Culture of four microalgal strains for bioenergy production and nutrient removal in the meliorative municipal wastewater

Microalgae have been considered as the most promising sources of alternative bioenergy. For the purpose of saving costs, the present work focused on the potential use of microalgae in the meliorative municipal wastewater, which contains 90% municipal wastewater and 10% dairy wash wastewater. Four microalgal species, Palmellococcus miniatus, Neochloris oleoabundans, Scenedesmus quadricanda #507, and Chlorella zofingiensis, were cultured in pure municipal wastewater and meliorative municipal wastewater, respectively, for 5 days. Their biomass accumulation and removal rates of nitrogen and phosphate were measured. Results showed that the growth rates of Neochloris oleoabundans, Palmellococcus miniatus, and Chlorella zofingiensis in meliorative municipal wastewater (>0.8 g·L^–1·d^–1) were significantly higher than that in municipal wastewater (2.6 g·L^–1·d^–1), while there was no significant difference between the growth rates of Scenedesmus quadricanda #507 in meliorative municipal wastewater and in municipal wastewater. Neochloris oleoabundans exhibited the highest growth rate (0.86 g·L^–1·d^–1) and relatively high nutrient removal capacity. Scenedesmus quadricanda #507 had the highest P removal rate of over 94%. The four species have a similar N removal rate at about 90%. The results showed that the highest average removal rate of N and P were about 23.1 mg·L^–1·d^–1 and 7.1 mg·L^–1·d^–1. Furthermore, the content of lipid or carbohydrates increased and a different profile of fatty acids were found compared to those in municipal wastewater. Cellular components changes of microalgae in meliorative municipal wastewater were favorable as raw materials for bioethanol and biodiesel production. Cultivation with meliorative municipal wastewater is a win-win culture mode that facilitates the biomass production, lipid and carbohydrate accumulation, and wastewater purification.     

同步脱氮脱硫技术的研究进展

废水同步脱氮脱硫技术因其具有成本低、时间短、二次污染少等优势而成为研究热点;基于废水同步脱氮脱硫的技术,废水脱氮与沼气脱硫同步进行也成为可能;综述了同步脱氮脱硫技术的化学基础、微生物基础,以及其工艺条件等方面的最新研究进展。     

Comparison of dairy wastewater and synthetic medium for biofuels production by microalgae cultivation

This study is concerned with comparing raw dairy wastewater (DWW) with blue-green medium (BG11 medium) for biofuel production. Three microalgae strains (Chlorella sp., Scenedesmus sp., and Chlorella zofingiensis) were cultured in tubular bubble column photobioreactors with two media separately. After 8 days of cultivation, DWW was demonstrated to be more suitable medium for microalgae biomass and lipid production than BG11 medium. The biomass and lipid produced within wastewater provided suitable feedstocks for anaerobic digestion and biodiesel conversion. Nutrients in wastewater were efficiently removed (>90% total nitrogen removal, approximately 100% ammonia removal, and >85% total phosphorus removal) during this process.     

Effects of metals in wastewater on hydrogen gas production using electrohydrolysis

Hydrogen gas was produced from metal plating wastewater by electro hydrolysis. Wastewater contains chrome, copper and nickel metals which can accelerate the production of hydrogen gas. Effects of kind of metals, the voltage and reaction time on percent hydrogen gas (HGP) were investigated. After application of different DC voltages on each metallic wastewater, percent hydrogen gas (HGP), cumulative hydrogen gas volume (CHGV), hydrogen gas formation rate (HFR) and total organic carbon (TOC) removal were also evaluated. Hydrogen gas percent was obtained as %99 at 4 V for chrome plating wastewater while percent hydrogen gas was achieved as 50% H₂ gas at 4 V for copper and nickel metal plating wastewater. Maximum CHGV achieved with 4 V DC voltage for all metal plating wastewater. Maximum CHGV (4000 mL), HFR (985 mL H₂ d⁻¹) and percent hydrogen gas (99%) was observed with chrome plating wastewater at 4 V DC voltage. Hydrogen gas produced from chrome metal plating wastewater using electro hydrolysis method can be efficiently used for fuel cells as a source due to nearly pure hydrogen gas.     

生物质气化发电燃气焦油脱除方法的探讨

生物质气化发电技术的最大难点之一就是如何除去燃气中含有的焦油等污染物,这些成分会对燃气轮机或内燃机等设备造成一定的影响.因此生物质气化发电过程中燃气焦油的脱除是目前国内外重点研究和解决的课题之一.文章在研究国内外大量有关文献资料的基础上,深入阐述了气化过程中焦油产生的机理、影响焦油生成的因素以及焦油的脱除方法,重点探讨了目前较为有效的焦油热化学脱除方法,即焦油的热裂解和催化裂解方法,以期为生物质气化发电燃气焦油的脱除提供一些思路和参考.     

Performance modelling of a carbon dioxide removal system for power plants

In this paper, a carbon dioxide removal and liquefaction system, which separates carbon dioxide from the flue gases of conventional power plants, was modelled. The system is based on an amine chemical absorption stripping system, followed by a liquefaction unit to treat the removed CO₂ for transportation and storage. The effect of the main parameters on the absorption and stripping columns is presented. The main constraints set for the model are a capture efficiency of 90% and the use of an aqueous solution with a maximum 30% amine content by weight. The goal of this study is to remove the CO₂ with minimum energy requirements for the process when it is integrated in a fossil fuel fired power plant. Results of the simulation are compared to experimental and literature data from feasibility studies and existing plants.

The power plant to which the removal system is connected is a 320 MW steam power plant with steam reheat and 8 feedwater heaters. Two different fossil fuels were considered: coal and natural gas. The effect of the modifications necessary to integrate the CO₂ removal system in the power plant is also studied.

The capital cost of the removal and liquefaction system is estimated, and its influence on the cost of generated electricity is calculated.     

Investigation on transport and thermal studies of solid polymer electrolyte based on carboxymethyl cellulose doped ammonium thiocyanate for potential application in electrochemical devices

In this work, a free standing and flexible solid polymer electrolyte (SPE) based on non-hazardous and environmental friendly material, carboxymethyl cellulose (CMC) was successfully produced in order to overcome environmental and pollution issues. The effect of doping ammonium thiocyanate (NH₄SCN) into SPE based on carboxymethyl cellulose (CMC) on transport, thermal and electrochemical stability window properties have been investigated for potential application in electrochemical devices. CMC-NH₄SCN SPE was prepared via solution casting technique. The properties of the prepared CMC-NH₄SCN SPE were characterized via Fourier transform infrared spectroscopy (FTIR) deconvolution, transference number measurement (TNM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and linear sweep voltammetry (LSV) techniques. FTIR deconvolution was performed in order to investigate the dissociation of ions and transport properties of CMC-NH₄SCN SPE system and it can be correlated with the ionic conductivity of CMC-NH₄SCN SPE system. The result of TNM was obtained via a DC polarization method where the ionic transference number for the highest conducting CMC-NH₄SCN SPE was found to be 0.93. Thus, it can be suggested that the conducting species for the highest conducting CMC-NH₄SCN SPE are mainly due to ions. TGA was performed to investigate the thermal stability of CMC-NH₄SCN SPE. The value of glass transition temperature of CMC-NH₄SCN SPE was obtained from DSC analysis. Electrochemical stability window of the highest conducting CMC-NH₄SCN SPE obtained from LSV technique was up to 1.6 V. As a result, it can be inferred that the highest conducting CMC-NH₄SCN SPE had shown a promising performance and has a great potential to be applied in electrochemical devices application such as proton batteries.     

电混凝法处理电镀废水中的Cu^2＋和Zn^2＋

利用电混凝法处理含Cu^2＋和Zn^2＋的电镀废水,系统地考察了电解电压、进水pH值、极板间距、电解时间等因素对废水处理效果的影响,确定了最佳的电解条件。实验结果表明,电混凝法处理的电镀废水出水水质较好。当电压为80 V,pH值为5,电解时间30 min,极板间距为10 mm时,处理后的废水中Zn2＋浓度为0.36mg/L,去除率达到97.9%,Cu^2＋浓度为0.0049 mg/L,去除率达到99.9%,均可达到国家规定的排放标准,且该法运行方便,处理时间短,是较理想的电镀废水处理工艺。     

Simultaneous antibiotic degradation,nitrogen removal and power generation in a microalgae-bacteria powered biofuel cell designed for aquaculture wastewater treatment and energy recovery

A novel microalgae-bacteria powered biofuel cell (MBBFC) is designed for aquaculture wastewater treatment and energy recovery, in which algal-bacterial cooperation coupling with cathodic bioelectrochemiccal process for efficient nitrogen removal while simultaneously driving anodic bioelectrochemical degradation of antibiotic florfenicol (FLO) with instantaneous electrons uptake from co-substrate. 100 mg/L of ammonia nitrogen is removed completely within 90 h in the algal-bacterial biocathode of MBBFC, mainly attributed to the activity of ammonia oxidizers in the presence of photosynthetic oxygen and the resultant nitrate/nitrite are acceleratively removed by the cathodic bioelectrochemical denitrification. The antibacterial activity of FLO is eliminated through anodic bioelectrochemical enhanced co-metabolic reductive dehalogenation. The feeding 0.5 mg/L of FLO to the anode promotes the growth of Pseudomonas species, which results in a 3.2-fold increase in power output. FLO diffused from the anode to the cathode can exert a selection pressure to the cathodic bacterial community and thereby affecting the nitrogen removal performance of the microalgal-bacterial cathode. The MBBFC shows a great potential for aquaculture wastewater treatment with simultaneously bioelectrical energy recovery.     

Inhibition of hydrogen production reactions in the wet dust removal system using CeCl3 solutions

For treatment of aluminum dust, a wet dust removal system has been used worldwide. During treatment, aluminum dust is inhaled into a water tank of the dust collector. As hydrogen production reactions are likely to take place in the water tank, there exists a great risk of fire or explosion accidents associated with the wet dust removal system. Based on field research and laboratory experiments, Hydrogen Inhibition Method (HIM) by using CeCl₃ solutions was proved capable of inhibiting reactions between aluminum dust and water. When the concentration of CeCl₃ solutions reached 6.02 g/L, there was basically no hydrogen gas produced. SEM, EDS and XPS characterizations were used to assess the aluminum particles before and after being reacted with water or CeCl₃ solutions, respectively. Shrinking core model was utilized to identify the corresponding chemical reaction kinetics. Additionally, a physicochemical mechanism was established to explain these phenomena.     

Development and evaluation of magnetic iron-carbon sorbents for mercury removal in coal combustion flue gas

In order to get a cost effective and recyclable sorbent for mercury removal, a series of magnetic iron-carbon (Fe–C-x) sorbents was developed by co-precipitation. The physical and chemical properties of obtained sorbents were evaluated through various characterization methods. According to the results, Fe₃O₄ precipitate on carbon weakens the surface properties, but mercury removal performance in simulated flue gas is excellent. For flue gas components, HCl promotes mercury oxidation and adsorption on sorbents, O₂ has limited effect on mercury removal and SO₂ plays an inhibitive role. NO could enhance mercury oxidation with O₂ existence because of the generation of NO₂, which could react with Hg⁰ through heterogeneous reaction over iron-carbon surface. Besides, effects of temperature and regeneration performance were further researched under simulated flue gas. Apart from higher temperature will decompose mercury compounds and cause the removal efficiency decrease, Fe–C-3 sorbent shows excellent Hg⁰ removal performance at the temperature window of 100–200 °C. Exceptional regeneration performance on Hg⁰ removal indicates that spent sorbent could be regenerated.     

Effect of hydraulic retention time on hydrogen production and chemical oxygen demand removal from tapioca wastewater using anaerobic mixed cultures in anaerobic baffled reactor (ABR)

This study evaluated hydrogen production and chemical oxygen demand removal (COD removal) from tapioca wastewater using anaerobic mixed cultures in anaerobic baffled reactor (ABR). The ABR was conducted based on the optimum condition obtained from the batch experiment, i.e. 2.25 g/L of FeSO₄ and initial pH of 9.0. The effects of the varying hydraulic retention times (HRT: 24, 18, 12, 6 and 3 h) on hydrogen production and COD removal in a continuous ABR were operated at room temperature (32.3 ± 1.5 °C). Hydrogen production rate (HPR) increased with a reduction in HRT i.e. from 164.45 ± 4.14 mL H₂/L.d (24 h HRT) to 883.19 ± 7.89 mL H₂/L.d (6 h HRT) then decreased to 748.54 ± 13.84 mL H₂/L.d (3 h HRT). COD removal increased with reduction in HRT i.e. from 14.02 ± 0.58% (24 h HRT) to 29.30 ± 0.84% (6 h HRT) then decreased to 21.97 ± 0.94% (3 h HRT). HRT of 6 h was the optimum condition for ABR operation as indicated.     

A review of recent advances in hydrogen purification for selective removal of oxygen: Deoxo catalysts and reactor systems

As a response to climate change caused by a surge in greenhouse gas emissions and the associated transition to sustainable energy systems, hydrogen (H₂) is considered as an attracting alternative energy source. In that context, water electrolysis combined with renewable energy source, so called green H₂, has been recently receiving great attention from worldwide. However, for stable use of H₂ as an energy source in various type of fuel cells to produce electricity, the purity of H₂ must not only meet the required level but also be maintained stably. Among possible impurities in the produced H₂ steam, oxygen (O₂) must be controlled below certain level in any circumstances for safety, hence catalytic purification for intensive and selective removal of O₂ in H₂ steam is nowadays regarded as an essential technology for commercial application of green H₂ because of the intermittent nature of renewable energy. Nevertheless, the catalytic purification technology, especially the technology for catalyst and process development, is still in the basic stage, and the reported technologies have not been systemically organized yet. Therefore, this review 1) briefly summarizes the developmental trends and current available technologies of various H₂ purification technologies, such as membrane separation, pressure swing adsorption, metal hydride, and cryogenic separation 2) and introduces the developmental of deoxo catalysts and catalytic H₂ purification technologies with future research perspectives and suggestions.     

农村生活与生产综合污水生物处理的A/O工艺启动策略与特性研究

为实现新时期各类典型性农村综合污水的治理,选择了一种农村生活与生产综合污水作为研究对象,研究了利用兼氧/好氧(A/O)工艺处理农村生活和生产综合污水的启动过程。结果表明：采用逐步递增生产废水和污泥接种培养的启动策略能够实现处理工艺的快速启动;pH、化学需氧量(COD)、氨氮(NH₄⁺-N)、总磷(TP)以及色度在启动过程中各阶段的变化情况的分析结果表明,A/O工艺能够通过兼氧池和好氧池的协同配合达到理想的污水处理效果。     

Risk‐reduction of passive decay heat removal system by using gallium‐water for UCFR and SMR

Employing a gallium‐based passive decay heat removal system (PDHRS), which enables the use of water as an ultimate heat sink, was proposed for the UCFR‐100. The gallium‐based PDHRS has replaced the previous sodium‐based PDHRS. To evaluate the safety and thermal performance of the gallium‐based PDHRS, safety analysis and heat exchanger tests were performed. The safety analysis, using both deterministic and probabilistic analyses methods, confirmed the unique safety feature of the UCFR‐100. The transient analysis for design basis accidents showed the rapid cooling characteristic of the gallium‐based PDHRS of the UCFR‐100. In addition, compared with the sodium‐based PDHRS, the probabilistic safety analysis, using the level‐1 Probabilistic Safety Assessments method, showed the significant decrease of the minimal cut sets and the significant reduction of the failure probability of the gallium‐based PDHRS of the UCFR‐100. Finally, compared with the sodium‐to‐air feature in the sodium‐based PDHRS, the gallium‐to‐water heat exchanger in the gallium‐based PDHRS enhanced the heat transfer performance and facilitated economic advantages to the entire system. In conclusion, the gallium‐water PDHRS represented risk reduction of the entire reactor system with the effective thermal performance. Copyright © 2016 John Wiley & Sons, Ltd.     

Experimental study on the heat transfer characteristics of fluoride salt in the new conceptual passive heat removal system of molten salt reactor

A new conceptual design of a passive residual heat removal system (PRHRS) has been proposed for molten salt reactor. High‐temperature heat pipes are used in this new design to improve the system inherent safety and make the PRHRS more compact. An experimental system using fluoride salt FLiNaK has been constructed to validate and support the future design of PRHRS of molten salt reactors. In this research, tests on the natural convection heat transfer of FLiNaK in the drain tank with an inclined heat pipe inserted at different heights were performed. The temperature distribution of fluoride salt in the tank was analyzed. The height of heat pipe and the bulk temperature of FLiNaK have little influence on the normalized salt temperature distribution. However, with the height of heat pipe increasing, the temperature difference of molten salt decreases and heat transfer coefficient of natural convection increases. In addition, the empirical correlations of natural convection heat transfer between liquid FLiNaK and inclined heat pipe are obtained within the range of Rayleigh numbers from 3.97 × 10⁶ to 1.16 × 10⁷. The comparisons show that a good agreement with less than 5% deviation is obtained between the proposed correlations and the test data.     

An intelligent control of NH3 injection for optimizing the NOx/NH3 ratio in SCR system

The distribution of nitrogen oxides (NO_x) flux within the cross-section area in front of ammonia injection grid (AIG) under different operating conditions was obtained by computational fluid dynamics (CFD) method. Weight of NO_x flux in the sub-zone corresponding to each of the ammonia (NH₃) injection branch-pipes of AIG system was analyzed and the sensitivity of which against the plant power load was figured out. A number of “critical” ammonia injection branch-pipes were determined with regard to the weight sensitivity analysis. The selected “critical” branch-pipes were changed to be controlled by the automatic valves, and an intelligent tuning strategy was proposed. The NO_x/NH₃ mixing stoichiometry over the cross-section area in front of AIG system was significantly modified for the high utilization ratio of ammonia. A case work was launched on the selective catalytic reduction (SCR) system of a 660 MW plant. As a result, the ammonia consumption rate (ACR) was found to be reduced by 6.44% compared to that under previous control system, and was 9.31% lower than that of the unapplied system. The methodology for determining the “critical” branch-pipes and intelligent tuning strategy of ammonia injection notably saved the ammonia consumption of SCR system, and the formation of ammonium bisulfate (ABS) were greatly confined.     

Experimental study of primary and secondary side coupling natural convection heat transfer characteristics of the passive residual heat removal system in AP1000

Passive residual heat removal heat exchanger (PRHR HX), which is a newly designed equipment in the advanced reactors of AP1000 and CAP1400, plays an important role in critical accidental conditions. The primary and secondary side coupling heat transfer characteristics of the passive residual heat removal system (PRHRS) determine the capacity to remove core decay heat during the accidents. Therefore, it is necessary to investigate the heat transfer characteristics and develop applicable heat transfer formulas for optimized design. In the present paper, an overall scaled-down natural circulation loop of PRHRS in AP1000, which comprises a scaled-down in-containment refueling water storage tank (IRWST) and PRHR HX models and a simulator of the reactor core, is built to simulate the natural circulation process in residual heat removal accidents. A series of experiments are conducted to study thermal-hydraulic behaviors in both sides of the miniaturized PRHR HX which is simulated by 12 symmetric arranged C-shape tubes. For the local PRHR HX heat transfer performance, traditional natural convection correlations for both the horizontal and vertical bundles are compared with the experimental data to validate their applicability for the specific heat transfer condition. Moreover, the revised natural convection heat transfer correlations based on the present experimental data are developed for PRHR HX vertical and lower horizontal bundles. This paper provides essential references for the PRHRS operation and further optimized design.     

Experimental analysis of an ejector for anode recirculation in a 10 kW polymer electrolyte membrane fuel cell system

For analyzing ejector's performance in the system, an ejector for a 10 kW polymer electrolyte membrane fuel cell (PEMFC) system was first designed, manufactured, and a 10 kW PEMFC system bench was built up. A proportional valve and PI pressure feedback control method were adopted to control the hydrogen supply and anode inlet pressure. During the test, performances between dead-ended anode (DEA) mode and ejector mode were compared. Ejector's performances in the system, i.e., volume flow recirculated ratio, difference pressure, dynamic responses of primary pressure, anode inlet pressure, and recirculated gas flow rate during the purge process and current variation condition, were investigated. The results show that pressure adjustment is accurate, continuous, and fast using the proportional valve and PI pressure feedback control method. The hydrogen consumption rate in the ejector mode can reduce from 5% to 10% compared with the rate in the DEA mode except for the stack current 5 A and 10 A conditions. For better water removal out of the anode channel in ejector mode, the maximum stack power increases from 5.11 kW (DEA mode) to 9.56 kW (ejector mode). Anode pressure surge caused by the purge valve switching enhances the ejector's recirculated performance significantly.