Microalgae Applications in Wastewater Treatment

The main issues with the industrial revolution are how to deal with the excessive usage of fossil fuels and lessen the harmful effects that industrial waste has on the environment. The need for renewable energy is growing concurrently with the depletion of fossil fuel resources. Industrial wastes, in addition to agricultural wastes, are the principal contributors to water contamination. In comparison to other physical-chemical treatment techniques, microalgae provide the most appealing biological alternatives to address both energy emergencies and wastewater treatment1. A more affordable and environmentally responsible alternative to traditional wastewater treatment methods is a microalgae-based wastewater treatment system2. Due to improved phytoremediation, the capacity of microalgae to use carbon, nitrogen, and phosphorus presents considerable prospects for their capture in high-volume biomass production. CO2 is absorbed and the nitrogen and phosphorus from the wastewater are removed from the environment when microalgae are used in the wastewater environment. Incorporating microalgae into CO2 capture and wastewater treatment offers numerous benefits, as was already mentioned: (1) As a reliable CO2 scavenger, microalgae can grow from the exhaust gas by consuming CO2, (2) nitrogen and phosphorus representing a tertiary wastewater treatment system that is both cutting edge and environmentally beneficial2.

The main types of nitrogen present in wastewater are nitrates, nitrites, and ammonia. Phosphorus exists in the forms of phosphates and orthophosphates, both of which are crucial for the metabolism of microalgae. These essential nutrients can be present in wastewater in sufficient quantities and in the right forms to meet the needs of microalgae growth. The resulting biomass can be utilized for a range of things, such as renewable biopolymers that can be made into a substrate for the manufacture of biogas, lipids, biodiesel, fertilizers, and packaging materials. The fatty acid profiles of various microalgae species were examined by Hempel et al. in 2012. (Chlorella sp., Cosmarium sp., Spirulina sp., etc.). According to reports, the screened microalgae species have around 90% of the total fatty acid content in key fatty acids such as palmitic acid, oleic acid, and linolenic acid, which are appropriate for producing biodiesel. In wastewater, microalgae for biodiesel production can be produced sustainably while reducing the N, P, and K loads of the wastewater significantly3. The synthesis of algal lipids with the ideal fatty acid profile has been the subject of numerous studies4,5,6.

Numerous microalgae species have been investigated for the treatment of wastewater and concurrent biomass generation. Chlorella species when the majority of the fatty acids are made up of short-chain fatty acids (C14-C18), which make up the majority of biodiesel, these types are thought to be superior for producing biofuel7. Only a few of the strains from various species, such as Scenedesmus sp. and Chlorella sp., are known to adapt effectively to various wastewater. In order to effectively manage wastewater, it is necessary to screen and characterize strong algal strains that are tailored to the local climate. It is well known that microalgae strains that are locally isolated outperform those obtained from collections of algae. In order to create strains of resistance with high performance, breeding, genetic, and/or breeding alterations can be used8. When dairy wastewater was treated with 10% CO2 supplementation, a group of 10 naturally occurring algal strains (derived from dairy wastewater) produced 153.54 t ha-1 year-1 of biomass and had a lipid content of 16.89%. More than 98% of the wastewater’s chemical oxygen demand was also satisfied9.

Microalgae are efficient in recovering nutrients from wastewater and producing biofuel. The economic barrier preventing the adoption of this approach might be overcome by using microalgae simultaneously for wastewater treatment and biofuel production. It is necessary to look into more practical and effective methods for treating wastewater and growing microalgae for biofuel. It appears that improving wastewater management and achieving energy generation are not priorities given the state of the environment today. The most promising answer in this situation is thought to be microalgae, which may be used to remediate wastewater and produce biofuel at the same time1.

References:

  1. Hussain F, Shah SZ, Ahmad H, et al. Microalgae an ecofriendly and sustainable wastewater treatment option: Biomass application in biofuel and bio-fertilizer production. A review. Renew Sustain Energy Rev. 2021;137:110603. doi:10.1016/J.RSER.2020.110603
  2. Aziz MA, Ng WJ. Feasibility of wastewater treatment using the activated-algae process. Bioresour Technol. 1992;40(3):205-208. doi:10.1016/0960-8524(92)90143-L
  3. Christenson L, Sims R. Production and harvesting of microalgae for wastewater treatment, biofuels, and bioproducts. Biotechnol Adv. 2011;29(6):686-702. doi:10.1016/J.BIOTECHADV.2011.05.015
  4. Shekh AY, Shrivastava P, Krishnamurthi K, et al. Stress-induced lipids are unsuitable as a direct biodiesel feedstock: A case study with Chlorella pyrenoidosa. Bioresour Technol. 2013;138:382-386. doi:10.1016/J.BIORTECH.2013.04.010
  5. Shekh AY, Shrivastava P, Krishnamurthi K, et al. Stress enhances poly-unsaturation rich lipid accumulation in Chlorella sp. and Chlamydomonas sp. Biomass and Bioenergy. 2016;84:59-66. doi:10.1016/J.BIOMBIOE.2015.11.013
  6. Fulke AB, Mudliar SN, Yadav R, et al. Bio-mitigation of CO(2), calcite formation and simultaneous biodiesel precursors production using Chlorella sp. Bioresour Technol. 2010;101(21):8473-8476. doi:10.1016/J.BIORTECH.2010.06.012
  7. Gülyurt MÖ, Özçimen D, İnan B. Biodiesel Production from Chlorella protothecoides Oil by Microwave-Assisted Transesterification. Int J Mol Sci 2016, Vol 17, Page 579. 2016;17(4):579. doi:10.3390/IJMS17040579
  8. Zhou W, Chen P, Min M, et al. Environment-enhancing algal biofuel production using wastewaters. Renew Sustain Energy Rev. 2014;36:256-269. doi:10.1016/J.RSER.2014.04.073
  9. Hena S, Fatimah S, Tabassum S. Cultivation of algae consortium in a dairy farm wastewater for biodiesel production. Water Resour Ind. 2015;10:1-14. doi:10.1016/J.WRI.2015.02.002

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