BIOREMEDIATION OF AGRO-INDUSTRIAL EFFLUENTS MEDIATED BY MICROALGAE

Every year, large amounts of agro-industrial effluents are produced all over the world and its sustainable management is still a technological challenge. This thesis addresses the remediation of four agro-industrial effluents (aquaculture, cattle, swine, and poultry) and an industrial effluent (landfill leachate) by treatment with biomass ash and microalgae. The pre-treatment with biomass ash allowed the partial precipitation of total solids, reduction of the turbidity and microbial load of the effluents, resulting in a partially treated effluent and a precipitate rich in mineral and organic components. The aqueous effluents were treated in batch and semi-continuous modes with the microalgae Chlorella vulgaris (Cv), Auxenochlorella protothecoides (Ap), Tetradesmus obliquus (To), Isochrysis galbana (Ig), Microchloropsis salina (Ms), and Spirulina major (Sm). Maximum biomass yields were reached for microalgae Cv (193.6 to 879.8 mg L-1 day-1) and To (236.7 to 811.7 mg L-1 day-1) in agro-industrial effluents. The remediation of effluents allowed reaching discharge values mandatory by law for total nitrogen and total phosphorus, COD, BOD5, and total solids. The precipitate obtained in the pre-treatment of the effluents and the algal biomass showed positive effects as biostimulants for the germination of watercress (Nasturtium officinale) and wheat (Triticum aestivum) seeds. The microalgae biomass was characterised and evaluated as a food supplement for mussels (Mytilus edulis) for 45 days, with changes in the contents of lipids, carbohydrates, and ash of the mussels being observed. The torrefaction of algae biomass and its mixtures with lignocellulosic biomass made it possible to obtain biochars with potential for energy recovery, use as biostimulants for seed germination, or as adsorbents for cationic pigments. The work carried out allowed to demonstrate the feasibility of treating the studied effluents by chemical precipitation and bioremediation with microalgae and to suggest different ways of valuing the solid by-products generated.Anualmente, grandes quantidades de efluentes agroindustriais são produzidas em todo o mundo e a sua gestão sustentável constitui, ainda, um desafio tecnológico. Esta tese aborda a remediação de quatro efluentes agroindustriais (aquacultura, gado bovino, gado suíno e aviário) e um efluente industrial (lixiviado de aterro) por tratamento com cinzas de biomassa e microalgas. O pré-tratamento com cinzas de biomassa permitiu provocar uma precipitação parcial dos sólidos totais, reduzir a turvação e a carga microbiana dos efluentes, originando um efluente parcialmente tratado e um precipitado rico em componentes minerais e orgânicos. Os efluentes aquosos foram tratados em modos descontínuo e semi-contínuo com as microalgas Chlorella vulgaris (Cv), Auxenochlorella protothecoides (Ap), Tetradesmus obliquus (To), Isochrysis galbana (Ig), Microchloropsis salina (Ms) e Spirulina major (Sm). Foram atingidas produtividades máximas de biomassa para as microalgas Cv de 193,6 a 879,8 mg L-1 dia-1 e To de 236,7 a 811,7 mg L-1 dia-1 em efluentes agroindustriais. A remediação dos efluentes permitiu atingir valores de descarga obrigatórios por lei para azoto total, fósforo total, CQO, CBO5 e sólidos totais. O precipitado obtido no pré-tratamento dos efluentes e a biomassa algal apresentaram efeitos positivos como bioestimulantes da germinação de sementes de agrião (Nasturtium officinale) e de trigo (Triticum aestivum). A biomassa microalgal foi caracterizada e avaliada como suplemento alimentar de mexilhões (Mytilus edulis) durante 45 dias, tendo-se observado alterações nos teores de lípidos, hidratos de carbono e cinzas dos mexilhões. A torrefação de biomassa algal e das suas misturas com biomassa lenhocelulósica permitiu obter biocarvões com potencial para valorização energética, utilização como bioestimulantes na germinação de sementes ou adsorventes para pigmentos catiónicos. O trabalho realizado demonstrou a viabilidade do tratamento dos efluentes analisados por precipitação química e biorremediação com microalgas e sugerir diferentes vias de valorização dos subprodutos sólidos gerados

Bioenergy production and nutrients removal by green microalgae with cultivation from agro-wastewater palm oil mill effluent (POME) - A review

Environmental pollution specifically wastewater is gaining attention both in the developed and developing countries. Malaysia is considered as one of the major palm oil producers in the world. Therefore, it is important to develop an environmental friendly and economic method to treat palm oil mill effluent (POME). The wastewater can serve as an economical nutrient source or substrate that can support the cultivation of microalgae. This can be a great nutrient for algal cultivation at the same time as remediating effluent and generating biomass. Nowadays, many microalgae species are being investigated to determine their potential and effectiveness for phytoremediation application, especially high growth rate. However, using synthetic media for growing microalgae in a mass scale is costly. It is acknowledged that POME (as nutrients enriched media) assisted enhanced microalgae growth under certain condition can considerably reduce the presence of organic and inorganic compounds. In this review, the potential of wide range of the predominant microalgae species with main focus on green microalgae (high removal efficiency): Chlamydomonas sp and Chlorella sp were investigated. Moreover, we discussed about the history, methods and future prospects in nutrients removal by green microalgae comprehensively. This review discusses several potential strategies for tackling the environmental issue generated by agro-waste water POME with enhancement of biomass productivity which can be used as an alternative for energy production

The Influence of Microalgae Addition as Co-Substrate in Anaerobic Digestion Processes

Growth microalgae could be used as co-substrates in anaerobic digestion processes to produce biogas of a high-calorific value, which could be expended as heat or electricity in cogeneration engines. Lignocellulosic and high-carbon content wastes, due to their characteristics, hinder anaerobic digestion processes. The use of microalgae as a co-substrate with high-carbon content residues can adjust the C/N ratio and thereby obtain, in some cases, a higher biogas production and greater biodegradability of wastes during anaerobic digestion than without co-digestion options. In addition, microalgae and cyanobacteria are photosynthetic microorganisms that can produce oxygen and oxidize the organic matter and NH4+ contained in wastewaters. The growth of microalgae in industrial effluents and wastewaters can considerably reduce the organic matter contained in them and their pollutant load. This growth can take advantage of the nutrients that still remain in industrial effluents, avoiding the use of clean water for the growth of biomass. The chapter will focus on an overview of microalgae anaerobic co-digestion with different wastes and the benefits of this option

Utilization of microalgal-bacterial energy nexus improves CO2 sequestration and remediation of wastewater pollutants for beneficial environmental services

Carbon dioxide (CO2) emissions from the combustion of fossil fuels and coal are primary contributors of greenhouse gases leading to global climate change and warming. The toxicity of heavy metals and metalloids in the environment threatens ecological functionality, diversity and global human life. The ability of microalgae to thrive in harsh environments such as industrial wastewater, polluted lakes, and contaminated seawaters presents new, environmentally friendly, and less expensive CO2 remediation solutions. Numerous microalgal species grown in wastewater for industrial purposes may absorb and convert nitrogen, phosphorus, and organic matter into proteins, oil, and carbohydrates. In any multi-faceted micro-ecological system, the role of bacteria and their interactions with microalgae can be harnessed appropriately to enhance microalgae performance in either wastewater treatment or algal production systems. This algal-bacterial energy nexus review focuses on examining the processes used in the capture, storage, and biological fixation of CO2 by various microalgal species, as well as the optimized production of microalgae in open and closed cultivation systems. Microalgal production depends on different biotic and abiotic variables to ultimately deliver a high yield of microalgal biomass

Microalgal systems for wastewater treatment: technological trends and challenges towards waste recovery

Wastewater (WW) treatment using microalgae has become a growing trend due the economic and environmental benefits of the process. As microalgae need CO2, nitrogen, and phosphorus to grow, they remove these potential pollutants from wastewaters, making them able to replace energetically expensive treatment steps in conventional WW treatment. Unlike traditional sludge, biomass can be used to produce biofuels, biofertilizers, high value chemicals, and even next-generation growth media for “organically” grown microalgal biomass targeting zero-waste policies and contributing to a more sustainable circular bioeconomy. The main challenge in this technology is the techno-economic feasibility of the system. Alternatives such as the isolation of novel strains, the use of native consortia, and the design of new bioreactors have been studied to overcome this and aid the scale-up of microalgal systems. This review focuses on the treatment of urban, industrial, and agricultural wastewaters by microalgae and their ability to not only remove, but also promote the reuse, of those pollutants. Opportunities and future prospects are discussed, including the upgrading of the produced biomass into valuable compounds, mainly biofuels.This research was funded by the Foundation for Science and Technology (FCT) through UIDB/04326/2020 and the GreenTreat (PTDC/BTA-BTA/31567/2017) and Red CYTED P319RT0025— RENUWAL—Red Iberoamericana para el Tratamiento de Efluentes con Microalgas projects and CRESC-Algarve and the European Regional Development Fund (ERDF) programs via the ALGAVALOR (ALG-01-0247-FEDER-035234) project.info:eu-repo/semantics/publishedVersio

Using Microalgae to Remediate Food and Bio-Digester Effluents from Western New York Agro Industries and Prospecting Harvested Algae Biomass for Biofuel Feedstocks

Agro-industries of Western NY contributes to the US economy in diverse ways. Among these are dairy, poultry, cheese, tofu and Greek Yogurt plants whose processes discharge effluents high in pollutants such as NH3, PO4, NO3, and Fe which adversely affect aquatic systems and the watershed if discharged untreated. Waste hauling causes an economic burden to industries as WWTPs remain restrictive to these effluents, but Algae Remediation Technology provides a sustainable alternative to treating agricultural wastewaters onsite. This study sampled, assessed and treated effluents from selected production plants within NY State with various algae. The research applied free suspended Algae technology to treat food-based waste waters that have pollutant levels exceeding USEPA limits. While Botyroccocus sp and Chlorella sp reduced 99% of NO3 from Synergy’s dairy and bio digester effluents within 5 days residence time, all algae species removed 75% of phosphorus within 5 days Residence Time (RT). Nostoc sp removed 98% NO3 from Kreher farm’s Egg wash effluents but moderately removed PO4 within 6 days RT while Anabaena and Chlorella sp impressively removed 90% PO4 and over 90% NO3 within an average of 3 and 12-days RT respectively. Tofu, cheese, and Greek yogurt whey all achieved bioremediation targets in less than 15 days RT. Post-treatment biomass harvested contained triglycerides and FFA fraction. Ultrasonication did not influence lipids, glucose and methane yields. Chlorella sp showed an avg 27g/L sugar yield compared to coffee and other algae biomass which yielded only avg 10g/L sugars. Lipid or lipid-sugar extractions from biomass increased Bio methane potential (BMP) by 1 and 5-fold respectively to 10ml meth/gVS and 25ml meth/g VS. Analysis and results indicate that algae are effective at reducing pollutants in agro-industrial effluents while producing high quality biomass for bioenergy purpose

Microalgae Growth under Mixotrophic Condition Using Agro-Industrial Waste: A Review

Microalgae has a great potential to produce biofuels and bioproduct but the cost is still too high mainly due to the biomass production. Mixotrophic cultivation has been pointed as microalgae cultivation mode for biomass/bioenergy production with lower cost and able to make remediation of organic waste. The proposals of this work was to make a review of microalgae growth under mixotrophic condition using agro-industrial waste. Agro-industrial by-products and wastes are of great interest as cultivation medium for microorganisms because of their low cost, renewable nature, and abundance. However biotechnological technologies are necessary to develop the production of microalgae on a large scale

Diverse application and future prospects for commercial cultivation of microalgae species: A review

Industrial revolutions, advancements in health care, pharmaceuticals, transportation can be attributed to advancements made in the field of science and technology. Environment and natural resources has paid a heavy cost for most of industrial development. Rapid depletion of non-renewable sources of energy eventually leading towards the energy crisis, direct or indirect release of industrial effluents into soil and natural water bodies, global warming are among major consequences of industrialization. Ever since these environmental concerns have been recognized substantial studies have been conducted to minimize, control pollution and restore environment and natural resources. Among several measures cultivation of algae on large scale stands out to be a multipurpose solution. Inherent potential of microalgae species to accumulate lipids makes algae an efficient source of biofuel. Beside this ability of algae to detoxify polluted water and industrial effluent support utilization of algae for environment management and restoration. Efficient CO2 fixation, ability to tolerate wide range of environmental conditions, minimal nutritional requirements further support commercial cultivation of algal species to achieve their widespread application. However, efforts are required to develop large scale cultivation protocols (beyond the range of photobioreactors) so as to achieve practical applicability of algae and their products. Alongwith, cultivation protocols there is simultaneous need of either selection of naturally occurring high yielding strains / species or genetic improvement. Standardization of optimum cultivation conditions along with harvesting procedure is equally important

Potential use of algae for heavy metal bioremediation, a critical review

Algae have several industrial applications that can lower the cost of biofuel co24 production. Among these co-production applications, environmental and wastewater bioremediation are increasingly important. Heavy metal pollution and its implications for public health and the environment have led to increased interest in developing environmental biotechnology approaches. We review the potential for algal biosorption and/or neutralization of the toxic effects of heavy metal ions, primarily focusing on their cellular structure, pretreatment, modification, as well as potential application of genetic engineering in biosorption performance. We evaluate pretreatment, immobilization, and factors affecting biosorption capacity, such as initial metal ion concentration, biomass concentration, initial pH, time, temperature, and interference of multi metal ions and introduce molecular tools to develop engineered algal strains with higher biosorption capacity and selectivity. We conclude that consideration of these parameters can lead to the development of low-cost micro and macroalgae cultivation with high bioremediation potential