Role of culture solution pH in balancing CO2 input and light intensity for maximising microalgae growth rate.

The interplay between CO2 input and light intensity is investigated to provide new insight to optimise microalgae growth rate in photobioreactors for environmental remediation, carbon capture, and biomass production. Little is known about the combined effect of carbon metabolism and light intensity on microalgae growth. In this study, carbonated water was transferred to the microalgae culture at different rates and under different light intensities for observing the carbon composition and growth rate. Results from this study reveal opposing effects from CO2 input and light intensity on the culture solution pH and ultimately microalgae growth rate. Excessive CO2 concentration can inhibit microalgae growth due to acidification caused by CO2 dissolution. While increasing light intensity can increase pH because the carboxylation process consumes photons and transfers hydrogen ions into the cell. This reaction is catalysed by the enzyme RuBisCO, which functions optimally within a specific pH range. By balancing CO2 input and light intensity, high microalgae growth rate and carbon capture could be achieved. Under the intermittent CO2 transfer mode, at the optimal condition of 850 mg/L CO2 input and 1089 µmol/m2/s light intensity, leading to the highest microalgae growth rate and carbon fixation of 4.2 g/L as observed in this study.

Strategies to improve membrane performance in wastewater treatment.

Membrane technology has rapidly gained popularity in wastewater treatment due to its cost-effectiveness, environmentally friendly tools, and elevated productivity. Although membrane performance in wastewater treatment has been reviewed in several past studies, the key techniques for improving membrane performance, as well as their challenges, and solutions associated with the membrane process, were not sufficiently highlighted in those studies. Also, very few studies have addressed hybrid techniques to improve membrane performance. The present review aims to fill those gaps and achieve public health benefits through safe water processing. Despite its higher cost, membrane performance can result in a 36% reduction in flux degradation. The issue with fouling has been identified as one of the key challenges of membrane technology. Chemical cleaning is quite effective in removing accumulated foulant. Fouling mitigation techniques have also been shown to have a positive effect on membrane photobioreactors that handle wastewater effluent, resulting in a 50% and 60% reduction in fouling rates for backwash and nitrogen bubble scouring techniques. Membrane hybrid approaches such as hybrid forward-reverse osmosis show promise in removing high concentrations of phosphorus, ammonium, and salt from wastewater. The incorporation of the forward osmosis process can reject 99% of phosphorus and 97% of ammonium, and the reverse osmosis approach can achieve a 99% salt rejection rate. The control strategies for membrane fouling have not been successfully optimized yet and more research is needed to achieve a realistic, long-term direct membrane filtering operation.

Selection of microalgae strains for sustainable production of aviation biofuel.

This study develops and applies the PROMETHEE-GAIA method as a new tool to select microalgae strains for aviation fuel production. Assessment involves 19 criteria with equal weighting in three aspects, namely biomass production, lipid quality, and fatty acid methylester properties. Here, the method is demonstrated for evaluating 17 candidate microalgae strains. Chlorella sp. NT8a is assessed as the most suitable strain for aviation fuel production. The results also show that unmodified biofuel from the most suitable strain could not meet all jet fuel standards. In particular, microalgae-based fuel could not satisfy the required density, heating value and freezing points of the international jet fuel standards. These results highlight the need for a broad action plan including improvement in the processing or modification of biofuel produced from microalgae and revision of the current jet fuel standards to facilitate the introduction of microalgae-based biofuel for the aviation industry.

SARS-CoV-2 variants and environmental effects of lockdowns, masks and vaccination: a review.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is continuously evolving and four variants of concern have been identified so far, including Alpha, Beta, Gamma and Delta variants. Here we review the indirect effect of preventive measures such as the implementation of lockdowns, mandatory face masks, and vaccination programs, to control the spread of the different variants of this infectious virus on the environment. We found that all these measures have a considerable environmental impact, notably on waste generation and air pollution. Waste generation is increased due to the implementation of all these preventive measures. While lockdowns decrease air pollution, unsustainable management of face mask waste and temperature-controlled supply chains of vaccination potentially increases air pollution.

Simultaneous nutrient recovery and algal biomass production from anaerobically digested sludge centrate using a membrane photobioreactor.

This study aims to evaluate the performance of C. vulgaris microalgae to simultaneously recover nutrients from sludge centrate and produce biomass in a membrane photobioreactor (MPR). Microalgae growth and nutrient removal were evaluated at two different nutrient loading rates (sludge centrate). The results show that C. vulgaris microalgae could thrive in sludge centrate. Nutrient loading has an indiscernible impact on biomass growth and a notable impact on nutrient removal efficiency. Nutrient removal increased as the nutrient loading rate decreased and hydraulic retention time increased. There was no membrane fouling observed in the MPR and the membrane water flux was fully restored by backwashing using only water. However, the membrane permeability varies with the hydraulic retention time (HRT) and biomass concentration in the reactor. Longer HRT offers higher permeability. Therefore, it is recommended to operate the MPR system in lower HRT to improve the membrane resistance and energy consumption.

Recent developments in physical, biological, chemical, and hybrid treatment techniques for removing emerging contaminants from wastewater.

Emerging contaminants (ECs) in wastewater have recently attracted the attention of researchers as they pose significant risks to human health and wildlife. This paper presents the state-of-art technologies used to remove ECs from wastewater through a comprehensive review. It also highlights the challenges faced by existing EC removal technologies in wastewater treatment plants and provides future research directions. Many treatment technologies like biological, chemical, and physical approaches have been advanced for removing various ECs. However, currently, no individual technology can effectively remove ECs, whereas hybrid systems have often been found to be more efficient. A hybrid technique of ozonation accompanied by activated carbon was found significantly effective in removing some ECs, particularly pharmaceuticals and pesticides. Despite the lack of extensive research, nanotechnology may be a promising approach as nanomaterial incorporated technologies have shown potential in removing different contaminants from wastewater. Nevertheless, most existing technologies are highly energy and resource-intensive as well as costly to maintain and operate. Besides, most proposed advanced treatment technologies are yet to be evaluated for large-scale practicality. Complemented with techno-economic feasibility studies of the treatment techniques, comprehensive research and development are therefore necessary to achieve a full and effective removal of ECs by wastewater treatment plants.

Source, distribution and emerging threat of micro- and nanoplastics to marine organism and human health: Socio-economic impact and management strategies.

The nature of micro- and nanoplastics and their harmful consequences has drawn significant attention in recent years in the context of environmental protection. Therefore, this paper aims to provide an overview of the existing literature related to this evolving subject, focusing on the documented human health and marine environment impacts of micro- and nanoplastics and including a discussion of the economic challenges and strategies to mitigate this waste problem. The study highlights the micro- and nanoplastics distribution across various trophic levels of the food web, and in different organs in infected animals which is possible due to their reduced size and their lightweight, multi-coloured and abundant features. Consequently, micro- and nanoplastics pose significant risks to marine organisms and human health in the form of cytotoxicity, acute reactions, and undesirable immune responses. They affect several sectors including aquaculture, agriculture, fisheries, transportation, industrial sectors, power generation, tourism, and local authorities causing considerable economic losses. This can be minimised by identifying key sources of environmental plastic contamination and educating the public, thus reducing the transfer of micro- and nanoplastics into the environment. Furthermore, the exploitation of the potential of microorganisms, particularly those from marine origins that can degrade plastics, could offer an enhanced and environmentally sound approach to mitigate micro- and nanoplastics pollution.

Impact of COVID-19 on the social, economic, environmental and energy domains: Lessons learnt from a global pandemic.

COVID-19 has heightened human suffering, undermined the economy, turned the lives of billions of people around the globe upside down, and significantly affected the health, economic, environmental and social domains. This study aims to provide a comprehensive analysis of the impact of the COVID-19 outbreak on the ecological domain, the energy sector, society and the economy and investigate the global preventive measures taken to reduce the transmission of COVID-19. This analysis unpacks the key responses to COVID-19, the efficacy of current initiatives, and summarises the lessons learnt as an update on the information available to authorities, business and industry. This review found that a 72-hour delay in the collection and disposal of waste from infected households and quarantine facilities is crucial to controlling the spread of the virus. Broad sector by sector plans for socio-economic growth as well as a robust entrepreneurship-friendly economy is needed for the business to be sustainable at the peak of the pandemic. The socio-economic crisis has reshaped investment in energy and affected the energy sector significantly with most investment activity facing disruption due to mobility restrictions. Delays in energy projects are expected to create uncertainty in the years ahead. This report will benefit governments, leaders, energy firms and customers in addressing a pandemic-like situation in the future.

Harvesting Porphyridium purpureum using polyacrylamide polymers and alkaline bases and their impact on biomass quality.

This study aims to examine the flocculation efficiency of Porphyridium purpureum (i.e. a red marine microalga with high content of pigments and fatty acids) grown in seawater medium using polyacrylamide polymers and alkaline flocculation. Polymers Flopam™ and FO3801 achieved the highest flocculation efficiency of over 99% at the optimal dose of 21 mg per g of dry biomass through charge neutralisation and bridging mechanism. The addition of sodium hydroxide, potassium hydroxide, and sodium carbonate also achieved flocculation efficiency of 98 and 91%, respectively, but high doses were required (i.e. > 500 mg per g of dry biomass). Calcium hydroxide was not as effective and could only achieve 75% flocculation efficiency. Precipitation of magnesium hydroxide was identified as the major cause of hydroxide-induced flocculation. On the other hand, sodium carbonate addition induced flocculation via both magnesium and calcium carbonate co-precipitation. The large mass of precipitates caused a sweeping effect and enmeshed the microalgal cells to trigger sedimentation. Cell membrane integrity analysis of flocculated P. purpureum indicated that polyacrylamide polymers led to significant compromised cells (i.e. 96%), compared to the alkaline bases (70-96% compromised cells). These results appear to be the first to demonstrate the high efficiency of polyacrylamide polymer and alkaline flocculation of P. purpureum but at the expense of the biomass quality.

Effect of nanocatalysts on the transesterification reaction of first, second and third generation biodiesel sources- A mini-review.

Biodiesel is a fuel that has numerous benefits over traditional petrodiesel. The transesterification process is the most popular method for biodiesel production from various sources, categorized as first, second and third generation biodiesel depending on the source. The transesterification process is subject to a variety of factors that can be taken into account to improve biodiesel yield. One of the factors is catalyst type and concentration, which plays a significant role in the transesterification of biodiesel sources. At present, chemical and biological catalysts are being investigated and each catalyst has its advantages and disadvantages. Recently, nanocatalysts have drawn researchers' attention to the efficient production of biodiesel. This article discusses recent work on the role of several nanocatalysts in the transesterification reaction of various sources in the development of biodiesel. A large number of literature from highly rated journals in scientific indexes is reviewed, including the most recent publications. Most of the authors reported that nanocatalysts show an important influence regarding activity and selectivity. This study highlights that in contrast to conventional catalysts, the highly variable surface area of nanostructure materials favours interaction between catalysts and substrates that efficiently boost the performance of products. Finally, this analysis provides useful information to researchers in developing and processing cost-effective biodiesel.

Toward Enhanced State of Charge Estimation of Lithium-ion Batteries Using Optimized Machine Learning Techniques.

State of charge (SOC) is a crucial index used in the assessment of electric vehicle (EV) battery storage systems. Thus, SOC estimation of lithium-ion batteries has been widely investigated because of their fast charging, long-life cycle, and high energy density characteristics. However, precise SOC assessment of lithium-ion batteries remains challenging because of their varying characteristics under different working environments. Machine learning techniques have been widely used to design an advanced SOC estimation method without the information of battery chemical reactions, battery models, internal properties, and additional filters. Here, the capacity of optimized machine learning techniques are presented toward enhanced SOC estimation in terms of learning capability, accuracy, generalization performance, and convergence speed. We validate the proposed method through lithium-ion battery experiments, EV drive cycles, temperature, noise, and aging effects. We show that the proposed method outperforms several state-of-the-art approaches in terms of accuracy, adaptability, and robustness under diverse operating conditions.

Finned spacer for efficient membrane fouling control in produced water filtration.

Membrane based technologies are highly reliable for water and wastewater treatment, including for removal of total oil and grease from produced water. However, performances of the pressure driven processes are highly restricted by membrane fouling and the application of traditional air bubbling system is limited by their low shear stress due to poor contacts with the membrane surface. This study develops and assesses a novel finned spacer, placed in between vertical panel, for membrane fouling control in submerged plate-and-frame module system for real produced water filtration. Results show that permeability of the panel is enhanced by 87% from 201 to 381 L/(m2 h bar). The spacer system can be operated in switching mode to accommodate two-sided panel aeration. This leads to panel permeability increment by 22% higher than the conventional vertical system. The mechanisms of finned spacer in encouraging the flow trajectory was proven by visual observation and flow simulation. The fins alter the air bubbles flow trajectory toward the membrane surface to effectively scour-off the foulant. Overall results demonstrate the efficacy of the developed spacer in projecting the air bubble trajectory toward the membrane surface and thus significantly enhances membrane panel productivity.

Latest development in microalgae-biofuel production with nano-additives.

BACKGROUND: Microalgae have been experimented as a potential feedstock for biofuel generation in current era owing to its' rich energy content, inflated growth rate, inexpensive culture approaches, the notable capacity of CO2 fixation, and O2 addition to the environment. Currently, research is ongoing towards the advancement of microalgal-biofuel technologies. The nano-additive application has been appeared as a prominent innovation to meet this phenomenon. MAIN TEXT: The main objective of this study was to delineate the synergistic impact of microalgal biofuel integrated with nano-additive applications. Numerous nano-additives such as nano-fibres, nano-particles, nano-tubes, nano-sheets, nano-droplets, and other nano-structures' applications have been reviewed in this study to facilitate microalgae growth to biofuel utilization. The present paper was intended to comprehensively review the nano-particles preparing techniques for microalgae cultivation and harvesting, biofuel extraction, and application of microalgae-biofuel nano-particles blends. Prospects of solid nano-additives and nano-fluid applications in the future on microalgae production, microalgae biomass conversion to biofuels as well as enhancement of biofuel combustion for revolutionary advancement in biofuel technology have been demonstrated elaborately by this review. This study also highlighted the potential biofuels from microalgae, numerous technologies, and conversion processes. Along with that, the study recounted suitability of potential microalgae candidates with an integrated design generating value-added co-products besides biofuel production. CONCLUSIONS: Nano-additive applications at different stages from microalgae culture to end-product utilization presented strong possibility in mercantile approach as well as positive impact on the environment along with valuable co-products generation into the near future.

Second generation bioethanol potential from selected Malaysia's biodiversity biomasses: A review.

Rising global temperature, worsening air quality and drastic declining of fossil fuel reserve are the inevitable phenomena from the disorganized energy management. Bioethanol is believed to clear out the effects as being an energy-derivable product sourced from renewable organic sources. Second generation bioethanol interests many researches from its unique source of inedible biomass, and this paper presents the potential of several selected biomasses from Malaysia case. As one of countries with rich biodiversity, Malaysia holds enormous potential in second generation bioethanol production from its various agricultural and forestry biomasses, which are the source of lignocellulosic and starch compounds. This paper reviews potentials of biomasses and potential ethanol yield from oil palm, paddy (rice), pineapple, banana and durian, as the common agricultural waste in the country but uncommon to be served as bioethanol feedstock, by calculating the theoretical conversion of cellulose, hemicellulose and starch components of the biomasses into bioethanol. Moreover, the potential of the biomasses as feedstock are discussed based on several reported works.

Cost-benefit analysis and emission reduction of energy efficient lighting at the Universiti Tenaga Nasional.

This paper reports the result of an investigation on the potential energy saving of the lighting systems at selected buildings of the Universiti Tenaga Nasional. The scope of this project includes evaluation of the lighting system in the Library, Admin Building, College of Engineering, College of Information Technology, Apartments, and COE Food court of the university. The main objectives of this project are to design the proper retrofit scenario and to calculate the potential electricity saving, the payback period, and the potential environmental benefits. In this survey the policy for retrofitting the old lighting system with the new energy saving LEDs starts with 10% for the first year and continues constantly for 10 years until all the lighting systems have been replaced. The result of the life cycle analysis reveals that after four years, the selected buildings will bring profit for the investment.