This review summarizes the recent development and studies of anaerobic membrane bioreactor (AnMBR) to control fouling issues. AnMBR is an emerging waste water treatment technology mainly because of ...its low sludge residual, high volumetric organic removal rate, complete liquid-solid separation, better effluent quality, efficient resource recovery and the small footprint. This paper surveys the fundamental aspects of AnMBRs, including its applications, membrane configurations, and recent progress for enhanced reactor performance. Furthermore, the membrane fouling, a major restriction in the practical application of AnMBR, its mechanism and antifouling strategies like membrane cleaning, quorum quenching, ultrasonic treatment, membrane modifications, and antifouling agents are briefly discussed. Based on the review, the key issues that require urgent attention to facilitate large scale and integrated application of AnMBR technology are identified and future research perspectives relating to the prevalent issues are proposed.
•Recent advancements in anaerobic membrane bioreactors (AnMBR) are concisely reviewed.•The fouling mechanism and the advanced antifouling strategies are summarized.•Costs incurred in different operational steps of AnMBR are compared.•Future research is needed for techno-economic analysis of large scale applications.
An investigation into the effect of stepwise saline introduction (3–20 g·L−1 NaCl) on the anaerobic ammonium oxidation (anammox) process in a lab-scale sequencing batch reactor was carried out for ...252 days by evaluating the changes in influent and effluent nitrogen concentrations, conductivity, microbial extracellular polymeric substances' (EPS) ionic content, as well as stresses due to salinity, via microbial ATP analysis. It was observed that, effluent nitrogen concentrations remained stable at low saline levels of 3 g·L−1 to 10 g·L−1. Nonetheless, midway through 10 g·L−1 and the preliminary phase of 15 g·L−1 salinity presented a very unstable, highly fluctuating as well as deteriorating effluent nitrogen concentrations. A more satisfactory nitrogen removal efficiency of 83.7 ± 5.9% was obtained at higher saline concentrations implying that, the adaptation mechanism to tolerate increasing salinity was taking place. Saline induced stress, which measures the variation in viable anammox bacteria, was correlative to the formation of EPS and changes in its cationic contents along the increasing salinity. Although the specific anammox activity (SAA) dropped by approximately 15% from the beginning of the process to the midpoint, the drop in SAA after the midpoint was not as drastic as the initial phase. A change in microbial aggregation and dominance proved the existence of new saline-dependent species that can withstand high saline stresses. Recovery from abrupt high saline shocks in batch experiment was seen to be almost impossible.
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•Saline induced stress correlates uniquely to the saline adaptation of anammox.•Improvement in N-removal efficiency is observed at higher saline concentrations.•Granules formation and bacteria aggregation tailored the saline input profile.•MAB dominated the granules in the reactor by the latter end of 10 g·L−1 salinity.
Scaling, or inorganic fouling, is a major factor limiting the performance of membrane-based water treatment processes in long-term operation. Over the past few decades, extensive studies have been ...conducted to control the scale growth found in membrane processes and to develop sustainable and greener processes. This study details the role of CO2 in scale inhibition in membrane processes. The core concept of CO2 utilization is to reduce the influent pH and to minimize the risk of scale formation from magnesium or calcium salts. Three reverse osmosis (RO) units were operated with a control (U1), CO2 (U2), and a commercial antiscalant, MDC-220 (U3). The performances of all the units were compared in terms of change in transmembrane pressure (TMP). The overall efficiency trend was found as U1 > U3 > U2. The membrane surfaces were analyzed using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) for the morphological and elemental compositions, respectively. The surface analysis signified a significant increase in surface smoothness after scale deposition. The noticeable reduction in surface roughness can be described as a result of ionic deposition in the valley region. A sludge-like scale layer was found on the surface of the control membrane (U1) which could not be removed, even after an hour of chemical cleaning. After 20–30 min of cleaning, the U2 membrane was successfully restored to its original state. In brief, this study highlights the sustainable membrane process developed via CO2 utilization for scale inhibition, and the appropriate cleaning approaches.
CO2 capture and utilization (CCU) is a promising approach in controlling the global discharge of greenhouse gases (GHG). This study details the experimental investigation of CO2 utilization in ...membrane-based water treatment systems for lowering the potential of ionic precipitation on membrane surface and subsequent scale development. The CO2 utilization in feed water reduces the water pH that enables the dissociation of salts in their respective ions, which leave the system as a concentrate. This study compares the efficiency of CO2 and other antifouling agents (CA-1, CA-2, and CA-3) for fouling control in four different membrane-based wastewater reclamation operations. These systems include Schemes 1, 2, 3, and 4, which were operated with CA-1, CA-2, CA-3, and CO2 as antiscalants, respectively. The flux profile and percent salt rejection achieved in Scheme 4 confirmed the higher efficiency of CO2 utilization compared with other antifouling agents. This proficient role of CO2 in fouling inhibition is further endorsed by the surface analysis of used membranes. The SEM, EDS, and XRD examination confirmed the higher suitability of CO2 utilization in controlling scale deposition compared with other antiscalants. The cost estimation also supported the CO2 utilization for environmental friendly and safe operation.
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•The addition of mill scale enhanced the aggregation of sludge and improved its settleability.•The floc diameter of activated sludge is increased from 6.74 μm to 35.77 μm when mill ...scale of <45 μm size is added.•The functional relationship between settling velocity and SS concentration is well described by Vesilind model.•86 % BF recovery was observed via magnetic separation method.•ATP analysis did not show any significant cytotoxic effect of BF on living biomass.
One of the common biological methods in wastewater treatment is the activated sludge process. The efficiency of this process highly depends on the aggregation of microbes to form flocs that settle in the settling tank. The settleability of the activated sludge is commonly influenced by the biomass diversity, concentration, density and the size distribution of flocs. This study introduces mill scale as a ballasted flocculant (BF). The behavior of activated sludge is studied after the addition of BF, with the objective to improve the aggregation of activated sludge particles and enhance its settleability. The efficiency of BF is evaluated by varying its dosage (mill scale to sludge weight ratio = 0.2–2) and particle size (<45 and 45–75 μm). The zone settling velocity (ZSV) was 4.58 m h−1 for original sludge that was increased to 8 m h−1 when BF was added into the sludge. The microscopic analysis of the ballasted flocs indicated that the BF particles were finely embedded into the sludge particles. A significant increase in floc size was observed after addition of BF. The Vesilind, Cho and Takacs settling velocity models were applied to explain the relationship between settleability characteristics of the activated sludge. The experimental data was well fitted in Vesilind’s exponential model. Followed by sedimentation, the BF particles were finely recovered via magnetic separation technique. The maximum BF recovery is estimated 86 %, when 4 g of BF is used.
The rising demand for clean water and the environmental challenges associated with fossil fuels have encouraged the application of renewable and greener energy systems in desalination. Moreover, the ...small footprint and high productivity favored the membrane-based process in the water industry. In the past few decades, noticeable work has been performed on the development and applicability of membrane-based desalination processes powered by renewable energy sources such as solar, wind, tidal, and geothermal. Several integrated membrane desalination processes for producing clean water with sustainable and clean energy are introduced. This review details the source and performance efficiencies of existing renewable energy technologies and their application in membrane-based desalination processes, with a special focus on current advancements and challenges. This study reviews the interconnections between water, energy, and the environment and explores future energy-efficient desalination options for energy savings and environmental protection.
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•Brief summary of the existing knowledge regarding ECs.•Application and operational perspectives of classical and advanced treatment technologies.•The appropriateness of advanced ...integrated technologies for ECs removal.•Mechanisms involved in ECs removal processes.•Identification of the gap areas for future research and developments.
The presence and persistence of emerging contaminants(ECs) such as endocrine disrupting compounds (EDCs), personal care products (PCPs), pharmaceuticals and their transformed products are the matter of serious environmental and health concerns. This review details the sources, classification, fate and transport of ECs, and the classical, advanced, and integrated treatment technologies for their removal. Up to 100% of β-blockers, pharmaceuticals, EDCs, and pesticides can be removed via advanced oxidation process. The microalgae/fungal strains and the anaerobic membrane bioreactors are also promising processes for PPCPs and EDCs removal. RO and NF membranes exhibited excellent removal efficiencies for range of ECs, however, these processes are conditioned with fouling issues. The combination of membrane separation and electrochemical oxidation is appeared efficacious to lessen the major confines of both technologies such as fouling in membrane process and the mass transfer constraint in the electrochemical oxidation process. The effect of operational parameters on the process efficiency, and the mechanisms involved in different processes were discussed. This review will help in selecting the best available technology (BAT) for specific contaminant under particular conditions.
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This review details the sources, classification, fate and transport of emerging contaminants and the recent researches and advancements for their treatment/elimination.
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•Magnetite particles were synthesized from mill scale with reverse coprecipitation method.•Stable morphology of particles was observed at low pH (8.0–8.3).•Instrumental analysis ...confirmed the magnetic properties of the synthesize particles.•Particles were found effective to remove phosphate and arsenate from the contaminated water.
The industrial grade gram scale fine magnetite particles were synthesized from the mill scale. Mill scale, the reactant in this study, has higher ferrous to ferric ratio (≃2), in contrary to the standard ratio (0.5) required for the synthesis of spinel crystalline magnetite. A reverse coprecipitation method was developed for direct synthesis of magnetite particles without any arrangement for oxidation or reduction of ferrous or ferric ions present in the reactants. Particles were aged at two different pH levels (8 and 12) after synthesizing at higher pH and their stability and characteristics were compared. XRD confirmed the cubic spinel structure of magnetite. In agreement with XRD and Raman spectroscopy, FTIR identified the Fe-O band in octahedral and tetrahedral sites indicating the formation of cubic crystalline magnetite. The magnetization value was determined 68 emu/g. Spherical structures of magnetite were confirmed by SEM and TEM analysis. Specific surface area of black and brown magnetite was determined 75.7712 and 64.4382 m2/g, respectively. Newly synthesized magnetite particles were found very effective for the adsorptive removal of phosphate and arsenic from the contaminated water.
This study employed a reverse coprecipitation method to synthesize magnetite particles, utilizing three distinct schemes based on varied starting materials: mill scale (Scheme 1), chloride salts of ...ferrous and ferric (Scheme 2), and sulfate salts of ferrous and ferric (Scheme 3). Characterization techniques, including XRD, confirmed the cubic spinel structure in all schemes. BET surface area results showed variations, with Scheme 1 at 95.46 m2/g, increasing to 150.82 m2/g for Scheme 2 and 133.36 m2/g for Scheme 3. FTIR and XPS analyses validated the functionalities and chemical composition, confirming purity. VSM results confirmed the ferromagnetic nature of particles synthesized using all three schemes, with Scheme 1 exhibiting superior coercivity. SEM images revealed that particles synthesized using Scheme 1 were larger compared to those in Schemes 2 and 3. Scheme 3 showed the highest level of particle agglomeration, while Scheme 2 exhibited the least. TEM analysis confirmed consistently shaped nanoparticles with a uniform size distribution. EXD analysis confirmed Fe and O as the main constituents. The particles demonstrated effectiveness in phosphorus adsorption, with Scheme 1 exhibiting superior yield, P-recovery, and regeneration. These findings offer valuable insights into magnetite particle synthesis for optimal environmental performance, particularly in phosphorus removal.
•Diverse synthesis pathways enhance magnetite properties.•Comprehensive analysis reveals cubic spinel structure and varied morphologies.•Ferromagnetic nature, minimal coercivity, and scheme-dependent remanence.•Particles exhibit notable phosphorus recovery performance.•Diverse synthesis pathways offer sustainable solutions for practical applications.
This study investigates the lateral behavior of pile foundations socketed into bedrocks using 3D finite difference analysis. The lateral load-displacement curve, pile deflection, and bending moment ...distribution were obtained for different bedrock depths between 3 and 20 m. It was discovered that bedrocks that have a depth of 7 m (7D) or less influence the lateral behavior of the pile. The p-y curves were collected at depths of 2.0–4.5 m, and the effect of the bedrock on the curves was evaluated. It was observed that the p-y curves were significantly affected by the material properties of the bedrock if the rock is located in close proximity (within 3D), but the effect is diminished if the p-y curves were 3.5 m (3.5D) or farther from the bedrock.
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