Ammonia Recovery from Hydrolyzed Human Urine by Forward Osmosis with Acidified Draw Solution

Fertilizer-driven FO and MD integrated process for shale gas produced water treatment: Draw solution evaluation and PAC enhancement

It is a great challenge for effective treatment of shale gas produced water (SGPW), a typical industrial wastewater with complex composition. Single forward osmosis (FO) or membrane distillation (MD) process has been widely used for desalination of SGPW, with membrane fouling not well addressed. Fertilizer draw solution (DS) with high osmotic pressure is less likely to cause FO fouling and can be used for irrigation. An integrated process using fertilizer-driven FO (FDFO) and MD process was proposed for the first time for SGPW treatment, and characteristics of fertilizer DS and powdered activated carbon (PAC) enhancement were assessed. The DS using KCl and (NH4)2SO4 had high MD fluxes (36.8-38.8 L/(m2·h)) and low permeate conductivity (below 50 μS/cm), increasing the contact angle of the MD membrane by 113 % than that without FO, while the DS using MgCl2 and NH4H2PO4 produced a lower reverse salt flux (0.9-3.2 g/(m2·h)). When diluted DS was treated using PAC, the MD permeate conductivity was further reduced to 35 μS/cm without ammonia, and the membrane hydrophobicity was maintained to 71-83 % of the original. The mechanism of the FDFO-MD integrated process for mitigating MD fouling and improving permeate quality was analyzed, providing guidance for efficient SGPW treatment.

Ammonia recovery via direct contact membrane distillation: Modeling and performance optimization

Ammonia recovery from wastewater has positive environmental benefits, avoiding eutrophication and reducing production energy consumption, which is one of the most effective ways to manage nutrients in wastewater. Specifically, ammonia recovery by membrane distillation has been gradually adopted due to its excellent separation properties for volatile substances. However, the global optimization of direct contact membrane distillation (DCMD) operating parameters to maximize ammonia recovery efficiency (ARE) has not been attempted. In this work, three key operating factors affecting ammonia recovery, i.e., feed ammonia concentration, feed pH, and DCMD running time, were identified from eight factors, by a two-level Plackett-Burman Design (PBD). Subsequently, Box-Behnken design (BBD) under the response surface methodology (RSM) was used to model and optimize the significant operating parameters affecting the recovery of ammonia though DCMD identified by PBD and statistically verified by analysis of variance (ANOVA). Results showed that the model had a high coefficient of determination value (R2 = 0.99), and the interaction between NH4Cl concentration and feed pH had a significant effect on ARE. The optimal operating parameters of DCMD as follows: NH4Cl concentration of 0.46 g/L, feed pH of 10.6, DCMD running time of 11.3 h, and the maximum value of ARE was 98.46%. Under the optimized conditions, ARE reached up to 98.72%, which matched the predicted value and verified the validity and reliability of the model for the optimization of ammonia recovery by DCMD process.

Viability of Total Ammoniacal Nitrogen Recovery Using a Polymeric Thin-Film Composite Forward Osmosis Membrane: Determination of Ammonia Permeability Coefficient

Total ammoniacal nitrogen (TAN) occurs in various wastewaters and its recovery is vital for environmental reasons. Forward osmosis (FO), an energy-efficient technology, extracts water from a feed solution (FS) and into a draw solution (DS). Asymmetric FO membranes consist of an active layer and a support layer, leading to internal concentration polarization (ICP). In this study, we assessed TAN recovery using a polymeric thin-film composite FO membrane by determining the permeability coefficients of NH4+ and NH3. Calculations employed the solution-diffusion model, Nernst-Planck equation, and film theory, applying the acid-base equilibrium for bulk concentration corrections. Initially, model parameters were estimated using sodium salt solutions as the DS and deionized water as the FS. The NH4+ permeability coefficient was 0.45 µm/s for NH4Cl and 0.013 µm/s for (NH4)2SO4 at pH < 7. Meanwhile, the NH3 permeability coefficient was 6.18 µm/s at pH > 9 for both ammonium salts. Polymeric FO membranes can simultaneously recover ammonia and water, achieving 15% and 35% recovery at pH 11.5, respectively.

Bubble Turbulent Gas-Permeable Membrane for Ammonia Recovery from Swine Wastewater: Mass Transfer Enhancement and Antifouling Mechanisms

Recovering ammonium from swine wastewater employing a gas-permeable membrane (GM) has potential but suffers from the limitations of unattractive mass transfer and poor-tolerance antifouling properties. Turbulence is an effective approach to enhancing the release of volatile ammonia from wastewater while relying on interfacial disturbance to interfere with contaminant adhesion. Herein, we design an innovative gas-permeable membrane coupled with bubble turbulence (BT-GM) that enhances mass transfer while mitigating membrane fouling. Bubbles act as turbulence carriers to accelerate the release and migration of ammonia from the liquid phase, increasing the ammonia concentration gradient at the membrane-liquid interface. In comparison, the ammonium mass transfer rate of the BT-GM process applied to real swine wastewater is 38% higher than that of conventional GM (12 h). Through a computational fluid dynamics simulation, the turbulence kinetic energy of BT-GM system is 3 orders of magnitude higher than that of GM, and the effective mass transfer area is nearly 3 times that of GM. Seven batches of tests confirmed that the BT-GM system exhibits remarkable antifouling ability, broadens its adaptability to complex water quality, and practically promotes the development of sustainable resource recycling.

Banana Peel Derived Chitosan-Grafted Biocomposite for Recovery of NH4+ and PO43

Biomass-derived adsorbents afford accessible and inexpensive harvesting of nitrogen and phosphorus from wastewater sources. Human urine is widely accepted as a rich source of nitrogen and phosphorus. However, direct use of urine in agriculture is untenable because of its unpleasant smell, pathogen contamination, and pharmaceutical residues. In this work, we have grafted chitosan onto dried and crushed banana peel (DCBP) to generate the biocomposite DCBP/Ch. A combination of FTIR, TGA, XRD, FESEM, EDX, and NMR analyses were used to characterize DCBP/Ch and reveal condensation-aided covalent conjugation between O-H functionalities of DCBP and chitosan. The adsorption performance of DCBP/Ch toward NH4+ and PO43- is in sync with its attractive surface porosity, elevated crystallinity, and thermostability. The maximum adsorption capacity of DCBP/Ch toward NH4+/PO43- was estimated as 42.16/15.91 mg g-1 at an operating pH of 7/4, respectively, and ranks highly when compared to previously reported bioadsorbents. DCBP/Ch performs admirably when tested on artificial urine. While nitrogen and phosphorus harvesting from human urine using single techniques has been reported previously, this is the first report of a single adsorbent for recovery of NH4+ and PO43-. The environmental compatibility, ease of preparation, and economic viability of DCBP/Ch present it as an attractive candidate for deployment in waste channels.

A novel approach for enhancing nitrogen and hydrogen recovery from urine in microbial electrochemical gas-permeable membrane system

Source-separated urine is a readily accessible nutrients dense waste stream that can be used to recover nitrogen and hydrogen. In the research, the microbial electrochemical gas-permeable membrane system (MEGS) is creatively introduced for urine treatment in removing organics, recovering the total ammonia nitrogen and high-value product of hydrogen (H₂) as well as ammonium sulfate ((NH₄)₂SO₄). MEGS can simultaneously realize the functions of H₂ recovery, in-situ efficient alkali production at the cathode, and the efficient absorption capacity of the gas-permeable membrane (GPM). Under the action of the urease enzyme, urea is hydrolyzed into large amounts of carbonic acid and ammonium, causing the pH (7.87 ± 0.13) and conductivity (5.44 ± 0.21 mS cm^-1) of the anode to increase extremely rapidly. A large amount of NH₄⁺ was transported to the cathode chamber under the strengthening effect of the electric field, enriched, and then absorbed to produce the high-quality (NH₄)₂SO₄ to be recovered. The findings reveal that MEGS can achieve 100 % of urea removal, 88.52 ± 0.40 % of COD removal, 94.22 ± 2.57 % of nitrogen recovery, 0.58 ± 0.03 m³ m^-3 d^-1 of hydrogen yield, and 3.78 kg m^-3 of (NH₄)₂SO₄ production with 78.03 ± 3.51 % of coulombic efficiency during a 30-h cycle. A benefit of $18.29 can be achieved with the recovery of (NH₄)₂SO₄ and H₂ from 1 m³ of urine. The study presents a promising idea for the efficient nutrient-energy recovery and utilization of urine.

Efficient electrochemical generation of active chlorine to mediate urea and ammonia oxidation in a hierarchically porous-Ru/RuO2-based flow reactor

The electrochemical chlorination of urea to CO₂ and N₂ end-products, via active-chlorine-mediated oxidation under nearly neutral conditions, is an effective treatment for medium-concentrated urea-containing wastewater. Herein, we design a novel flow reactor integrated with three-dimensional hierarchically porous Ru/RuO₂ architectures anchored on a Ti mesh. The hierarchically macroporous electrode can create sufficient exposure of catalytically active sites and facilitate the microscopic mass transport and diffusion inside the active layer, thereby contributing to the increased removal efficiency of urea-N and ammonia-N. The combined results of electrochemical measurements, UV-visible spectrometry and in situ Raman spectrometry, show that the OCl^- species produced by chlorine evolution reaction (CER) are the main active constituents for removing urea-N. Theoretical calculations reveal thLTWAat the Ru/RuO₂ possesses a moderate Cl binding strength, lower theoretical overpotentials of CER and a higher conductivity, compared with pure RuO₂. On this basis, we assemble a circular flow reactor with the hierarchically porous electrodes in a two-electrode system to obtain an enhanced microfluidic process, which during 9 days of uninterrupted operation, at a high electrolysis current of 500 mA, achieve a total nitrogen removal of 92.6% and an energy consumption of 7.94 kWh kg^-1 N, demonstrating the promising application of the novel process.

Armor-Structured Interconnected-Porous Membranes for Corrosion-Resistant and Highly Permeable Waste Ammonium Resource Recycling

Ammonium recovery from wastewater by gas-permeable membranes is promising but suffers from the tradeoff between membrane stability and permeability under harsh operating conditions. Chemical-resistant membranes display modest permeability due to the poor solubility and processibility; chemically active membranes are easier to be endowed with better permeability however hinder by instability. To resolve such a problem, we cleverly design a novel membrane configuration via one-step solution-electrospinning, with the chemical-active component (low-strength fluorine polymer) as the inner skeleton to construct interconnected porous structures and the chemical-resistant component (high-strength fluorine polymer) as the outer armor to serve as a protective layer. Due to the significantly enhanced mass transfer coefficient, the interconnected-porous armor-structured membrane exhibited much higher permeability for NH₄⁺-N recovery, which was 1.4 and 5 times that of the traditional PTFE membrane and PP membrane, respectively. Through long-term intermittent and consecutive experiments, the reusability and durability of the armor-structured nanofibrous membrane were verified. When treating actual hoggery wastewater with complicated water quality, the armor-structured nanofibrous membrane also displayed robust stable performance with excellent antiwettability. The mechanisms of membrane formation, corrosion resistance, and mass transfer were discussed in detail.

Parahydrogen hyperpolarization of minimally altered urine samples for sensitivity enhanced NMR metabolomics

Parahydrogen hyperpolarization has been shown to enhance NMR sensitivity in urine analysis by several orders of magnitude if urine samples are prepared by solid phase extraction (SPE). We present a different approach, developed for minimal sample alteration before analysis. Removing SPE from the workflow allows to retain a wider range of metabolites and paves the way towards more universal hyperpolarized NMR metabolomics of low abundance metabolites.

Concentrating nutrients and recovering water and energy from source separated urine using osmotic microbial fuel cell

This work presents the use of osmotic microbial fuel cell (OsMFC), for the first time, to concentrate nutrients and recover water and energy from source separated urine. Four sets of concentration of fresh urine as feed and NaCl as draw were examined: 10% fresh urine vs 0.25 M NaCl; 10% fresh urine vs 2 M NaCl; fresh urine vs 0.25 M NaCl; and fresh urine vs 2 M NaCl. A maximum water flux of 14.27 LMH was attained when 10% of fresh urine and 2 M of NaCl were used as feed and draw solutions, respectively. Additionally, OsMFC concentrates ~99% of TOC, TN, NH₄⁺, and 100% of PO₄^3- and NO₃^- from urine at the feed side. Polarization studies indicate that the power generation in OsMFC is related to the rate of change of conductivity and the initial conductivity of the anolyte. The maximum (0.12187 W m^-3) and minimum power densities (5.3372 × 10^-4 W m^-3) were obtained for the conditions of fresh urine vs 0.25 M NaCl and 10% fresh urine vs 0.25 M NaCl, respectively. The study shows that OsMFC is an effective pretreatment process to concentrate nutrients from urine by recovering water and energy, simultaneously.

Bipolar Membrane Electrodialysis for Ammonia Recovery from Synthetic Urine: Experiments, Modeling, and Performance Analysis

Recovering nitrogen from source-separated urine is an important part of the sustainable nitrogen management. A novel bipolar membrane electrodialysis with membrane contactor (BMED-MC) process is demonstrated here for efficient recovery of ammonia from synthetic source-separated urine (∼3772 mg N L^-1). In a BMED-MC process, electrically driven water dissociation in a bipolar membrane simultaneously increases the pH of the urine stream and produces an acid stream for ammonia stripping. With the increased pH of urine, ammonia transports across the gas-permeable membrane in the membrane contactor and is recovered by the acid stream as ammonium sulfate that can be directly used as fertilizer. Our results obtained using batch experiments demonstrate that the BMED-MC process can achieve 90% recovery. The average ammonia flux and the specific energy consumption can be regulated by varying the current density. At a current density of 20 mA cm^-2, the energy required to achieve a 67.5% ammonia recovery in a 7 h batch mode is 92.8 MJ kg^-1 N for a bench-scale system with one membrane stack and can approach 25.8 MJ kg^-1 N for large-scale systems with multiple membrane stacks, with an average ammonia flux of 2.2 mol m^-2 h^-1. Modeling results show that a continuous BMED-MC process can achieve a 90% ammonia recovery with a lower energy consumption (i.e., 12.5 MJ kg^-1 N). BMED-MC shows significant potential for ammonia recovery from source-separated urine as it is relatively energy-efficient and requires no external acid solution.

Physico-chemical and biological treatment strategies for converting municipal wastewater and its residue to resources

An increase in urbanization and industrialization has not only contributed to an improvement in the lifestyle of people, but it has also contributed to a surge in the generation of wastewater. To date, conventional physico-chemical and biological treatment methods are widely used for the treatment of wastewater. However, the efficient operation of these systems require substantial operation and maintenance costs, and the application of novel technologies for the treatment and disposal of sludge/residues. This review paper focuses on the application of different treatment options such as chemical, catalyst-based, thermochemical and biological processes for wastewater or sludge treatment and membrane-based technologies (i.e. pressure-driven and non-pressure driven) for the separation of the recovered products from wastewater and its residues. As evident from the literature, a wide variety of treatment and resource recovery options are possible, both from wastewater and its residues; however, the lack of planning and selecting the most appropriate design (treatment train) to scale up from pilot to the field scale has limited its practical application. The economic feasibility of the selected technologies was critically analyzed and the future research prospects of resource recovery from wastewater have been outlined in this review.

Membrane technologies in toilet urine treatment for toilet urine resource utilization: a review

Membrane technologies have broad potential in methods for separating, collecting, storing, and utilizing urine collected from toilets. Recovering urine from toilets for resource utilization instead of treating it in a sewage treatment plant not only reduces extra energy consumption for the degradation of N and P but also saves energy in chemical fertilizer production, which will contribute to carbon emission reduction of 12.19-17.82 kg kgN -1 in terms of N alone. Due to its high efficiency in terms of volume reduction, water recycling, nutrient recovery, and pollutant removal, membrane technology is a promising technology for resource utilization from urine collected from toilets. In this review, we divide membrane technologies for resource utilization from urine collected from toilets into four categories based on the driving force: external pressure-driven membrane technology, vapor pressure-driven membrane technology, chemical potential-driven membrane technology, and electric field-driven membrane technology. These technologies influence factors such as: recovery targets and mechanisms, reaction condition optimization, and process efficiency, and these are all discussed in this review. Finally, a toilet with source-separation is suggested. In the future, membrane technology research should focus on the practical application of source-separation toilets, membrane fouling prevention, and energy consumption evaluation. This review may provide theoretical support for the resource utilization of urine collected from toilets that is based on membrane technology.

Performance and onsite regeneration of natural zeolite for ammonium removal in a field-scale non-sewered sanitation system

Natural zeolite clinoptilolite was used as the primary ammonium removal method from the permeate of an anaerobic membrane bioreactor (AnMBR) treating high-strength blackwater generated from a community toilet facility. This zeolite-based nutrient capture system (NCS) was a sub-component of a non-sewered sanitation system (NSSS) called the NEWgenerator and was field tested for 1.5 years at an informal settlement in South Africa. The NCS was operated for three consecutive loading cycles, each lasting 291, 110, and 52 days, respectively. Both blackwater (from toilets) and blackwater with yellow water (from toilets and urinals) were treated during the field trial. Over the three cycles, the NCS was able to remove 80 ± 28%, 64 ± 23%, and 94 ± 11%, respectively, of the influent ammonium. The addition of yellow water caused the rapid exhaustion of zeolite and the observed decrease of ammonium removal during Cycle 2. After Cycles 1 and 2, onsite regeneration was performed to recover the sorption capacity of the spent zeolite. The regenerant was comprised of NaCl under alkaline conditions and was operated as a recycle-batch to reduce the generation of regenerant waste. Modifications to the second regeneration process, including an increase in regenerant contact time from 15 to 30 h, improved the zeolite regeneration efficiency from 76 ± 0.7% to 96 ± 1.0%. The mass of recoverable ammonium in the regenerant was 2.63 kg NH4-N and 3.15 kg NH4-N after Regeneration 1 and 2, respectively. However, the mass of ammonium in the regenerant accounted for only 52.8% and 54.4% of the estimated NH4-N originally sorbed onto the zeolite beds after Cycles 1 and 2, respectively. The use of zeolite clinoptilolite is a feasible method for ammonium removal by NSSS that observe variable nitrogen loading rates, but further research is still needed to recover the nitrogen from the regenerant waste.