biological nutrient removal-activated sludge system. When acetate was added as an external carbon source, phosphate release was observed even in the presence of electron acceptors. The release rates were 1.7, 7.8, and 3.5 mg P/(g MLVSS·h) (MLVSS: mixed liquor volatile suspended solids), respectively, for dissolved oxygen, nitrate, and nitrite. In the case of ethanol, no phosphate release was observed in the presence of electron acceptors. Results of the experiments with nitrite showed that approximately 25 mg NO₂-N/L of nitrite inhibited anoxic phosphorus uptake regardless of the concentration of the tested external carbon sources. Furthermore, higher denitrification rates were obtained with acetate (1.4 and 0.8 mg N/(g MLVSS·h)) compared to ethanol (1.1 and 0.7 mg N/ (g MLVSS·h)) for both anoxic electron acceptors (nitrate and nitrite).
Biomass ; Bioreactors ; Carbon/chemistry* ; Denitrification ; Electrons ; Nitrates ; Nitrites ; Oxygen ; Phosphates ; Phosphorus/chemistry* ; Sewage ; Waste Disposal, Fluid/methods* ; Wastewater ; Water Pollutants, Chemical ; Water Purification/methods*

BACKGROUND: Currently, it is recognized that water polluted with toxic heavy metal ions may cause serious effects on human health. Therefore, the development of new materials for effective removal of heavy metal ions from water is still a widely important area. Melanin is being considered as a potential material for removal of heavy metal from water. METHODS: In this study, we synthesized two melanin-embedded beads from two different melanin powder sources and named IMB (Isolated Melanin Bead originated from squid ink sac) and CMB (Commercial Melanin Bead originated from sesame seeds). These beads were of globular shape and 2-3 mm in diameter. We investigated and compared the sorption abilities of these two bead materials toward hexavalent-chromium (Cr) in water. The isotherm sorption curves were established using Langmuir and Freundlich models in the optimized conditions of pH, sorption time, solid/liquid ratio, and initial concentration of Cr. The FITR analysis was also carried out to show the differences in surface properties of these two beads. RESULTS: The optimized conditions for isotherm sorption of Cr on IMB/CMB were set at pH values of 2/2, sorption times of 90/300 min, and solid-liquid ratios of 10/20 mg/mL. The maximum sorption capacities calculated based on the Langmuir model were 19.60 and 6.24 for IMB and CMB, respectively. However, the adsorption kinetic of Cr on the beads fitted the Freundlich model with R values of 0.992 for IMB and 0.989 for CMB. The deduced Freundlich constant, 1/n, in the range of 0.2-0.8 indicated that these beads are good adsorption materials. In addition, structure analysis data revealed great differences in physical and chemical properties between IMB and CMB. Interestingly, FTIR analysis results showed strong signals of -OH (3295.35 cm) and -C=O (1608.63 cm) groups harboring on the IMB but not CMB. Moreover, loading of Cr on the IMB caused a shift of broad peaks from 3295.35 cm and 1608.63 cm to 3354.21 cm and 1597.06 cm, respectively, due to -OH and -C=O stretching. CONCLUSIONS Taken together, our study suggests that IMB has great potential as a bead material for the elimination of Cr from aqueous solutions and may be highly useful for water treatment applications.
Adsorption ; Chromium ; chemistry ; Kinetics ; Melanins ; chemistry ; Waste Disposal, Fluid ; methods ; Water Pollutants, Chemical ; chemistry ; Water Pollution, Chemical ; prevention & control ; Water Purification ; methods

In order to broaden the application area of the new nitrogen removal technology, a full-scale system for short-cut nitrification and anaerobic ammonium oxidation (Anammox) was investigated in the nitrogen removal from a strong-ammonium pharmaceutical wastewater. When the influent ammonium concentration was (430.40 ± 55.43) mg/L, ammonia removal efficiency was (81.75 ± 9.10)%. The short-cut nitrification and Anammox system could successfully remove nitrogen from the pharmaceutical wastewater. The start-up of short-cut nitrification system took about 74 d and the nitrite accumulation efficiency was (52.11 ± 9.13)%, the two-step mode using synthetic wastewater and actual wastewater was suitable for the start-up of short-cut nitrification system. The start-up of Anammox system took about 145 d and the maximum volumetric nitrogen removal rate was 6.35 kg N/(m3·d), dozens of times higher than those for the conventional nitrification-denitrification process. The strategy achieving Anammox sludge by self-growth and biocatalyst addition was suitable for the start-up of Anammox system.
Ammonia ; chemistry ; Bioreactors ; Drug Industry ; Nitrification ; Nitrites ; chemistry ; Nitrogen ; chemistry ; Sewage ; microbiology ; Waste Disposal, Fluid ; methods ; Waste Water ; chemistry

The anaerobic granular sludge from an Internal Circulation (IC) reactor of a paper mill wastewater treatment plant were seeded in an Anammox upflow anaerobic sludge blanket reactor. After 185 days operation, the reactor was finally started up by increasing the influent ammonium and nitrite concentrations to 224 mg/L and 255 mg/L, respectively, with volumetric nitrogen removal rate increasing to 3.76 kg/(m3·d). The physicochemical characteristics of the cultivated Anammox granules were observed by scanning electron microscope, transmission electron microscope and Fourier Transform infrared spectroscopy (FTIR). Results suggested that during the start-up course, the granular sludge initially disintegrated and then re-aggregated. FTIR spectra results revealed that the Anammox granular sludge contained abundant functional groups, indicating that it may also possess good adsorption properties. The ecological structure of the granular sludge, analyzed by the metagenomic sequencing methods, suggested that the relative abundance of the dominant bacterial community in the seeding sludge, i.e., Proteobacteria, Firmicutes, Bacteroidetes, significantly reduced, while Planctomycetes which contains anaerobic ammonium oxidation bacteria remarkably increased from 1.59% to 23.24% in the Anammox granules.
Ammonia ; chemistry ; Bacteria ; Bioreactors ; Nitrogen ; chemistry ; Sewage ; microbiology ; Waste Disposal, Fluid ; methods ; Waste Water ; chemistry

In order to simultaneously remove carbon and nitrogen from organic-rich wastewater, we used an up-flow anaerobic sludge bed/blanket (UASB) reactor that was started up with anammox with high concentration of carbon and nitrogen by gradually raising the organic loading of influent. We optimized the removal of nitrogen and carbon when the chemical oxygen demand (COD) concentration varied from 172 to 620 mg/L. During the entire experiment, the ammonium and total nitrogen removal efficiency was higher than 85%, while the average COD removal efficiency was 56.6%. The high concentration of organic matter did not restrain the activity of anammox bacteria. Based on polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and tapping sequencing analyses, the Planctomycete, Proteobacteria, Chloroflexi, Chlorobi bacteria are detected in the UASB reactor, which indicated complex removal pathway of carbon and nitrogen coexisted in the reactor. However, a part of Planctomycete which referred to anammox bacteria could tolerate a high content of organic carbon, and it provided help for high performance of nitrogen removal in UASB reactor.
Ammonia ; chemistry ; Biological Oxygen Demand Analysis ; Bioreactors ; Carbon ; chemistry ; Nitrogen ; chemistry ; Sewage ; Waste Disposal, Fluid ; methods ; Waste Water ; chemistry

We studied the effects of the oxygen on partial nitrification in a membrane bioreactor (MBR), to find out critical dissolved oxygen (DO) concentrations for the optimal partial nitrification by monitoring the oxygen uptake rate (OUR) and oxygen supply rate (OSR). The nitrite accumulation occurred at a DO concentration of 1 mg/L, while the ratio of nitrite to ammonia in effluent was close to 1 at a DO concentration of 0.5 mg/L which was suitable to serve as the feed of an ANNAMOX system. When the mixed liquid suspended solids(MLSS) was 20 g/L in MBR, OUR and OSR were 19.86 mg O2/(L·s) and 0.369 mg O2/(L·s) respectively, indicating that the oxygen supply was the bottleneck of partial nitrification. "Low DO and high aeration rate" were suggested as a control strategy to further improve the efficiency of partial nitrification.
Ammonia ; chemistry ; Bioreactors ; Membranes, Artificial ; Nitrification ; Nitrites ; chemistry ; Oxygen ; chemistry ; Waste Disposal, Fluid ; methods

Anaerobic ammonium oxidation (ANAMMOX), as its essential advantages of high efficiency and low cost, is a promising novel biological nitrogen elimination process with attractive application prospects. Over the past two decades, many processes based on the ANAMMOX reaction have been continuously studied and applied to practical engineering, with the perspective of reaching 100 full-scale installations in operation worldwide by 2014. Our review summarizes various forms of ANAMMOX processes, including partial nitritation-ANAMMOX, completely autotrophic nitrogen removal over nitrite, oxygen limited autotrophic nitrification and denitrification, denitrifying ammonium oxidation, aerobic deammonification, simultaneous partial nitrification, ANAMMOX and denitrification, single-stage nitrogen removal using ANAMMOX and partial nitritation. We also compare the operating conditions for one-stage and two-stage processes and summarize the obstacles and countermeasures in engineering application of ANAMMOX systems, such as moving bed biofilm reactor, sequencing batch reactor and granular sludge reactor. Finally, we discuss the future research and application direction, which should focus on the optimization of operating conditions and applicability of the process to the actual wastewater, especially on automated control and the impact of special wastewater composition on process performance.
Ammonia ; chemistry ; Bioreactors ; Denitrification ; Nitrification ; Nitrites ; chemistry ; Nitrogen ; chemistry ; Oxygen ; chemistry ; Sewage ; chemistry ; Waste Disposal, Fluid ; methods ; Waste Water ; chemistry

We screened for laccase from a marine metagenomic library and obtained a bacterial laccase Lac15 and studied its decolorization ability. Using synthetic azo dyes and anthraquinonic dyes as substrates, we investigated the dye decolorization ability of recombinant Lac15 (rLac15). The purified rLac15 had better decolorization ability towards the azo dyes than the anthraquinonic dyes. When incubated at 45 degrees C and pH 8.5 for 1 h with methylsyringate as the mediator, 20 U/L of rLac15 could decolorize 95% of 100 micromol/L Acid Red 6B (AR-6B), 93% of Reactive Blue 194 (M-2GE), 76% of Reactive Brilliant Orange (K-7R) and 66% of Reactive Blue 171 (KE-R). The decolorization ability of rLac15 decreased with the dye concentration increasing. However, more than 80% of M-2GE and AR-6B were degraded even when the dye concentration was up to 200 micromol/L. At room temperature, rLac51 exhibited significant decolorization ability, with 96% of AR-6B, 86% of M-2GE, 66% of K-7R and 66% of KE-Rdegraded within 24 h at 25 degrees C. rLac15 has the potential of industrial applications.
Anthraquinones ; isolation & purification ; Azo Compounds ; isolation & purification ; Bacteria ; enzymology ; isolation & purification ; Biodegradation, Environmental ; Coloring Agents ; isolation & purification ; Escherichia coli ; genetics ; metabolism ; Laccase ; genetics ; metabolism ; Recombinant Proteins ; genetics ; metabolism ; Seawater ; microbiology ; Waste Disposal, Fluid ; methods ; Waste Water ; chemistry

Municipal wastewater is usually problematic for the environment. The process of oleaginous microalgal culture requires large amounts of nutrients and water. Therefore, we studied the feasibility of oleaginous microalgal culture of Scenedesmus dimorphus in bubbled column photobioreactor with municipal wastewater added with different nutrients. S. dimorphus could adapt municipal nutrient-rich wastewater by adding some nutrients as nitrogen, phosphorus, ferric ammonium citrate and trace elements, and the amounts of such nutrients have significant effects on cell growth, biomass yield and lipid accumulation. At optimum compositions of wastewater medium, the algal cell concentration could reach 8.0 g/L, higher than that of 5.0 g/L in standard BG11. Furthermore, S. dimorphus had strong capacity to absorb inorganic nitrogen and phosphorus from its culture water. There was almost no total nitrogen and phosphorus residues in culture medium after three or four days culturing when the adding mounts of nitrate and phosphate in wastewater medium were no more than 185.2 mg/L and 16.1 mg/L respectively under the experimental conditions. As a conclusion, it was feasible to cultivate oleaginous microalgae with municipal nutrient-rich wastewater, not only producing feedstock for algal biodiesel, but also removing inorganic nitrogen and phosphorus from wastewater.
Biofuels ; Cities ; Culture Techniques ; methods ; Lipids ; biosynthesis ; Microalgae ; metabolism ; Photobioreactors ; Scenedesmus ; growth & development ; metabolism ; Waste Disposal, Fluid ; methods ; Waste Products