Treatment of fish processing wastewater with microalgae-containing microbiota

Circular economy approaches for the production of high-value polysaccharides from microalgal biomass grown on industrial fish processing wastewater: A review

The discharge of high-strength wastewater from the fish-processing industries, comprising undefined blends of toxic and organic compounds, has always been a subject of great disquiet worldwide. Despite a large number of effluent treatment methodologies known to date, biosorption with the aid of naturally grown microalgae has been recognized recently to possess promising outcomes in eradicating pollutants comprising organic compounds from liquid effluents. Interestingly, the microalgal biomass harvested from phytoremediation of fish effluent was identified to be abundant in bio compounds that exhibited potential application in pharmaceutical, nutraceutical, and, aquaculture feed, generating a circular economy. In this context, the focus of the review is to emphasize the applications of microalgal species as naturally occurring and zero-cost adsorbents for the elimination of organic contaminants from fish liquid effluents. The summary of the literature encompassed in this work is supposed to benefit the readers to comprehend the primary mechanisms by which microalgae uptakes the organic matter from fish processing effluents and converts them into various biological molecules. From the scientific works assessed through this review, the most promising microalgae species regards to nutrient uptake and removal efficiency from fish effluent, were identified as Chlorella sp. > Spirulina sp. > Scenedesmus sp. The review further revealed supercritical fluid extraction as the robust extraction tool for the extraction of targeted bioproducts from microalgal biomass grown within fish effluents. Eventually, the information presented through this review establishes phytoremediation using microalgal biomass to be a natural cost-effective, sustainable circular bio-economy approach that could be robustly applied for the efficient treatment of wastewater discharged from food processing industries.

Heterotrophic growth of Galdieria sulphuraria on residues from aquaculture and fish processing industries

The study aimed at zero-waste utilization of fish processing streams for cultivation of microalgae Galdieria sulphuraria. Wastewater from a fish processing facility, slam (mix of used fish feed and faeces), and dried pellet (sediments after enzymatic hydrolysis of rainbow trout) were investigated as potential sources of carbon, nitrogen, and phosphate for cultivation of G. sulphuraria. The pellet extract was found to support the growth of G. sulphuraria when appropriate diluted, at concentrations below 40 % (v/v). It was revealed that wastewater does not impact the growth negatively, however free amino nitrogen and carbon sources need to be supplied from another source. Therefore, only proteolyzed pellet extract (20 %, v/v) was selected for upscaling and a biomass concentration of 80 g L^-1 (growth rate was 0.72 day^-1) was achieved in a non-sterile fed-batch culture. Even though biomass was produced under non-sterile conditions no pathogens such as Salmonella sp. could be detected.

Wastewater treatment by microalgae

The growth of the world's population increases the demand for fresh water, food, energy, and technology, which in turn leads to increasing amount of wastewater, produced both by domestic and industrial sources. These different wastewaters contain a wide variety of organic and inorganic compounds which can cause tremendous environmental problems if released untreated. Traditional treatment systems are usually expensive, energy demanding and are often still incapable of solving all challenges presented by the produced wastewaters. Microalgae are promising candidates for wastewater reclamation as they are capable of reducing the amount of nitrogen and phosphate as well as other toxic compounds including heavy metals or pharmaceuticals. Compared to the traditional systems, photosynthetic microalgae require less energy input since they use sunlight as their energy source, and at the same time lower the carbon footprint of the overall reclamation process. This mini-review focuses on recent advances in wastewater reclamation using microalgae. The most common microalgal strains used for this purpose are described as well as the challenges of using wastewater from different origins. We also describe the impact of climate with a particular focus on a Nordic climate.

Potential of Microalgae in Bioremediation of Wastewater

The increase in global pollution, industrialization and fast economic progress are considered to inflict serious consequences to the quality and availability of water throughout the world. Wastewater is generated from three major sources, i.e. industrial, agricultural, and municipal which contain pollutants, such as: xenobiotics, microplastics, heavy metals and augmented by high amount of carbon, phosphorus, and nitrogen compounds. Wastewater treatment is one of the most pressing issues since it cannot be achieved by any specific technology because of the varying nature and concentrations of pollutants and efficiency of the treatment technologies. The degradation capacity of these conventional treatment technologies is limited, especially regarding heavy metals, nutrients, and xenobiotics, steering the researchers to bioremediation using microalgae (Phycoremediation). Bioremediation can be defined as use of microalgae  for removal or biotransformation of pollutants and CO2 from wastewater with concomitant biomass production. However, the usage of wastewaters for the bulk cultivation of microalgae is advantageous for reducing carbon, nutrients cost, minimizing the consumption of freshwater, nitrogen, phosphorus recovery, and removal of other pollutants from wastewater and producing sufficient biomass for value addition for either biofuels or other value-added compounds. Several types of microalgae like Chlorella and Dunaliella have proved their applicability in the treatment of wastewaters. The bottlenecks concerning the microalgal wastewater bioremediation need to be identified and elucidated to proceed in bioremediation using microalgae. This objective of this paper is to provide an insight about the treatment of different wastewaters using microalgae and microalgal potential in the treatment of wastewaters containing heavy metals and emerging contaminants, with the specialized cultivation systems. This review also summarizes the end use applications of microalgal biomass which makes the bioremediation aspect more environmentally sustainable. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

High-performance biological treatment of tuna wash processing wastewater using Yarrowia lipolytica

It is well known that the lack of an effective treatment of tuna wash processing wastewater may pose substantial environmental and public health hazards. The present work investigates the performance of biological treatment of tuna wash processing wastewater (TWPW) by using Yarrowia lipolytica. Under optimized experimental conditions (pH "6.40-6.50" and 29 °C), Y. lipolytica reduced the pollution level of the crude and the diluted TWPW after only 7 days of incubation. The Yarrowia treatment leaded to a reduction of 66% chemical oxygen demand, 69.8% total organic carbon, 66% salinity, and phosphorus total (100%) removal of the crude TWPW, while the treated-diluted TWPW revealed significant reductions in chemical oxygen demand and total organic carbon (75% and 74%, respectively), as well as salinity (68%). Interestingly, a total removal of nitrogen and phosphorus from the diluted TWPW was obtained. Under high salinity, an important Y. lipolytica biomass of 5 g L^-1 is produced with high levels of lipids and protein contents at around 336 ± 12.2 mg g^-1 and 302.15 ± 5.44 mg g^-1, respectively. The phytotoxicity assessment of the treated TWPW on fenugreek seeds shows promising results, which reveals the good performance of Yarrowia treatment in reducing the toxicity of this wastewater.

Bioremediation of aquaculture wastewater with the microalgae Tetraselmis suecica: Semi-continuous experiments, simulation and photo-respirometric tests

Tetraselmis suecica was cultivated in a semi-continuously operated tubular photobioreactor fed on aquaculture wastewater (AW) testing two hydraulic retention times (HRT): 10 and 7 days (RUN_1 and RUN_2, respectively). The integrated mechanistic model BIO_ALGAE was validated with experimental data in order to simulate the biomass production and nutrient uptake of T. suecica. Moreover, AW was used as substitute synthetic cultivation medium to test the production of lipids, proteins, and carbohydrates in the microalgal biomass. Preliminary photo-respirometric tests were carried out on the AW suspension containing microalgae and bacteria. Dissolved Inorganic Nitrogen (DIN) and Dissolved Inorganic Phosphorus (DIP) were analyzed for the two RUNs, and no significant difference was highlighted (p > 0.05). On the contrary, the productivity of the Total suspended solids (TSS) was significantly higher (p < 0.05) for RUN_1 (900 mg TSS/L) than for RUN_2 (550 mg TSS/L). The analysis of the biochemical composition of biomass has demonstrated a higher content of proteins than of lipids and carbohydrates for the two RUNs. BIO_ALGAE model was validated by comparing simulated results to experimental data. The model was able to reproduce the pattern of these experimental data quite well, for both nutrient uptake and biomass production. The simulated curve follows the same pattern as the experimental data for both RUNs. The wavelike trend indicates the good accuracy of the simulated curves to reproduce the microalgae growth and nutrient uptake that occurring during daytime and at night. With this study, BIO_ALGAE Model was demonstrated to be useful to simulate bioremediation and microalgae production in aquaculture wastewater in a semi-continuous system with different environmental factors. The photo-respirometric outputs were compared with the process rates affecting dissolved oxygen dynamics computed by the mathematical model.

Anaerobic Co-Digestion Effluent as Substrate for Chlorella vulgaris and Scenedesmus obliquus Cultivation

Anaerobic digestate supernatant can be used as a nutrient source for microalgae cultivation, thus integrating phytoremediation processes with high value products storage in microalgae biomass. Microalgae are able to use nitrogen and phosphorous from digestate, but high nutrient concentration can cause growth inhibition. In this study, two microalgae strains (C. vulgaris and S. obliquus) were cultivated on the anaerobic co-digestion supernatant (obtained from the organic fraction of municipal solid waste (OFMSW) and waste activated sludge (WAS)) in a preliminary Petri plate screening at different dilutions (1:10 and 1:5) using a synthetic medium (ISO) and tap water (TW). Direct Nile red screening was applied on colonies to preliminarily identify hydrophobic compound storage and then a batch test was performed (without air insufflation). Results show that C. vulgaris was able to grow on digestate supernatant 1:5 diluted, while Nile red screening allowed the preliminary detection of hydrophobic compound storage in colonies. The analysis carried out at the end of the test on ammonia, phosphate, nitrate and sulphate showed a removal percentage of 47.5 ± 0.8%, 65.0 ± 6.0%, 95.0 ± 3.0% and 99.5 ± 0.1%, respectively.

Anaerobic microbial communities can influence algal growth and nutrient removal from anaerobic digestate

The objective of this work was to test the impact of anaerobic digester microorganisms on algal growth, composition, and nutrient removal from digestate. Culture studies were carried out to determine the impacts of the microbial community on treatment of poultry litter anaerobic digestate by two strains of green algae: Auxenochlorella protothecoides and Chlorella sorokiniana. The results showed that the community doubled the growth of A. protothecoides but had no impact on C. sorokiniana growth. A similar result was observed for nutrient removal where the microbial community increased the capacity of A. protothecoides to remove ammonium and phosphate. The impact of the microbial community on biomass composition was minimal for both algae types.

High-rate algal pond coupled with a matrix of Spirogyra sp. for treatment of rural streams with nutrient pollution

This study evaluated the unique features of a filamentous algae matrix (FAM) that can be applied to high rate algal ponds (HRAPs) as a promising way to remove nutrient from polluted rural streams. The results show that the HRAPs, coupled with the FAM, effectively removed nitrogen and phosphorus (79.8% and 81.2%, respectively), and achieved high production of DO, with a maximum of 11.0 g O₂ g FAM^-1 d^-1. The FAM functioned wells as a screen to prevent excessive algae loss from the system and obtained relatively high biomass growth rate (0.032 mg L^-1 d^-1 for nitrogen and 0.344 mg L^-1 d^-1 for phosphorus). The harvested FAM was a useful fertilizer and the rate of addition of FAM were 1.52 kg d^-1 ha^-1 of nitrogen and 0.44 kg d^-1 ha^-1 of phosphorus. Thus, combining the HRAP with the FAM was an effective nutrient removal and resource utilization system for rural streams.

Efficient bioremediation of tannery wastewater by monostrains and consortium of marine Chlorella sp. and Phormidium sp

This study evaluated the bioremediation potential of two marine microalgae Chlorella sp. and Phormidium sp., both individually and in consortium, to reduce various pollutants in tannery wastewater (TW). The microalgae were grown in hazardous 100% TW for 20 days, and the reductions in biochemical oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN), total phosphorous (TP), chromium (Cr) and total dissolved solids (TDS) of the wastewater monitored periodically. Both marine isolates reduced the BOD and COD by ≥90% in the consortium and by over 80% individually. Concentrations of TN and TP were reduced by 91.16% and 88%, respectively, by the consortium. Removal/biosorption efficiencies for chromium ranged from 90.17-94.45%. Notably, the TDS, the most difficult to deal with, were reduced by >50% within 20 days by the consortium. The novel consortium developed in this study reduced most of the ecologically harmful components in the TW to within the permissible limits of discharge in about 5 to 15 days of treatment. Thus, both the tested marine strains of Chlorella and Phormidium sp. are promising for bioremediating/detoxifying TW and adequately improve the water quality for safe discharge into open water bodies, in particular when used as a consortium.

Comparing Nutrient Removal from Membrane Filtered and Unfiltered Domestic Wastewater Using Chlorella vulgaris

The nutrient removal efficiency of Chlorella vulgaris cultivated in domestic wastewater was investigated, along with the potential to use membrane filtration as a pre-treatment tool during the wastewater treatment process. Chlorella vulgaris was batch cultivated for 12 days in a bubble column system with two different wastewater treatments. Maximum uptake of 94.18% ammonium (NH₄-N) and 97.69% ortho-phosphate (PO₄-P) occurred in 0.2 μm membrane filtered primary wastewater. Membrane filtration enhanced the nutrient uptake performance of C. vulgaris by removing bacteria, protozoa, colloidal particles and suspended solids, thereby improving light availability for photosynthesis. The results of this study suggest that growing C. vulgaris in nutrient rich membrane filtered wastewater provides an option for domestic wastewater treatment to improve the quality of the final effluent.

Algal cultivation in urban wastewater: an efficient way to reduce pharmaceutical pollutants

The purpose of this study was to investigate whether pharmaceutical pollutants in urban wastewater can be reduced during algal cultivation. A mixed population of wild freshwater green algal species was grown on urban wastewater influent in a 650 L photobioreactor under natural light and with the addition of flue gases. Removal efficiencies were very high (>90 %), moderate (50-90 %), low (10-50 %), and very low or non-quantifiable (<10 %) for 9, 14, 11, and 18 pharmaceuticals, respectively, over a 7-day period. High reduction was found in the following pharmaceuticals: the beta-blockers atenolol, bispropol, and metoprolol; the antibiotic clarithromycine; the antidepressant bupropion; the muscle relaxant atracurium; hypertension drugs diltiazem and terbutaline used to relive the symptoms of asthma. Regression analysis did not detect any relationship between the reduction in pharmaceutical contents and light intensity reaching the water surface of the algal culture. However, the reduction was positively correlated with light intensity inside the culture and stronger when data collected during the night were excluded. Algae cultivation can remove partially or totally pharmaceutical pollutants from urban wastewater, and this opens up new possibilities for treating urban wastewater.

Microalgae consortia cultivation in dairy wastewater to improve the potential of nutrient removal and biodiesel feedstock production

The potential of microalgae consortia used in dairy wastewater treatment combined with microalgae biodiesel feedstock production was evaluated by comparing the nutrient removal of dairy wastewater, the growth of cells, and the lipid content and composition of biomass between monoalgae and microalgae consortia cultivation system. Our results showed that higher chemical oxygen demand (COD) removal (maximum, 57.01-62.86 %) and total phosphorus (TP) removal (maximum, 91.16-95.96 %) were achieved in almost microalgae consortia cultivation system than those in Chlorella sp. monoalgae cultivation system (maximum, 44.76 and 86.74 %, respectively). In addition, microalgae consortia cultivation except the mixture of Chlorella sp. and Scenedesmus spp. reached higher biomass concentration (5.11-5.41 g L(-1)), biomass productivity (730.4-773.2 mg L(-1) day(-1)), and lipid productivity (143.7-150.6 mg L(-1) day(-1)) than those of monoalgae cultivation (4.72 g L(-1), 674.3, and 142.2 mg L(-1) day(-1), respectively) on the seventh day. Furthermore, the fatty acid methyl ester (FAME) profiles indicated the lipids produced from microalgae consortia cultivation system were more suitable for biodiesel production. The microalgae consortia display superiority in dairy wastewater treatment and the getting feedstock for biodiesel production.

Effects of various organic carbon sources on the growth and biochemical composition of Chlorella pyrenoidosa

The aim of this study was to investigate the effects of various organic carbon sources (glucose, galactose, fructose, sucrose, maltose, lactose and starch) on the growth and biochemical composition of Chlorella pyrenoidosa. Monosaccharides were found to exert stronger stimulative effects on the algal growth than disaccharides and starch. After 10-day culture, addition of 0.5-5.0 g L(-1) glucose and galactose significantly reduced the cellular protein contents by 27.7-63.7% and 22.6-60.5%, respectively, and significantly increased the carbohydrate contents by 103.2-266.5% and 91.9-240.0%, respectively. However, addition of 0.5-5.0 g L(-1) disaccharides and starch did not significantly affect the contents of lipid, protein and carbohydrate. Similar to the normal nitrogen condition, the cellular biochemical composition was not significantly affected by addition of 3.0 g L(-1) disaccharides and starch under the low nitrogen condition. Finally, the significance of this work in the biotechnological application of mixotrophic cultivation of C. pyrenoidosa was further discussed.

Concentrated microalgae cultivation in treated sewage by membrane photobioreactor operated in batch flow mode

This study investigated the microalgae biomass production and nutrients removal efficiency from treated sewage by newly developed membrane photobioreactor in which Chlorella vulgaris was cultured in batch flow mode. Its performance was compared with conventional photobioreactor. The results show that the volumetric microalgae productivity was 39.93 and 10.36 mg L(-1)d(-1) in membrane photobioreactor and conventional photobioreactor, respectively. The nutrients removal rate in membrane photobioreactor was 4.13 mg N L(-1)d(-1) and 0.43 mg P L(-1)d(-1), which was obviously higher than that in conventional photobioreactor (0.59 mg N L(-1)d(-1) and 0.08 mg P L(-1)d(-1)). The better performance of membrane photobioreactor was due to the submerged membrane module in the reactor which acted as a solid-liquid separator and thereby enabled the reactor to operate with higher supply flow rate of cultivation medium. Moreover, in the outflow stage of the membrane photobioreactor, the microalgae culture liquor in the reactor could be further concentrated.

Wastewater treatment to enhance the economic viability of microalgae culture

Microalgae culture is still not economically viable and it presents some negative environmental impacts, concerning water, nutrient and energy requirements. In this context, this study aims to review the recent advances on microalgal cultures in wastewaters to enhance their economic viability. We focused on three different culture concepts: (1) suspended cell systems, (2) cell immobilization, and (3) microalgae consortia. Cultures with suspended cells are the most studied. The nutrient removal efficiencies are usually high for wastewaters of different sources. However, biomass harvesting is difficult and a costly process due to the small cell size and lower culture density. On the other hand, the cell immobilization systems showed to be the solution for this problem, having as main limitation the nutrient diffusion from bulk to cells, which results in a reduced nutrient removal efficiency. The consortium between microalgae and bacteria enhances the growth of both microorganisms. This culture concept showed to be a promising technology to improve wastewater treatment, regarding not only nutrient removal but also biomass harvesting by bioflocculation. The aggregation mechanism must be studied in depth to find the process parameters that would lead to an effective and cheap harvesting process.

Treatment of agro-industrial wastewater using microalgae-bacteria consortium combined with anaerobic digestion of the produced biomass

Two combined processes were studied in order to produce second generation biofuels: microalgae biomass production and its further use to produce biogas. Two 5 L photobioreactors for treating wastewater from a potato processing industry (from now on RPP) and from a treated liquid fraction of pig manure (from now on RTE) were inoculated with Chlorella sorokiniana and aerobic bacteria at 24±2.7 °C and 6000 lux for 12 h per day of light supply. The maximum biomass growth was obtained for RTE wastewater, with 26.30 mg dry weight L(-1) d(-1). Regarding macromolecular composition of collected biomass, lipid concentration reached 30.20% in RPP and 4.30% in RTE. Anaerobic digestion results showed that methane yield was highly influenced by substrate/inoculum ratio and by lipids concentration of the biomass, with a maximum methane yield of 518 mL CH4 g COD(-1)added using biomass with a lipid content of 30% and a substrate/inoculum ratio of 0.5.