Separation of algae from water is one of the challenges of biological processes that require membranes with low fouling. Emulsion PVC-based (EPVC) ultrafiltration membranes were prepared via phase inversion using NMP as solvent and modified with detonation nanodiamonds (DNDs) at varying concentrations (0.1-2 wt%). The membranes were characterized by SEM, EDX, TGA, and water contact angle measurements. The membranes were evaluated for permeability, BSA rejection, and fouling resistance using a dead-end filtration system at 1.0 bar. Among all compositions, the membrane with 1 wt% DND showed the best performance, with high water flux (51 L/m2.h), excellent BSA rejection (98.4%), and strong fouling resistance. Pressure-dependent testing confirmed stable performance up to 4 bar. These membranes were further applied for the separation and concentration of microalgal biomass from its cultivation medium under 0.2-1.2 bar. Visual inspection revealed increased surface fouling with pressure, yet removal efficiencies exceeded 97% for all conditions except 0.2 bar. At 1 bar, the maximum removal efficiency was recorded at 99.72%, indicating optimal separation performance. These findings highlight the potential of DND-modified EPVC membranes for enhancing the performance of UF membranes and for effective microalgal harvesting in bioresource applications.

Wastewater streams provide a nutrient-rich resource for algal cultivation, with human urine being particularly promising due to its high nitrogen and phosphorus content. Elevated ammonium concentrations, however, can inhibit growth, and dilution is often reported but remains unsustainable, highlighting the need for pretreatment. This study evaluated ion exchange-pretreated human urine as a growth medium for fed-batch cultivation of Spirulina platensis (S. platensis), a protein-rich cyanobacterium, and compared two membrane materials, polyethersulfone (PES) and polyvinylidene fluoride (PVDF), for biomass harvesting. S. platensis was successfully cultivated in the pretreated urine, reaching biomass concentrations of 1.07–1.37 g/L. PES and PVDF membranes produced permeates of comparable quality, with turbidity values of 0.82 and 0.77 NTU, respectively. PES achieved the target permeate volume in a shorter filtration time, while PVDF required longer duration, although SEM-EDX and FTIR analyses indicated similar fouling characteristics for both membranes. Harvested biomass exhibited a protein content of approximately 75%, demonstrating substantial nutritional value. These findings highlight the feasibility of using pretreated human urine for protein-rich algal biomass production and indicate that both PES and PVDF membranes are suitable for efficient biomass harvesting, with differences in filtration duration reflecting membrane properties.

Human urine, rich in nitrogen and phosphorus, holds significant potential as a nutrient source for algal cultivation. However, its high ammonia concentration can inhibit algal growth, necessitating dilution that increases water demand and limits sustainability. In this study, Spirulina platensis was successfully cultivated in pretreated source-separated human urine, followed by biomass harvesting using alum coagulant and macromolecular composition analysis. The urine was pretreated via ion exchange, which reduced the ammonium concentration by approximately 75%. S. platensis achieved a specific growth rate of 0.185 day⁻¹ and a final biomass concentration of 1.62 g/L in photobioreactor cultivation. Jar tests showed that alum at a concentration of 1250 mg/L yielded a harvesting efficiency of 97.3%, while chitosan achieved 38.9%. The biomass recovered with alum contained an average protein content of 70%. These results demonstrated that ion exchange effectively conditioned human urine for algal cultivation, enabling nitrogen recovery in a bioavailable form and supporting nutrient circularity within sustainable algae-based biotechnologies.

Efficient harvesting of microalgae is one of the most significant challenges in large-scale microalgae production, which significantly affects both process performance and overall costs. This study compared the performance of alum and chitosan for harvesting microalgae cultivated in anaerobic membrane bioreactor (AnMBR) permeate. Two harvesting scenarios were evaluated: Scenario-1, using a mixture of Bold’s Basal Medium (BBM) and AnMBR permeate from mono-digestion of sewage sludge as a medium (Permeate-1), and Scenario-2, using BBM mixed with AnMBR permeate from co-digestion of sewage sludge and food waste as a medium (Permeate-2). Microalgal biomass was harvested using alum (Scenario-1a and Scenario-2a) and chitosan (Scenario-1b and Scenario-2b), with optimum dosages determined as 225 mg/L for alum and 65 mg/L for chitosan. Macromolecular analyses showed that biomass from Scenario-2 had higher protein content, whereas chitosan-harvested biomass exhibited higher lipid content in both scenarios. Scanning electron microscopy showed that chitosan-harvested biomass had a more compact and uniform structure, while alum-harvested biomass contained Al(OH)3 precipitates, reflecting lower biomass purity. Cost assessment indicated that Scenario-2 had higher estimated revenue potential due to its elevated protein content, although the higher cost of chitosan compared to alum presented an economic limitation. Future studies should aim to optimize flocculation conditions to improve the efficiency and sustainability of microalgae-based systems.

Mixing performance and energy efficiency are critical parameters in the operation of anaerobic digesters, yet the combined effects of fluid dynamics and operational variables remain insufficiently characterized. This paper evaluates the effect of impeller rotation rate and solids content on the mixing performance and energy consumption of a pilot-scale portable anaerobic digester processing food waste. For a 5% solids content, increasing the impeller rotation rate from 15 to 60 rpm reduced dead zone formation from 94% to 69%, whereas for a 10% solids content, the reduction was from 97% to 81%. A further increase to 120 rpm reduced dead zones to 58%. A non-linear relationship was observed between rotation rate and mixing energy, characterized by an exponential increase in energy demand beyond 60 rpm, while substantial improvements in intermediate velocities were achieved between 30 and 90 rpm. These results suggest that while lower rotation rates yield unfavorable mixing efficiency and large dead zones, balancing mixing performance against energy demand makes 60–90 rpm the optimal operational range for efficient digester performance.

As metabolic intermediates, volatile fatty acids (VFAs) can be recovered by separation and purification and contribute to the economy. It was necessary, however, to investigate the optimization of liquid–liquid extraction (LLE) in this study because of the technical difficulties encountered during the recovery of VFAs. For this reason, the organic solvents diethyl ether, trioctylamine, and toluene were investigated as LLE solvents to extract VFAs from Baker’s yeast industry effluent, which contains high levels of organic matter. An optimal pH value of 3 was determined by a pH scan performed between pH 2.5 and pH 7.5. Principal component analysis (PCA) was used to determine the effects of organic solvents and pH on extraction efficiency. The extraction efficiency was evaluated using the optimal pH and multi-stage extraction experiments. In a three-stage extraction, diethyl ether recovered 82% of the VFAs, making it a promising organic solvent for extracting VFAs from anaerobic fermentation broth. PCA revealed that an opposite correlation between VFA recovery and pH for each organic solvent. Based on the results of the cost analysis, it was determined that the costs of recovering VFAs were reduced by 90% per kilogram.

Wastewater-based epidemiology (WBE) is a powerful method that allows community surveillance to identify diseases/pandemic dynamics in a city, especially in metropolitan areas with high overpopulation. This study investigated the detection and quantification of SARS-CoV-2 RNA in wastewater and sewage sludge in two different wastewater treatment plants (WWTPs) in Istanbul, the 5th largest city in the world, during the COVID-19 pandemic. Statistical analysis was performed to examine the relationships between SARS-CoV-2 concentrations and COVID-19 case numbers, seasonal variations, and key WWTP parameters, including total phosphorus (TP), total nitrogen (TN), and chemical oxygen demand (COD), using principal component analysis (PCA). SARS-CoV-2 N genes were analyzed in influent, treated effluent and sludge samples collected between June 2021 and January 2022 by reverse transcription–polymerase chain reaction (RT-qPCR). Viral genes were detected in 23 out of 26 influent wastewater samples (88

Efficient microalgae harvesting and dewatering are critical processes for a range of applications, including the production of raw materials, nutritional supplements, pharmaceuticals, sustainable biofuels, and wastewater treatment. The optimization of these processes poses significant challenges due to the need for high efficiency and sustainability while managing costs and energy consumption. This review comprehensively addresses these challenges by focusing on the development and application of various membrane filtration technologies specifically designed for the effective harvesting and dewatering of algal biomass. Membrane filtration has emerged as a predominant method due to its ability to handle large volumes of microalgae with relatively low energy requirements. This review systematically examines the different membrane-based technologies and their effectiveness in recovering valuable components from algal biomass, such as lipids, proteins, and carbohydrates. The discussion begins with an overview of the physical characteristics of microalgae and their cultivation conditions, which are critical for understanding how these factors influence the performance of membrane filtration processes. Key aspects such as the features of algal cells, the presence of algal organic matter, and transparent exopolymer particles are explored in detail. The review also delves into various strategies for improving membrane antifouling properties, which are essential for maintaining the efficiency and longevity of the filtration systems. In addition, the advantages and disadvantages of different membrane techniques are reviewed, highlighting their respective performance in separating microalgae and dewatering. Finally, the review offers insights into future research directions and technological advancements that could further enhance the efficiency and sustainability of microalgae processing. This comprehensive evaluation aims to provide a thorough understanding of current membrane technologies, their applications, and the ongoing developments necessary to overcome existing limitations and improve overall process performance.

"Solid waste can contain large amounts of plastic; most are not biodegradable. For this reason, the disposal of waste plastics is a critical issue for society and sustainable life. It is important to note that solid waste landfills are the most common method for disposing plastics. Nowadays, energy recovery from waste plastics is gaining importance due to the energy production potential of waste plastics. Thermal methods such as incineration, gasification and pyrolysis can be used to obtain energy from plastic waste, but the conversion of plastic waste into liquid fuels, including diesel and gasoline, is also being researched. Although these methods reduce the environmental impact of plastic waste and provide alternative energy sources, the recovery of high-value-added products in parallel with energy generation is also important to minimize emissions, ensure adequate waste treatment, and promote environmental sustainability. As an example, the burning potential of polystyrene, which comprises 22 percent of waste plastics, is compatible with the circular economy concept while simultaneously reducing petroleum fuel consumption by recycling high value-added materials such as polycarbonate and polyamide.. Through the use of polymer recycling in conjunction with energy recovery from waste plastics, environmentally friendly, cost-effective waste management can be achieved."

Human urine, a highly saline solution rich in plant-available nutrients, leaves behind significant organic matter after nutrient recovery, necessitating additional treatment for environmental protection. While nutrient recovery from human urine is well-documented in the literature, research on the safe handling of the residual liquid phase is notably lacking. This study investigates nutrient recovery from source-separated human urine using clinoptilolite for the ion exchange/adsorption process and evaluates the safe management of the residual liquid through anaerobic granular sludge and a second-stage of sorption. The results indicated that the ion exchange/adsorption process, using an ammonium loading of 15 mg NH4+/g clinoptilolite, removed the majority of nutrients, achieving 82% ammonium removal and 100% phosphorus removal, along with 30% removal of organic matter. The residual liquid phase from the nutrient removal stage was treated separately with anaerobic digestion and a second-stage of sorption for further processing. Results showed that anaerobic processing removed 68%-84% of organic matter, with no additional nitrogen removal observed as expected, and produced 0.20-0.46 L CH4/L urine. The second-stage of sorption removed 59%-62% of organic matter and nearly all nitrogen. Both processes effectively removed organic matter, with sorption also eliminating nitrogen and anaerobic processing potentially generating biogas, making them recommended for improving the quality of the residual liquid phase before final disposal.

A significant increase in atmospheric greenhouse gases over the last century has led to the development of several methods and technologies to remove carbon dioxide (CO2). Microorganisms produce carbonate minerals through the natural mineralization of CO2; however, the feasibility of this process remains in research. This work aimed to study the cultivation of different microalgae under alkaline pH to maintain their potential for carbon mitigation. According to the results, the highest carbonic anhydrase activity has been reached (4.64 mg/g) for Chlamydomonas reinhardtii at a pH of 10. C. reinhardtii, at a pH of 9.5, yielded the highest chlorophyll content (23.58 mg/g), while Spirulina at a pH of 8.5 produced the highest biomass (882.9 mg/L). Also, a positive correlation existed between pH and lipid content for C. reinhardtii. Spirulina, however, exhibits the opposite effect. According to a principal component analysis, there is an opposite relationship between pH and carbonic anhydrase (CA) activity for C. reinhardtii and filamentous-type cyanobacteria from Salda Lake. The following order of the suitability of the microalgae species for high carbon capture is determined by the Analytic hierarchy process method: Spirulina> C. reinhardtii > Chlorella vulgaris > Coccus-type cyanobacteria > Filamentous-type cyanobacteria from Salda Lake. Additionally, this study provided important results regarding the cyanobacteria species isolated from an alkaline lake, Lake Salda. This would contribute to future studies of carbon capture and carbon mitigation mechanisms.

In recent years especially during COVID-19, the increased usage of antiviral drugs has led to increased interest in monitoring their presence in wastewater worldwide. In this study, it was examined the occurrence, fate and environmental risks of favipiravir which is used for COVID-19 treatment in two wastewater treatment plants (WWTPs) with different treatment processes in Istanbul, Turkey. Favipiravir was measured in WWTPs influent samples, effluent samples and sludge samples with maximum concentrations of 97 mu g/L, 64.11 mu g/L and 182.47 mu g/g, respectively. Favipiravir had removal efficiency below 55 % for both WWTPs. Mass balance analysis showed that favipiravir removal in WWTPs mainly attributed to biodegradation/biotransformation. Statistical analysis revealed a significant correlation between favipiravir concentration and COVID-19 incidence in Istanbul. The microbial distribution analysis indicated that comparison of collected COVID-19 pandemic sludge and postpandemic period sludge samples, a noteworthy reduction in the Chloroflexi and Actinobacteriota phyla at the phylum level was observed. Environmental risk assessment using risk quotients ranged from 168 to 704, indicating that the presence of this antiviral drug posed significant ecological risks to aquatic organisms. The study concluded that WWTPs were releasing antiviral drugs into the environment, thereby posing risks to both the

Landfill leachate contains a significant amount of organic matter, making it a valuable source for CH 4 production. However, due to its liquid form, the mono-digestion of leachate could result in a reduced CH 4 yield per unit reactor volume. This necessitates its utilization in anaerobic digesters alongside solid waste streams. The objective of this study was to evaluate co-digestion performance of landfill leachate with different wastes using biomethane potential test and assess the optimum combination in terms of CH 4 productivity. Modified Gompertz model was used for kinetic characterization. Experiments were held under mesophilic conditions and lasted for 30 days. Among mono-digestion of substrates, landfill leachate exhibited the highest CH 4 productivity and yield: 83.17 mL/gVS.d and 793 ± 6.85 mL/gVS, respectively. Fish waste was found to have the lowest energy potential with 350 mL/gVS CH 4 yield and 18.24 mL/gVS.d CH 4 productivity. CH 4 productivities for co-digestion cases ranged from 5.48 to 67.85 mL/gVS.d. Mixing landfill leachate and chicken manure with the same amount on wet weight basis yielded the highest CH 4 productivity. On the other hand, inclusion of fish waste consistently resulted in decreased CH 4 yield and productivity for all incubations, which suggests that fish waste may not be suitable as a co-substrate for landfill leachate in terms of CH 4 production. Monitoring of chemical parameters revealed that buffering capacity of the system and free ammonia formation were the main parameters governing CH 4 production.

Although wastewater with high ammonia concentration is an ideal alternative environment for microalgae cultivation, high ammonia concentrations are toxic to microalgae and inhibit microalgae growth. In this study, the ammonia responses of four widely used microalgae species were investigated. Chlorella vulgaris, Chlorella minutissima, Chlamydomonas reinhardtii and Arthrospira platensis were grown in batch reactors maintained at seven different NH4Cl concentrations at a constant pH of 8. Growth and nitrogen removal kinetics were monitored. IC50 values for the mentioned species were found as 34.82 mg-FA/L, 30.17 mg-FA/L, 27.2 mg-FA/L and 44.44 mg-FA/L, respectively, while specific growth rates for different ammonia concentrations ranged between 0.148 and 1.271 d−1. C. vulgaris demonstrated the highest biomass growth under an ammonia concentration of 1700.95 mg/L. The highest removal of nitrogen was observed for A. platensis with an efficiency of 99.1%. The results showed that all tested species could grow without inhibition in ammonia levels comparable to those found in municipal wastewater. Furthermore, it has been concluded that species C. vulgaris and A. platensis can tolerate high ammonia levels similar to those found in high strength wastewaters.

Food waste is a significant environmental issue today, as it contributes to depleting natural resources and greenhouse gas emissions from improper management. To address this, alternative food waste management and recovery strategies must be developed to promote nutrient recirculation and move towards decarbonization. University campuses could play a crucial role in pioneering such strategies, through pilot studies and implementation of effective waste management. The aim of this study is to devise a food waste management strategy that provides a more circular and decarbonized economy. A case example was developed based on ITU Ayazağa Campus, Turkey, with annual separated food waste of 577 tonne per year. A Life Cycle Assessment was conducted using the EASETECH software. Four scenarios were evaluated: anaerobic digestion, composting, incineration, and landfill. Of these, incineration resulted in the highest CO 2 ‐eq savings, but lacked decoupling and circularity of resources. Conversely, anaerobic digestion demonstrated the highest circularity and lowest toxicity. Based on these findings, anaerobic digestion was selected for further investigation. Economic transactions for the anaerobic digestion system's business models were analyzed, including revenues, municipality fees, and operating costs. The new economic model is expected to align with circular economy strategies and promote stakeholder collaboration as a significant social outcome.

This study employs several approaches to enhance environmental sustainability: First, algal biomass (with 52.5% protein content) was converted into value-added products. Second, residual algal biomass from protein extraction and pigment extraction and raw algal biomass were used to manufacture bioplastics. Third, radiation shielding performance of bioplastics has been investigated. As an alternative to plastics originated from petroleum-based raw materials, environmentally friendly bioplastics were derived from residual algae biomass after extraction. The gamma-ray radiation shielding properties of the produced bioplastic have been investigated using WinXCOM theoretical calculation and GEANT4 Monte Carlo (MC) simulation. Fast neutron shielding performance of the considered materials also evaluated with help of theoretical calculation and the same MC simulation. The produced bioplastics are similar to ones with commercially available PLA polymer. Sample 1 was found to be better gamma-ray attenuator while Sample 2 has the highest value of the effective neutron removal cross section. Additionally, the boron addition has resulted in lower water absorption capacity in the prepared samples. Using algae to produce more than one product as a raw material source will be an effective step toward sustainable life, and they could be an alternative gamma-ray shielding material to existing commercial polymers.

Nitrogen stress can influence microalgae’s growth characteristics, and microalgae grown in nitrogen-deficient conditions may produce higher or lower levels of biotechnological products as a result of metabolic changes. In photoautotrophic and heterotrophic cultures, nitrogen limitation has been proven effective in promoting lipid accumulation. In spite of this, no study has demonstrated a significant correlation between lipid content and other biotechnological products such as bioactive compounds (BACs). This research examines a strategy for lipid accumulation as well as the potential production of BACs with antibacterial properties in parallel with that strategy. This concept involved the treatment of the microalga Auxenochlorella protothecoides with low and high concentrations of ammonium (NH 4 + ). This particular experiment reached a maximum lipid content of 59.5% using a 0.8 mM NH 4 + concentration, resulting in the yellowing of the chlorophyll levels. Agar diffusion assays were conducted to determine the antibacterial activity of different extracts derived from the biomass when stressed with different levels of nitrogen. Algal extracts prepared by a variety of solvents showed different levels of antibacterial activity against representative strains of both gram-negative ( Escherichia coli ) and gram-positive ( Staphylococcus aureus ) bacteria. Among the extracts tested, 500 mg/L ethyl acetate extract had the greatest antibacterial activity against Escherichia coli . In order to identify the components responsible for the extract’s antibacterial activity, fatty acid methyl ester (FAME) analysis was performed. It has been suggested that the lipid fraction may be a valuable indicator of these activities since some lipid components are known to possess antimicrobial properties. In this regard, it was found that the amount of polyunsaturated fatty acid (PUFA) significantly decreased by 53.4% under the conditions with the highest antibacterial activity observed.

Rapid growth and high carbon-fixation properties make microalgal biomass a preferred source of energy-production technologies, particularly biodiesel and bioethanol, as well as nutritional supplements and pharmaceuticals. Today, microalgal biofuel technology, which is continuing to be developed as a surrogate for fossil-fuel technology, is the focus of constant research and development, especially regarding biomass yield and lipid production. Single stressors on microalgae have been commonly examined for efficient biofuel production; however, the synergetic effects of stressors on the lipid and biomass productivity of microalgae might lead to enhanced lipid properties. In addition, considering more than one parameter might be time-consuming; thus, many models, such as the surface-response methodology, can enable significant optimization of microalgal productivity economically. As well as multiple stressors, adaptive stressors considered in “adaptive laboratory evolution” could provide robust strains that alter low lipid yields. Although the field has progressed substantially in recent years, much about microalgae, their biological potential, how to efficiently utilize them, and their metabolic responses to various stressors remain unknown. Using an extensive review of recent developments in single-stress strategies, combined-stress strategies, and adaptive stress strategies, this paper gives an overview of recent developments in microalgal biofuel production under stress conditions. Further, it has also been suggested that an integrated microalgal biorefinery that also produces high-value chemicals alongside biofuel might significantly enhance its economic feasibility. It is expected that this document will provide an understanding of how to develop commercially viable microalgae strains for biofuel applications, taking several types of stress into consideration.