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Needle-like SiC whiskers were synthesised by microwave heating using graphite sheets and tetraethoxysilane (TEOS) as raw materials. It was found that SiC powder could be synthesised at 1000?C for 10min, lower than that of samples made from a granular C source. Furthermore, the heating rate of the samples made with graphite sheets was higher than that of a granular C source. The main morphology of the SiC whiskers was needle-like, which appeared when samples were heated at 1200?C for 10min. Size of the SiC whiskers made with graphite sheets was more uniform than that of a granular C source, which was attributed to the 2D thermal effect. Moreover, the size and the amount of the SiC whiskers increased as the heating temperature increased from 1200 to 1400?C for 10min. The SiC whiskers were oxidised and decomposed into SiC particles when heated to 1500?C for 10min and only SiC particles existed when longer holding times were used.

The chemical modification of natural palm fibers with an alkali treatment and the silane coupling agent KH570 were studied to determine the superior mechanical performance and solid engineering app...

Dewatering of sludge is a key problem that must be solved in the sewage sludge disposal industry. In this study, a series of process optimization tests were conducted to learn how to improve sludge treatment. The optimum process of sludge leaching treatment was studied in a specially designed 100-L reactor system. Four factors were investigated and nine batches of bioleaching tests were run at three levels of these factors. Orthogonal experiments showed that the effect of sludge return ratio and aeration rate on the sludge moisture content was significant and hydraulic retention time (HRT) had a clear effect, but nutrient types had a reduced effect on the moisture content of sludge. The primary and secondary order of each factor is reflux ratio > aeration rate > HRT > nutrient type. Under the optimal process, three batches of sludge were processed and the moisture content of the filter press cake was reduced to less than 60%, the organic matter content reduced to below 5%, and the concentration of heavy metals (Cu, Zn, Pb, and Cr) was much lower than the agricultural standard limit, which is suitable for landscaping, composting, and incineration power generation and other resource applications.

In this study, the degradation performance of nutrients in zeolite trickling filter (ZTF) with different influent C/N ratios and aeration conditions was investigated. Microaeration was beneficial for enhancing NH4+-N removal performance. Due to the sufficient carbon source supply under a C/N ratio of 8, a high removal efficiency of NH4+-N and TN was simultaneously observed in ZTF. In addition, TN removal mainly occurred at the bottom, which might be explained by the sufficient nutrients available for bacteria to multiply in this zone. The abundant genera were Acinetobacter, Gemmobacter, Flavobacterium, and Pseudomonas, all of which are heterotrophic nitrification-aerobic denitrification (HNAD) bacteria. In addition, biofilm only slowed down the adsorption rate but did not significantly reduce the adsorption capacity of zeolite. Bio-zeolite had NH4+-N well adsorption capacity and bio-desorption capacity. Biological nitrogen removal performance was superior to physicochemical absorption of zeolite. The results suggested that the physicochemical of zeolite and biochemical reactions of microorganism coupling actions may be the main nitrogen transformation pathway in ZTF. Our research provides a reference for further understanding the nitrogen removal mechanism of zeolite bioreactors.

In this study, we isolated two bacterial strains, P2 (Pseudomonas geniculata ATCC 19374, P. geniculata ATCC 19374) and B1 (Bacillus cereus EC3, B. cereus EC3) from pig farm soil, which were mixed to construct a novel bacterial mixture (P2:B1 = 1:1). We studied the heterotrophic nitrification capablity and growth characteristics of bacterial mixture in heterotrophic nitrification medium (HNM). And the factors affecting the nitrogen removal of the bacterial mixture such as C/N ratio, NH4+-N load and inoculation size of the bacterial mixture were investigated in this study. Furthermore, we used the bacterial mixture to treat livestock wastewater to remove NH4+-N, TN and COD. The results showed that the optimal C/N ratio and inoculation size for the bacterial mixture were 12 and 5%, respectively. It is worth to mention that the bacterial mixture shows excellent NH4+-N removal ability under low C/N ratio, indicating that the bacterial mixture had the potential to be applied to wastewater with C/N lower than 8. When the initial NH4+-N concentration was 500 mg/L, the NH4+-N removal efficiency exceeded 90% with a 5% inoculation size of the bacterial mixture after 72 h. When the single bacteria and bacterial mixture were employed to treat livestock wastewater, the removal efficiencies of bacterial mixture on NH4+-N, TN and COD within 72 h were 70.06%, 58.12% and 81.48%, respectively, which were higher than that of single bacteria. The bacterial mixture has potential application value in enhancing the ability of reactors and constructed wetlands to remove pollutants from livestock wastewater and developing a novel and efficient biological nitrogen removal technology. Our current research provides a research basis for the application of the bacterial mixture in the future.

The environmental problems related to rural domestic sewage treatment are becoming increasingly serious, and society is also concerned about them. A baffled vertical flow constructed wetland (BVFCW) is a good choice for cleaning wastewater. Herein, a drinking-water treatment sludge-BVFCW (D-BVFCW) parallel with ceramsite-BVFCW (C-BVFCW) planted with Oenanthe javanica (O. javanica) to treat rural domestic sewage was investigated, aiming to compare nitrogen and phosphorus removal efficiency in different BVFCWs. A removal of 23.9% NH4+-N, 24.6% total nitrogen (TN) and 76.7% total phosphorus (TP) occurred simultaneously in the D-BVFCW; 56.4% NH4+-N, 60.8% TN and 55.2% TP respectively in the C-BVFCW. The root and plant height increased by an average of 7.9 cm and 8.3 cm, respectively, in the D-BVFCW, and by 0.7 cm and 1.1 cm, respectively, in the C-BVFCW. These results demonstrate that the D-BVFCW and C-BVFCW have different effects on the removal of N and P. The D-BVFCW mainly removed P, while C-BVFCW mainly removed N.

A heterotrophic nitrifying bacterium was isolated from the activated sludge and identified as Pseudomonas stutzeri GEP-01. Strain GEP-01 exhibited an efficient heterotrophic nitrification capability and a high nitrogen utilization rate, 48 mg/L NH4+-N was removed after culturing for 24 h without NO2−-N or NO3−-N accumulation, and 64.7% of the NH4+-N was removed by heterotrophic nitrification. Single-factor experiments indicated that factors such as the carbon source, temperature, NH4+-N load, and inoculum size had significant effects on the ammonium removal efficiency of strain GEP-01. The preferred conditions for heterotrophic nitrification were sodium citrate, 30 °C, 40 mg/L NH4+-N, and 5% inoculum size. When the initial NH4+-N amounts were 100, 200, 500 and 1000 mg/L, the removal rates were approximately 100%, 93%, 90.4%, and 78.9%, respectively, and higher ammonium concentrations require longer culture time. Nitrogen balance demonstrated that 40% of the initial nitrogen was lost, which was probably removed in the form of gas products under optimum culture conditions, and 36.3% of NH4+-N was converted to biomass. When incubated (adding a small amount of sodium citrate as carbon source and no carbon source) in swine wastewater containing 835 mg/L of ammonium, the removal ratio reached 56.3% and 24.8%. Strain GEP-01 has potential applications in the treatment of ammonium-rich wastewater.

The novel iron-based reductive particles, functionalized with amino and carboxylic functional groups, were synthesized to remove Cr(VI) and Cd(II) ions from aqueous solutions. The morphological structure and surface functional groups of new composites were characterized with SEM, XRD, FTIR, BET, and other techniques. The influence of pH, initial concentration, adsorbent dosing, and temperature on removal efficiencies were explored by batch experiments. The adsorption capacity of Cr(VI) and Cd(II) increased by 159.95% and 76.60%, respectively, compared with Fe

In this study, an artificial wetland filler matrix capable of effectively fixing phosphorus was prepared using a non-combustion process to save energy. To evaluate the adsorption performance of this filler, adsorption experiments were performed and the phosphorus adsorption mechanism characterization was studied. An alkaline environment was found to be conducive to the increase of adsorption capacity, but excessive alkalinity was not conducive to adsorption. Static adsorption experiments showed that the phosphorus removal rate could reach 95% in the simulated phosphorus-containing wastewater after adsorption completion. The adsorption process is closely simulated by the pseudo-second-kinetic adsorption model. The isothermal adsorption experiment data were consistent with the Langmuir and the Freundlich adsorption isotherms. The characterization results showed a large number of micropores and adsorption binding sites inside and on the surface of the filler. Speciation analysis on the adsorbed phosphorus revealed that chemisorption by calcium in this filler was the dominant adsorption mechanism. The research results of this study provide the basis and reference for the development of high-efficiency phosphorus removal filler in constructed wetlands.

A composite material of sodium dodecyl benzene sulfonate- (SDBS-) modified maifanite and anhydride-modified Fe@SiO2@PEI (PEI) was used as an adsorbent for the removal of hexavalent chromium (Cr(VI)) and bivalent cadmium (Cd(II)) from groundwater by using column experiments and simulated PRB test. In this study, the optimum proportion of SDBS-modified maifanite and anhydride-modified Fe@SiO2@PEI was 5 : 1. In the column experiments, it was found that the penetration time increased with the increase of the initial concentrations (30, 60, and 90 mg/L) and the decrease of the flow rates (5.45, 10.9, and 16.35 mL/min) at an influent pH of 6.5 ± 0.3 . It was also obtained that the removal rates of Cr(VI) and Cd(ІІ) reached 99.93% and 99.79% at an initial Cr(VI) and Cd(ІІ) concentration of 30 mg/L with the flow rate of 10.9 mL/min, respectively, at 6 h. Furthermore, excellent removal effectiveness of Cr(VI) and Cd(ІІ) (85.94% and 83.45%, respectively) was still achieved in simulated PRB test at a flow rate of 5.45 mL/min with the heavy metal solution concentration of 5.0 ± 0.5 mg/L (Cr(VI) and Cd(II) concentration were, respectively, 5.0 ± 0 . 5 mg/L); and the adsorbent had not completely failed by the end of the trial. Yoon-Nelson model was successfully applied to predict the breakthrough curves for the assessment of composite material heavy metal removal performance and was in good agreement with the experimental data of the heavy metal removal efficiency. The strong removal ability of the adsorbent could be attributed to the fact that maifanite with a large diameter can provide support and increase the permeability coefficient and porosity and that zero-valent iron (ZVI) can convert Cr(VI) to Cr(III) and improve the adsorption capacity of maifanite. The obtained results suggested that the novel PRB fillers have great significance for preventing and controlling Cr(VI)/Cd(ІІ)-contaminated groundwater.

As an inevitable industrial by-product, polyaluminum chloride residue (PACR) will cause serious harm to the environment if directly buried and dumped. The aim of this paper was searched a new economical, environmental, and practical way of utilization for PACR. In this paper, a novel non-burning PACR compound filler was made from mainly PACR. The prepared compound filler has excellent physical properties and phosphate adsorption efficiency of up to 99.9%. Static adsorption experiments showed that the adsorption process of phosphorus by the compound filler conformed to the pseudo-second-order kinetic model and intra-particle diffusion model. Langmuir and Freundlich isotherm models described the phosphorus adsorption process well, and the maximum phosphate adsorption capacity arrived at 42.55 mg/g. The phosphate adsorption by the compound filler is a spontaneous endothermic process. The main mechanisms are ligand exchange and Lewis acid-base interactions; calcium and aluminum play important roles in the adsorption of phosphorus by the compound filler. Dynamic column experiments showed that as much as 90% of the phosphorus removal by compound filler, and the phosphorus concentration decreased from 1 to ~0.1mg/L. The results provide a new waste resource utilization method for PACR and show the good application potential of prepared compound filler in constructed wetlands.

The removal efficiency of contaminants in large-scale integrated vertical-flow constructed wetland (IVCW) and vertical-flow constructed wetland (VCW) for wastewater treatment plant (WWTP) tail-water was evaluated, and the microbial community was also investigated in this study. The results for 14 months study period indicated that 40.05% chemical oxygen demand (COD), 45.47% ammonia nitrogen (NH4+-N), 62.55% total phosphorus (TP), 55.53% total nitrogen (TN) and 57.20% total suspended solids (TSS) average removal efficiencies were achieved in the IVCW. There was a poor performance of TN removal in the VCW, with an average removal efficiency of 38.13%. There was no significant seasonal difference in TP removal, and a strong positive correlation between influent TP load and removed load. The high-throughput sequencing analysis revealed that Proteobacteria, Planctomycetes, Bacteroidetes and Acidobacteria were dominant in nature and wetland systems. The relative abundance of nitrifying bacteria, denitrifying bacteria and anammox bacteria confirmed that nitrification, denitrification and anammox may be the main processes for nitrogen removal in the IVCW.

In this study, the evergreen Iris sibirica plant was planted in a constructed wetland during the low-temperature season. Microcosmic subsurface vertical flow constructed wetlands (MVFCWs) were fed with simulated Cd polluted river water for three months under different Cd supply and the seasonal growth changes and Cd uptake ability of Iris sibirica were investigated. The treatment performance of MVFCWs and removal mechanisms and distribution of Cd were evaluated. The amount of rhizospheric microorganisms (bacteria, fungi, and actinomyces) and the enzyme activities (urease, sucrase, alkaline phosphatase and catalase) were also monitored. Iris sibirica proves to be a good accumulator of Cd with the highest accumulation of Cd in below-ground parts of 443.3 mg/kg when exposed to 8 mg/L Cd for three months. Under 1, 2, 4 and 8 mg/L Cd supply in low-temperature seasons, the MVFCWs exhibit average Cd removals of 94.9%, 97.4%, 95.6% and 96.2%, respectively. The predominant removal process of Cd in MVFCWs is substrate adsorption, which accounts for about 50% of Cd removal. Under the same Cd supply, the removal rates of Cd, amount of rhizospheric microbes and activities of enzymes in planted wetland are higher than those in unplanted wetland.

A symbiotic microalgal-bacterial system may be an optional technology for wastewater treatment. In this study, co-immobilized of a bacterium isolated from a municipal wastewater treatment plant ( Pseudomonas putida ) and a microalgae Chlorella vulgaris was used in the study of cell growth and nutrient removal during wastewater treatment under batch and continuous culture conditions. Under batch culture conditions, co-immobilization treatment significantly increased the cell density of C. vulgaris and P. putida compared with other treatments. The co-immobilized treatment also showed higher removal of ammonium, phosphate and COD than any single treatment, indicating that the nutrient uptake capability of C. vulgaris and P. Putida was mutually enhanced mutually. When tested in continuous mode, the treatment with a hydraulic retention time of 24 h at the organic load rate of 1159.2 mg COD L −1 d −1 was most appropriate for wastewater treatment.

Dewatering is recognized as an important method for treating sewage sludge before its disposal. In this paper, the nonionic surfactant Tween-20 was used for the first time to improve the dewaterability of sewage sludge during bioleaching. The specific resistance to filtration (SRF), water content (WC) and bound water content (BW) of the sludge cake were used to evaluate sludge dewaterability. The results indicated that a 1 g/L Tween-20 dosage with an inoculum ratio of 20%, a S0 dosage of 2 g/L and a FeSO4 · 7H2O dosage of 10 g/L provided oxidation efficiencies up to 100% for Fe2+ and 65.8% for S0. The SRF of the bioleached sludge decreased to as low as 0.81 × 1012 m/kg from the initial 12.6 × 1012 m/kg for raw sludge. A WC of 47.16% was achieved while 48.1% of BW was released during bioleaching. The results from this study indicate that adding of an appropriate amount of Tween-20 to sewage sludge is a promising method to enhance dewaterability by bioleaching.

Ammonia has been a major reason of macrophyte decline in the water environment, and ammonium ion toxicity should be seen as universal, even in species frequently labeled as "NH4+ specialists". To study the effects of high NH4+-N stress of ammonium ion nitrogen on tolerant submerged macrophytes and investigate the pathways of nitrogen assimilation in different organisms, Myriophyllum aquaticum was selected and treated with various concentrations of ammonium ions at different times. Increasing of ammonium concentration leads to an overall increase in incipient ammonia content in leaves and stems of plants. In middle and later stages, high concentrations of NH4+ ion nitrogen taken up by M. aquaticum decreased, whereas the content of NO3- ion nitrogen increased. Moreover, in M. aquaticum, the activities of the enzymes nitrate reductase, glutamine synthetase and asparagine synthetase changed remarkably in the process of alleviating NH4+ toxicity and deficiency. The results of the present study may support the studies on detoxification of high ammonium ion content in NH4+-tolerant submerged macrophytes and exploration of tissue-specific expression systems.

Enrichment of the hyperaccumulator bank is important for phytoremediation, and studying new hyperaccumulators has become a research hotspot. In this study, cadmium (Cd), the main representative factor of heavy-metal-polluted water, was the research object, and the Cd bioenrichment ability and tolerance of Myriophyllum aquaticum were studied for the first time. The experiment was conducted for 28 days by establishing experimental groups with different Cd concentrations (0, 10, 20, 40, 80, and 160 mg/L). The results show that M. aquaticum is a new Cd hyperaccumulator. There was no notable damage in the 40 mg/L Cd treatment group, and the Cd enrichment ability of M. aquaticum reached 17,970 ± 1020.01 mg/kg, while the bioconcentration factor (BCF) reached 449.25. At the same time, the antioxidant system (superoxide dismutase (SOD) and peroxidase (POD)) and proline (Pro) levels of M. aquaticum maintained normal plant physiology, but there were physiological anomalies in M. aquaticum at high concentrations and under long-term treatment. The results show that M. aquaticum has a high Cd bioenrichment ability and tolerance in water and can be used for phytoremediation of river water polluted by Cd.

Excess sludge contains a high amount of protein, which can be recovered to prepare protein foaming agents and other products with high added value. Enzymatic hydrolysis (EH) is a promising technology for the recovery of protein from excess sludge, and ultrasound has been identified as a potential method to assist in sludge disintegration. Ultrasonic pretreatment was combined with alkaline protease hydrolysis to extract protein from excess sludge produced by A2/O treatment (S1) and an oxidation ditch treatment (S2), and the extraction effects and changes in sludge dewatering performance were studied. The effects of the six factors ultrasonic power density, ultrasonication time, enzyme dose, pH, hydrolysis temperature and hydrolysis time were analyzed. The results showed that the ultrasound-enhanced enzymatic method could effectively extract sludge protein. Although the extraction efficiencies for the different municipal sludges were different, their extraction conditions were relatively similar. Considering the protein extraction rate and sludge dewatering performance, the selected extraction conditions were as follows: ultrasonic power density, 1 W/mL; ultrasonication time, 20 min; enzyme dose, 3500 U/g; pH 11; hydrolysis temperature, 60 °C; and hydrolysis time, 3 h. Under these conditions, the protein extraction rate (Rp) of S1 and S2 reached 55.9% and 52.3%, respectively. Moreover, the improvement in sludge dewatering performance (Dw) of S1 and S2 was 49.5% and 52.4%, respectively. Comparison of the protein, polypeptide, and amino acid contents obtained from ultrasound-assisted enzymatic hydrolysis (UEH), EH, and ultrasonic hydrolysis (UH) further demonstrated the beneficial effect of ultrasound application on enzymatic hydrolysis.

Three submerged macrophytes, Ceratophyllum demersum (CD), Myriophyllum spicatum (MS) and Myriophyllum aquaticum (MA), were treated with various concentrations of ammonia for different lengths of time. Ammonium ions (NH4+) in the medium severely inhibited plant growth and led to a reduction in total chlorophyll (chl a and b) in CD and MS. The addition of ammonia significantly decreased the soluble protein content and increased the free amino acid content of CD and MS in treatments with high concentrations of NH4+, but MA showed no significant physiological response. The antioxidant enzyme system of MA was activated, which in turn reduced the peroxidation level in the plant and maintained the plant’s normal physiological activities when the ammonia nitrogen in the culture fluid increased. The study continued to use higher concentrations (25, 50, 100, 200 and 400 mg/L) of ammonium nitrogen to treat and observe the peroxidation level and corresponding enzyme production for this species of MA in vivo to explore its resistance mechanism. The experiments show that MA can normally live for a period of time in a high-ammonia environment of up to 100 mg/L. The results of the present study will assist in studies of the detoxification of high ammonium ion contents in submersed macrophytes and the selection of plants suitable for macrophyte recovery.

A series of Mn2O3 catalysts were prepared by different hydrothermal temperatures and employed to the catalytic oxidation of benzene due to their high activity. The Mn-120 sample with three-dimensional (3D) hierarchical cube-like morphology mainly exposed (2 1 1) crystal plane exhibited the best catalytic activity for the oxidation of benzene and achieved the benzene conversion of 90% at 248 °C. Meanwhile, the best catalytic performance of the Mn-120 sample was attributed to the most amounts of the Mn3+ species and surface-adsorbed oxygen. With the increase of Mn3+ species, the oxygen binding capacity of Mn-120 was reduced, which could increase its oxygen mobility. The abundant adsorbed oxygen species of Mn-120 could improve the replenishment capacity of lattice oxygen species, and the reaction pathway of catalytic oxidation of benzene over MnO2 obeyed the Mars-Van-Krevelen (MVK) mechanism.

The objective of the present study was to determine the effect of total ammonia N concentration and pH on N metabolism of Ceratophyllum demersum and to evaluate stress as a result of inorganic N enrichment in the water column on submerged macrophytes. Carefully controlled pH values distinguished between the effects of un-ionized NH3 and ionized NH4(+). The results showed that the most obvious consequence of ammonia addition was an overall increase in ammonia content and decrease in nitrate content in all tissues of fertilized plants. The activities of nitrate reductase and glutamine synthetase were inhibited by long-term ammonia addition. At the same time, ammonia addition significantly decreased soluble protein content and increased free amino acid content in all treatments. Another clear effect of ammonia addition was a decrease in carbon reserves. Therefore, the authors concluded that increased ammonia availability could affect plant survival and lead to a decline in C. demersum proliferation through a decrease in their carbon reserves. This interaction between N and C metabolism helps to explain changes in benthic vegetation as a result of steadily increasing coastal water eutrophication.

In this study, the tips of Myriophyllum aquaticum (M. aquaticum) plants were planted in open-top plastic bins and treated by simulated wastewater with various ammonium-N concentrations for three weeks. The contents of related carbohydrates and key enzyme activities of carbon metabolism were measured, and the mechanisms of carbon metabolism regulation of the ammonia tolerant plant M. aquaticum under different ammonium-N levels were investigated. The decrease in total nonstructural carbohydrates, soluble sugars, sucrose, fructose, reducing sugar and starch content of M. aquaticum were induced after treatment with ammonium-N during the entire stress process. This finding showed that M. aquaticum consumed a lot of carbohydrates to provide energy during the detoxification process of ammonia nitrogen. Moreover, ammonia-N treatment led to the increase in the activitives of invertase (INV) and sucrose synthase (SS), which contributed to breaking down more sucrose to provide substance and energy for plant cells. Meanwhile, the sucrose phosphate synthase (SPS) activity was also enhanced under stress of high concentrations of ammonium-N, especially on day 21. The result indicated that under high-concentration ammonium-N stress, SPS activity can be significantly stimulated by regulating carbon metabolism of M. aquaticum, thereby accumulating sucrose in the plant body. Taken together, M. aquaticum can regulate the transformation of related carbohydrates in vivo by highly efficient expression of INV, SPS and SS, and effectively regulate the osmotic potential, thereby delaying the toxicity of ammonia nitrogen and improving the resistance to stress. It is very important to study carbon metabolism under ammonia stress to understand the ammonia nitrogen tolerance mechanism of M. aquaticum.

With the increase of tap water demand and treatment volume, the by-product of the water supply plant-drinking water treatment sludge (DWTS) is increasing, and its final disposal urgently needs to be reasonably resolved. Therefore, the reuse of DWTS can not only solve the “waste” problem but also generate favorable economic benefits. This is the first study to use DWTS to prepare a regular, industrialized and efficient DWTS composite substrate (DWTSCS) for phosphorus removal in constructed wetlands by using DWTS as the main material and bentonite, zeolite and fly ash as the additive. The optimal weight ratio of DWTSCS was determined by combining orthogonal test and mixture design experiments: cement = 22.32%, DWTS = 51.62%, bentonite = 13.03%, zeolite = 4.34%, fly ash = 8.69%. The microstructure and phase analysis were performed using SEM and XRD. The static adsorption experiments showed that the adsorption behavior of DWTSCS to phosphorus conforms to a quasi-second-order kinetic model and the adsorption process can be simulated using Langmuir and Freundlich models. The maximum adsorption capacity of phosphorus by DWTSCS was calculated as 40 mg/g, and the adsorption of phosphorus with the DWTSCS was a spontaneous exothermic process. Under acidic conditions, it was favorable for DWTSCS to adsorbed phosphorus. The concentration of adsorbed phosphorus with the DWTSCS ranged from 0.5 mg/L to 0.2 mg/L. This research provides a basis for the application of DWTSCSs in constructed wetlands.

Bioleaching has been demonstrated to be an effective technology for the removal of heavy metals and sludge dewaterability. Since bacteria gain nutrients by diffusion of soluble compounds, the insolubility of elemental sulfur may slow the growth of bacteria. Thus, it is very important to find an energy substance quickly become available to Acidithiobacillus thiooxidans. This paper studies the improvement of sludge dewaterability and heavy metal removal with sodium thiosulfate as the source of energy for Acidithiobacillus thiooxidans. Through orthogonal experiments with specific resistance to filtration (SRF) as the target index, four factors (FeSO

A novel process for sewage sludge bioleaching by mixed Thiobacilli (Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans) using a 12-stage, 180 L working volume continuous plug-flow bioreactor, is presented. The objective of the present study was to assess the impact of some parameters on the sludge dewaterability and to improve the sludge dewaterability by optimization of these parameters. The parameters examined were sludge moisture content, nutrients dosage, aeration rate, and the number of reactors. The order of the influence of these factors on sludge dewaterability was found to be sludge moisture content > nutrients dosage > aeration rate > number of reactors. The optimized conditions were: sludge moisture content, 98.0%, nutrients dosage, 9 g/L, aeration rate, 8 m3/h, and 10 reactors. Confirmation experiments conducted under optimum conditions demonstrate the sludge dewaterability to be remarkably improved. After 2 days of bioleaching, the moisture of bioleached sludge cake was reduced to below 60%.

Due to the increasingly serious river pollution of heavy metals, especially cadmium (Cd), the Cd pollution issues have aroused more and more political and academic attentions. In this study, microcosmic subsurface vertical flow constructed wetlands (MVFCWs) were planted with Iris sibirica to treat simulated polluted river water with different concentrations of Cd. The objective of this study was to investigate the Cd removal capacity of I. sibirica , plant growth characteristics and plant uptake, in order to fill the blank in the research of I. sibirica purification mechanism of Cd polluted water and meet the needs of the actual constructed wetland project. The plants grew well under any Cd treatments over the study period. The maximum Cd content in belowground parts was 1669.4 mg/kg and in aboveground parts 12.8 mg/kg on a dry weight basis when exposed to 6 mg/L Cd for 50 days. The maximum bioconcentration factor (BCF) values for root and shoot tissues were 323.2 and 3.8 respectively, obtained for 3 mg/L Cd, which indicated that the plants can play an important role for removal of Cd through phytoextraction. The test results showed that the average removing rate of Cd from the wastewater could reach 91.8%. High removal efficiency in the study proved that wastewater polluted by Cd could be treated effectively using MVFCWs with I. sibirica plant.

In the present study, carefully controlled pH ranges (7 and 9) were used to distinguish between the effects of un-ionized NH3 and the NH4+ ion. The objective was to find the effect of different total ammonia nitrogen concentrations and pH values on the carbon metabolism of Ceratophyllum demersum. The authors investigated the effects of ammonia on the nonstructural carbohydrate content in shoots of C. demersum. Ammonia treatment decreased the contents of nonstructural carbohydrate, soluble sugar, sucrose, fructose, and starch in leaves. Meanwhile, increasing the pH value exacerbated the decline of the C. demersum nonstructural carbohydrate content. In addition, the activity of invertase was increased during the experiment. These results suggest that ammonia severely inhibits plant growth by disturbing nonstructural carbohydrate content. It has been suggested that ammonia has toxic effects on C. demersum and that the higher the pH in water, the more obvious the physiological responses that C. demersum exhibits. The results of the present study can provide some reference for studying the living conditions of submersed macrophytes under the stress of NH3. Environ Toxicol Chem 2015;34:843–849. © 2014 SETAC

Fluoride can either inhibit or enhance the growth of aquatic macrophytes, depending upon fluoride concentration and exposure time. To investigate fluoride toxicity, the submerged plant Hydrilla verticillata was treated with various concentrations of fluoride (F) (0, 10, 20, and 40 mg/L) for different lengths of time (7, 14, 21, and 28 days). At exposure to 10 mg/L F, the content of chlorophyll, protein, and carbohydrates content increased in leaves of H. verticillata, and the activity of guaiacol peroxidase (POD) and superoxide dismutase (SOD) slightly increased in plants compared with the control. When fluoride concentration increased to 20 mg/L, the toxic effect generated by fluoride led to a reduction of chlorophyll, protein, and carbohydrates in H. verticillata, but the activity of guaiacol peroxidase and SOD and the amount of ascorbic acid (AsA) and glutathione (GSH) were enhanced significantly. After exposure to fluoride at 40 mg/L for a long period, these physiological parameters showed a sharp decrease, and inactivation was observed in H. verticillata. These results suggested that a certain concentration of fluoride induced antioxidant response, and excess fluoride induced metabolism imbalance and oxidative damage in H. verticillata.

Aquatic plants easily wither and go into dormancy in winter when temperature is extremely low. Little is known about nitrogen and phosphorus uptake by plants and its role in removing nutrient in constructed wetlands (CWs). Investigating the performance of CWs planted with overwintering plants and selecting out which plants will support an effective CW over the winter period are important. In this study, microcosmic subsurface vertical flow constructed wetlands (MVFCWs) were planted with Iris sibirica for treating simulated polluted river water and evaluated for nutrient removal, plant growth characteristics and plant nutrient uptake under different nutrient concentrations. Treatment performances indicated that the highest average total nitrogen (TN), ammonia nitrogen (NH 4 + -N), total phosphorus (TP), soluble reactive phosphorus (SRP), and chemical oxygen demand (COD) removal efficiencies were obtained in MVFCW units with medium nutrient (10–16 mg/L TN, 7–10 mg/L NH 4 + -N, 1.8–2.5 mg/L TP, and 80–120 mg/L COD); the removal efficiencies were 45.8 ± 15.4%, 62.1 ± 8.8%, 57.7 ± 8.3%, 59.1 ± 10.1%, and 39.3 ± 12.1%, respectively. MVFCW units with low nutrient (5–8 mg/L TN, 3.5–5 mg/L NH 4 + -N, 0.9–1.25 mg/L TP, and 40–60 mg/L COD) exhibited the worst treatment effects. Plant nutrient uptake in the different MVFCW units ranged from 19.86% to 50.19% of N removal and from 13.19% to 22.32% of P removal at the end of experiment. The N and P accumulation ability of the below-ground part of plants was better than that of the above-ground part. The I. sibirica plants demonstrated high nutrient uptake in winter, and MVFCWs facilitated a certain degree of nutrient removal. Thus, I. sibirica can be considered an effective overwintering plant selection in CWs for restoring polluted river water and potentially be suitable for generalizing elsewhere, especially over the winter period.

The modified Mongolian scotch pine tree sawdust char (MMSC), fabricated from the natural Mongolian scotch pine tree sawdust char (MSC) using phosphoric acid-microwave method, was used as the F− adsorbent of aqueous solution. MMSC was prepared according to the optimized method as follows. MSC and 25% (vol) phosphoric acid (v/v = 1:4) were mixed in Bunsen beaker at 25°C for 24 h. The mixer was then radiated for 3 min (Radiation power 630 W), followed by filtration, generating the desired MMSC, which was washed with distilled water until the pH reached around 7.0, and then dried in an oven at 50°C till constant weight for further fabrication. No obvious difference of MMSC and MSC was observed in color. The adsorption capacity of MMSC reached 885 mg kg−1 for F− in high-fluoride resource water. The concentration was reduced to below the recommended value (1.5 mg L−1) from the concentration of 20 mg L−1 when the high dosage of MMSC was used. Compared with MSC, the MMSC can be used as potential F− adsorb...

The objective of this study was to investigate the effects of the main parameters on phosphate removal from continuous phosphate-contaminated water by electrocoagulation based on removal rate and system energy consumption. In the experiment, aluminum and iron plates were used as alternate electrodes and experiment parameters included initial phosphate concentration, current density, flow rate, and initial pH. The results indicated that increases of initial phosphate concentration and flow rate had reduced removal rate and energy consumption. Removal rate and system energy consumption increased by increasing current density. The maximum removal efficiency of 90% was obtained at flow rate 40 mL/min. The minimum energy consumption was 0.165 kWh/m3 at flow rate 100 mL/min. With the increase of initial pH from 4 to 8, the removal rate increased and energy consumption decreased. When the pH was above 8, the removal rate decreased and energy consumption increased. The maximum removal efficiency of 92% and minimu...

In order to explore a new treatment process applying to decentralized domestic sewage treatment, and enhance removal of total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD), a novel system integrating anoxic-anaerobic-aerobic (reversed A2O) and electro-coagulation (EC) process was studied, and complex biological media (CMB) was used as suspended carrier for biofilm development. In this work, TN, TP and COD removal performance were investigated with consideration of three major factors, hydraulic retention time (HRT), organic loading rate (OLR) and sludge recycle ratio (SRR). Results showed that (1) The optimum HRT was between 8 and 12 h. The removal efficiencies of TN, TP and COD were about 68%, 95% and 95%, respectively. (2) With the increase of OLR, the removal efficiency of TN increased slowly. But it increased first and then declined for COD and TP removal. Their maximum were attained when OLR was 1.8 g(COD)/(L d), and they were 96% and 93%, respectively. (3) The optimum SRR was 75%. The COD, TN and TP removal efficiencies were about 95%, 72% and 98%, respectively. In this system, the maximum TN and COD removal were achieved in anoxic tank, but it was achieved in aerobic tank for TP removal. The EC bed enhanced the effluent quality, especially the efficiency in advanced P removal. From these results, it was concluded that the new process could be a reliable option for providing excellent effluent quality.

The objective of this study was to enhance removal of chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) from domestic sewage in a sequencing batch reactor with added new materials. A modified anoxic/anaerobic/oxic (MAAO) process, integrating a micro-electrolysis (ME) bed in an anoxic tank, and complex biological media (CBM) in anoxic, anaerobic and oxic tanks to treat domestic sewage, and their performances were investigated. The MAAO system was operated at controlled hydraulic retention time (HRT) of 8 h and mixed liquor recirculation (MLR) at 75%. The results showed that the MAAO system could effectively remove COD, TN and TP with average rates of 93%, 80% and 94%, respectively, in March, and 94%, 76% and 91%, respectively, in August. In this system, TP was primarily removed from the anoxic tank regardless of the operational conditions; removal contribution ratios to TP of the anoxic tank reached 56% both in March and August, indicating that the ME bed can effectively enhance phosphorus removal. TN was primarily removed from the anoxic and anaerobic tanks; removal contribution ratios to TN of anoxic and anaerobic tanks reached 36-38% and 37-38%, respectively. The oxic tank had the highest share of COD removal (56% both in March and August) in the removal of phosphorus. The outflow concentrations of COD, TN and TP were 3-46, 7-14 and 0.3-0.5 mg/L, respectively, in March, and 26-49, 9-15 and 0.04-0.1 mg/L, respectively, in August. COD and TN removal performances indicated that the innovative materials of the ME bed and CBM can effectively enhance COD and TN removal.

Phase-pure nano-LiFePO4 was successfully fabricated under hydrothermal condition at different temperatures. We found that the obtained particle morphologies and sizes were temperature-dependent. Compared with other samples, the as-received LiFePO4 synthesized at 200°C for 3 h presented monodisperse state. Moreover, this product possessed excellent electrochemical performance and cycling stability after annealing at 700°C for 1 h with glucose as carbon source.

Single-phased nanosized LiFePO4 with thinner thickness along [010] crystallographic direction were successfully fabricated under solvothermal condition by using glycerol as co-solvent. The as-obtained product with thinner thickness is beneficial for fast migration of Li ions in the olivine-structured LiFePO4, hence exhibiting excellent electrochemical performance.

In order to provide a reference for the ecological restoration of polluted river and technical guidance for Jialu River floodplain constructed wetlands (CWs) renovation scheme, a demonstration project that two-stage baffled surface-flow constructed wetland (BSFCW) with a total area of 7400 m 2 , hydraulic loading of 14 cm/d and substrate of high viscosity silt loam was constructed along the Jialu River floodplain in Zhengzhou city of China. Its plants configuration was a combination of emerging plants + submerged plants + floating plants + emerging plants, and it had been operated for two years. Treatment effects indicated that the mean removal rates of total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH 4 + -N), chemical oxygen demand (COD cr ), suspended solid (SS) were about 75%, 78%, 85%, 40%, 80% respectively in summer and autumn. While it decreased in winter, the average removal rates were respectively about 30%, 73%, 45%, 25%, 78%. Analysis of the results showed that the BSFCW system was performed steadily and great potential to improve the water quality, in addition, it was easy in maintenance and simpler in operation, thus, it could be considered an effective treatment option for restoring polluted river and potentially be suitable for generalizing elsewhere. This paper could also hopefully help researchers to gain a broader perspective on processes evolving in the BSFCW in future polluted river ecological restoration.

The current article investigated the effects of ammonia nitrogen concentration and pH on peroxidation damage and antioxidative capability of Ceratophyllum demersum. The pH ranges (7 and 9) were carefully controlled to distinguish between the effects of unionized ammonia (NH3) and ionized ammonia ( ). The addition of ammonia significantly decreased chlorophyll a content. Peroxidase and superoxide dismutase activities as well as glutathione content under high ammonia conditions (10 mg N/L) significantly increased at pH 7 but were no different or reduced at pH 9. Catalase activity as well as ascorbic acid and malondialdehyde contents significantly increased under all ammonia treatments at pH 7 and 9. C. demersum suffered from stress at pH 9 under high ammonia conditions. Higher pH in water may induce C. demersum to exhibit more severe physiological responses.

The increasingly serious ecological security issues of lake systems have aroused increasing political and academic attention. Based on research regarding ecological security domestically and abroad, this study brings forth the concept of lake ecological security. A new selection-system-weight-standardization-standards-calculation framework for ecological security at the watershed scale was proposed, and it integrates several existing methods, including the “driver-pressure-state-impact-response” framework, the analytic hierarchy process and the fuzzy assessment model, to systematize the lake ecology security assessment process and meet the needs of watershed management. This systematic framework was applied to comprehensively assess the ecological security of an interior lake basin in China from 2005 to 2013, using the year 2000 as a comparative reference. The results illustrated that the ecological security index (ESI) values in 2000 and 2013 were 0.58 at the “common” level and 0.61 at the “good” level, respectively, in the study area. From 2005 to 2012, the ESI values were stable, mostly between 0.4 and 0.6 at the “common” level with the exception of 2007 at the “poor” level. Then, with the result of the individual assessment in 2000 was used as the reference level, we found that the response was better than the reference level, the state was nearly equal to the reference level, and the driving force was close to the reference level; however, the pressure and impact were relatively not ideal. These results can be used as the basis for lake eco-environmental management.