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Recently, hybrid systems, such as those incorporating high-rate algal ponds (HRAPs) and biofilm reactors (BRs), have shown promise in treating domestic wastewater while cultivating microalgae. In this context, the objective of the present study was to determine an improved scraping frequency to maximize microalgae biomass productivity in a mix of industrial (fruit-based juice production) and domestic wastewater. The mix was set to balance the carbon/nitrogen ratio. The scraping strategy involved maintaining 1 cm wide stripes to retain an inoculum in the reactor. Three scraping frequencies (2, 4, and 6 days) were evaluated. The findings indicate that a scraping frequency of each 2 days provided the highest biomass productivity (18.75 g total volatile solids m -2 d -1 ). The species' behavior varied with frequency: Chlorella vulgaris was abundant at 6-day intervals, whereas Tetradesmus obliquus favored shorter intervals. Biomass from more frequent scraping demonstrated a higher lipid content (15.45%). Extrapolymeric substance production was also highest at the 2-day frequency. Concerning wastewater treatment, the system removed 93% of dissolved organic carbon and ∼100% of ammoniacal nitrogen. Combining industrial and domestic wastewater sources to balance the carbon/nitrogen ratio enhanced treatment efficiency and biomass yield. This study highlights the potential of adjusting scraping frequencies in hybrid systems for improved wastewater treatment and microalgae production., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Scenedesmus obliquus (ACOI 204/07) microalgae were cultivated in cattle wastewater in vertical alveolar flat panel photobioreactors, operated in batch and continuous mode, after previous digestion in a hybrid anaerobic reactor. In batch operation, removal efficiencies ranges of 65 to 70% of COD, 98 to 99% of NH 4 + and 69 to 77.5% of PO 4 -3 after 12days were recorded. The corresponding figures for continuous flow were from 57 to 61% of COD, 94 to 96% of NH 4 + and 65 to 70% of PO 4 -3 with mean hidraulic retention time of 12days. Higher rates of CO 2 fixation (327-547mgL -1 d -1 ) and higher biomass volumetric productivity (213-358mgL -1 d -1 ) were obtained in batch mode. This microalgae-mediated process can be considered promising for bioremediation and valorization of effluents produced by cattle breeding yielding a protein-rich microalgal biomass that could be eventually used as cattle feed., (Copyright © 2018 Elsevier B.V. All rights reserved.)

New data on biogas production and treatment of cattle wastewater were registered using an upflow anaerobic sludge blanket-anaerobic filter (UASB-AF) hybrid reactor under mesophilic temperature conditions (37 °C). The reactor was operated in semi-continuous mode with hydraulic retention times of 6, 5, 3 and 2 days and organic loading rates of 3.8, 4.6, 7.0 and 10.8 kg COD t m -3 d -1 . Biogas volumes of 0.6-0.8 m 3 m -3 d -1 (3.8-4.6 kg COD t m -3 d -1 ) and 1.2-1.4 m 3 m -3 d -1 (7.0-10.8 kg COD t m -3 d -1 ), with methane concentrations between 69 and 75%, were attained. The removal of organic matter with values of 60-81% (COD t ) and 51-75% (COD s ) allowed methane yields of 0.155-0.183 m 3 CH 4 kg -1 COD t and 0.401-0.513 m 3 CH 4 kg -1 COD s to be obtained. Volatile solids were removed in 34 to 69%, with corresponding methane yields of 0.27 to 0.42 m 3 CH 4 kg -1 VS removed . The good performance of the novel hybrid reactor was demonstrated by biogas outputs higher than reported previously in the literature, along with the quality of the gas obtained in the various experimental phases. The hybrid reactor investigated in this study presents comparative advantages, particularly in relation to conventional complete mixture units, considering economic factors such as energy consumption, reactor volume and installation area.

The increased demand for energy results in an increase in fossil fuel consumption. However, the planet's oil deposits will soon reach unsustainable levels, presenting an opportunity for biofuels. In this study, cattle wastewater (CWW) was used to cultivate a microalgae consortium in photobioreactors. Seven rounds of experiments were carried out with the addition of CO2 (ControlCO2), ozone application for 10, 20, and 30 min (O3T10, O3T20, and O3T30), and a combination of CO2 and ozone (O3T10CO2 and O3T20CO2). Maximum dry biomass (18.63 g/L) and CO2 biofixation (8047.79 mg/L/d) were obtained in O3T20CO2. A total of 48% of lipid was registered in O3T30 and O3T20, indicating that microalgae were stressed when exposed to ozonized wastewater. C16:0 was detected in higher concentrations in all experiments. O3T30, O3T10CO2, and O3T20CO2 had values for C18:3 in accordance with the requirements of EN 14,214. Projections show that a farm with 2000 animals could produce 430 g of biofuels per kg of biomass and fixed 2.67 tCO2/y. Removals of up to 100% for NH3–N, 99.6% for P, and 91.7% for COD were recorded. The data indicates a possibility for CWW bioremediation and biofuel production in significant quantity and quality in comparison to the current scenario of microalgae cultivation. [ABSTRACT FROM AUTHOR]

The large volume of effluents generated by intensive cattle production can become an environmental problem, requiring solutions that combine treatment and disposal of reuse water. The quality of cattle wastewater (CWW) treated by ozonation, the water requirement and its effect on the growth of seedlings of Dalbergia nigra cultivated with sewage sludge were determined under different light conditions. The study was carried out in a split plot scheme with 2 shading levels (0%—C1, and 49.4% attenuation—C2) and 3 types of irrigation water (control–T1, 1 h ozonation–T2, and 2 h–T3), with 4 repetitions. Direct sowing was realized into 280 cm3 tubes which were irrigated by drip irrigation with automatic management. The height and collar diameter were measured every 21 days, and at the end of the nursery phase, and the Dickson quality index (DQI) and irrigation water productivity (WPir) were determined. In addition, seedlings were transplanted in a forest restauration area (FRA) of Atlantic Forest, with height and diameter monitoring for 200 days. With ozonation, there was an increase in pH and a reduction in electrical conductivity, total solids and turbidity in the CWW, allowing its use for irrigation of forest seedlings. The maximum volumes of water applied were 2.096 and 1.921 L plant-1, with water supply T2 and T1, respectively, and coverages C1 and C2. In these conditions, the seedlings reached DQI of 0.47 and 0.17, and WPir of 2.35 and 1.48 g L-1, respectively. The initial vegetative growth of the seedlings planted in the FRA was benefited by the nutrients provided by the CWW treated. Therefore, the use of sewage sludge and CWW treated has the potential to produce forest seedlings, reducing the release of waste and effluents into the environment. [ABSTRACT FROM AUTHOR]

Microalgal biofuel production is a useful process to produce sustainable and carbon-neutral biofuels. The choice of microalgal species and the processes adopted in various production stages determine biofuel production. In this review, recent technological advancements made in various stages of microalgal biofuel production are discussed. This review also discussed the recent progress made in harvesting microalgal biomass and lipid extraction. In addition, the viability of using wastewater as a nutrient source for microalgae and its nutrient removal capabilities has been discussed in detail. This is the first study that enlists and compares the minimum achievable cost of biofuel produced in different studies. Also, process optimization strategies adopted to minimize the cost are discussed. The reported biofuel production cost varied from 0.14 $/L to 24.33 $/L based on the variation in the microalgae strains, production method, and optimization strategies. [ABSTRACT FROM AUTHOR]

The aim of this study is to cultivate Spirulina platensis and Scenedesmus obliquus microalgae in consortia using effluents of cattle waste anaerobic treatment in order to give possibilities to the production of microalgae biomass to biorefineries uses. The biomasses obtained were characterized to evaluate the potential for the production of biofuels and other bioproducts. The effluent was used in sterile and non-sterile conditions to better understand the influence of other microorganisms in N and P removal. The biomass obtained with the addition of 10% of sterile effluent in Zarrouk media (20%) presented 44.12 and 34.62% of carbohydrates, using Spirulina platensis in monoculture or the 50%/50% consortia of Spirulina and Scenedesmus, respectively, this biomass presenting the potential to be used to bioethanol production. Nitrogen and phosphorous removal were higher in non-sterile conditions and reached 92.7 and 49.66% of nitrogen and phosphorous removal, respectively, using the consortia and with the addition of 30% effluent in the media. The cultivation of microalgae in a consortium may be used to assist the treatment of water concurrently with the production of biomass to different applications. [ABSTRACT FROM AUTHOR]

Microalgae biomasses offer important benefits regarding macromolecules that serve as promising raw materials for sustainable production. In the present study, the microalgae Arthrospira platensis DHR 20 was cultivated in horizontal photobioreactors (HPBR), with and without temperature control, in batch mode (6 to 7 days), with anaerobically digested cattle wastewater (ACWW) as substrate. High dry biomass concentrations were observed (6.3–7.15 g L−1). Volumetric protein, carbohydrate, and lipid productivities were 0.299, 0.135, and 0.108 g L−1 day−1, respectively. Promising lipid productivities per area were estimated between 22.257 and 39.446 L ha−1 year−1. High CO2 bio-fixation rates were recorded (875.6–1051 mg L−1 day−1), indicating the relevant potential of the studied microalgae to mitigate atmospheric pollution. Carbon concentrations in biomass ranged between 41.8 and 43.6%. ACWW bioremediation was satisfactory, with BOD5 and COD removal efficiencies of 72.2–82.6% and 63.3–73.6%. Maximum values of 100, 95.5, 92.4, 80, 98, and 94% were achieved concerning the removal of NH4+, NO3−, Pt, SO42−, Zn, and Cu, respectively. Total and thermotolerant coliform removals reached 99–99.7% and 99.7–99.9%. This microalgae-mediated process is, thus, promising for ACWW bioremediation and valuation, producing a microalgae biomass rich in macromolecules that can be used to obtain friendly bio-based products and bioenergy. [ABSTRACT FROM AUTHOR]

The Brazilian environmental, economic, and social conditions for the long-term establishment of mass culture of microalgae for either biofuel production or greenhouse gases (GHG) abatement are described in detail. A brief historical introduction of the microalgal biotechnology is presented followed by a compilation of Brazilian published research works on microalgae, with special emphasis on microalgal Brazilian biodiversity and applied phycology. Several case studies on Brazilian microalgal biorefineries are presented with special emphasis on wastewater (WW) treatment. The manuscript also adds valuable new information about which regions of the country offer better growing conditions for dozens of endemic species. Favorable climatic and environmental conditions for the cultivation of several microalgae (green) and cyanobacteria species in specific regions of the country are suggested. Finally, based on realistic biomass productivities and product yields for the Brazilian context, several scenarios for biofuel production and/or carbon dioxide (CO2) abatement have been designed, and results are presented and critically discussed. Brazilian self-sufficiency on either fuels for transportation or GHG abatement using exclusively microalgae is quite challenging but achievable accordingly with the present state of the art. [ABSTRACT FROM AUTHOR]

Recent research interest has focused on microalgae cultivation for biogas slurry purification and biogas upgrading due to the requirement of high efficiency for nutrient uptake and CO2 capture, with economic feasibility and environmental benefits. Numerous studies have suggested that biogas slurry purification and biogas upgrading can occur simultaneously via microalgae-based technology. However, there is no comprehensive review on this technology with respect to the nutrient removal from biogas slurry and biogas upgrading. This article summarizes microalgal cultivation with biogas slurry and biogas from anaerobic digestion. The parameters, techniques, and modes of microalgae cultivation have been discussed in detail to achieve high efficiency in biogas slurry purification and biogas upgrading. In addition, the evaluation of energy efficiency and safety has also been explored. Compared with mono-cultivation of microalgae and co-cultivation of microalgae and bacteria, microalgae-fungi symbiosis has demonstrated greater development prospect and higher energy efficiency and the energy consumption for pollutants and CO2 removal were 14.2–39.0% · USD−1 and 19.9–23.3% · USD−1, respectively. Further, a sustainable recycling scheme is proposed for the purification of biogas slurry from anaerobic digestion process and biogas upgrading via microalgae-based technology. [ABSTRACT FROM AUTHOR]

In order to reduce the cost of microalgae harvesting, biofilm algal cultivations have received attention as a potential platform for algal biomass production and wastewater treatment. Two 50-L ponds containing vertically oriented geotextiles, cotton textiles, and polyethylene sheets were fed secondary effluent to examine the growth of algal biofilms. The removal of total phosphorus, PO43−-P and NO3−-N ranged from 52 to 97%, 59 to 93%, and 0 to 99%, respectively. The highest biomass productivity was 1.4 and 0.5 g m−2 day−1, and the lipid content of the attached biomass was quite low, 0.36 and 0.48%, in the cotton textile and polyethylene-baffled pond, respectively. The lipid content of the suspended biomass of the cotton textile and polyethylene pond was very low and similar (0.5%), but it increased to 13.8 and 3.4%, respectively, after a starvation period of 13 days. [ABSTRACT FROM AUTHOR]

The current study demonstrates a comprehensive investigation on clean water generation from raw dairy wastewater (RDW) using a robust microalgal strain, Ascochloris sp. ADW007 and its growth, biomass, and lipid productivities in outdoor conditions. Microalgal treatment studies were conducted in column photobioreactor (CPB) and flat-pate photobioreactor (FPB), where the volumetric algal biomass productivity in RDW was significantly increased in both CPB (0.284 ± 0.0017 g/L/d) and FPB (0.292 ± 0.0121 g/L/d) as compared to synthetic mediums viz., BG11 and TAP, respectively, with enhanced lipid content. Maximum lipid accumulation of 33.40% was obtained within 7 d growth. The volumetric and areal lipid productivities in CPB and FPB were 94 mg/L/d and 5.597 g/m2/d, and 98 mg/L/d and 9.754 g/m2/d, respectively. Chemiflocculation, filtration, and centrifugation techniques were employed for harvesting microalgal biomass. Among the flocculants, 0.08% (w/v) FeCl3 harvested >99% of algal cells within 5 min, while 0.03% (w/v) cetyl trimethyl ammonium bromide and 0.125% (w/v) sodium hydroxide harvested >96% of the cells in 30 and 60 min. After microalgal treatment, >80% of clean and odorless water was obtained with reduction in 94–96% of COD, 72–80% of nitrate and 80–97% of total phosphate, respectively. Highlights Utilization of 100% raw dairy wastewater without any treatment. Production of clean and odorless water for recycle and reuse. COD, nitrate and total phosphate reduction by 94–96%, 72–80%, and 80–97% after treatment. Microalgal treatment studies in simple column and flat-plate photobioreactors. Biomass and lipid production as other value added by-products. [ABSTRACT FROM AUTHOR]