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•Chlorella vulgaris was tolerant to levofloxacin, and could withstand its high doses.•96h EC50 of levofloxacin for C. vulgaris was 58.6mgL−1.•The acclimation of C. vulgaris enhanced ...the removal of levofloxacin.•Sodium chloride stimulated the biodegradation of levofloxacin up to 91%.•NaCl (1%w/v) increased the degradation rate constant (k) of LEV from 0.011 to 0.257d−1.
The extensive contamination of levofloxacin (LEV) in aquatic ecosystems has attracted increasing attention because of the potential for development of bacterial resistance and its eco-toxicity to non-target organisms. Biodegradation of LEV was significantly improved upon the acclimation of a freshwater microalga, Chlorella vulgaris and in the presence of elevated salinity. Among the six wild species (Chlamydomonas mexicana, Chlamydomonas pitschmannii, Chlorella vulgaris, Ourococcus multisporus, Micractinium resseri, Tribonema aequale), C. vulgaris showed the highest removal capacity (12%) of LEV at 1mgL−1. The acclimated C. vulgaris, which was pre-exposed to 200mgL−1 of LEV for 11days, exhibited enhanced removal of 1mgLEVL−1 by 16% after 11days of cultivation. The addition of 1% (w/v) sodium chloride into the microalgal media significantly improved LEV removal by >80% in the C. vulgaris culture. The bioaccumulation of LEV at day 11 in C. vulgaris cells without NaCl was 34μgg−1, which was elevated to 101μgg−1LEV at 1% NaCl. The bioconcentration factor for LEV was 34 and 1004 in 0 and 1% NaCl, respectively. The mass balance analysis of LEV showed that more than 90% of LEV was biodegraded by C. vulgaris at day 11 with the addition of 1% NaCl. These results demonstrated that the enhanced removal of LEV by salinity was mainly through bioaccumulation and subsequent intracellular biodegradation by C. vulgaris cells.
•Biomass composition with suitable pre-treatment is vital for successful biorefinery.•A technique that has high yield, low COD and low CO2 is ideal.•Integrated conversion technique with process ...integration is a suitable approach.•Combining microalgae with intermittent dark/photo fermentation in series is suggested.
A constant shift of society's dependence from petroleum-based energy resources towards renewable biomass-based has been the key to tackle the greenhouse gas emissions. Effective use of biomass feedstock, particularly lignocellulosic, has gained worldwide attention lately. Lignocellulosic biomass as a potent bioresource, however, cannot be a sustainable alternative if the production cost is too high and/ or the availability is limited. Recycling the lignocellulosic biomass from various sources into value added products such as bio-oil, biochar or other biobased chemicals in a bio-refinery model is a sensible idea. Combination of integrated conversion techniques along with process integration is suggested as a sustainable approach. Introducing ‘series concept’ accompanying intermittent dark/photo fermentation with co-cultivation of microalgae is conceptualised. While the cost of downstream processing for a single type of feedstock would be high, combining different feedstocks and integrating them in a bio-refinery model would lessen the production cost and reduce CO2 emission.
•Microalgae-based wastewater treatment conforms the new trends of wastewater treatment in future.•Most wastewater with inappropriate C/N and N/P ratios for microalgae cultivation.•Factors affecting ...nutrients recovery by microalgae are strongly related to the wastewater characteristics.•More research is needed on the design and operation of microalgae-based wastewater treatment process to be more economical.
The water resource crisis and concerns with environmental pollution are pushing for upgrading of conventional wastewater treatment process. Microalgae-based wastewater treatment process has shown many advantages that can meet the new demand for improved wastewater treatment. However, considering the issues related to the complexity of wastewater characteristics and adaptability of microalgae species, and the challenges to the design and optimization of treatment processes in order to achieve higher removal efficiencies with lower costs, further exploration and research are still needed. This review provides an overview of microalgae strains commonly used for wastewater treatment, physical and chemical properties of various wastewaters and their suitability for algae cultivation, factors affecting algae growth, nutrient assimilation/removal and biomass productivity. The design and operation of microalgae-based wastewater treatment processes are also discussed. Moreover, the issues and limitations of microalgae-based wastewater treatment are also discussed and suggestions are proposed for the further research and development.
Derivation of biofuel from microalgae biomass has been widely researched in the past few decades. Microalgae is capable of producing 58,700 litres oil per hectare that can generate 121,104 litres ...biodiesel per hectare, which seemingly a promising transition over conventional fossil fuels. Nevertheless, economic sustainability of commercial scale production of microalgae biomass is still in shadows of doubt, especially the cultivation and harvesting process. Apparently, the microalgae cultivation system has evolved from traditional open pond to various modern photobioreactor (PBR) designs. However, with regards to tubular and flat panel PBRs as the most ubiquitous systems for biofuel production at commercial level, extensive discussion on reactor configurations and design betterment was presented in this review, along with precise technical comparison on cost and energy requirements for the cultivation systems. This review intended to serve as guideline for long term adoption of these well-established cultivation technologies in biofuel plants given the numerous economic benefits. Besides that, in attempt to lower the harvesting cost, potential use of various waste biomass as bioflocculants to recover microalgae biomass was introduced in this review. This article also deliberates direction on potential policy interventions to produce microalgae biofuel in a more sustainable and cost-effective manners in near future.
•Microalgae-derived biofuel is the potential substitute over fossil fuel.•Cultivation and harvesting steps are the bottlenecks to produce microalgae biofuel.•Wise selection of cultivation technology ensures sustainable biofuel production.•Bioflocculants from waste biomass are cheap, non-toxic, easily extracted.•Suitable policy framework ensures successful microalgae biofuel commercialization.
•Swine wastewater (SWW) is rich in ammonia-N with potential environmental threats.•Natural treatment systems employ simple ponds with indigenous flora.•Biological methods are carried out in closed ...systems with effective nutrient removal.•Microalgae can assimilate the nutrients in SWW under hetero/mixo-trophic conditions.•Microalgae-based SWW treatment is beneficial compared to other methods.
There is an exponential increase in swine farms around the world to meet the increasing demand for proteins, resulting in a significant amount of swine/piggery wastewater. The wastewater produced in swine farms are rich in ammonia with high eutrophication potential and negative environmental impacts. Safe methods for treatment and disposal of swine wastewater have attracted increased research attention in the recent decades. Conventional wastewater treatment methods are limited by the high ammonia content and chemical/biological oxygen demand of swine wastewater. Recently, microalgal cultivation is being proposed for the phytoremediation of swine wastewater. Microalgae are tolerant to high ammonia levels seen in swine wastewater and they also ensure phosphorus removal simultaneously. This review first gives a brief overview on the conventional methods used for swine wastewater treatment. Microalgae-based processes for the clean-up of swine wastewater are discussed in detail, with their potential advantages and limitations. Future research perspectives are also presented.
•Emerging contaminant removal technologies have been summarized.•MBR, microalgae and activated sludge are effective biological removal processes.•Ozonation/H2O2 and photo-Fenton are highly effective ...chemical removal processes.•Many hybrid systems have enhanced removal capacity of emerging contaminants.•Future research regarding emerging contaminant removal has been proposed.
This review focuses on the removal of emerging contaminants (ECs) by biological, chemical and hybrid technologies in effluents from wastewater treatment plants (WWTPs). Results showed that endocrine disruption chemicals (EDCs) were better removed by membrane bioreactor (MBR), activated sludge and aeration processes among different biological processes. Surfactants, EDCs and personal care products (PCPs) can be well removed by activated sludge process. Pesticides and pharmaceuticals showed good removal efficiencies by biological activated carbon. Microalgae treatment processes can remove almost all types of ECs to some extent. Other biological processes were found less effective in ECs removal from wastewater. Chemical oxidation processes such as ozonation/H2O2, UV photolysis/H2O2 and photo-Fenton processes can successfully remove up to 100% of pesticides, beta blockers and pharmaceuticals, while EDCs can be better removed by ozonation and UV photocatalysis. Fenton process was found less effective in the removal of any types of ECs. A hybrid system based on ozonation followed by biological activated carbon was found highly efficient in the removal of pesticides, beta blockers and pharmaceuticals. A hybrid ozonation-ultrasound system can remove up to 100% of many pharmaceuticals. Future research directions to enhance the removal of ECs have been elaborated.
•Potential of microalgae biorefinery for producing high value products is assessed.•Conventional processes of microalgae biorefinery are discussed.•Recent technologies on microalgae biorefinery are ...reviewed.•Techno-economic analysis and LCA assessment on microalgal biorefinery are addressed.•Advantages of microalgae biorefinery and derived high-value products are emphasized.
Microalgae have received much interest as a biofuel feedstock in response to the uprising energy crisis, climate change and depletion of natural sources. Development of microalgal biofuels from microalgae does not satisfy the economic feasibility of overwhelming capital investments and operations. Hence, high-value co-products have been produced through the extraction of a fraction of algae to improve the economics of a microalgae biorefinery. Examples of these high-value products are pigments, proteins, lipids, carbohydrates, vitamins and anti-oxidants, with applications in cosmetics, nutritional and pharmaceuticals industries. To promote the sustainability of this process, an innovative microalgae biorefinery structure is implemented through the production of multiple products in the form of high value products and biofuel. This review presents the current challenges in the extraction of high value products from microalgae and its integration in the biorefinery. The economic potential assessment of microalgae biorefinery was evaluated to highlight the feasibility of the process.
Hydrogen is a promising alternative to fossil fuel for a source of clean energy due to its high energy content. Some strains of phototrophic microorganisms are known as important object of scientific ...research and they are being explored to raise biohydrogen (BioH2) yield. BioH2 is still not commonly used in industrial area because of the low biomass yield and valuable down streaming process. This article deals with the methods of the hydrogen production with the help of two large groups of phototrophic microorganisms – microalgae and cyanobacteria. Microalgal hydrogen is environmentally friendly alternative to conventional fossil fuels. Algal biomass has been considered as an attractive raw source for hydrogen production. Genetic modified strains of cyanobacteria are used as a perspective object for obtaining hydrogen. The modern photobioreactors and outdoor air systems have been used to obtain the biomass used for hydrogen production. At present time a variety of immobilization matrices and methods are being examined for their suitability to make immobilized H2 producers.
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•Hydrogen production from microalgae and cyanobacteria.•Mechanisms of biohydrogen metabolism.•Bioreactors for biohydrogen production process.•Enzymes of biohydrogen production.
•Macroalgae residue is promising raw material for producing biochar.•Biochar derived from pigments-extracted macroalgae is a promising adsorbent.•The malachite green adsorption capacity of MDBC800 is ...5306.2 mg/g.
Biochar is known to efficiently adsorb dyes from wastewater. In this study, biochar was derived from macroalgae residue by pyrolysis, and the influence of varying temperature (from 400 °C to 800 °C) on biochar characteristics was investigated. Among the biochar samples tested, macroalgae-derived biochar possessing highly porous structure, special surface chemical behavior and high thermal stability was found to be efficient in removing malachite green, crystal violet and Congo red. The biochar derived by pyrolysis at 800 °C showed the highest adsorption capacity for malachite green (5306.2 mg g−1). In this study, the transformation of microalgae residue into a highly efficient dye adsorbent is a promising procedure for economic and environmental protection.
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