Impact of reverse nutrient diffusion on membrane biofouling in fertilizer-drawn forward osmosis

Membrane Technologies for Nitrogen Recovery from Waste Streams: Scientometrics and Technical Analysis

The concerns regarding the reactive nitrogen levels exceeding the planetary limits are well documented in the literature. A large portion of anthropogenic nitrogen ends in wastewater. Nitrogen removal in typical wastewater treatment processes consumes a considerable amount of energy. Nitrogen recovery can help in saving energy and meeting the regulatory discharge limits. This has motivated researchers and industry professionals alike to devise effective nitrogen recovery systems. Membrane technologies form a fundamental part of these systems. This work presents a thorough overview of the subject using scientometric analysis and presents an evaluation of membrane technologies guided by literature findings. The focus of nitrogen recovery research has shifted over time from nutrient concentration to the production of marketable products using improved membrane materials and designs. A practical approach for selecting hybrid systems based on the recovery goals has been proposed. A comparison between membrane technologies in terms of energy requirements, recovery efficiency, and process scale showed that gas permeable membrane (GPM) and its combination with other technologies are the most promising recovery techniques and they merit further industry attention and investment. Recommendations for potential future search trends based on industry and end users' needs have also been proposed.

Removal and Fouling Influence of Microplastics in Fertilizer Driven Forward Osmosis for Wastewater Reclamation

Insufficient removal of microplastics (MPs) and nanoplastics (NPs) may exert negative effects on the environment and human health during wastewater reclamation. The fertilizer-driven forward osmosis (FDFO) is an emerging potential technology to generate high-quality water for irrigation of hydroponic systems. In this study, the removal of MPs/NPs by the FDFO process together with their impact on FDFO membrane fouling was investigated, due to FDFO’s low molecular weight cut-off and energy requirement by using fertilizer as draw solution. Plastic particles with two different sizes (100 nm and 1 μm) and extracellular polymers released by real wastewater bacteria were utilized as model compounds for FDFO performance comparison. Results show that FDFO membrane system could generate high-quality irrigation water with only fertilizer, completely removing extracellular polymers, MPs and NPs from wastewater. It was found that the MPs and NPs themselves do not cause a significant membrane fouling. Moreover, it could help to reduce the membrane fouling caused by extracellular substances. That is probably because MPs and NPs helped to form a loose and porous fouling layer. Therefore, the FDFO process could be a long-term stable (low fouling) process for the reclamation of wastewater with high-quality requirements.

Evaluating Fertilizer-Drawn Forward Osmosis Performance in Treating Anaerobic Palm Oil Mill Effluent

Fertilizer-drawn forward osmosis (FDFO) is a potential alternative to recover and reuse water and nutrients from agricultural wastewater, such as palm oil mill effluent that consists of 95% water and is rich in nutrients. This study investigated the potential of commercial fertilizers as draw solution (DS) in FDFO to treat anaerobic palm oil mill effluent (An-POME). The process parameters affecting FO were studied and optimized, which were then applied to fertilizer selection based on FO performance and fouling propensity. Six commonly used fertilizers were screened and assessed in terms of pure water flux (J_w) and reverse salt flux (J_S). Ammonium sulfate ((NH₄)₂SO₄), mono-ammonium phosphate (MAP), and potassium chloride (KCl) were further evaluated with An-POME. MAP showed the best performance against An-POME, with a high average water flux, low flux decline, the highest performance ratio (PR), and highest water recovery of 5.9% for a 4-h operation. In a 24-h fouling run, the average flux decline and water recovered were 84% and 15%, respectively. Both hydraulic flushing and osmotic backwashing cleaning were able to effectively restore the water flux. The results demonstrated that FDFO using commercial fertilizers has the potential for the treatment of An-POME for water recovery. Nevertheless, further investigation is needed to address challenges such as J_S and the dilution factor of DS for direct use of fertigation.

Effect of organic micropollutants on biofouling in a forward osmosis process integrating seawater desalination and wastewater reclamation

This study systematically investigated the effect of organic micropollutants (OMPs) on biofouling in forward osmosis (FO) integrating wastewater treatment and seawater dilution. Synthetic seawater (0.6 M sodium chloride) was used as a draw solution and synthetic municipal wastewater as a feed solution. To evaluate the impact of OMPs in a replicate parallel study, wastewater was supplemented with a mixture of 7 OMPs (OMPs-feed) and without OMPs (control) during 8 batch filtration cycles with feed and draw solution replacement after each filtration. The FO performance (water flux), development and microbial composition properties of biofilm layers on the wastewater side of the FO membrane were studied. Compared to the control without OMPs, the FO fed with OMPs containing wastewater showed (i) initially the same water flux and flux decline during the first filtration cycle, (ii) with increasing filtration cycle a lower flux decline and (iii) lower concentrations for the total cells, ATP, EPS carbohydrates and proteins in biofilm layers, and (iv) a lower diversity of the biofilm microbial community composition (indicating selective pressure) and (v) increasing rejection of 6 of the 7 OMPs. In essence, biofouling on the FO membrane showed (i) a lower flux decline in the presence of OMPs in the feed water and (ii) a higher OMPs rejection, both illustrating better membrane performance. This study has a significant implication for optimizing osmotic dilution in terms of FO operation and OMPs rejection.

Forward osmosis membrane technology for nutrient removal/recovery from wastewater: Recent advances, proposed designs, and future directions

In recent years, the concept of nutrient removal/recovery has been applied as a sustainable solution to develop and design various modern wastewater treatment technologies for recovering nutrients from waste streams and is one of the high-priority research areas. Forward osmosis (FO) technology has received increasing interests as a potential low-fouling membrane process and a new approach to remove/recover nutrients from wastewater and sludge. The main objective of this review is to summarize the state of FO technology for nutrient removal/recovery from wastewater and sludge in order to identify areas of future improvements. In this study, nutrient removal processes, FO membrane technology, main factors affecting the FO process performance, the source water for nutrient recovery, the previous studies on the FO membrane process for nutrient removal/recovery from wastewater and sludge, membrane fouling, and recent advances in FO membranes for nutrient removal/recovery were briefly and critically reviewed. Then, the proposed possible designs to apply FO process in conventional wastewater treatment plants (WWTPs) were theoretically presented. Finally, based on the gaps identified in the area, challenges ahead, future perspectives, and conclusions were discussed. Further investigations on the properties of FO associated with real wastewater, wastewater pre-treatment, the long-term low fouling operation, membrane cleaning strategies, water flux and the economic feasibility of the FO process are still desirable to apply FO technology for nutrient removal/recovery at full-scale (decentralized or centralized) in the future.

On-Site Treatment of Shale Gas Flowback and Produced Water in Sichuan Basin by Fertilizer Drawn Forward Osmosis for Irrigation

Fertilizer drawn forward osmosis (FDFO) was proposed to extract fresh water from flowback and produced water (FPW) from shale gas extraction for irrigation, with fertilizer types and membrane orientations assessed. The draw solution (DS) with NH₄H₂PO₄ displayed the best performance, while the DS with (NH₄)₂HPO₄ resulted in the most severe membrane fouling. The DS with KCl and KNO₃ led to substantial reverse solute fluxes. The FDFO operation where the active layer of the membrane was facing the feed solution outperformed that when the active layer was facing the DS. The diluted DS and diluted FPW samples were used for irrigation of Cherry radish and Chinese cabbage. Compared to deionized water, irrigation with the diluted DS (total dissolved solid (TDS) = 350 mg·L^-1) promoted plant growth. In contrast, inhibited plant growth was observed when FPW with high salinity (TDS = 5000 mg·L^-1) and low salinity (TDS = 1000 mg·L^-1) was used for irrigation of long-term (8-week) plant cultures. Finally, upregulated genes were identified to illustrate the difference in plant growth. The results of this study provide a guide for efficient and safe use of FPW after FDFO treatment for agricultural application.

Research on Forward Osmosis Membrane Technology Still Needs Improvement in Water Recovery and Wastewater Treatment

Forward osmosis (FO) has become an evolving membrane separation technology to recover water due to its strong retention capacity, sustainable membrane fouling, etc. Although a good deal of research has been extensively investigated in the past decades, major challenges still remain as follows: (1) the novel FO membrane material properties, which significantly influence the fouling of the FO membranes, the intolerance reverse solute flux (RSF), the high concentration polarization (CP), and the low permeate flux; (2) novel draw solution preparation and utilization; (3) salinity build-up in the FO system; (4) the successful implementation of the FO process. This work critically reviews the last five years’ literature in development of the novel FO membrane material, structure in modification, and preparation, including comparison and analysis on the traditional and novel draw solutes coupled with their effects on FO performance; application in wastewater treatment, especially hybrid system and integrated FO system; fouling mechanism; and cleaning strategy as discussed in the literature. The current barriers of the research results in each hotspot and the areas that can be improved are also analyzed in detail. The research hotspots in the research and development of the novel membrane materials in various countries and regions have been compared in recent years, and the work of variation in pop research hotspots in the past 10 years has been analyzed and the ideas that fill the blank gaps also have been proposed.

Understanding the organic micropollutants transport mechanisms in the fertilizer-drawn forward osmosis process

We systematically investigated the transport mechanisms of organic micropollutants (OMPs) in a fertilizer-drawn forward osmosis (FDFO) membrane process. Four representative OMPs, i.e., atenolol, atrazine, primidone, and caffeine, were chosen for their different molecular weights and structural characteristics. All the FDFO experiments were conducted with the membrane active layer on the feed solution (FS) side using three different fertilizer draw solutions (DS): potassium chloride (KCl), monoammonium phosphate (MAP), and diammonium phosphate (DAP) due to their different properties (i.e., osmotic pressure, diffusivity, viscosity and solution pH). Using KCl as the DS resulted in both the highest water flux and the highest reverse solute flux (RSF), while MAP and DAP resulted in similar water fluxes with varying RSF. The pH of the FS increased with DAP as the DS due to the reverse diffusion of NH₄⁺ ions from the DS toward the FS, while for MAP and DAP DS, the pH of the FS was not impacted. The OMPs transport behavior (OMPs flux) was evaluated and compared with a simulated OMPs flux obtained via the pore-hindrance transport model to identify the effects of the OMPs structural properties. When MAP was used as DS, the OMPs flux was dominantly influenced by the physicochemical properties (i.e., hydrophobicity and surface charge). Those OMPs with positive charge and more hydrophobic, exhibited higher forward OMP fluxes. With DAP as the DS, the more hydrated FO membrane (caused by increased pH) as well as the enhanced RSF hindered OMPs transport through the FO membrane. With KCl as DS, the structural properties of the OMPs were dominant factors in the OMPs flux, however the higher RSF of the KCl draw solute may likely hamper the OMPs transport through the membrane especially those with higher MW (e.g., atenolol). The pore-hindrance model can be instrumental in understanding the effects of the hydrodynamic properties and the surface properties on the OMPs transport behaviors.

Recent Progresses of Forward Osmosis Membranes Formulation and Design for Wastewater Treatment

Production of potable water or reclaimed water with higher quality are in demand to address water scarcity issues as well as to meet the expectation of stringent water quality standards. Forward osmosis (FO) provides a highly promising platform for energy-efficient membrane-based separation technology. This emerging technology has been recognized as a potential and cost-competitive alternative for many conventional wastewater treatment technologies. Motivated by its advantages over existing wastewater treatment technologies, the interest of applying FO technology for wastewater treatment has increased significantly in recent years. This article focuses on the recent developments and innovations in FO for wastewater treatment. An overview of the potential of FO in various wastewater treatment application will be first presented. The contemporary strategies used in membrane designs and fabrications as well as the efforts made to address membrane fouling are comprehensively reviewed. Finally, the challenges and future outlook of FO for wastewater treatment are highlighted.

Differential effects of coral-giant clam assemblages on biofouling formation

To prevent the settlement and/or the growth of fouling organisms (i.e. bacteria, fungi or microalgae), benthic sessile species have developed various defense mechanisms among which the production of chemical molecules. While studies have mostly focused on the release of chemical compounds by single species, there exist limited data on multi-species assemblages. We used an integrative approach to explore the potential interactive effects of distinct assemblages of two corals species and one giant clam species on biofouling appearance and composition. Remarkably, we found distinct biofouling communities suggesting the importance of benthic sessile assemblages in biofouling control. Moreover, the assemblage of 3 species led to an inhibition of biofouling, likely through a complex of secondary metabolites. Our results highlight that through their different effect on their near environment, species assemblages might be of upmost importance for their survival and therefore, should now be taken into account for sustainable management of coral reefs.