Application of wastewater for algal biomass production can not only lead to production of thousands of tons of biomass for subsequent biofuel production, but also can provide for significant removal of contaminants in wastewater. The aim of the present study is to evaluate the growth, contaminant removal, and biochemical component (lipid, carbohydrate, and protein) accumulation potential of Chlorella vulgaris, Scenedesmus obliquus, and Oocystis minuta cells in wastewater supplemented with different concentrations of sulfate, nitrate, and phosphate. The results show maximum biomass productivity of 33, 19, and 98 mg dw/L/d for C. vulgaris, S. obliquus, and O. minuta, respectively. Phosphate removal (more than 90%) was highest in the culture with O. minuta; about 93% nitrate was removed by C. vulgaris, and the highest sulfate removal of 36% was observed in the culture with S. obliquus. The biochemical composition of the microalgae cells is in the ranges of 22-65% carbohydrate, 19-38% protein, and 8-17% lipid. This indicates that carbohydrate and protein are preferentially accumulated as compared to lipids under the growth conditions investigated for each of the microalgae strains.Keywords Remediation · Lipids · Microalgae · Carbohydrate · Photosynthetic organism
Abbreviations
ODOptical density AFDW Ash-free dry weight R 2 Coefficient of determination P Biomass productivity t 1 , t 2 Culture duration, time t 1 and t 2 C 1 , C 2 Biomass concentrations at time, t 1 and t 2 A Mass of lipid in the extract BMass of dried microalgae biomass BSA Bovine serum albumin * Sheriff Olalekan AjalaPublisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
The cybernetic modeling framework developed by Ramkrishna and co-workers has been applied to a case of bacterial metabolite production, namely the production of siderophores (iron-chelating agents) associated with iron-limiting fermentation conditions. Experimental growth data showed that, even though final biomass levels were controlled by exhaustion of the carbon source, iron-limiting conditions also affected the biomass yield. A structured model which includes the process of an iron-limiting energy resource production was able to quantitatively account for this apparent dual-substrate limitation over a wide range of batch and continuous operating conditions. The experiments data also showed quite large difference in iron uptake over the wide range of operating condition and iron levels investigated. The inclusion in the model of the processes of low and high (siderophore-mediated) affinity iron transport, and siderophore production led to simulation results that were in good quantitative agreement with the siderophore, medium and cell iron levels, in both batch and steady-state continuous culture operating conditions.
In the present study, the flocculating viability of bio-based alkali derived from cocoa pod husk ash was investigated by using a D-optimal design of the response surface methodology (RSM). The interactive effects of biomass concentration and flocculant dose on flocculation efficiency and concentration factors were examined. The generalization ability of modeling and predictive tools such as RSM and artificial neural network (ANN) was also examined. Moreso, the flocculation process was optimized using RSM and response surface methodology coupled with genetic algorithm (RSM-GA). The flocculation process results showed that the bio-based alkali effectively flocculated microalgae with more than 90% flocculation efficiency at the optimum condition predicted by RSM and RSM-GA. Both RSM and ANN have described the flocculation process with high accuracy, based on the values of statistical indices evaluated but ANN has demonstrated a higher generalization potential as compared to RSM. The results of elemental analysis of the bio-based alkali shown that the concentration of K + (51,489 ppm) was highest, followed by Ca 2+ (1450 ppm) and Na + (210 ppm). This undoubtedly showed the alkaline nature of the bio-based alkali obtained from cocoa pod husk ash that was employed as the flocculant for harvesting microalgae. This study confirms that ash derived alkali can be used to effectively and efficiently harvest microalgae.
The authors would like to thank the SRNL Analytical Department for supporting the sample analyses for this work especially AJ Boggess for the methylmercury results. A special thanks is given to Dr. Brian Looney for his fast turnaround and accurate results for all the total mercury analyses. Dr. Charles Nash performed a thorough review of the report and the data that supply the results, which is also greatly appreciated. Discussions with Dr. Christine Langton on understanding the nature of saltstone were very beneficial and very much appreciated, as well as with Dr. Bill Wilmarth to better understand mercury chemistry. The authors dedicate this report in memory of Dr. Wilmarth (1958-2020 who recently passed away on January 14, 2020, for his 31+ years of invaluable service to the SRNL and SRS.
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