Shining a Light on Wastewater Treatment with Microalgae (original) (raw)
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Environmental Technology Reviews, 2015
This review explores the use of microalgae for nutrient removal in municipal wastewater treatment, considering recent improvements in the understanding of removal mechanisms and developments of both suspended and non-suspended systems. Nutrient removal is associated to both direct and indirect uptake, with the former associated to the biomass concentration and growth environment (reactor). Importantly, direct uptake is influenced by the Nitrogen:Phosphorus content in both the cells and the surrounding wastewater, with opposite trends observed for N and P. Comparison of suspended and non-suspended systems revealed that whilst all were capable of achieving high levels of nutrient removal, only nonsuspended immobilized systems could do so with reduced hydraulic retention times of less than 1 day. As microalgae are photosynthetic organisms, the metabolic processes associated with nutrient assimilation are driven by light. Optimization of light delivery remains a key area of development with examples of improved mixing in suspended systems and the use of pulsating lights to enhance light utilization and reduce costs. Recent data provide increased confidence in the use of microalgae for nutrient removal in municipal wastewater treatment, enabling effluent discharges below 1 mg L −1 to be met whilst generating added value in terms of bioproducts for energy production or nutrient recovery. Ultimately, the review suggests that future research should focus on non-suspended systems and the determination of the added value potential. In so doing, it is predicted that microalgae systems will be significant in the delivery of the circular economy.
Evaluation of microalgae production coupled with wastewater treatment
Environmental technology, 2017
In the present study the feasibility of microalgae production coupled with wastewater treatment was assessed. Continuous cultivation of Chlorella sorokiniana with wastewater was tested in lab-scale flat panel photobioreactors. Biomass productivity was determined for four dilution rates (4.32 d(-1), 3.6 d(-1), 1.8 d(-1) and 0.72 d(-1)). The productivity peak was 1.524 g l(-1)d(-1) at the dilution rate of 2.41 d(-1). Nitrogen and phosphorus removals were found to be inversely proportional to dilution rates, while COD removal was found to be 50% at all the tested conditions. The biomass obtained at the highest dilution rate was characterized for its content of lipids, proteins and pigments. The average yields of fatty acid methyl esters (FAME), protein, lutein, chlorophylls and β-carotene was 62.4 mg, 388.2 mg, 1.03 mg, 11.82 mg and 0.44 mg per gram dry biomass, respectively. Economic analysis revealed that potentially more than 70% of revenue was from the production of pigments, i.e. ...
Water
The treatment of different types of wastewater by physicochemical or biological (non-microalgal) methods could often be either inefficient or energy-intensive. Microalgae are ubiquitous microscopic organisms, which thrive in water bodies that contain the necessary nutrients. Wastewaters are typically contaminated with nitrogen, phosphorus, and other trace elements, which microalgae require for their cell growth. In addition, most of the microalgae are photosynthetic in nature, and these organisms do not require an organic source for their proliferation, although some strains could utilize organics both in the presence and absence of light. Therefore, microalgal bioremediation could be integrated with existing treatment methods or adopted as the single biological method for efficiently treating wastewater. This review paper summarized the mechanisms of pollutants removal by microalgae, microalgal bioremediation potential of different types of wastewaters, the potential application of...
Algal Research, 2019
Microalgae immobilised within a resin shaped into beads have demonstrated the ability to remediate nutrients from wastewater effluents within hydraulic retention times as low as 3 hours. Methods to further optimise performance consider parameters relating to the bead with the impact of external conditions seldom investigated. Light is an essential parameter for microalgal growth with its effect on suspended cultures well documented. This work explores the influence of light on nutrient remediation by immobilised microalgae in order to recommend an optimal lighting solution for an immobilised microalgae technology based on Scenedesmus obliquus encapsulated within calciumalginate beads. White light (400-700 nm) at a photon flux density (PFD) of 200 µmol•m-2 •s-1 was determined optimal when illuminating a packed bed configuration. When considering phosphate, these conditions supported a remediation rate
Microalgae and sustainable wastewater treatment: a Review
Bayero Journal of Pure and Applied Sciences, 2019
INTRODUCTION Wastewaters from homes and industries require certain level of treatment prior to discharge into natural water courses. wastewater has traditionally been treated using waste stabilisation ponds (WSP), activated sludge (AS), trickling filters, etc. wastewater treatment involves the use of energy with consequent emission of carbon dioxide (CO 2) into the atmosp example, AS process requires considerable amount of energy usually generated through the combustion of fossil fuels. However, stringent regulations on reducing carbon emissions (Department of Energy and Climate Change, 2009; Environment Agency, 2009 coupled with escalating energy for the need to develop energy carbon-neutral wastewater treatment technologies. Treatment processes that couple carbon capture and wastewater treatment with low or no carbon emission (Mohammed, 2013 considered as the most sustainable option Microalgae use light, CO 2 , nutrients and water to produce biomass through photosynthesis (Hsueh et al., 2009). Commercial cultivation of microalgae usually involves the use of freshwater resources and considerable amount of nutrients. Synthetic fertilisers are also used as source of nutrients in such systems and this adds to the overall cost of the process.
Applications of Microalgae in Wastewater Treatments: a Review
2016
Water is the most important resource for mankind existence and development. Therefore, maintaining the water to a high quality is crucial. Wastewater treatment technologies are constantly evolving. Nowadays, the focus has shifted to the use of microalgae cultures, an interesting step for wastewater treatments, which can improve the treatment process in order to get a clean and healthy water. Microalgae by definition are unicellular algal species that can survive individually or in chains or clusters. They exist in both suspended forms (that free-float in a water body) and attached forms (that adhere to a submerged surface) and are one of the most important groups of organisms on the planet. Microalgae cultures offer a modern solution of wastewater tertiary treatment together with the production of potentially valuable biomass, which can be used for several purposes (biogas and biofuel production, composting, as animal feed or in aquaculture and production of fine chemicals). The mic...
Microalgae and wastewater treatment
Organic and inorganic substances which were released into the environment as a result of domestic, agricultural and industrial water activities lead to organic and inorganic pollution. The normal primary and secondary treatment processes of these wastewaters have been introduced in a growing number of places, in order to eliminate the easily settled materials and to oxidize the organic material present in wastewater. The final result is a clear, apparently clean effluent which is discharged into natural water bodies. This secondary effluent is, however, loaded with inorganic nitrogen and phosphorus and causes eutrophication and more long-term problems because of refractory organics and heavy metals that are discharged. Microalgae culture offers an interesting step for wastewater treatments, because they provide a tertiary biotreatment coupled with the production of potentially valuable biomass, which can be used for several purposes. Microalgae cultures offer an elegant solution to tertiary and quandary treatments due to the ability of microalgae to use inorganic nitrogen and phosphorus for their growth. And also, for their capacity to remove heavy metals, as well as some toxic organic compounds, therefore, it does not lead to secondary pollution. In the current review we will highlight on the role of micro-algae in the treatment of wastewater.
Microalgal Technology: A Promising Tool for Wastewater Remediation
2020
Many species of microalgae have excellent ability to remove nitrogen, phosphorus, heavy metals, pesticides, organic and inorganic compounds, and pathogens from wastewater. Microalgae species grow well in wastewater and may be used for treatment of municipal, industrial, agro-industrial, and livestock wastewaters. Furthermore, microalgae biomass is an excellent source of production of various valuable products. In this chapter, applications of microalgae for treatment of wastewater and production of valuable products are discussed.
Production and harvesting of microalgae for wastewater treatment, biofuels, and bioproducts
Biotechnology Advances, 2011
The integration of microalgae-based biofuel and bioproducts production with wastewater treatment has major advantages for both industries. However, major challenges to the implementation of an integrated system include the large-scale production of algae and the harvesting of microalgae in a way that allows for downstream processing to produce biofuels and other bioproducts of value. Although the majority of algal production systems use suspended cultures in either open ponds or closed reactors, the use of attached cultures may offer several advantages. With regard to harvesting methods, better understanding and control of autoflocculation and bioflocculation could improve performance and reduce chemical addition requirements for conventional mechanical methods that include centrifugation, tangential filtration, gravity sedimentation, and dissolved air flotation. There are many approaches currently used by companies and industries using clean water at laboratory, bench, and pilot scale; however, large-scale systems for controlled algae production and/or harvesting for wastewater treatment and subsequent processing for bioproducts are lacking. Further investigation and development of large-scale production and harvesting methods for biofuels and bioproducts are necessary, particularly with less studied but promising approaches such as those involving attached algal biofilm cultures.
Microalgae: A Renewable Source for Wastewater Treatment and Feedstock Supply for Biofuel Generation
Biointerface Research in Applied Chemistry
The search and exploitation of renewable clean energy sources have become crucial, because of the developing day by day interest for clean water and energy affected by the improvement of the economy, population, industrialization, urbanization, insufficient energy, climate abnormalities, and environmental pollution. The major cause of emissions of harmful gases into the environment is due to the high utilization of petroleum derivatives. In this way, it is paramount to explore environmentally sustainable energy sources for feasible advancement, to satisfy these expanding energy demands and to secure the environment. To mitigate these global problems, academic, industrial, and governmental sectors have engaged in a lot of brainstorming and research to surmount these difficulties, which have brought a steady flow of new information in the area of cultivation of microalgae in innovative technologies including photobioreactors and high rate algal ponds. In this respect, biomass generatio...