Nutrient removal and energy production in a urine treatment process using magnesium ammonium phosphate precipitation and a microbial fuel cell technique

Urine pretreatment has attracted increasing interest as it is able to relieve the nitrogen and phosphorus overloading problems in municipal wastewater treatment plants. In this study, an integrated process, which combines magnesium ammonium phosphate (MAP) precipitation with a microbial fuel cell (MFC), is proposed for the recovery of a slow-release fertilizer and electricity from urine. In such a two-step process, both nitrogen and phosphorus are recovered through the MAP process, and organic matters in the urine are converted into electricity in the MFCs. With this integrated process, when the phosphorus recovery is maximized without a dose of PO(4)(3-)-P in the MAP precipitation process, removal efficiencies for PO(4)(3)-P and NH(4)(+)-N of 94.6% and 28.6%, respectively, were achieved with a chemical oxygen demand (COD) of 64.9% accompanied by a power output of 2.6 W m(-3). Whereas removal efficiencies for PO(4)(3)-P and NH(4)(+)-N of 42.6% and 40%, respectively, and a COD of 62.4% and power density of 0.9 W m(-3) were obtained if simultaneous recovery of phosphorus and nitrogen was required through dosing with 620 mg L(-1) of PO(4)(3-)-P in the MAP process. This work provides a new sustainable approach for the efficient and cost-effective treatment of urine with the recovery of energy and resources.     

Ammonium-Nitrogen Recovery from Wastewater by Struvite Crystallization Technology

Struvite crystallization is one of the sustainable approaches for recovering ammonium nitrogen (NH₄-N) from wastewater in the form of a valuable material, in parallel with improving wastewater treatment efficiency. Focusing on NH₄-N recovery, this review discusses the factors influencing struvite crystallization including the effect of foreign elements. It is shown that more than 95% of NH₄-N could be recovered in the form of struvite, a magnesium-ammonium phosphate (MAP) salt, from some kinds of wastewater. This review emphasizes the role of utilizing alternative sources of Mg and P in improving the process sustainability. Additionally, it also explains how the MAP precipitation process could result with significant reduction of other pollutants contributing to total organic carbon, of color and turbidity, which support MAP integration with other treatment methods. The main options of lowering MAP recovery cost are presented; it was shown that applying low-cost materials of both Mg and P could save more than 65% of the process’s cost. Finally, the future research directions to improve NH₄-N recovery are pointed out.     

Biomass derived nitrogen doped carbon with porous architecture as efficient electrode materials for supercapacitors

Developing porous carbon materials with low-cost, sustainable and eco-friendly natural resources is emerging as an ever important research field in the application of high-performance supercapacitor. In this paper, a simple synthetic method to fabricate nitrogen doped porous carbon(NPC) is developed via a one-pot carbonization of sodium alginate and urea. The as-prepared NPC annealed at 700℃ with mesoand macro-porous structure exhibits excellent specific capacitance(180.2 F/g at 1 A/g) and superior cycling life when serves as electrode materials for supercapacitor. Moreover, the investigation on the annealing temperature demonstrates that NPC pyrolysis at 700℃ possesses relatively high pyrrole nitrogen and pyridine nitrogen, which is favorable for enhancing supercapacitor performance. This work extends biomass derived carbon materials in energy storage applications.     

Transition metal chalcogenides as emerging electrocatalysts for urea electrolysis

Urea electrolysis is an up-and-coming approach to realize sustainable energy-saving hydrogen fuel production and purification of urea-bearing wastes (e.g. urine, industrial wastewater). To attain a high urea electrolysis efficiency, high-performance electrocatalysts are highly required. Of late, transition metal (TM) chalcogenides-based materials are emerging as promising candidates for urea electrolysis. The catalytic performance of TM chalcogenides-based catalysts is optimized by tuning the internal/external characteristics, including nanostructure control, composition optimization, and heterostructuring. In this review, recent achievements in high-efficiency electrocatalysts based on TM chalcogenides for urea electrolysis are critically discussed. First, the electrochemistry of urea electrolysis is analyzed. Next, recent progress in TM chalcogenides-based electrocatalysts for urea electrolysis is detailed. The electrocatalyst design strategies are particularly elucidated, as well as the catalyst structure–performance correlation. Ultimately, perspectives on crucial scientific issues in this booming field are highlighted.     

Characterization of urease derived from Citrullus lanatus (watermelon) seeds to estimate total Kjeldahl nitrogen in human urine

A urease extract prepared by decanting liquid from a suspension of finely ground Citrullus lanatus (watermelon) seeds was characterized and applied to dilute urine samples to demonstrate a low-cost field method to estimate total Kjeldahl nitrogen (TKN) concentrations in human urine. The extract exhibited a Michaelis-Menten constant, K_m, of 3.00 mM urea and a specific activity of up to 12.2 U/mg protein at an optimum pH of 8.1. A statistical F-test on 54 samples demonstrated that TKN can be estimated as the total ammonium-nitrogen recovered upon addition of urease in dilute fresh and stale urine samples. The total ammonium-nitrogen in urine samples determined after treatment with watermelon seed urease was consistent with that determined using traditional acid digestion techniques. The extract retained 85% of its initial capacity after three months of refrigeration. The effectiveness of this method to assay nitrogen in unbuffered urine samples will be useful in nitrogen analyses in nutrient recovery and urine or slurry storage contexts. Accordingly, this study is useful in understanding the kinetics of a plant-derived urease acting in dilute urine.     

Wastewater To Resource: Design of a Sustainable Phosphorus Recovery System

To enable a more sustainable wastewater treatment processes, a transition towards resource recovery methods that have minimal environmental impact while being financially viable is imperative. Phosphorus (P) is a finite resource that is being discharged into the aqueous environment in excessive quantities. As such, understanding the financial and environmental effectiveness of different approaches for removing and recovering P from wastewater streams is important to reduce the overall impact of wastewater treatment. In this study, a process-systems modelling framework for comprehensively evaluating these approaches in terms of both economic and environmental impacts is developed. Applying this framework, treatment pathways are designed, simulated and analysed to determine the most suitable approaches for P removal and recovery. The purpose of this methodology is not only to assist with plant design, but also to identify the principal economic and environmental factors acting as barriers to implementing a given technology, incorporating the impact of waste recovery. The results suggest that the chemical and ion-exchange approaches studied deliver sustainable advantages over biological pathways, both economically and environmentally, with each possessing different strengths. The assessment methodology developed enables a more rational and environmentally sound wastewater plant design approach to be taken.     

类水滑石材料在核废水处理领域的应用

核能已成为我国能源结构的重要组成部分, 但含放射性物质的废水所带来的危害不容忽视. 如何高效解决核废水污染问题迫在眉睫. 类水滑石材料是一类阴离子型粘土化合物, 因其层板组成及层间阴离子种类的可调控性、 较大的比表面积及粒径和形貌的可调控性等特点已在含放射性核素废水的处理中崭露头角. 本文主要阐述了类水滑石材料对废水中放射性核素的吸附行为及其作用机制, 探讨了存在的问题及可能的解决方法, 并对其发展前景进行了展望.     

Biohydrolysis of urea from urea-bearing wastewater

Biological stabilization of urea is a two staged process; (i) urea hydrolysis and (ii) ammonia stripping/nitrification-denitrification. Ammonia thus produced is either stripped off by usual methods or after converting into nitrate using chemoautotrophic bacteria. On denitrification, nitrate is finally converted into nitrogen gas by means of heterotrophic bacteria. Details of stabilization of urea from urea bearing wastewater using urea biohydrolyser are presented in this paper.     

顺酐生产中废水治理方法的改进

目前普遍应用的两种顺酐废水治理方法,生物法和传统真空蒸发法,都存在着运行成本高和不能将废水中有用物质充分回收的缺点.经过对传统真空蒸发法的改进和完善,使顺酐废水的治理既达到零排放的目的,又回收生产了富马酸合格产品,创造了经济效益.     

Optimal production of polyhydroxyalkanoates in activated sludge biomass

Polyhydroxyalkanoates (PHAs) have been recognized as good candidates for biodegradable plastics, but their high price compared with conventional plastics has limited their use. In this study, actiated sludge microorgan isms from a conventional wastewater treatment process were induced, bycontrol-lingthe carbon: nitrogen (C:N) ratioin the reacorliquor, toaccumulate PHAs. In addition, an intermittent nitrogen feeding program was established to optimize the volumetric PHA productivity in a wastewater treatment process. The optimal overall polymer production yield of 0.111 g of polymer/g of carbonaceous substrate consumed was achieved under a C:N ratio of 96:1 by feeding nitrogen in the reactor liquor onceevery four cycles. At the same time, the amount of excess sludge generated from the wastewater treatment process was reduced by22.9%.     

生物质基氮掺杂多孔炭材料的制备及对水中亚甲基蓝的吸附性能

以柳树落叶为生物质碳源, 氨水为氮源, 采用溶胶-凝胶法制备了一系列氮掺杂多孔炭材料(WNC), 并对其结构和物理化学性质进行了表征. 结果表明, WNC材料具有较高的比表面积(528~618 m²/g)和多级孔结构; 材料表面含有丰富的含氧和含氮官能团(氮摩尔分数为8.9~9.9%); WNC材料对水体系中的亚甲基蓝(MB)表现出良好的吸附性能, 吸附为自发吸热过程, 符合Langmuir等温吸附和准二级动力学模型, 在pH值为5、 室温下最大吸附量为263.2 mg/g, 且材料可以多次循环使用. 对WNC-2及吸附染料MB后的WNC-2样品进行高温再焙烧处理, 所得样品(WNC-2-R和WNC-2-MB)的ζ电位明显升高, 表面碱性增强, 吸附容量分别提高到之前的1.3倍和1.6倍. 结合各种表征结果, 可以认为WNC材料的高比表面积和多级孔结构有利于吸附质(亚甲基蓝离子)的传输, 并能与材料表面的羰基、 醌基和吡啶氮等基团发生较强的相互作用, 从而使其表现出较高的吸附速率和吸附量.     

Oxalic acid cross-linked sodium alginate and carboxymethyl chitosan hydrogel membrane for separation of dye/NaCl at high NaCl concentration

Dye desalination is a challenge in the treatment of textile wastewater with high salt concentration. It is imperative to develop salt resistance membrane that is from sustainable materials to effectively treat dye/salt mixtures. And most polymer membrane materials are non-renewable petrochemical resources.In this paper, a green hydrogel membrane(CMCS-OA-Na Alg) was prepared by non-metallic ions of oxalic acid(OA) cross-linking of two natural macromolecules of sodium alginate(Na Alg) and carboxym...     

Improving ORR activity of carbon nanotubes by hydrothermal carbon deposition method

Nitrogen doped carbons are an important family of materials with ideal activity for oxygen reduction reaction(ORR). It is always interesting to search functional carbons with high heteroatom contents and desirable structure for ORR. Within this study, the surface modification of carbon nanotubes(CNTs) via hydrothermal carbonization(HTC) technique in the presence of glucose and urea was reported, where the surface of CNTs is successfully coated by nitrogen containing hydrothermal carbon layers. The resulting composite combines both advantages of the outstanding electrical conductivity of CNTs and the effective ORR active sites provided by doped nitrogen in the HTC carbon layers. By controlling the ratio of glucose and urea, the nitrogen contents coated on the surface of CNTs can reach up to 1.7 wt%. The resulting materials show outstanding electrochemical activity towards ORR in alkaline electrolyte, making it one of the valuable metal-free electrode materials and a competent alternative to the state-of-the-art Pt/C catalyst.     

金黄地鼠与大白鼠尿液成分的比较分析

通过比较分析，发现金黄地鼠尿液中蛋白、尿素氮、钾、钠、钙等明显高于大白鼠；金黄地鼠尿液粘稠，比重大，干枯后显白色，主要与尿液中高磷酸盐结晶、高蛋白及高尿素氮等有关。提出在蛋白尿中大量损失后，仍未见金黄地刀出现蛋白质缺乏性病理变化，其原因值得深究。金黄地鼠能否作为自发性高蛋白尿实验动物模型，有待进一步研究。     

高浓度甲醛废水预处理工艺研究

采用“尿素缩合-粉煤灰吸附-Fenton氧化”复合工艺来处理高浓度甲醛废水,对影响甲醛去除率的因素进行了试验探讨,并确定了工艺优化条件．用该工艺处理高浓度甲醛废水,甲醛的总去除率可达到99％以上,能满足最终生化处理的要求．     

Two-dimensional self-healing hydrogen-bond-based supramolecular polymer film

A monolayer hydrogen-bond-based supramolecular polymer (HSP) film has self-healing properties at the two-dimensional limit after destroyed by tip of atomic force microscopy and it can also modify the SiO₂ dielectric for copper phthalocyanine field effect transistor with improved mobility.     

A new urea gelator: incorporation of intra- and intermolecular hydrogen bonding for stable 1D self-assembly

A new bisurea gelator derived from 2,6-diaminopyridine has been developed. It efficiently gelates common organic and liquid crystalline (LC) solvents by forming elongated self-assembled fibres in solvents. X-Ray crystallography and 1H NMR measurements reveal that two urea groups in pyridine-based bisurea compounds form different hydrogen bonding patterns. One of two urea units is involved in intramolecular hydrogen bonding with the pyridyl nitrogen, while the other urea unit forms bifurcated intermolecular hydrogen bonding. This hydrogen-bonded structure is key for the fibrous self-assembly along with the efficient gelation. In addition, LC gels based on the pyridine-based gelator exhibit good electrooptic properties. These results indicate that the pyridine-based bisurea compound is a good gelator not only effective in gelation but also useful as a component of functional soft materials.     

极性基团修饰金属有机框架材料吸附分离CO2的研究进展

基于从废气中脱除回收CO_2的迫切现实需求,通过对金属有机框架材料(MOFs)进行功能化修饰,构筑具有高容量、高选择性CO_2吸附的耐水MOFs材料成为当前的研究热点。本文首先对MOFs材料的高压CO_2吸附进行了简单的介绍;进而,针对实际工业应用中低压条件下的CO_2捕集,对作为调节MOFs材料CO_2低压吸附分离性能的有效手段的含氮以及杂原子极性基团修饰进行了综述。     

Effective purification of oily wastewater using lignocellulosic biomass: A review

Due to the frequent occurrence of oil spills and the large-scale production of oily wastewater, the treatment of oily sewage has become an important issue for sustainable development. Recently, materials prepared from lignocellulosic biomass(LCB) for oil-water separation have been found to be effective due to their high separation efficiency, good recyclability, and superior sustainability. However, few reviews have focused on the advantages and limitations of LCB for sewage treatment. This revi...     

Construction of hierarchical nanostructures and NiO nanosheets@nanorods for efficient urea electrooxidation

Hierarchical NiO nanosheets@nanorods have been rationally designed and constructed for efficient urea electrooxidation in an alkaline solution. The critical synthetic strategy, engaging the one-step anion-competitive reaction, precisely integrates two nickel-based materials into a heterostructure with Ni(OH)₂ nanosheets and NiC₂O₄ nanorods. Benefiting from the hierarchically porous structure and high specific surface area, the NiO NNs can improve the escape efficiency of gas in electrochemical reactions and maintain sustainability. Furthermore, this distinctive structure can expose highly dispersed active sites for enhancing urea molecules' adsorption, surface-dependent redox reactions, and electrical conductivities. As a result, these hierarchical NiO nanosheets@nanorods exhibit superior activity with a low overpotential of 156 mV at 10 mA/cm², and a slight Tafel slope of 40.7 mV/dec, and high stability with almost no decay of 12,000 s for urea electrooxidation. This work promotes the application of well-designed hierarchical structure in electrooxidizing urea and provides a possibility for highly efficient electrolysis of alkaline urea wastewater.