Initial Phosphorus Concentration Research Articles

Migration and transformation of phosphorus in sediment-water system in storm and sewage sewers.

During rainfall, phosphorus in drainage pipe sediments is easily washed and released. This study investigates the migration of phosphorus between sediments and water in storm and sewage sewers, the microbial community structure in sediments, and phosphorus transformation under biological action. Results showed that when the initial concentration of phosphorus in stormwater (water column) in storm sewer was high (1-2mg/L), the total phosphorus (TP) level decreased in the water column but increased in the sediments, showing a trend of phosphorus migration from the water column to the sediments. Moreover, under high concentration (2mg/L), the TP level decreased by 83.19% in the water column within 210min, which was greater than 64.9% of the medium-concentration stormwater (1mg/L). In sewage sewer, when the initial concentration of phosphorus in sewage was about 2mg/L, phosphorus would migrate from the sediments and interstitial water to the water column because of the high concentration of phosphorus in the sediments. In addition, the variation in phosphorus was caused not only by concentration gradient but also by microbial communities. Phosphate accumulating organisms, such as Alphaproteobacteria, Gammaproteobacteria, and Actinobacteria, existed in the storm and sewage sewers, which could ingest dissolved reactive phosphorus in the water column and interstitial water and convert it into phosphorus in organisms. In storm sewers, Acidimicrobiia transferred phosphorus from the water column and interstitial water to the sediments through biochemical reactions and physical adsorption. In sewage sewers, organic acids secreted by Clostridia, Bacteroidia, and Bacilli could dissolve some insoluble phosphorus in sediments and then transfer them to interstitial water.

Dynamic Adsorption Characteristics of Phosphorus Using MBCQ

Biochar is a new type of adsorption material with excellent performance, but it has some problems, such as light texture, poor sedimentation, and difficult recovery, which limits its practical application. In this study, biochar microspheres (MBCQ) were prepared by the sol–gel method using powdery biochar from Hydrocotyle vulgaris as raw material and sodium alginate as a granular carrier. Experiments were performed to investigate the dynamic adsorption characteristics of phosphorus by MBCQ in the adsorption column and the influences of particle size, initial phosphorus concentration, flow rate, and column height on the breakthrough curve. The results showed that the static adsorption properties of different particles varied and that 3-millimeter particles were optimal. The breakthrough time positively correlated with column height and negatively correlated with initial phosphorus concentration, flow rate, and particle size. Flow velocity significantly impacted breakthrough time and length of mass transfer. The bed depth/service time model accurately predicted the relationship between breakthrough times and column heights. When ct/c0 = 0.6, the average relative deviation between predicted and measured values was the lowest. The Thomas model described the MBCQ adsorption process of Ph (R2 > 0.95), which indicated that diffusion in MBCQ adsorption was not a rate-limiting step.

Calcium-modified granular attapulgite removed phosphorus from synthetic wastewater containing low-strength phosphorus

Traditional biological processes combined with chemical precipitation methods can effectively reduce phosphate concentration in wastewater. However, discharge standards required additional advanced treatment technologies, and the removal of low phosphorus concentration is complicated and expensive. This study proposes application of a simple and recyclable adsorbent to remove low-concentration phosphorus from water. The removal efficiency of phosphorus from low-strength synthetic wastewater was investigated and the adsorption mechanism was analyzed. When the initial phosphorus concentration was 2.0 mg/L, the phosphorus adsorption capacity of Ca-GAT increased to 0.891 mg/g from 0.074 mg/g for GAT at 298 K and pH of 7. Phosphorus adsorption on Ca-GAT performs well when the solution pH is in the range of 5–10, and it is not conducive to the adsorption reaction when the solution pH exceeds 11. The competing anions (such as NO3−, SO42−, HCO3− and F−) existed, Ca-GAT still performed better in removing phosphorus. Then, the saturated absorbents could be effectively regenerated with a 0.5 mos/L NaOH solution, while desorption efficiency was reduced from 97.11% to 33.06% after fifth regeneration cycle. Finally, Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the Ca2+ content on the Ca-GAT surface played an important role in capturing phosphate ions from wastewater. Phosphorus was mainly removed via the formation of Ca-phosphorus precipitation. To some extent, ligand exchanges of CO32− and OH- with HPO42− and H2PO4− were also beneficial for phosphorus removal. The present work shows that attapulgite has sustainable and beneficial potential in the removal of low-strength phosphorous in wastewater, and the phosphorus loaded adsorbent can be used in the agriculture as slow-release fertilizer.

The mechanism study of attached microalgae cultivation based on reverse osmosis concentrated water (WROC)

Reverse osmosis membrane is widely applied in advanced wastewater treatment. Along with the production of clean water, 30%∼50% reverse osmosis concentrated water (WROC), containing massive nitrogen and phosphorus, is also produced. WROC would bring ecological risk if discharged into the natural water body. Hence, attached microalgae cultivation based on WROC was proposed to recovery the nutrients from water in this study. The results showed that the initial concentrations of nitrogen and phosphorus in WROC (TN≈50 mg/L, TP≈10 mg/L) were not too high to inhibit attached microalgae growth. Among the complex chemicals in WROC, non-oxidizing bacteriostatic agent had the worst impact on the growth of microalgae with an 8-day inhibition ratio of 25%. Compared with the microalgae cultured by nutrient medium, the lipid and protein contents in attached microalgae cultured by WROC were relatively high and stable during the whole cultivation period. Seen from the micro level, there was no obvious resistance to the transfer of TN and TP in the microalgae biofilm. However, the photosynthetic rate of microalgae in the biofilm decreases along with the depth. In conclusion, uneven light distribution in biofilm and the non-oxidizing bacteriostatic agent in WROC were the main resistance to the growth of attached cultured microalgae, which should be optimized or per-treated.

Thermal annealing ambiance effect on phosphorus passivation and reactivation mechanisms in silicon-based Schottky diodes hydrogenated by MW-ECR plasma

The main objective of this work is to investigate the effect of thermal annealing in forming gas atmosphere on the mechanism of deactivation and reactivation of phosphorus in silicon-based Schottky diodes. Firstly, the microwave plasma power, initial phosphorus concentration in the samples and hydrogen flux were fixed as 650 W, 1015 cm–3, and 30 sccm, respectively, to investigate the behavior of different working parameters of diodes, specifically the duration and temperature of hydrogenation. Secondly, few samples hydrogenated at 400 °C for 1 h were annealed under the forming gas (10% H2 + 90% N2) within the temperature range from 100 to 700 °C for 1 h. The profiles of active phosphorus concentration were monitored by evaluating the change in concentration of phosphorus after hydrogenation or thermal annealing in a forming gas environment through capacitance-voltage measurements. The obtained results depict the temperature and duration of hydrogenation, which ultimately reveals the complex behavior of phosphorous and hydrogen in silicon. However, the phosphorus passivation rate is homogeneous over all the depths measured at 400 °C. The thermal annealing in a forming gas indicates the increase in passivation rate of phosphorus as a function of annealing temperature, till the passivation rate attains saturation in the sample annealed at 400 °C. At higher temperatures, a decrease in the concentration of phosphorous-hydrogen complexes is observed due to the dissociation of these complexes and reactivation of phosphorus under thermal effect.

An insight into the phosphorus distribution in extracellular and intracellular cell of Chlorella vulgaris under mixotrophic cultivation

Phosphorus is non-substitutable and geographically restricted resource in our environment as an essential nutrient for all life. Microalgae have great performance in phosphorus recovery. However, there are few studies on the dynamics of how phosphorus is taken up and distributed in microalgae. The aim of this study was to investigate the effects of different initial ortho-phosphate concentrations (0, 2, 4, 6, 8, 10 mg P/L) on the phosphorus distribution in soluble microbial products, extracellular polymeric substances and intracellular polymeric substances of Chlorella vulgaris under mixotrophic cultivation. The results showed that the initial phosphorus concentration affected the distribution of phosphorus. And the absorption rate of phosphorus would decrease if the phosphorus concentrations were more than 6 mg P/L. Inorganic phosphate is mainly absorbed and stored in extracellular polymeric substances. Excessive phosphorus promoted the transformation of inorganic phosphate in extracellular polymeric substances to organic phosphate in intracellular polymeric substances. Results are beneficial to the treatment of phosphorus-containing wastewater and subsequent utilization of phosphorus-based fertilizer.

Removal of phosphorus from aqueous solution using multi-wall carbon nanotube (MWCNT) as adsorbent: Kinetics and isotherms

The discharge of phosphorus from urban and industrial wastewater into water bodies causes eutrophication and algae blooms. What it seems essential is that treatment of such wastewater before its discharge into the environment. The main purpose of this study is to investigate phosphorus adsorption from aqueous solutions by using multi-walled carbon nanotubes (MWCNT) as the adsorbent. In experiments, Scanning Electron Microscope (SEM) is applied for characterizing the adsorbent. The impact of variables effecting the adsorption of phosphorus such as amount of adsorbent, the initial concentration of phosphorus and pH are studied at room temperatures. Furthermore, for assessing data, isotherm and kinetic models are considered. The results indicate that the elevation of pH and the amount of adsorbent enhance the efficiency of phosphorus adsorption, while an increase in phosphorus concentration decrease adsorption. The results also show that phosphorus adsorption follows the Freundlich isotherm model. To determine the adsorption kinetics, in traparticle diffusion, pseudo-first-order and pseudo-second-order kinetics are widely used. Finding results indicate that a good compliance with a pseudo-second-orderkinetic model. Finally, results demonstrate that thatmulti-walled carbon nanotubes (MWCNT) is good adsorbent for the elimination of phosphorus from aqueous solutions in a relatively short time, owing to their highcapacity of adsorption.

Preparation and application of an innovative integrated agent product for phosphorus control and oxygen release

Abstract In this study, an oxygen-releasing and phosphorus-controlling agent (ORPC) consisting of calcium peroxide (CaO2), bentonite, cement, stearic acid (SA), citric acid (CA) and fine sand was synthesized successfully and used to purify phosphorus-rich river water. The removal of phosphorus using ORPC was studied in actual river water and the results found that over 75.0% phosphorus was removed by adding ORPC at 30 mL h−1 flow rate in initial phosphorus concentrations of 0.76 mg L−1. The ORPC was further used to evaluate the changes of aluminum phosphate (Al-P), ferric phosphate (Fe-P) and calcium phosphate (Ca-P) in sediment. Fe-P, Al-P, and Ca-P in the sediment increased from 0.14, 0.196, and 1.63 mg g−1 to 0.159, 0.372, and 2.74 mg g−1 respectively within 28 days, indicating that the total dissolved phosphorus in the overlying water could be adsorbed by ORPC and further transformed into Al-P, Ca-P, and Fe-P in the sediment, thus inhibiting the release of endogenous phosphorus in sediment to the water. In addition, the performance of ORPC with various contents of SA and CaO2 was investigated. In summary, ORPC can be employed to adsorb phosphorus in water and prevent phosphorus release from sediment, therefore achieving the purpose of controlling phosphorus and maintaining DO at a reasonable level.

In-situ remediation of nitrogen and phosphorus of beverage industry by potential strains Bacillus sp. (BK1) and Aspergillus sp. (BK2)

The bioremediation of beverage (treated and untreated) effluent was investigated in the current study by using the potential strains of Bacillus sp. (BK1) and Aspergillus sp. (BK2). Effluent was collected from the beverage industry (initial concentration of nitrogen were 3200 ± 0.5 mg/L and 4400 ± 0.6 mg/L whereas phosphorus were 4400 ± 2 mg/L and 2600 ± 1 mg/L in treated and untreated effluent correspondingly). Further, the BK1 and BK2 exhibited high removal competence after 1 week of incubation; BK1 removed phosphorus 99.95 ± 0.7% and BK2 95.69 ± 1% in treated effluent while nitrogen removed about 99.90 ± 0.4% by BK1 and 81.25 ± 0.8% by BK2 (initial concentration of phosphorus 4400 ± 2 mg/L and nitrogen 3200 ± 0.5 mg/L). Next, in the untreated effluent BK1 removed 99.81 ± 1% and BK2 99.85 ± 0.8% of phosphorus while removed nitrogen 99.93 ± 0.5% by BK1 and 99.95 ± 1.2% by BK2 correspondingly, (initial concentration of phosphorus 2600 ± 1 mg/L and nitrogen 4400 ± 0.6 mg/L). The physiochemical composition of sample such as pH, total carbohydrates, total proteins, total solids of treated and untreated effluent were also analysed before and after treatment of both the samples. BK1 and BK2 increased the pH by 8.94 ± 0.3 and 9.5 ± 0.4 correspondingly in treated effluent whereas 6.34 ± 0.5 and 7.5 ± 0.2 correspondingly in untreated effluent (initial pH of treated and untreated effluent 7.07 ± 0.8 and 4.85 ± 0.3 correspondingly). Total Carbohydrates removed about 17,440 ± 4.6 mg/L and 10,680 ± 3.2 mg/L by BK1 and BK2 correspondingly in treated effluent whereas 18,050 ± 3.5 mg/L and 18,340 ± 2.3 mg/L correspondingly in untreated effluent (initial concentration of treated and untreated effluent 25,780 ± 1.6 mg/L and 35,000 ± 1.5 mg/L correspondingly) while BK1 and BK2 removed total proteins by 30.336 ± 4.6 mg/L and 40.417 ± 2.3 mg/L correspondingly in treated effluent whereas 18.929 ± 1.2 mg/L and 17.526 ± 0.8 mg/L correspondingly in untreated effluent (initial concentration of treated and untreated effluent 49.225 ± 1.5 mg/L and 20.565 ± 1 mg/L correspondingly). Next, total solids removed by BK1 and BK2 2.5 ± 0.3 mg/L and 1.6 ± 0.6 mg/L correspondingly in treated effluent whereas 5.5 ± 0.8 mg/L and 4.6 ± 0.6 mg/L in untreated effluent (initial concentration of treated and untreated effluent 5.6 ± 1.5 mg/L and 9.48 ± 1.2 mg/L correspondingly). Both the strains BK1 and BK2 are highly efficient in the nitrogen and phosphorus removal therefore this strain may be applied for the potential remediation.

Removal of phosphorus in wastewater by sinusoidal alternating current coagulation: performance and mechanism

ABSTRACT The effects of initial total phosphorus (TP) concentration, current density, conductivity and initial pH value on the removal rate of TP and energy consumption, as well as the behaviour and mechanism of phosphorus removal, were investigated by sinusoidal alternating current coagulation (SACC). The flocs produced by SACC were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy FTIR and X-ray photo electron spectroscopy. The thermodynamic and kinetic behaviours of phosphorus removal by iron sol adsorption were also studied in detail. In a self-made SACC reactor equipped with five sets of parallel iron electrodes spacing 10 mm, the removal rate of TP reached 90.9% for a pH 7.0 wastewater with 5 mg dm−3 TP (κ = 800 μS cm−1) after being treated for 60 min by applying 2.12 mA cm−2 sinusoidal alternating current. Compared with direct current coagulation (DCC), SACC exhibits a higher removal efficiency of phosphorus due to the stronger adsorption of the produced flocs. It was found that the adsorption in the SACC process follows pseudo-second-order kinetic with the involvement of the intra-particle model. The adsorption of iron sol to phosphorus was an endothermic and spontaneous process, and its adsorption behaviour can be characterized with Langmuir and Redlich–Peterson isothermal adsorption models. SACC may be employed for the treatment of more complex wastewater combined with biological and/or electrochemical techniques.

Modeling of Phosphate Removal by Mg-Al Layered Double Hydroxide Functionalized Biochar and Hydrochar from Aqueous Solutions

Layered double hydroxide functionalized biochar and hydrochar composites are environmentally friendly and low-cost adsorbents for the removal of phosphate from aqueous solutions. In the present study, Mg-Al layered double hydroxide functionalized apple wood biochar and hydrochar were prepared and their phosphate adsorption characteristics were examined through batch experiments. Moreover, important factors affecting adsorption including initial phosphorus concentration (25-200 mg/L), contact time (5-120 min), ionic strength (deionized water, and 0.001, 0.01, and 0.1 mol/L KCl), pH (3-10), and adsorbent dosage (1, 2, 3, and 4 g/L) were investigated. Based on the results, the phosphate adsorption by Mg-Al layered double hydroxide modified biochar and hydrochar were comparable with Mg-Al layered double hydroxide and were greater than biochar and hydrochar. As expected, phosphate adsorption was decreased by increasing solution pH and ionic strength. The highest phosphate removal was attained at pH 4, adsorbent dosage of 4 g/L, and in the presence of deionized water as a background solution. Determination of adsorption characteristics of the adsorbents revealed that the phosphate adsorption mechanism involved a combination of electrostatic attraction, interlayer anion exchange, and formation of surface complexes. The Mg-Al layered double hydroxide modified biochar and hydrochar composites as cost-effective and efficient adsorbents suggest alternative biochar- and hydrochar-based composites for the phosphate removal from contaminated waters that could be used as P-fertilizers.

From wastes to functions: A paper mill sludge-based calcium-containing porous biochar adsorbent for phosphorus removal

With the increased awareness of reusing solid wastes for higher sustainability and the concern of water pollution associated with phosphorus over-emission, there are strong interests in developing solid waste based adsorbents for purifying phosphorus-containing wastewater. As a rich calcium resource, paper mill sludge (i.e., a major solid waste from pulping industry) can be used as phosphorus removal adsorbent after calcination. Thus, in this work, a simple and clean thermally treating route has been proposed for preparing calcium-containing biochar from paper mill sludge. The effect of the physicochemical properties of paper mill sludge and its carbonization condition on phosphorus adsorption has been analyzed. Moreover, the influence of some key adsorption parameters, e.g., biochar dosage, initial pH of solution, co-existing anions, initial phosphorus concentration and contact time has also been investigated. The results showed that the phosphorus adsorption data could be fitted well with pseudo-second-order kinetic and Langmuir isothermal models. The calculated maximum adsorption capacity of the as-prepared optimal calcium-containing biochar could reach to 68.49 mg·g−1 at 25 °C. Combined with the characterization results, it can be reasonably inferred that the adsorption process was chemisorption-dominated. Lastly, the application of this spent adsorbent in agriculture field has also been discussed. In brief, this work provided a feasible strategy for converting paper mill solid waste to an environmental functional material (i.e., calcium-rich biochar) for remediation of eutrophic water.

Experimental study on phosphorus removal of water by Zn/Mg/Al layered double hydroxide

Zn/Mg/Al layered double hydroxide (Zn/Mg/Al-LDH) was prepared by co-precipitation method. The structure of Zn/Mg/Al-LDH was characterized by XRD. The results show that the samples have typical hydrotalcite structure. They were used as adsorbents to remove phosphorus from wastewater. The effects of pH value, phosphorus concentration, adsorbent dosage, oscillation intensity and reaction time on phosphorus adsorption capacity were investigated by single factor control variable method. The results show that the adsorption equilibrium of Zn/Mg/Al-LDH can be reached after 24 h. The optimal experimental conditions are as follows: stirring rate is 180 R/min, pH value is 6, and reaction temperature is 50 °C. Under above conditions, when the initial phosphorus concentration is 50mg/L, the adsorption capacity of Zn/Mg/Al-LDH for phosphorus is 54.10mg/g when the adsorption equilibrium is reached. When the initial phosphorus concentration is 200mg/L, the adsorption capacity is 69.70mg/g, and the saturated adsorption capacity is 70.37mg/g. In the simulated practical engineering application, when the discharged phosphorus meets the standard, the phosphorus adsorption capacity of Zn/Mg/Al-LDH is 37.09mg/g, and the phosphorus removal rate is as high as 99.76%.

Effect of extracellular polymeric substances on the phosphorus adsorption characteristics of sediment particles

Extracellular polymeric substances (EPS) have a great impact on the characteristics of sediment particles and their environmental effects in hydro-environmental systems, yet little effort has been made to study the considerable variability in the element adsorption process of sediment particles caused by EPS. Understanding the variability of the adsorption characteristics of sediment particles associated with EPS and quantifying the scale of the adsorption isotherm parameters are important for understanding how EPS mediate sediment properties and environmental factors. In this paper, isothermal equilibrium adsorption experiments are done on phosphorus to study the influence of EPS on the adsorption characteristics of sediment particles, and the Langmuir adsorption isotherm is applied to analyze the adsorption rule of sediment particles under the impact of EPS. The current research demonstrates that significant differences will take place in the adsorption characteristics of sediments coated with EPS at different development phases and the phosphorus adsorption capacity of sediment particles increases with the growth of EPS. The difference in the adsorption percentage between sediment particles coated with EPS of 0 and 6 weeks growth time is about 42%–60% for different initial aqueous phosphorus concentration. A formula describing the adsorption isotherm parameter of the maximum material (element) adsorption capacity of sediment particles change over time is further proposed based on the experimental data. The current study provides some evidence for the interaction of sediment particles, EPS, and adsorbed elements in the water environment.

Phosphate adsorption onto bagasse iron oxide biochar: Parameter optimization, kinetic analysis, and study of mechanism

This study combined chemical ultrasonic modifications and microwave oven heating to prepare a novel adsorbent, bagasse iron oxide biochar, (BIBC) to remove phosphate from aqueous solutions. The characterization of BIBC was made by energy dispersive spectrometry (EDS), Brunauer–Emmett–Teller (BET), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses, and the mechanism of phosphorus adsorption on BIBC was researched by adsorption batch experiments with emphasis on pH, dosages of BIBC, initial phosphorus concentration, and adsorption time. The BIBC’s BET specific surface area and pore volumes were 81.94 m2 g−1 and 26.74 cm3 g−1, respectively. The pH for the optimal phosphorus adsorption by BIBC ranged from 5.0 to 7.0. The maximum adsorption capacities of phosphorus (according to the Langmuir model) were 3.62, 4.06, and 4.32 mg g-1 at temperatures of 25, 35, and 45 °C, respectively. Electrostatic interaction, surface adsorption of phosphorus on BIBC, and ion exchange were the main mechanisms of phosphorus adsorption. According to XPS results, Fe2p was involved in the adsorption reaction. The adsorption of phosphorus by BIBC is considered to be mainly chemical adsorption. The BIBC was stable under a pH range from 4.0 to 10.0 and secondary pollution did not result.

Effects of zebra mussels (Dreissena polymorpha) on phytoplankton under eutrophic conditions

We conducted two mesocosm experiments (2014 and 2017) to determine how invasive zebra mussels affected abundance and structure of phytoplankton community. Algae reaction was different for the introduction of D. polymorpha in 2014 and 2017. There was no influence of zebra mussels on the phytoplankton total abundance; however, it changed the biomass of individual taxa. Cyanoprokaryota reaction as a result the zebra mussels introduction was influenced by the initial phytoplankton structure and initial nitrogen and phosphorus concentrations in water. The biomass of Сyanoprokaryotа decreased at low N:P ratios and increased at high N:P ratios. Dreissena increased the biomass of large green filamentous algae, which is a poor food resource for zooplankton.

ADSORPTION PROPERTIES OF ORGANIC PHOSPHORUS IN WATER BY WATER TREATMENT RESIDUAL

The adsorption kinetics, thermodynamics experiments and adsorption isothermal models of adsorption of adenosine monophosphate(AMP) on aluminum-based water treatment residual (Al-WTR) were studied by batch test. The effects of initial phosphorus concentration, temperature and particle size on the adsorption of AMP were analyzed. The experimental results showed that AMP uptake was favored under neutral and acidic conditions. The smaller the particle size, the larger the adsorption amount. The Al-WTR with size of 1.0~2.0 mm was most suitable for practical application. The pseudo-second-order kinetic model well fitted the adsorption process of Al-AMP on WTR, which indicated that the adsorption was mainly based on chemical adsorption. The Langmuir isotherm model described the adsorption equilibrium well, and the thermodynamic analysis manifested that the adsorption process was a spontaneous, endothermic and entropy-increasing process. The analysis of Fourier-transform infrared spectrum analysis (FTIR) showed that there was a loss of hydroxy groups associated with Al and an increase in Al-O-P bonds during the adsorption of AMP on Al-WTR. This phenomenon was enhanced by the increase of initial phosphorus concentration, indicating that the adsorption of Al-WTR on AMP mainly fulfilled through ligand exchange.

Facile Fabrication of Calcium-Doped Carbon for Efficient Phosphorus Adsorption.

High phosphorus concentrations mainly result in environmental problems such as agricultural pollution and eutrophication, which have great negative influence on many natural water bodies. In this work, calcium lignosulfonate was employed to produce calcium-doped char at 400 and 800 °C. To compare the phosphorus adsorption behaviors of the two carbon materials, batch adsorption experiments were conducted in a phosphorus microenvironment. The factors including the initial solution pH, phosphorus concentration, and adsorbent amount were considered, and the main characteristics of calcium-doped chars before and after adsorption were assessed. The results revealed that the phosphorus removal processes fitted both the Freundlich and pseudo-second-order-kinetic models. According to the Langmuir model, the maximum adsorption capacities of the two adsorbents obtained at 400 and 800 °C toward phosphorus (50 °C) were 53.22 and 17.77 mg/g adsorbent, respectively. The former was rich in calcium carbonate (CaCO3) and hydroxyl and carboxyl groups, and it mainly served as a precipitant and a chelating agent, while the latter with a high surface area was dominant in P adsorption.

Water purification efficiency and resource utilization of three tuberous emergent aquatic plants

Objective This study aims to investigate the purification capacity for nutrients in polluted water and the yield of tuber starch of three common tuberous aquatic plants, and estimate the feasibility and potential risk of starch resource utilization. Method Purification efficiency of Iris pseudacorus, Canna indica and Calla palustris for polluted water body was compared using hydroponic experiment, and three replicates were set for each group. No plant treatment was used as control group. Removal efficiency of ammonium nitrogen, total nitrogen and total phosphorus in water was investigated. The contents of nitrogen and phosphorus in plant roots, stems, leaves and tubers were analyzed. The content of starch and heavy metals including Cu, Zn, Cr and Pb in plant tubers were measured. Result When initial concentrations of ammonium nitrogen and total phosphorus were 7.37−7.53 and 0.41−0.45 mg·L−1, concentrations of ammonium nitrogen, total nitrogen and total phosphorus in plant treatment groups decreased to 0.01−0.07, 0.61−0.91, and 0.025−0.031 mg·L−1 respectively after 20 days of treatment, which met the Class Ⅲ standard for surface water environmental quality (GB 3838−2002). The starch extracted from tubers of I. pseudacorus, C. indica and C. palustris was 61.3, 14.1 and 64.0 g·kg−1, respectively. Starch yields of these plant species were 14.3, 1.2 and 2.6 kg·m−2 respectively in the 100 m2 trial plot. The tuber could accumulate heavy metals. As initial concentrations of Cu2+, Zn2+, Cr3+ and Pb2+ in water were 2.01−2.08, 2.56−2.87, 0.22−0.26, and 0.24−0.26 mg·L−1, the contents of Cu, Zn, Cr and Pb in tuber starch of I. pseudacorus were 10.30, 46.7, 12.03, and 1.74 mg·kg−1, respectively and those of C. indica were 12.68, 44.67, 8.15 and 1.32 mg·kg−1, respectively, while those of C. palustris were 19.28, 66.91, 9.63 and 3.97 mg·kg−1, respectively. Conclusion The three tuberous aquatic plants can effectively purify nutrients such as nitrogen and phosphorus, and recover a considerable amount of starch. However if heavy metals coexist in the polluted water, plant tubers are not recommended for resource utilization. [Ch, 4 fig. 17 ref.]

Nitrate and Phosphate Removal Efficiency of Synechococcus elongatus Under Mixotrophic and Heterotrophic Conditions for Wastewater Treatment

Growing nutrient content of surface waters causes environmental concerns about eutrophication due to the immethodical release of nutrient containing effluent. The potential of microorganisms to decrease nitrogen and phosphorus concentration has drawn increasing attention. The present study is performed to evaluate the nutrient removal potential of cyanobacterium Synechococcus elongatus in different trophic cultivations. For this purpose, 15 experiments were designed by the Box-Behnken method using modified BG-11, including the initial concentrations of phosphorus, nitrogen, and glucose up to 10 mg L−1, 600 mg L−1, and 10 g L−1, respectively. Different trophic conditions were applied by changing carbon sources and light–dark cycles. The maximal removal of phosphorus and nitrogen were obtained in mixotrophic condition with 85.1% and 87.4%, respectively, and the specific growth rate of microalga was 0.99 day−1. Besides, its nutrient removal efficiency in dairy effluent was about 92% in mixotrophic culture, while the heterotrophic condition was not efficient. Based on the obtained results, mixotrophic cultivation of the cyanobacteria S. elongatus would be useful for application in N-riched and P-riched effluents.