Continuous cultivation of Chlorella pyrenoidosa using anaerobic digested starch processing wastewater in the outdoors

A critical review on the symbiotic effect of bacteria and microalgae on treatment of sewage with biofertilizer production

Wastes like sewage, kitchen and industrial are the major sources of environmental pollution and health hazards. Sewage contains 99.9% water and 0.1% solid waste including urinal waste and faecal matter alongwith large amounts of nitrate, nitrite, ammonium and phosphate ions. Sewage may also contain a variety of harmful contaminants like analgesics, antihypertensive drugs, antibiotics, dioxin, furans, polychlorinated biphenyls, chlorinated hydrocarbon pesticides, chlorine derivatives and plasticizers etc. making it more harmfull to environment and public health. Hence, sewage must be adequately treated by an effective process before its final discharge into the environment. Biological treatment of sewage is an emerging idea in recent years, which has diverse economic and environmental advantages. Sewage treatment by bacteria and microalgae has numerous advantages as it removes various excessive nutrients from waste with large biomass production and also prevents the utilization of toxic chemicals in conventional treatment process. Microalgae-bacterial biomass have potential to be used as biofertilizers, bio-stimulants and bio-seed primers in agricultural field as these contain various biologically active substances like polysaccharides, carotenoids, free fatty acids, phenols, and terpenoids. This review paper mainly discussing the sewage characteristics and different kinds of organic and inorganic pollutants it contained alongwith its harmfull impacts on environment and public health. It also deals the different conventional as well as emerging treatment technologies and different factors affecting the treatment efficiency. In addition, the utilization of developed microalgal and bacterial biomass as biofertilizer and its effects on crop plant alongwith future prospects has been also discussed in detail.

Treatment of carpet and textile industry effluents using Diplosphaera mucosa VSPA: A multiple input optimisation study using artificial neural network-genetic algorithms

The wastewater treatment efficiency of Diplosphaera mucosa VSPA was enhanced by optimising five input parameters and increasing the biomass yield. pH, temperature, light intensity, wastewater percentage (pollutant concentration), and N/P ratio were optimised, and their effects were studied. Two competitive techniques, response surface methodology (RSM) and artificial neural network (ANN), were applied for constructing predictive models using experimental data generated according to central composite design. Both MATLAB and Python were used for constructing ANN models. ANN models predicted the experimental data with high accuracy and less error than RSM models. Generated models were hybridised with a genetic algorithm (GA) to determine the optimised values of input parameters leading to high biomass productivity. ANN-GA hybridisation approach performed in Python presented optimisation results with less error (0.45%), which were 7.8 pH, 28.8 °C temperature, 105.20 μmol m-2 s-1 light intensity, 93.10 wastewater % (COD) and 23.5 N/P ratio.

Cultivation of microalgae on food waste: Recent advances and way forward

Microalgae are photosynthetic microbes that can synthesize compounds of therapeutic potential with wide applications in the food, bioprocessing and pharmaceutical sector. Recent research advances have therefore, focused on finding suitable economic substrates for the sustainable cultivation of microalgae. Among such substrates, food derived waste specifically from the starch, meat, dairy, brewery, oil and fruit and vegetable processing industries has gained popularity but poses numerous challenges. Pretreatment, dilution of waste water supernatants, mixing of different food waste streams, utilizing two-stage cultivation and other biorefinery approaches have been intensively explored for multifold improvement in microalgal biomass recovery from food waste. This review discusses the advances and challenges associated with cultivation of microalgae on food waste. The review suggests that there is a need to standardize different waste substrates in terms of general composition, genetically engineered microalgal strains, tackling process scalability issues, controlling wastewater toxicity and establishing a waste transportation chain.

One-step co-cultivation and flocculation of microalgae with filamentous fungi to valorize starch wastewater into high-value biomass

A novel method of one-step co-cultivation and harvesting of microalgae and fungi, for efficient starch wastewater treatment and high-value biomass production was developed. By combination of Aspergillus oryzae and Chlorella pyrenoidosa, nutrients in wastewater could be converted to useful microbial biomass, while the wastewater was purified. Moreover, the microalgae C. pyrenoidosa could gradually be encapsulated in fungal pellets which promoted the biomass harvesting. The free algal cells could be completely harvested by fungal pellets within 72 h. The synergistic effects between them greatly improved the removal efficiencies of main pollutants as the removal efficiency of COD, TN, and TP reached 92.08, 83.56, and 96.58 %, respectively. In addition, the final biomass concentration was higher than that of individual cultures. The protein and lipid concentration was also significantly improved and reached 1.92 and 0.99 g/L, respectively. This study provides a simple and efficient strategy for simultaneous wastewater treatment and high-value biomass production.

Sustainability and carbon neutrality trends for microalgae-based wastewater treatment: A review

As the global economy develops and the population increases, greenhouse gas emissions and wastewater discharge have become inevitable global problems. Conventional wastewater treatment processes produce direct or indirect greenhouse gas, which can intensify global warming. Microalgae-based wastewater treatment technology can not only purify wastewater and use the nutrients in wastewater to produce microalgae biomass, but it can also absorb CO₂ in the atmosphere or flue gas through photosynthesis, which demonstrates great potential as a sustainable and economical wastewater treatment technology. This review highlights the multifaceted roles of microalgae in different types of wastewater treatment processes in terms of the extent of their bioremediation function and microalgae biomass production. In addition, various newly developed microalgae cultivation systems, especially biofilm cultivation systems, were further characterized systematically. The performance of different microalgae cultivation systems was studied and summarized. Current research on the technical approaches for the modification of the CO₂ capture by microalgae and the maximization of CO₂ transfer and conversion efficiency were also reviewed. This review serves as a useful and informative reference for the application of wastewater treatment and CO₂ capture by microalgae, aiming to provide a reference for the realization of carbon neutrality in wastewater treatment systems.

Evaluation of the effects of input variables on the growth of two microalgae classes during wastewater treatment

Wastewater treatment carried out by microalgae is usually affected by the type of algal strain and the combination of cultivation parameters provided during the process. Every microalga strain has a different tolerance level towards cultivation parameters, including temperature, pH, light intensity, CO2 content, initial inoculum level, pretreatment method, reactor type and nutrient concentration in wastewater. Therefore, it is vital to supply the right combination of cultivation parameters to increase the wastewater treatment efficiency and biomass productivity of different microalgae classes. In the current investigation, the decision tree was used to analyse the dataset of class Trebouxiophyceae and Chlorophyceae. Various combinations of cultivation parameters were determined to enhance their performance in wastewater treatment. Nine combinations of cultivation parameters leading to high biomass production and eleven combinations each for high nitrogen removal efficiency and high phosphorus removal efficiency for class Trebouxiophyceae were detected by decision tree models. Similarly, eleven combinations for high biomass production, nine for high nitrogen removal efficiency, and eight for high phosphorus removal efficiency were detected for class Chlorophyceae. The results obtained through decision tree analysis can provide the optimum conditions of cultivation parameters, saving time in designing new experiments for treating wastewater at a large scale.

Sustainable microalgal biomass production in food industry wastewater for low-cost biorefinery products: a review

Microalgae are recognized as cell factories enriched with biochemicals suitable as feedstock for bio-energy, food, feed, pharmaceuticals, and nutraceuticals applications. The industrial application of microalgae is challenging due to hurdles associated with mass cultivation and biomass recovery. The scale-up production of microalgal biomass in freshwater is not a sustainable solution due to the projected increase of freshwater demands in the coming years. Microalgae cultivation in wastewater is encouraged in recent years for sustainable bioeconomy from biorefinery processes. Wastewater from the food industry is a less-toxic growth medium for microalgal biomass production. Traditional wastewater treatment and management processes are expensive; hence it is highly relevant to use low-cost wastewater treatment processes with revenue generation through different products. Microalgae are accepted as potential biocatalysts for the bioremediation of wastewater. Microalgae based purification of wastewater technology could be a universal alternative solution for the recovery of resources from wastewater for low-cost biomass feedstock for industry. This review highlights the importance of microalgal biomass production in food processing wastewater, their characteristics, and different microalgal cultivation methods, followed by nutrient absorption mechanisms. Towards the end of the review, different microalgae biomass harvesting processes with biorefinery products, and void gaps that tend to hinder the biomass production with future perspectives will be intended. Thus, the review could claim to be valuable for sustainable microalgae biomass production for eco-friendly bioproduct conversions.

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Ultrahigh recovery rate of nitrate from synthetic wastewater by Chlorella-based photo-fermentation with optimal light-emitting diode illumination: From laboratory to pilot plant

To achieve ultrahigh recovery rate of nitrate from synthetic wastewater by Chlorella pyrenoidosa-based photo-fermentation, light-emitting diode (LED) spectrum was firstly evaluated in 5-L glass photo-fermenter with surrounding LED panels. Results showed that warm white LED was favorable to improve biomass yield and recovery rate of nutrients than mixed white LED. When scaling up from laboratory (50-L, 500-L) to pilot scale photo-fermenter with inner LED panels, the maximum recovery rates of NO₃^- (5.77 g L^-1 d^-1) and PO₄^3- (0.44 g L^-1 d^-1) were achieved in 10,000-L photo-fermenter, along with high productivity of biomass (11.06 g L^-1 d^-1), protein (3.95 g L^-1 d^-1) and lipids (3.79 g L^-1 d^-1), respectively. This study demonstrated that photo-fermenter with inner warm white LED illumination is a superhigh-efficient system for nitrate and phosphate recovery with algal biomass coproduction, providing a promising application in pilot demonstration of wastewater bioremediation and facilitating novel facility development for green manufacturing.

Use of reverse osmosis reject from drinking water plant for microalgal biomass production

The present study evaluates the use of reverse osmosis (RO) reject, termed as ROR, for microalgal biomass production. The supplementation of ROR from two different sources, namely domestic RO unit (ROR1) and commercial-scale RO plant (ROR2), showed a synergistic effect on the growth and biochemical composition of Chlorella pyrenoidosa. Among the tested ROR1 doses, the highest biomass production (1.27±0.06 g L^-1) was observed with 25% ROR1 supplemented growth media. In contrast, the lipid content (28.85±3.13% of TS) in C. pyrenoidosa at 50% ROR1 dose was almost twice that in BG11 (positive control). Interestingly, the microalgae showed relatively higher biomass production (1.37±0.07 g L^-1) and higher lipid content (33.23±3.92% of TS) when 50% ROR2 was used in growth media. At the same time, the estimated carbohydrate and protein contents were 28.41±0.73 and 29.75±0.31% of TS, respectively. Furthermore, the lipid productivity (28.98±2.79 mg L^-1 d^-1) was relatively higher than the nutrient media (12.35±1.34 mg L^-1 d^-1). The present findings revealed that the RO reject from drinking water purifiers can efficiently be utilized for lipid-rich microalgal biomass production. Hence, the dependency on freshwater resources for mass scale microalgae cultivation through recycling of RO reject can be reduced.

Recent Progress and Prospects in Catalytic Water Treatment

Presently, conventional technologies in water treatment are not efficient enough to completely mineralize refractory water contaminants. In this context, the implementation of catalytic processes could be an alternative. Despite the advantages provided in terms of kinetics of transformation, selectivity, and energy saving, numerous attempts have not yet led to implementation at an industrial scale. This review examines investigations at different scales for which controversies and limitations must be solved to bridge the gap between fundamentals and practical developments. Particular attention has been paid to the development of solar-driven catalytic technologies and some other emerging processes, such as microwave assisted catalysis, plasma-catalytic processes, or biocatalytic remediation, taking into account their specific advantages and the drawbacks. Challenges for which a better understanding related to the complexity of the systems and the coexistence of various solid-liquid-gas interfaces have been identified.

Characterization of alginate extracted from Sargassum latifolium and its use in Chlorella vulgaris growth promotion and riboflavin drug delivery

Alginates derived from macroalgae have been widely used in a variety of applications due to their stability, biodegradability and biocompatibility. Alginate was extracted from Egyptian Sargassum latifolium thallus yielding 17.5% w/w. The chemical composition of S. latifolium is rich in total sugars (41.08%) and uronic acids (47.4%); while, proteins, lipids and sulfates contents are 4.61, 1.13 and 0.09%, respectively. NMR, FTIR and TGA analyses were also performed. Crystallinity index (0.334) indicates alginate semicrystalline nature. Sodium alginate hydrolysate was evaluated as Chlorella vulgaris growth promoter. The highest stimulation (0.7 g/L biomass) was achieved by using 0.3 g/L alginate hydrolysate supplementation. The highest total soluble proteins and total carbohydrates were 179.22 mg/g dry wt and 620.33 mg/g dry wt, respectively. The highest total phenolics content (27.697 mg/g dry wt.), guaiacol peroxidase activity (2.899 µmol min-1 g-1) were recorded also to 0.3 g/L alginate hydrolysate supplementation. Riboflavin-entrapped barium alginate-Arabic gum polymeric matrix (beads) was formulated to achieve 89.15% optimum drug entrapment efficiency (EE%). All formulations exhibited prolonged riboflavin release over 120 min in simulated gastric fluid, followed Higuchi model (R2 = 0.962-0.887) and Korsmeyer-Peppas model with Fickian release (n ranges from 0.204 to 0.3885).

Advanced near-zero waste treatment of food processing wastewater with water, carbon, and nutrient recovery

A near-zero waste treatment system for food processing wastewater was developed and studied. The wastewater was treated using an anaerobic membrane bioreactor (AnMBR), polished using an outdoor photobioreactor for microalgae cultivation (three species were studied), and excess sludge was treated using hydrothermal carbonization. The study was conducted under arid climate conditions for one year (four seasons). The AnMBR reduced the total organic carbon by 97%, which was mostly recovered as methane (~57%) and hydrochar (~4%). Microalgal biomass productivity in the AnMBR effluent ranged from 0.25 to 0.8 g·L^-1·day^-1. Nitrogen (N) and phosphorous (P) uptake varied seasonally, from 18 to 45 mg·L^-1·day^-1 and up to 5 mg·L^-1·day^-1, respectively. N and P mass balance analysis demonstrated that the process was highly efficient in the recovery of nitrogen (~77%), and phosphorus (~91%). The performance of the microalgal culture changed among seasons because of climatic variation, as a result of variation in the wastewater chemistry, and possibly due to differences among the microalgal species. Effluent standards for irrigation use were met throughout the year and were achieved within two days in summer and 4.5 days in winter. Overall, the study demonstrated a near-zero waste discharge system capable of producing high-quality effluent, achieving nutrient and carbon recovery into microalgae biomass, and energy production as biogas and hydrochar.

Removal of pharmaceutical and personal care products (PPCPs) from wastewater using microalgae: A review

Pharmaceuticals and personal care products (PPCPs) are a group of emerging micro-pollutants causing detrimental effects on living organisms even at low doses. Previous investigations have confirmed the presence of PPCPs in the environment at hazardous levels, mainly due to the inefficiency of conventional wastewater treatment plants (CWWTPs). Their stable structure induces longer persistence in the environment. Microalgae are currently used to bioremediate numerous pollutants of different characteristics and properties released from the domestic, industrial, agricultural, and farm sectors. CO₂ mitigation during culture and the use of biomass as feedstock for biodiesel or biofuel production are, briefly, other benefits of microalgae-mediated treatment over CWWTPs. This review provides a comprehensive summary of recent literature, an overview of approaches and treatment systems, and breakthrough in the field of algal-mediated removal of PPCPs in wastewater treatment processes. The mechanisms involved in phycoremediation, along with their experimental approaches, have been discussed in detail. Factors influencing the removal of PPCPs from aqueous media are comprehensively described and assessed. A comparative study on microalgal strains is analyzed for a more efficient implementation of future processes. The role of microalgae to mitigate the most severe environmental impacts of PPCPs and the generation of antibiotic-resistant bacteria is discussed. Also, a detailed assessment of recent research on potential toxic effects of PPCPs on microalgae was conducted. The current review highlights microalgae as a promising and sustainable approach to efficiently bio-transform or bio-adsorb PPCPs.

Linking nitrous oxide emissions from starch wastewater digestate amended soil to the abundance and structure of denitrifier communities

Anaerobic digestion is widely used in starch wastewater pre-treatment and can remove the COD effectively, however, the effluents are nutritious and often need supplemental aerobic treatments to remove nutrients prior to discharge. The objective of this study was to investigate the feasibility of using the liquid digestate of starch wastewater (LDSW) as a fertilizer. This pot experiment was conducted with Ipomoea aquatica Forsk in a greenhouse with six treatment groups. The crop growth was significantly promoted, while the accumulation of soil nitrate was not influenced after LDSW addition, compared to the control. In addition, at the same nitrogen input, the yield of high-LDSW treatment was 65.2%, 92.3% and 69.2% higher than those of chemical fertilizer treatment during the three growth periods. Furthermore, average N₂O emission with high-LDSW addition was 15.8 g N/(ha.d), accounting for 15.0% of which under high chemical fertilizer treatment, due to the significantly enhanced denitrification genes (nirK, nirS and nosZ) abundance. Besides, the changes of soil N₂O-reducing bacteria were performed by high-throughput sequencing of nosZ. Our findings suggested that LDSW had many opportunities for sustainable agriculture to guarantee high yields while reducing negative environmental impacts.

Current practices and challenges in using microalgae for treatment of nutrient rich wastewater from agro-based industries

Considerable research activities are underway involving microalgae species in order to treat industrial wastewater to address the waste-to-bioenergy economy. Several studies of wastewater treatment using microalgae have been primarily focused on removal of key nutrients such as nitrogen and phosphorus. Although the use of wastewater would provide nutrients and water for microalgae growth, the whole process is even more complex than the conventional microalgae cultivation on freshwater media. The former one adds several gridlocks to the system. These gridlocks are surplus organic and inorganic nutrients concentration, pH of wastewater, wastewater color, total dissolved solids (TDS), microbial contaminants, the scale of photobioreactor, batch versus continuous system, harvesting of microalgae biomass etc. The present review discusses, analyses, and summarizes key aspects involved in the treatment of wastewaters from distillery, food/snacks product processing, and dairy processing industry using microalgae along with sustainable production of its biomass. This review further evaluates the bottlenecks for individual steps involved in the process such as pretreatment of wastewater for contaminants removal, concentration tolerance/dilutions, harvesting of microalgae biomass, and outdoor scale-up. The review also describes various strategies to optimize algal biomass and lipid productivities for various wastewater and photobioreactor type. Moreover, the review emphasizes the potential of co-cultivation of microorganism such as yeast and bacteria along with microalgae in the treatment of industrial wastewater.

The influence of four pharmaceuticals on Chlorellapyrenoidosa culture

There has been a developing technology in algae with pharmaceuticals wastewater. However, the effect and the underlying mechanism of pharmaceuticals on algae are not well understood. To investigate the effect and mechanism of pharmaceuticalson microalgae, four pharmaceuticals of clofibric acid (CLF), ciprofloxacin (CIP), diclofenac (DCF) and carbamazepine (CBZ) on C. pyrenoidosa culture were analyzed. At low concentrations (<10 mg/L), the pharmaceuticals, especially the DCF, exhibited positive effects on both the structure and function of algal cultures; algal growth (i.e., chlorophyll a accumulation, lipid accumulation) and activities of antioxidant enzymes were stimulated. The algal metabolite differences of various DCF concentrations were investigated and a total of 91 substances were identified, whose samples were clustered and clearly separated. The key metabolomics pathway analysis found that the DCF promoted the carbohydrate and fatty acid metabolic pathway in C. pyrenoidosa under relatively low concentrations (<10 mg/L). However, the algae metabolomics pathway was disturbed significantly under the action of a high concentration of DCF (>100 mg/L). The study detected the effects of four pharmaceuticals on C. pyrenoidosa and demonstrated that the usage of metabolomics analysis complemented with DCF could be an effective approach to understand the mechanism of molecular evolution in C. pyrenoidosa for microalgal biomass and bioenergy from wastewater in researches of biological resources.

Performance of a novel photobioreactor for nutrient removal from piggery biogas slurry: Operation parameters, microbial diversity and nutrient recovery potential

Photobioreactor is deemed to be one of limiting factors for the commercial application of wastewater treatment based on microalgae cultivation. In this study, a novel Flat-Plate Continuous Open Photobioreactor (FPCO-PBR) was developed to treat piggery biogas slurry. The operation parameters, microbial stability and nutrient recovery potential of FPCO-PBR were investigated. Results showed that the appropriate influent mode for FPCO-PBR was multi-point or spraying mode. The optimal hydraulic retention time and interval time for biomass harvesting of FPCO-PBR were both 2 d. Nitrogen and phosphorus recovery rate were 30 mg L^-1 d^-1 and 7 mg L^-1 d^-1 respectively under optimal operating parameters. Microbial diversity remained relatively stable in FPCO-PBR. Biomass production rate of FPCO-PBR was 0.47 g L^-1 d^-1 under optimal operating parameters. The revenue generated from biomass was estimated to be 15.06 $ kg^-1, which means that treating one ton of wastewater can generate $ 7.08 in revenue.

Outdoor microalgae cultivation in airlift photobioreactor at high irradiance and temperature conditions: effect of batch and fed-batch strategies, photoinhibition, and temperature stress

The microalgae Scenedesmus abundans cultivated in five identical airlift photobioreactors (PBRs) in batch and fed-batch modes at the outdoor tropical condition. The microalgae strain S. abundans was found to tolerate high temperature (35-45 °C) and high light intensity (770-1690 µmol m^- 2 s^- 1). The highest biomass productivities were 152.5-162.5 mg L^- 1 day^- 1 for fed-batch strategy. The biomass productivity was drastically reduced due to photoinhibition effect at a culture temperature of > 45 °C. The lipid compositions showed fatty acids mainly in the form of saturated and monounsaturated fatty acids (> 80%) in all PBRs with Cetane number more than 51. The fed-batch strategies efficiently produced higher biomass and lipid productivities at harsh outdoor conditions. Furthermore, the microalgae also accumulated omega-3 fatty acid (C18:3) up to 14% (w/w) of total fatty acid at given outdoor condition.

The dual function of the algal treatment: Antibiotic elimination combined with CO2 fixation

The study provided an algal treatment to achieve dual function with antibiotic elimination and CO₂ fixation simultaneously. Two widely used antibiotics, cefradine and amoxicillin were selected as the target compounds. First of all, we assessed the influence of light intensity on algal growth and antibiotic removal efficiency to obtain the optimal light intensity. Secondly, after the algal antibiotic treatment, the CO₂ capture capacities at varied CO₂ volume concentrations were assessed and compared. Significant improvement in the removal efficiency of cefradine occurred when CO₂ was added into the treatment. Change in the content of photosynthetic pigments and the activities of RuBisCO and carbonic anhydrase occurred as the algal responses to the treatment condition. Our results showed that Chlorella pyrenoidosa performed better than Microcystis aeruginosa in both the antibiotic removal efficiency and the CO₂ capture capacity. In the integrated algal treatment, the remove rate of antibiotic has been improved by 30.16% and at the same time, the CO₂ absorption rate has been promoted by 10.94%. Metabolite analyses also revealed the mechanism involved, which proved the crucial role of the algae in the biodegradation of the target antibiotic.

Optimization of nutrient stress using C. pyrenoidosa for lipid and biodiesel production in integration with remediation in dairy industry wastewater using response surface methodology

The present study illustrates optimization and synergetic potential of alga Chlorella pyrenoidosa for lipid production and remediation of Dairy industry wastewater (DIWW) through response surface methodology (RSM). Maximum lipid productivity of 34.41% was obtained under 50% DIWW supplemented with 0 mg L-1 nitrate (NO3-), and 50 mg L-1 phosphate (PO4-3). While maximum biomass productivity (1.54 g L-1) was obtained with 50% DIWW supplemented with 100 mg L-1 NO3-, and 50 mg L-1, PO4-3. Maximum removal of COD (43.47%), NO3- (99.80%) and PO4-3 (98.24%) was achieved with 8th run (75% DIWW, 150 mg L-1 NO3-, 75 mg L-1 PO4-3), 15th run (50% DIWW, 0 mg L-1 NO3-, 50 mg L-1, PO4- 3) followed by 1st run (25% DIWW, 50 mg L-1 NO3-, and 25 mg L-1, PO4-3), respectively. Lipid (bio-oil) obtained from 15th run of experiment was converted in biodiesel through base catalyze transesterification process. Fatty acid methyl ester (FAME) analysis of biodiesel confirmed the presence of major fatty acids in C. pyrenoidosa grown in DIWW were C11:0, C14:0, C16:0, C16:1, C18:1 and C18:2. Results of study clearly demonstrate enhanced growth and lipid accumulation by C. pyrenoidosa in surplus PO4-3 and limitation of NO3- sources with DIWW and its suitability as potential alternative for commercial utilization.

Tofu whey wastewater is a promising basal medium for microalgae culture

Tofu whey wastewater (TWW) is an abundant, nutrient riched and safety wastewater and is regarded as an excellent alternative medium in fermentation. In this study, the feasibility of algal cultivation using TWW as the basal medium was investigated. Results indicated that through simple pH adjustment, TWW presented a better culture performance at autotrophic, heterotrophic, and mixotrophic modes compared with that of regular green algae medium, BG-11. The biomass productivities of Chlorella pyrenoidosa at each trophic mode were 4.76, 1.97, and 2.08 times higher than that cultured in BG-11 medium, respectively. Although a comparative or even lower lipid and protein content was obtained, much higher lipid and protein productivities were obtained in TWW compared to that of BG-11. The algal biomass accumulated in TWW can be used to produce high-value products. Therefore, TWW is a better alternative medium for efficient algal culture.

MAB2.0 project: Integrating algae production into wastewater treatment

Different species of microalgae are highly efficient in removing nutrients from wastewater streams and are able to grow using flue gas as a CO2 source. These features indicate that application of microalgae has a promising outlook in wastewater treatment. However, practical aspects and process of integration of algae cultivation into an existing wastewater treatment line have not been investigated. The Climate-KIC co-funded Microalgae Biorefinery 2.0 project developed and demonstrated this integration process through a case study. The purpose of this paper is to introduce this process by phases and protocols, as well as report on the challenges and bottlenecks identified in the case study. These standardized technical protocols detailed in the paper help to assess different aspects of integration including biological aspects such as strain selection, as well as economic and environmental impacts. This process is necessary to guide wastewater treatment plants through the integration of algae cultivation, as unfavourable parameters of the different wastewater related feedstock streams need specific attention and management. In order to obtain compelling designs, more emphasis needs to be put on the engineering aspects of integration. Well-designed integration can lead to operational cost saving and proper feedstock treatment enabling algae growth.

The effect of amino acids on lipid production and nutrient removal by Rhodotorula glutinis cultivation in starch wastewater

In this paper, the components of amino acids in mixed starch wastewater (corn steep water/corn gluten water=1/3, v/v) were analyzed by GC-MS. Effects of amino acids on lipid production by Rhodotorula glutinis and COD removal were studied. The results showed that mixed starch wastewater contained 9 kinds of amino acids and these amino acids significantly improved the biomass (13.63g/L), lipid yield (2.48g/L) and COD removal compared to the basic medium (6.23g/L and 1.56g/L). In a 5L fermentor containing mixed starch wastewater as substrate to culture R. glutinis, the maximum biomass, lipid content and lipid yield reached 26.38g/L, 28.90% and 7.62g/L, with the associated removal rates of COD, TN and TP reaching 77.41%, 69.12% and 73.85%, respectively. The results revealed a promising approach for lipid production with using amino acids present in starch wastewater as an alternative nitrogen source.

Performance, 5-aminolevulinic acid (ALA) yield and microbial population dynamics in a photobioreactor system treating soybean wastewater: Effect of hydraulic retention time (HRT) and organic loading rate (OLR)

Effects of hydraulic retention time (HRT) and influent organic loading rate (OLR) were investigated in a photobioreactor containing PNSB (Rhodobacter sphaeroides)-chemoheterotrophic bacteria to treat soybean wastewater. Pollutants removal, biomass production and ALA yield in different phases were investigated in together with functional microbial population dynamics. The results showed that proper HRT and OLR increased the photobioreactor performance including pollutants removal, biomass and ALA productions. 89.5% COD, 90.6% TN and 91.2% TP removals were achieved as well as the highest biomass production of 2655mg/L and ALA yield of 7.40mg/g-biomass under the optimal HRT of 60h and OLR of 2.48g/L/d. In addition, HRT and OLR have important impacts on PNSB and total bacteria dynamics.

Performance, carotenoids yield and microbial population dynamics in a photobioreactor system treating acidic wastewater: Effect of hydraulic retention time (HRT) and organic loading rate (OLR)

Effects of hydraulic retention time (HRT) and influent organic loading rate (OLR) were investigated in a photobioreactor containing PNSB (Rhodopseudomonas palustris)-chemoheterotrophic bacteria to treat volatile fatty acid wastewater. Pollutants removal, biomass production and carotenoids yield in different phases were investigated in together with functional microbial population dynamics. The results indicated that properly decreasing HRT and increasing OLR improved the nutrient removal performance as well as the biomass and carotenoids productions. 85.7% COD, 89.9% TN and 91.8% TP removals were achieved under the optimal HRT of 48h and OLR of 2.51g/L/d. Meanwhile, the highest biomass production and carotenoids yield were 2719.3mg/L and 3.91mg/g-biomass respectively. In addition, HRT and OLR have obvious impacts on PNSB and total bacteria dynamics. Statistical analyses indicated that the COD removal exhibited a positive relationship with OLR, biomass and carotenoids production. PNSB/total bacteria ratio had a positive correlation with the carotenoids yield.