Integration of wastewater treatment with microalgae-for-biodiesel production
Development of a novel, economically viable bio-process integrating wastewater treatment with production of microalgae-for-biodiesel
Tech Area / Field
- BIO-IND/Industrial Biotechnology/Biotechnology
- BIO-SFS/Biosafety and BioSecurity/Biotechnology
- ENV-WPC/Water Pollution and Control/Environment
- NNE-FUE/Fuels/Non-Nuclear Energy
3 Approved without Funding
Agricultural University of Georgia, Georgia, Tbilisi
- Institute of Agrochemistry and Food Technology (IATA), Spanish Council for Science (CSIC), Spain, Paterna, Valencia\nMeisei University, Japan, Tokyo\nThe University of Buckingham, UK, Buckingham\nValladolid University, Spain, Valladolid
Project summaryThe Project aim: Wastewater treatment which is an integral part of water management in general includes physical, chemical, and biological processes to remove contaminants and produce environmentally safer treated effluent. Most of the recent biological treatment technologies involve the use of bacteria, however microalgae (unicellular algae) based biological treatment now is considered advantageous since numerous species of microalgae unlike bacteria are able to remove a wide variety of organic and inorganic toxic substances at high removal rate and low retention time. Moreover, certain species of microalgae can improve the wastewater treatment by decreasing the pathogen content in the final effluent. Several hypotheses were made to explain the causes of pathogens reduction including presence of antibacterial substances excreated by microalgae, high pH levels common in microalgae based treatment systems, production of toxic extracellular compounds by certain species, high oxidation reduction potential etc (Bulent Sen et al., Relationship of Algae to Water Pollution and Waste Water Treatment, http://dx.doi.org/10.5772/51927). Besides that, microalgae were indicated as a beneficial tool for evaluating long-term alters in ecosystem such as those related to eutrophication, water management, alters in land use at the scale of watershed, and climate changes. In this sense, algae/microalgae appear a useful biological indicator because they respond rapidly to alterations in ecosystem situations, thus enabling a quick assessment of water quality.
Along with biological treatment of wastewater numerous species of microalgae are able to produce excessive oil-rich biomass that is considered a technically viable alternative energy resource for third generation biodiesel production (Tsukahara, Sawayama, 2005. Wang, et al., 2010. Anaerobic digested dairy manure as a nutrient supplement for cultivation of oil-rich green microalgae Chlorella sp. Bioresour. Technol. 101, 2623–2628). In its turn, microbial biofuels (referred to as third generation biofuels) production from renewable sources is recognized to be one of the most effective alternatives to fossil fuels and a viable means for economic and environmental sustainability (Nigam, and Singh, Production of liquid biofuels from renewable resources, Progress in Energy and Combustion Science, 37(1): 52–68), 2011).
The overall goal of the project is the development of economically viable bioprocess integrating heterotrophic microalgae based treatment of brewery and dairy wastewater with microalgae-for-biodiesel production.
Current status: Over the past decades the use of obligate phototrophic microalgae with simple growing requirements in naturally or artificially illuminated environments like open ponds and/or photobioreactors (PBR) was prevailing approach for integration wastewater biological treatment with biofuel production. In spite of relatively low construction and operating costs, efficiency of open pond systems for algal biomass-for-biodiesel commercial production proved to be limited due to low productivity of oils producing algal biomass caused by poor light diffusion inside the pond decreasing with depth; constant contamination of monoculture by fungi, bacteria and protozoa; poor utilization of CO2 due to evaporation or stripping, dependence of environmental growth parameters of cultivation primarily on local weather conditions; laborious and costly harvesting; increasing costs for land use etc. Similar to the open-pond concept, large-scale PBR that are protected from direct fallout, relatively safe from invading microorganisms, where temperatures are controlled with an enhanced CO2 fixation have some disadvantages that make their use uneconomical for microalgae-for-biodiesel production. In particular, at operational volumes of 50-100 l or higher it is no longer possible to disperse light efficiently evenly inside the PBR as developed microalgae biofilm fouls PBR surfaces and thereby limits light penetration into the culture; PBR needs high initial investment in infrastructure and increased costs for maintenance.
Referring to recent publications microalgae capable to treat wastewater in heterotrophic growth conditions with production of vast amount of oil rich biomass are considered promising for microalgae-for -biodiesel low-cost production at any scale. Bumbak et al.,2015, Rohit et al.,2011; Moreover, microalgae heterotrophic cultivation, which may allow large volume applications such as wastewater treatment combined, or separated with production of biofuels is far cheaper, simpler to construct facilities, and easier than autotrophic cultivation to maintain on a large scale (Hidalgo. AOP J Environ Waste Management 2015, 05/12) microalgae based wastewater treatment resulting both in pollutants removal and microalgae-for-biodiesel production is a relatively new field of research, the main biological challenges include bringing into industrial culture heterotrophic microalgae species with ‘optimal’ attributes such as high growth rate, high lipid content and tolerance to growth inhibitors (Espinosa-González et al., 2014, Bioresour Technol 155:170-176; Gómez et al., 2013. Appl Microbiol Biotechnol 97(5): 2239-2249). The other challenge in microalgae based biodiesel production is the lack of cost effective technology for microalgae oil extraction. Number of methods like expeller/oil press, liquid–liquid extraction (solvent extraction), supercritical fluid extraction (SFE) and ultrasound technique applied for microalgae oil extraction didn’t show significant economic efficiency. Therefore, development of new methods both for disruption of cells and microalgae oil recovery becomes of high importance for making overall process cost effective. The participants’ expertise: Project builds on the extensive research and management experience of project participants in the creation and characterization of collections of microorganisms of all taxonomic groups. Development of environment protection and biofuels like biogas, bio-hydrogen and cellulosic ethanol production technologies are the main fields of research. From 1997 Up to now, project team members participated in 16 international R&D projects funded by NATO, ISTC, STCU, World Bank, CRDF Global, DTRA etc. Published more than 40 research papers, Chapters and monographs.
Scope of activities: Project aims to cover all stages of microalgae based treatment of brewery and dairy wastewater and microalgae oil production. Project realization includes creation and general characterization of microalgae collection for wastewater treatment abilities, water pollution control properties and high value compounds accumulation. In-depth studies will cover identification and screening of microalgae strains able to accumulate lipids in heterotrophic growth; study of optimal conditions and culture management for high effective treatment of brewery and dairy wastewater and sustainable high biomass and oil yields; design, construction and testing of lab-scale system that will be best suited to the selected strains and culture media and development of cost-effective method for microalgae oil extraction. Microalgae biomass residual after oil extraction will be studied for application as fertilizer and/or feed. Finally, ecological, energetic and economical parameters of the integrated process will be assessed.
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