Consideration of Potential Technologies for Ammonia Removal and Recovery from Produced Water

New insight in the biotreatment of produced water: Pre-oxidation paves a rapid pathway for substrate selection in microbial community

The deep treatment of produced water (PW) had emerged as a formidable challenge due to the coexistence of hydrocarbons, surfactants, ammonium nitrogen, and other refractory organics. On the basis of the pre-oxidation coupled heterotrophic ammonia assimilation (PHAA) system constructed in previous research, this work refined the catalyst selection and reduced the hydraulic retention time. The stable running PHAA system removed 96.2 % of total organic carbon (TOC). The study simulated the effects of organic loading fluctuations on the system and dissected the mechanism of pre-oxidation process and its contribution to microbial community. Pre-oxidation significantly improved the ability of microbial community to handle loading shocks and improved organic degradation efficiency in PW during long-term reactor operation. The PHAA process effectively removed medium to long chain alkanes above C24 in PW and proposed potential degradation pathways and direction. The determination of hydrocarbon enzymes activity showed that pre-oxidation changed the substrate selection, making more aldehydes available as auxiliary carbon sources for microorganisms. Pre-oxidation also enriched and preserved microbial diversity, facilitating the accumulation of functional microorganisms in the PHAA process.

Enhancing microfiltration membrane performance by sodium percarbonate-based oxidation for hydraulic fracturing wastewater treatment

Low pressure membrane takes a great role in hydraulic fracturing wastewater (HFW), while membrane fouling is a critical issue for the stable operation of microfiltration (MF). This study focused on fouling mitigation by sodium percarbonate (SPC) oxidation, activated by ultraviolet (UV) and ferrous ion (Fe(II)). The higher the concentration of oxidizer, the better the anti-fouling performance of MF membrane. Unlike severe MF fouling without oxidation (17.26 L/(m2·h)), UV/SPC and Fe(II)/SPC under optimized dosage improved the final flux to 740 and 1553 L/(m2·h), respectively, and the latter generated Fe(III) which acted as a coagulant. Fe(II)/SPC oxidation enabled a shift in fouling mechanism from complete blocking to cake filtration, while UV/SPC oxidation changed it to standard blockage. UV/SPC oxidation was stronger than Fe(II)/SPC oxidation in removing UV254 and fluorescent organics for higher oxidizing capacity, but the opposite was noted for DOC removal. The deposited foulants on membrane surface after oxidation decreased by at least 88% compared to untreated HFW. Correlation analysis showed that UV254, DOC and organic fraction were key parameters responsible for membrane fouling (correlation coefficient＞0.80), oxidizing capacity and turbidity after oxidation were also important parameters. These results provide new insights for fouling control during the HFW treatment.

Gravity-driven membrane integrated with membrane distillation for efficient shale gas produced water treatment

Substantial volumes of hazardous shale gas produced water (SGPW) generated in unconventional natural gas exploration. Membrane distillation (MD) is a promising approach for SGPW desalination, while membrane fouling, wetting, and permeate deterioration restrict MD application. The integration of gravity-driven membrane (GDM) with MD process was proposed to improve MD performance, and different pretreatment methods (i.e., oxidation, coagulation, and granular filtration) were systematically investigated. Results showed that pretreatment released GDM fouling and improved permeate quality by enrich certain microbes' community (e.g., Proteobacteria and Nitrosomonadaceae), greatly ensured the efficient desalination of MD. Pretreatment greatly influences GDM fouling layer morphology, leading to different flux performance. Thick/rough/hydrophilic fouling layer formed after coagulation, and thin/loose fouling layer formed after silica sand filtration improved GDM flux by 2.92 and 1.9 times, respectively. Moreover, the beneficial utilization of adsorption-biodegradation effects significantly enhanced GDM permeate quality. 100 % of ammonia and 53.99 % of UV254 were efficiently removed after zeolite filtration-GDM and granular activated carbon filtration-GDM, respectively. Compared to the surged conductivity (41.29 μS/cm) and severe flux decline (>82 %) under water recovery rate of 75 % observed in single MD for SGPW treatment, GDM economically controlled permeate conductivity (1.39-19.9 μS/cm) and MD fouling (flux decline=8.3 %-27.5 %). Exploring the mechanisms, the GDM-MD process has similarity with Janus MD membrane in SGPW treatment, significantly reduced MD fouling and wetting.

Benchmarking produced water treatment strategies for non-toxic effluents: Integrating thermal distillation with granular activated carbon and zeolite post-treatment

The management of produced water (PW) generated during oil and gas operations requires effective treatment and comprehensive chemical and toxicological assessment to reduce the environmental risks associated with reuse or discharge. This study evaluated a treatment train that included a low-temperature thermal distillation pilot system followed by granular activated carbon (GAC) and zeolite post-treatment for processing hypersaline Permian Basin PW. Our study provides a unique and comprehensive assessment of the treatment efficiency considering a targeted chemical scheme together with whole effluent toxicity (WET) tests across four trophic levels regarding aquatic critical receptors of concern (ROC): Raphidocelis subcapitata, Vibrio fischeri, Ceriodaphnia dubia, and Danio rerio. The distillate from the thermal distillation process met various numeric discharge standards for salinity and major ions. However, it did not meet toxicity requirements established by the United States National Pollutant Discharge Elimination System program. Subsequent post-treatment using GAC and zeolite reduced the concentration of potential stressors, including volatile organics, NH3, Cd, Cr, Zn, and Mn in the final effluent to below detection limits. This resulted in a consistent toxicity reduction across all WET tests, with no observable adverse effects for R. subcapitata, C. dubia, and D. rerio (no observed effect concentration >100%), and V. fischeri effects reduced to 19%. This study realizes the feasibility of treating PW to non-toxic levels and meeting reuse and discharge requirements. It underscores the importance of implementing integrated treatment trains to remove the contaminants of concern and provides a systematic decision framework to predict and monitor environmental risks associated with PW reuse.

Offshore produced water treatment by a biofilm reactor on the seabed: The effect of temperature and matrix characteristics

In many industrial processes a large amount of water with high salinity is co-produced whose treatment poses considerable challenges to the available technologies. The produced water (PW) from offshore operations is currently being discharged to sea without treatment for dissolved pollutants due to space limitations. A biofilter on the seabed adjacent to a production platform would negate all size restrictions, thus reducing the environmental impact of oil and gas production offshore. The moving bed biofilm reactor (MBBR) was investigated for PW treatment from different oilfields in the North Sea at 10 °C and 40 °C, corresponding to the sea and PW temperature, respectively. The six PW samples in study were characterized by high salinity and chemical oxygen demand with ecotoxic effects on marine algae S. pseudocostatum (0.4% Collapse

Key Words

• Biofilm
• Biological treatment
• High salinity
• Industrial wastewater
• Offshore
• Temperature

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MESH Headings

• Biofilms
• Bioreactors
• Temperature
• Water Purification/methods
• Salinity
• Biological Oxygen Demand Analysis
• Water Pollutants, Chemical

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Affiliation(s)

Ana Rita Ferreira Department of Environmental and Resource Engineering (DTU Sustain). Water Technology & Processes. Technical University of Denmark, Bygningstorvet 115, 2800, Lyngby, Denmark.
Lars Michael Skjolding Department of Environmental and Resource Engineering (DTU Sustain). Water Technology & Processes. Technical University of Denmark, Bygningstorvet 115, 2800, Lyngby, Denmark
Diego Francisco Sanchez Department of Environmental and Resource Engineering (DTU Sustain). Water Technology & Processes. Technical University of Denmark, Bygningstorvet 115, 2800, Lyngby, Denmark
Alexandros Georgios Bernar Ntynez Department of Environmental and Resource Engineering (DTU Sustain). Water Technology & Processes. Technical University of Denmark, Bygningstorvet 115, 2800, Lyngby, Denmark
Yanina Dragomilova Ivanova Danish Offshore Technology Centre (DTU Offshore). Technical University of Denmark, Elektrovej 375, 2800, Lyngby, Denmark
Karen Louise Feilberg Danish Offshore Technology Centre (DTU Offshore). Technical University of Denmark, Elektrovej 375, 2800, Lyngby, Denmark
Ravi K Chhetri Department of Environmental and Resource Engineering (DTU Sustain). Water Technology & Processes. Technical University of Denmark, Bygningstorvet 115, 2800, Lyngby, Denmark
Henrik R Andersen Department of Environmental and Resource Engineering (DTU Sustain). Water Technology & Processes. Technical University of Denmark, Bygningstorvet 115, 2800, Lyngby, Denmark

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Biological treatment of N-methylpyrrolidone, cyclopentanone, and diethylene glycol monobutyl ether distilled residues and their effects on nitrogen removal in a full-scale wastewater treatment plant

Manufacturing processes in semiconductor and photonics industries involve the use of a significant amount of organic solvents. Recycle and reuse of these solvents produce distillate residues and require treatment before being discharged. This study aimed to evaluate the performance of the biological treatment system in a full-scale wastewater treatment plant that treats wastewater containing distillate residues from the recycling of electronic chemicals. Batch experiments were conducted to investigate the optimal operational conditions for the full-scale wastewater treatment plant. To achieve good nitrogen removal efficiency with effluent ammonia and nitrate concentrations below 20 mg N/L and 50 mg N/L, respectively, it was suggested to control the ammonia concentration and pH of the influent below 500 mg N/L and 8.0, respectively. In addition, the biodegradability of N-methylpyrrolidone, diethylene glycol monobutyl ether, and cyclopentanone distillate residues from the electronic chemicals manufacturing process were evaluated under aerobic, anoxic, and anaerobic conditions. N-methylpyrrolidone and cyclopentanone distillate residues were suggested to be treated under anoxic condition. However, substrate inhibition occurred when using cyclopentanone distillate residue as a carbon source with chemical oxygen demand (COD) levels higher than 866 mg/L and nitrate levels higher than 415 mg N/L. Under aerobic condition, the COD from both N-methylpyrrolidone and cyclopentanone distillate residues could be easily degraded. Nevertheless, a negative effect on nitrification was observed, with a prolonged lag time for ammonia oxidation as the initial COD concentration increased. The specific ammonia oxidation rate and nitrate production rate decreased under high COD concentration contributed by N-methylpyrrolidone and cyclopentanone distillate residues. Furthermore, the biodegradability of diethylene glycol monobutyl ether distillate residue was found to be low under aerobic, anoxic, and anaerobic conditions. With respect to the abundance of nitrogen removal microorganisms in the wastewater treatment plant, results showed that Comammox may have an advantage over ammonia oxidizing bacteria under high pH conditions. In addition, Comammox may have higher resistance to environmental changes. Dominance of Comammox over ammonia oxidizing bacteria under high ammonia condition was first reported in this study.

Formation of oxidation byproducts during electrochemical treatment of simulated produced water

Electrochemical oxidation (EO) can effectively remove recalcitrant organic contaminants from produced water (PW) but the formation of toxic oxidation byproducts (OBPs) is an unintended consequence. This study has rigorously investigated the OBPs formation during the EO treatment of a simulated PW containing phenol - a common organic contaminant existing in PW, as a model contaminant. In the absence of ammonia, free chlorine was generated from Cl- oxidation to serve as the main oxidant for phenol oxidation. During the EO process, 2,4,6-trichlorophenol and 2,6-dichlorobenzoquinone were identified as the critical intermediates that led to the formation of carbonaceous OBPs (C-OBPs). Some C-OBPs like chloroform (TCM), chloral hydrate (CH), and trichloroacetic acid (TCAA) reached their peak concentrations of 15 - 180 μM that were then reduced to 1 - 115 μM via volatilization and/or electrochemical reduction. When ammonia was present, nitrogenous OBPs (N-OBPs) were formed with the peak levels of 1 - 10 μM at the chlorination breakpoint (when ammonia was completely removed) that were subsequently reduced below 1 uM via volatilization and/or hydrolysis. It was observed that ammonia significantly decreased the formation of both C-OBPs and chlorate due to the consumption of free chlorine. A higher current density accelerated OBPs formation rates with different effects on volatile and non-volatile OBPs. The results of this study will enhance our understanding of OBPs formation precursors and mechanisms during electrochemical process and help develop strategies for proper control of OBPs to achieve safer electrochemical wastewater treatment.

Implications of the Pore Size of Graphitic Carbon Nitride Monolayers on the Selectivity of Dual-Boron Atom Catalysts for the Reduction of N2 to Urea and Ammonia: A Computational Investigation

The formation of urea by electrocatalytic means remains a great challenge due to the lack of a suitable catalyst that is capable of not only activating inert N2 and CO2 molecules but also circumventing the complexity associated with subsequent reaction steps leading to urea formation. Herein, by means of comprehensive density functional theory simulations, we investigate the catalytic activity of highly stable transition-metal-free dual-boron atom-doped graphitic carbon-nitride monolayers with different pore sizes toward urea production under ambient conditions. As per the results, dual boron atoms impregnated in g-C2N and g-C6N6 monolayers with large pore diameters can successfully activate the N2 molecule and lead to the spontaneous formation of the *NCO*N intermediate, which is the most crucial step for urea formation via direct coupling of N2 and CO2. Interestingly, the B2@g-C2N and B2@g-C6N6 favor urea production with low limiting potentials of -1.11 and -1.18 V compared to very high limiting potentials of -1.71 and -1.88 V, respectively, for ammonia synthesis, leading to an almost 100% Faradaic efficiency for urea formation over ammonia. The dual-boron doping in g-C3N4 with a smaller pore size depicts comparatively weaker N2 adsorption than g-C2N and g-C6N6 counterparts. Further, B2@g-C3N4 prefers ammonia formation at a very low limiting potential of -0.40 V compared to a very high limiting potential of -2.11 V for urea formation. Thus, our findings clearly highlight the critical role played by the pore size of carbon-nitride monolayers in tuning the reactivity and catalytic activity of dual-boron atom catalysts toward urea formation in a selective manner, thereby providing valuable guidance in exploring other highly efficient urea catalysts.

A new strategy to simultaneous removal and recovery of nitrogen from wastewater without N2O emission by heterotrophic nitrogen-assimilating bacterium

Biological assimilation that recovery the nitrogen from wastewater in the form of biomass offers a more environmentally friendly solution for the limitations of the conventional wastewater treatments. This study reported the simultaneous removal and recovery of nitrogen from wastewater without N₂O emission by a heterotrophic nitrogen-assimilating Acinetobacter sp. DN1 strain. Nitrogen balance, biomass qualitative analysis, genome and enzyme studies have been performed to illustrate the mechanism of nitrogen conversion by strain DN1. Results showed that the ammonium removal followed one direct pathway (GOGAT/GDH) and three indirect pathways (NH₄⁺ → NH₂OH → NO → NO₂^- → NH₄⁺ → GOGAT/GDH; NH₄⁺ → NH₂OH → NO → NO₂^- → NO₃^- → NO₂^- → NH₄⁺ → GOGAT/GDH; NH₄⁺ → NH₂OH → NO → NO₃^- → NO₂^- → NH₄⁺ → GOGAT/GDH). Nitrogen balance and biomass qualitative analysis showed that over 70 % of the ammonium in the wastewater was converted into intracellular nitrogen-containing compounds and stored in the cells of strain DN1. Traditional denitrification pathway was not detected and the ammonium was removed through assimilation, which makes it more energy-saving for nitrogen recovery when compared with Haber-Bosch process. This study provides a new direction for simultaneous nitrogen removal and recovery without N₂O emission by the heterotrophic nitrogen-assimilating bacterium.

Unveiling the impact of imidazole derivative with mechanistic insights into neutralize interfacial polymerized membranes for improved solute-solute selectivity

Domestic wastewater (DWW) contains a reservoir of nutrients, such as nitrogen, potassium, and phosphorus; however, emerging micropollutants (EMPs) hinder its applications in resource recovery. In this study, a novel class of nanofiltration (NF) membranes was developed; it enabled the efficient removal of harmful EMP constituents while preserving valuable nutrients in the permeate. Neutral (IM-N) and positively charged (IM-P) imidazole derivative compounds have been used to chemically functionalize pristine polyamide (PA) membranes to synchronously inhibit the hydrolysis of residual acyl chloride and promote their amination. Owing to their distinct properties, these IM modifiers can custom-build the membrane physicochemical properties and structures to benefit the NF process in DWW treatment. The electroneutral NF membrane exhibited ultrahigh solute-solute selectivity by minimizing the Donnan effects on ion penetration (K, N, and P ions rejection < 25%) while imposing remarkable size-sieving obstruction against EMPs (rejection ratio > 91%). Moreover, the hydrophilic IM-modifier synergistically led to enhanced water permeance of 9.2 L m^-2 h^-1 bar^-1, reaching a 2-fold higher magnitude than that of the pristine PA membrane, along with excellent antifouling/antibacterial fouling properties. This study may provide a paradigm shift in membrane technology to convert wastewater streams into valuable water and nutrient resources.

Mapping the research on desulfurization wastewater: Insights from a bibliometric review (1991-2021)

Desulfurization wastewater in coal-fired power plants (CFPPs) is a great environmental challenge. This study aimed at the current status and future research trends of desulfurization wastewater by bibliometric analysis. The desulfurization wastewater featured with high sulfate (8000 mg/L), chlorite (8505 mg/L), magnesium (2882 mg/L) and calcium (969 mg/L) but low sodium (801.82 mg/L), and the concentrations of the main contaminants were critically summarized. There was an increasing trend in the annual publications of desulfurization wastewater in the period from 1991 to 2021, with an average growth rate of 15%. Water Science and Technology, Desalination and Water Treatment, Energy & Fuels, Chemosphere, and Journal of Hazardous Materials are the top 5 journals in this field. China was the most productive country (58.3% of global output) and the core country in the international cooperation network. Wordcloud analysis and keyword topic trend demonstrated that removal/treatment of pollutants dominated the global research in the field of desulfurization wastewater. The primary technologies for desulfurization wastewater treatment were systematically evaluated. The physicochemical treatment technologies occupied half of the total treatment methods, while membrane-based integrated processes showed potential applications for beneficial reuse. The challenges and outlook on desulfurization wastewater treatment for achieving zero liquid discharge are summarized.

A Petal-like Structured NiCuOOH-NF Electrode by a Sonochemical Combined with the Electrochemical Method for Ammonia Oxidation Reaction

Direct electrochemical oxidation, as an economical and efficient method, has recently received increasing attention for ammonia-nitrogen wastewater treatment. Developing a low-cost, efficient catalytic electrode is the key to solve the problem of sluggish ammonia oxidation reaction (AOR) kinetics. In this study, a three-dimensional (3D) Ni foam electrode coated with NiCuOOH petal-like cluster structures was prepared using a simple sonochemical method combined with a surface electrochemical reconstruction strategy. This structure has a large surface area and abundant NiCuOOH active sites, giving a good premise for extraordinary electrocatalytic activity of AOR. The results show that the maximum current density for AOR reaches 97.8 mA cm−2 at 0.60 V vs. saturated calomel electrode (SCE). Additionally, 96.53% of NH4+-N removal efficiency and 63.12% of TN removal efficiency were acquired in the electrolysis system based on the NiCuOOH-NF electrode, as well as a good stability for at least 24 h. It is a promising flow-through anode for the clean treatment of ammonia-nitrogen wastewater.