Anaerobic Digestion Effluent Research Articles

The growth and lipid productivity of Chlorella pyrenoidosa enhanced by plant hormones under ammonium stress

The high level of ammonium is a serious threat to algal lipid production when low quality water sources like piggery anaerobic digestion effluents were used as algal growth medium. Here, we aimed to investigate the effect of plant hormones (including indole‐3‐acide, cytokinin, and abscisic acid) on algal cells under ammonium stress particularly in respect to algal biomass and lipid productivities. Compared to those without hormones, the presence of plant hormones promotes algal growth under low levels of ammonium regardless of pH conditions. Exogenous plant hormones help in conferring tolerance to stress caused by high levels of ammonium and overcome the loss of algal productivities. Compared to the control, the lipid productivity increased by 298%, 637%, and 533% at pH 7, pH 8, and pH 9, respectively. In addition, the application of plant hormones suggested that indole‐3‐acide and cytokinin significantly increase cell density of algae subjected to ammonium stress while abscisic acid enhances the lipid accumulation. The results here demonstrate that it would be favorable alternative to grow algae for large‐scale biofuel production in low‐quality wastewater containing high ammonium content with the help of plant hormones. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1187–1193, 2017

Biocrude oil production from Chlorella sp. cultivated in anaerobic digestate after UF membrane treatment

Algae cultivation in animal wastewater could recover nutrient resources, and harvest considerable amount of algae biomass for biofuel conversion. In this study, Chlorella sp. cultivated in ultrafiltration (UF) membrane treated anaerobic digestion effluent of chicken manure was converted into biocrude oil through hydrothermal liquefaction (HTL). The potential of biocrude production from grown Chlorella sp. was studied through changing the operational conditions of HTL, i.e., holding temperature (HT, 250°C-330°C), retention time (RT, 0.5-1.5 h), and total solid (TS) (15 wt%-25 wt%) of the feedstock. The highest biocrude oil yield was 32.9% at 330°C, 1.5 h and 20 wt% TS. The single factor experiments of HT also suggested that the biocrude oil yield decreased when the temperature was higher than 330°C. There were no significant differences of elemental contents in biocrude samples. The maximum higher heating values (HHV) of Chlorella sp. biocrude was 40.04 MJ/kg at HT of 330°C, RT of 1 h and TS of 15 wt%. This study suggests the great potential for energy recovery from Chlorella sp. cultivated in UF membrane treated anaerobic digestion effluent via HTL. Keywords: microalgae, wastewater, hydrothermal liquefaction, anaerobic digestion effluent DOI: 10.3965/j.ijabe.20171001.2700 Citation: Wang M, Wang X F, Zhu Z B, Lu J W, Zhang Y H, Li B M, et al. Biocrude oil production from Chlorella sp. cultivated in anaerobic digestate after UF membrane treatment. Int J Agric & Biol Eng, 2017; 10(1): 148－153.

Source analysis of organic matter in swine wastewater after anaerobic digestion with EEM-PARAFAC

Swine wastewater is one of the most serious pollution sources, and it has attracted a great public concern in China. Anaerobic digestion technology is extensively used in swine wastewater treatment. However, the anaerobic digestion effluents are difficult to meet the discharge standard. The results from batch experiments showed that plenty of refractory organic matter remained in the effluents after mesophilic anaerobic digestion for 30days. The effluent total COD (tCOD) and soluble COD (sCOD) were 483 and 324mg/L, respectively, with the sCOD/tCOD ratio of 0.671. Fluorescence excitation-emission matrix (EEM) coupled with parallel factor analysis (PARAFAC) revealed that the dissolved organic matter in the effluents was tryptophan-like substance, humic acid substance, and fulvic acid substance. Based on the appearance time during anaerobic digestion, tryptophan-like substance and humic acid substance were inferred to originate from the raw swine wastewater, and the fulvic acid substance was inferred to be formed in the anaerobic digestion. This work has revealed the source of residual organic matter in anaerobic digestion of swine wastewater and has provided some valuable information for the post-treatment.

Recycling separated liquid-effluent to dilute feedstock in anaerobic digestion of dairy manure

The major concern of recycling anaerobic digestion (AD) effluent in the digester centers on accumulation of total ammonia nitrogen (TAN) and salinity, both of which can potentially inhibit methane production. In the current study, 30%, 50%, and 80% of separated-liquid AD effluent, were recycled in a series of batch AD experiments. The inhibitions to specific methane potential (SMP) caused by TAN and salinity were evaluated. Recycling up to 80% of un-treated effluent resulted in the best SMP averaging 0.265 ± 0.005 m3 [CH4] Kg−1 [volatile solids], which averaged 10% more compared to recycling 80% treated effluent and 5% more compared to no recycling (the control). After acclimation, up to 6.39 g N L−1 increase in TAN resulted in SMP averaging 0.112 ± 0.002 m3 [CH4] Kg−1 [volatile solids] and up to 12 parts per thousand increase in salinity resulted in SMP averaging 0.163 ± 0.005 m3 [CH4] Kg−1 [volatile solids]. A mass balance for a hypothetical 5000 cows dairy farm showed effluent recycle of up to 66% for maintaining 8% solids in anaerobic digester. Moreover, in the proposed system, the effluent going off-farm was on w/w basis 64% less water, 66% less solids, and 52% less nitrogen compared to the effluent produced with no recycle facility.

Microalgal post-treatment of anaerobically digested agro-industrial wastes for nutrient removal and lipids production

The aim of this study was to investigate the effectiveness of cultivating Parachlorella kessleri and Acutodesmus obliquus, in anaerobic digestion effluent (ADE) derived from the co-digestion of end-of-life dairy products with mixtures of agro-industrial wastes. To this end, their performance under sterile and non-sterile conditions and different ADE loadings was evaluated, in terms of biomass and lipid production, nutrient removal efficiency and vitality of the photosynthetic apparatus. 10% (v/v) ADE loading inhibited growth over 9–12days of cultivation, however biomass yields of 1.1 and 1gL−1, 22.7% and 19.5% (w/w) fatty acids concentration, as well as NH3-N assimilation of 49.7mgL−1 and 32.3mgL−1 and TP removal of 84.2% and 84% were recorded for P. kessleri and A. obliquus, respectively. Among all the ADE-based treatments tested, P. kessleri outperformed A. obliquus, with no differences observed between sterilized and non-sterilized ADE.

Cultivation of four microalgae species in the effluent of anaerobic digester for biodiesel production

This study investigated if an effluent from anaerobic digestion (AD) system can be used as a nutrients source for the microalgae cultivation, and in so doing, if the effluent can be properly treated. Nitrogen and phosphorus in the AD effluent well supported microalgal growth, and their removal efficiency reached >97.9% and 99.2%, respectively. Among four different algal species tested, Micractinium inermum particularly stood out, showing the highest biomass and FAME productivity: 0.16gL−1d−1 with 3.23gL−1 of dry cell weight, and 0.04gL−1d−1 with 27.54% (w/w) of FAME contents, respectively. As the concentrations of the nutrients decreased over time, the FAME contents were increased and its quality as well, satisfying several biodiesel quality standards. This study supports that the AD effluent can indeed serve as a cheap and nutrient-rich medium for microalgae cultivation, and equally importantly, microalgae can be a workable treatment option for it.

Phytoremediation of agriculture runoff by filamentous algae poly-culture for biomethane production, and nutrient recovery for secondary cultivation of lipid generating microalgae

An integrated system was implemented for water phytoremediation and biofuel production through sequential cultivation of filamentous algae followed by cultivation of lipid-producing microalgae Chlorella sorokiniana. Natural poly-culture of filamentous algae was grown in agricultural stormwater using the Algal Turf Scrubber®, harvested and subjected for lipid extraction and/or methane production using anaerobic digestion (AD). While filamentous algae lipid content was too low for feasible biodiesel production (<2%), both whole biomass and lipid-extracted algal residues (LEA) yielded ∼0.2LmethanepergVS at loading rates up to 5gVS/L-day. Importantly, essential macro-nutrients and trace elements captured from stormwater were released into the AD effluent as soluble nutrients and were successfully tested as fertilizer replacement for cultivation of lipid-accumulating C. sorokiniana in a subsequent stage. Accordingly, filamentous algae poly-culture was exploited for waste nutrient capturing and biofuel feedstock generation. These nutrients were recovered and reused as a concentrated supplement for potentially high-value microalgae.

Developing a vacuum thermal stripping – acid absorption process for ammonia recovery from anaerobic digester effluent

To prevent acetoclastic methanogens from ammonia inhibition in anaerobic digestion of protein-rich substrates, ammonia needs to be removed or recovered from digestate. This paper presents an innovative ammonia recovery process that couples vacuum thermal stripping with acid absorption. Ammonia is stripped out of digestate boiling at a temperature below the normal boiling point due to vacuum. Stripped ammonia is absorbed to a sulfuric acid solution, forming ammonium sulfate crystals as a marketable product. Three common types of digestate were found to have boiling point temperature-vacuum curves similar to water. Seven combinations of boiling temperature and vacuum (50 °C 16.6 kPa, 58 °C 20.0 kPa, 65 °C 25.1 kPa, 70 °C 33.6 kPa, 80 °C 54.0 kPa, 90 °C 74.2 kPa, and 100 °C 101.3 kPa) were tested for batch stripping of ammonia in dairy manure digestate. 93.3–99.9% of ammonia was stripped in 3 h. The Lewis-Whitman model fitted ammonia stripping process well. Ammonia mass transfer coefficient was significantly higher at boiling temperature 65–100 °C and vacuum pressure 25.1–101.3 kPa than 50–58 °C and 16.6–20.0 kPa. The low ammonia saturation concentrations (0–24 mg N/L) suggested a large driving force to strip ammonia. The optimum boiling point temperature – vacuum pressure for ammonia recovery in a recirculation line of a mesophilic digester was 65 °C and 25.1 kPa, at which the ammonia mass transfer coefficient was as high as 37.3 mm/h. Installation of a demister and liquid trap could avoid negative effects of higher stripping temperature and stronger vacuum on formation of ammonium sulfate crystals. Pilot tests demonstrated that high-purity ammonium sulfate crystals could be produced by controlling sulfuric acid content and maintaining acid solution saturated with ammonium sulfate. Although volatile organic compounds such as cyclohexene were found in the final acid solutions, no volatile organic compounds were found in the recovered crystals.

Stoichiometric evaluation of partial nitritation, anammox and denitrification processes in a sequencing batch reactor and interpretation of online monitoring parameters

A laboratory-scale sequencing batch reactor (SBR) performing partial nitritation – anammox and denitrification was used to treat anaerobic digester effluents. The SBR cycle consisted of a short mixing filling phase followed by oxic and anoxic reaction phases. Working at 25 °C, an ammonium conversion efficiency of 96.5%, a total nitrogen removal efficiency of 88.6%, and an organic carbon removal efficiency of 63.5% were obtained at a nitrogen loading rate of 0.15 kg N m−3 d−1, and a biodegradable organic carbon to nitrogen ratio of 0.37. The potential contribution of each biological process was evaluated by using a stoichiometric model. The nitritation contribution decreased as the temperature decreased, while the contribution from anammox depended on the wastewater type and soluble carbon to nitrogen ratio. Denitrification improved the total nitrogen removal efficiency, and it was influenced by the biodegradable organic carbon to nitrogen ratio. The characteristic patterns of conductivity, oxidation-reduction potential (ORP) and pH in the SBR cycle were well related to biological processes. Conductivity profiles were found to be directly related to the decreasing profiles of ammonium. Positive ORP values at the end of the anoxic phases were detected for total nitrogen removal efficiency of lower than 85%, and the occurrence of bending points on the ORP curves during the anoxic phases was associated with nitrite depletion by the anammox process.

The Influence of Anaerobic Digestion Effluents (ADEs) Used as the Nutrient Sources for Chlorella sp. Cultivation on Fermentative Biogas Production

PurposeThis study investigated the chemical characteristics and anaerobic digestion of Chlorella sp. microalgae cultivated on various anaerobic digestion effluents (ADEs) as a nutrient medium. Chlorella sp. was grown in anaerobically digested effluent of dairy wastewater (DW), municipal wastewater sludge (WS), maize silage and swine slurry, and cattle manure (CM).MethodsTo evaluate the anaerobic biodegradability of harvested biomass, 20-days batch anaerobic digestion experiments were used.ResultsIt was found that a nutrient medium directly affected nitrogen concentration in the cultivated biomass, as well as the C/N ratio value which ranged 7.2–12.9. Higher C/N ratio of the Chlorella sp. cultivated on DW and WS significantly enhanced the methane production, which was 241 ± 5.5 mL CH4/g VS and 267 ± 10.9 mL CH4/g VS, respectively. The highest biogas production rate of 61.28 ± 2.7 mL/g VS·d and methane concentration in biogas of 69.7 ± 4.1 % were obtained during the digestion of Chlorella sp. biomass cultivated on WS.ConclusionsThese results proved the applicability of ADEs as a nutrient medium for Chlorella sp. cultivation and the impact of a nutrient source on C/N ratio in harvested biomass, which subsequently affected the biogas/methane yield.

Assessing the effect of different treatments on decomposition rate of dairy manure

Confined animal feeding operations (CAFOs) contribute to greenhouse gas emission, but the magnitude of these emissions as a function of operation size, infrastructure, and manure management are difficult to assess. Modeling is a viable option to estimate gaseous emission and nutrient flows from CAFOs. These models use a decomposition rate constant for carbon mineralization. However, this constant is usually determined assuming a homogenous mix of manure, ignoring the effects of emerging manure treatments. The aim of this study was to measure and compare the decomposition rate constants of dairy manure in single and three-pool decomposition models, and to develop an empirical model based on chemical composition of manure for prediction of a decomposition rate constant. Decomposition rate constants of manure before and after an anaerobic digester (AD), following coarse fiber separation, and fine solids removal were determined under anaerobic conditions for single and three-pool decomposition models. The decomposition rates of treated manure effluents differed significantly from untreated manure for both single and three-pool decomposition models. In the single-pool decomposition model, AD effluent containing only suspended solids had a relatively high decomposition rate of 0.060 d−1, while liquid with coarse fiber and fine solids removed had the lowest rate of 0.013 d−1. In the three-pool decomposition model, fast and slow decomposition rate constants (0.25 d−1 and 0.016 d−1 respectively) of untreated AD influent were also significantly different from treated manure fractions. A regression model to predict the decomposition rate of treated dairy manure fitted well (R2 = 0.83) to observed data.

Volatile fatty acids recovery from the effluent of an acidogenic digestion process fed with grape pomace by adsorption on ion exchange resins

The purpose of this work was to perform the preliminary development and optimization of a volatile fatty acid (VFA) separation process from an actual effluent of grape pomace acidogenic anaerobic digestion by ion exchange (IE) resins. Batch IE and desorption tests were performed with acetic acid, VFA synthetic mixtures and an actual digestate. The comparison of four amino IE resins led to the selection of Amberlyst A21, a tertiary amino resin characterized by a relatively low price and high IE performances. The latter increased by increasing VFA chain length, this suggesting a relevant contribution of physical adsorption for high molecular weight VFAs. The best IE performances were obtained at pH 3–4.5 in the presence of acetic acid alone, and at pH 6.5 with the actual digestate. Basified ethanol allowed a complete desorption of all the adsorbed VFAs. Solvent recovery by evaporation, obtained with negligible losses of the desorbed VFAs, allowed the production of a highly concentrated water solution of the recovered VFAs. This result represents a crucial feature for the development of innovative VFA-fed biotechnological processes such as polyhydroxyalkanoate production ones. A model taking into account VFA IE, the competitive effect exerted by other anions and the HCO3−/CO32− buffering effect that characterizes actual digestates led to a satisfactory prediction of the experimental data, and represents an effective tool to identify the optimal operational conditions. Overall, Amberlyst A21 represents an effective candidate for the development of an adsorption/desorption process for VFA recovery from the effluents of acidogenic fermentations.

ChemInform Abstract: Research Advances in Deriving Renewable Energy from Biomass in Wastewater Treatment Plants

AbstractReview: 161 refs.

The Effect of Anaerobic and Aerobic Fish Sludge Supernatant on Hydroponic Lettuce

The mobilization of nutrients from fish sludge (i.e., feces and uneaten feed) plays a key role in optimizing the resource utilization and thus in improving the sustainability of aquaponic systems. While several studies have documented the aerobic and anaerobic digestion performance of aquaculture sludge, the impact of the digestate on plant growth has yet to be understood. The present study examines the impact of either an aerobic or an anaerobic digestion effluent on lettuce plant growth, by enriching a mixture of aquaculture and tap water with supernatants from both aerobic and anaerobic batch reactors. The lettuce plants grown in the hydroponic system supplied with supernatant from an anaerobic reactor had significantly better performance with respect to weight gain than both, those in the system where supernatant from the aerobic reactor was added, as well as the control system. It can be hypothesized that this effect was caused by the presence of NH4+ as well as dissolved organic matter, plant growth promoting rhizobacteria and fungi, and humic acid, which are predominantly present in anaerobic effluents. This study should therefore be of value to researchers and practitioners wishing to further develop sludge remineralization in aquaponic systems.

The influence of different pretreatment methods on biogas production from Jatropha curcas oil cake

Drought and pest resistance, together with high oil content in its seeds, make Jatropha curcas a good oil source for biodiesel. Oil cake from J. curcas is not suitable for animal feeding and thus may be profitably used for additional energy production by conversion into biogas; however, the anaerobic digestion process must be optimized to obtain good efficiency. We subjected oil cake to thermal and acidic pretreatment to deactivate protease inhibitors and partially hydrolyze phytate. We then digested the samples in batch conditions to determine the effects of pretreatment on biogas production. Thermal pretreatment changed the kinetics of anaerobic digestion and reduced protease inhibitor activity and the concentration of phytate; however, biogas production efficiency was not affected (0.281 m3 kg−1). To evaluate the possibility of recirculating water for SSF hydrolysis, ammonium nitrogen recovery from effluent was evaluated by its precipitation in the form of struvite (magnesium ammonium phosphate).Concentration of ammonium ions was reduced by 53% (to 980 mg L−1). We propose a water-saving concept based on percolation of J. curcas cake using anaerobic digestion effluent and feeding that percolate into a methanogenic bioreactor.

Cost benefit assessment of a novel thermal stripping – acid absorption process for ammonia recovery from anaerobically digested dairy manure

Thermal stripping – acid absorption is a novel technology recently developed to recover ammonia as marketable ammonium sulfate granules from anaerobic digester effluent. Taking a large-size dairy farm in New York State, USA, as an example, this study evaluates the costs and benefits of ammonia recovery from a recirculation line of mesophilic anaerobic digesters. Option 1 is the baseline without ammonia recovery. Option 2 is to draw digester effluent at 28% of the liquid manure loading rate, heat to 101 °C for ammonia recovery, and return the ammonia-recovered dairy manure to the digesters. Under option 2, the returned hot manure eliminates the need to heat the digesters. Option 3 is similar to Option 2, but the recirculation rate is only 14% of the manure loading rate. In this case, additional heating is needed for the digesters. Engineering unit cost and revenue models are developed for the thermal stripping – acid absorption process. Options 2 and 3 have benefit/cost ratios of 1.90 and 1.86, respectively. Option 2 produces greater net present value (NPV) ($1.34 million) than Option 2 ($0.72 million), while Option 1 yields a negative NPV (−$0.23 million). Ammonia recovery on this farm can create 1.5–3 jobs. Labor costs account for 62–70% of the total operating costs. Option 2 can generate a benefit of $0.018/L manure digestate or $0.50/d/cow. Any uncertainties relating to NPV and benefit/cost ratio are mainly associated with the sale price of ammonium sulfate and hourly wage rate.

Improving pollutants removal by microalgae Chlorella PY-ZU1 with 15% CO2 from undiluted anaerobic digestion effluent of food wastes with ozonation pretreatment

In order to purify various pollutants (3108mg COD/L, 2120mg NH3-N/L) in the undiluted anaerobic digestion effluent of food wastes (UADEFW), ozonation pretreatment was employed to improve pollutants removal by microalgae mutant Chlorella PY-ZU1 with 15% CO2. Ozonation pretreatment broke CC bonds and benzene rings of refractory organics such as unsaturated fatty acids and phenols in UADEFW and degraded them into low-molecular-weight organics such as methanoic acid and methanal, but excessive ozone induced the accumulation of toxic by-products. The microalgal growth rate and biomass yield markedly increased to the peaks of 456mg/L/d and 4.3g/L, respectively, when the UADEFW was pretreated with 2mg-O3/mg-C of ozone. The removal efficiencies of NH3-N, TP and COD reached 99%, 99% and 68%, respectively. The lipid and carbohydrate contents of microalgal biomass increased because of the relative lack of nitrogen when microalgae was cultured with 15% CO2 to purify the UADEFW with ozonation pretreatment.

Methane dependent denitrification- from ecosystem to laboratory-scale enrichment for engineering applications

Managing nitrogen and carbon cycles in engineered and natural ecosystems is an environmental challenge. In this manuscript, we report a process which connects these two cycles with immense ecological and engineering significance. Sediments, collected from Jordan River in Salt Lake City, Utah were used as seed to start a laboratory-scale denitrification coupled to anaerobic methane oxidation (n-DAMO) reactor fed with methane (CH4) and nitrite (NO2−). Methane (CH4)-dependent denitrification in sediments of a nutrient-impaired river was found to be in the range of 40 nmol kg−1 d−1 to 70 nmol kg−1 d−1. Post 19 months of operation of the lab scale reactor, the n-DAMO reactor achieved nitrite removal rate of 2.88 mmol L−1 d−1. Enrichment of n-DAMO prokaryotes was evident from the increase in 16S rRNA gene copy number of bacteria belonging to the NC10 phylum in the reactor, corroborating with increase in the oxidation rates of CH4 coupled with NO2−-N removal from 21 μM to 190 μM of CH4 d−1. Based on stable isotope experiments by other researchers, nitric oxide dismutase (nod) functional gene was hypothesized to be responsible for splitting nitric oxide to nitrogen and oxygen and this internally generated oxygen is utilized by n-DAMO prokaryotes to oxidize methane gas. Primers targeting the unique nitric oxide dismutase (nod) gene were developed and tested on the enrichment culture for the first time. This revealed that n-DAMO organisms are closely related yet distinct from, the M. oxyfera which had been enriched in earlier studies. The results emphasize tremendous future promise to use these novel organisms for wastewater treatment purposes, especially to take advantage of the dissolved methane present in anaerobic digester effluents.

Microbial removal of carboxylic acids from 1,3-propanediol in glycerol anaerobic digestion effluent by PHAs-producing consortium

Anaerobic fermentation of glycerol to 1,3-propanediol (1,3-PDO) is conceived as an economic feasible pathway to handle with increasing crude glycerol from biodiesel industry. However, glycerol anaerobic digestion effluent (ADE) consists of carboxylic acids and 1,3-PDO, imposing difficulties for separation. The objective of this study was, therefore, to investigate microbial removal of carboxylic acids from 1,3-PDO in glycerol ADE by polyhydroxyalkanoates (PHAs) producing consortium. Growth tests on carbon sources showed Corynebacterium hydrocarbooxydans had preference for butyrate while Bacillus megaterium for acetate and glycerol. Consequently, their consortium had a higher cell density and a faster substrate utilization rate than single strain grown in glycerol ADE. Acidic pH at 6.0 and 5.2 strongly inhibited cell growth and activity, while C:N ratio (w/w) at 8:1 could balance nitrogen demand for cell growth and PHA synthesis. Kinetic study further revealed over 80% of fed 1,3-PDO was preserved after depletion of carboxylic acids. Correspondingly, total organic carbon (TOC) contribution from 1,3-PDO rose from initial 55.8% to 84%. Produced PHAs comprised 3-hydroxybutyrate (3-HB) units. The results showed this study as the first attempt to provide a win-win solution to remove carboxylic acids from 1,3-PDO in glycerol ADE and converted them into PHAs as a secondary value-added product.

Using an environmentally friendly process combining electrocoagulation and algal cultivation to treat high-strength wastewater

This study investigated an alternative approach to treat a high-strength organic wastewater — anaerobic digestion effluent. Electrocoagulation (EC) and algal assemblage cultivation were integrated to carry out the treatment. An algal assemblage was cultured on the electrocoagulation (EC) treated liquid anaerobic digestion effluent to reduce excess nutrients and turbidity in the effluent as well as to accumulate algal biomass for potential chemical and/or biofuel production. Batch culture demonstrates similar maximum growth rates (0.201–0.207g TS L−1day−1) from the EC solution with two dilutions (2× and 5×). In addition, communities of the fresh water algal assemblage significantly changed in the media with different dilutions after 9-day cultivation. Semi-continuous culture established steady biomass productivities and nitrogen removal in 2× and 5× EC media. However, both conditions exhibited an increase of phosphorus removal rate which could be explained by the luxury uptake theory. Biomass composition analysis indicates that algae cultured in medium with higher nitrogen concentration accumulated more proteins but less carbohydrates and lipids.