Microalgae Consortium Research Articles

Consortium of Microalgae for Tannery Effluent Treatment

Abstract Wastewater generated in tanneries have essential elements for microalgae growth, but it has also some toxic compounds that may hinder or restrain the growth of microalgae in this environment. This work tested microalgae consortium growth originating from a deactivated effluent treatment decanter of a complete tannery (beamhouse to finished leather) for the treatment of wastewater of a tannery processing wet-blue leather to finished leather. It was initially evaluated the growth of the microalgae consortium in the three effluents diluted in 50% distilled water: raw effluent (50RE50W), effluent after primary coagulation/flocculation (50PE50W), and effluent after primary and secondary biological treatment (50BE50W). After 16 days of cultivation, the 50PE50W presented the highest biomass concentration (1.77 g L−1). The highest removal values for effluents 50RE50W, 50PE50W and 50BE50W were 51.02%, 99.90%, 82.88%, and 91.75% for chemical oxygen demand (COD), N-NH3, TKN, and P-PO4-, respectively. It was verified low levels of nutrient removal in the raw effluent (100RE), since the consortium was not able to grow in this medium. Finally, at concentrations of 25RE75BE (25% raw effluent diluted with 75% effluent after the biological treatment) and 50RE50B (50% raw effluent diluted with 50% effluent after the biological treatment), effective removal values were reached. Biomass growth concentration up to 1.3 g L-1 and removal values for N-NH3, TKN, P-PO4, COD, total organic carbon (TOC) and biological oxygen demand (BOD5), of 99.90%, 79.36%, 87.82%, 14.26%, 35.82%, and 42.86%, respectively, were reached in 50RE50B.

Bio-crude oil production using catalytic hydrothermal liquefaction (HTL) from native microalgae harvested by ozone-flotation

This work explored bio-crude oil production and the hydrocarbon distribution resulting from a catalytic HTL process with a feedstock composed by native consortium of microalgae (mostly cyanobacteria) with low lipid and high protein content. Two harvesting methods ozone-flotation and centrifugation were compared. Also, the effect of the catalysts, HZSM-5 zeolite, content (0, 5 and 7 wt% loading with respect to dry biomass) were studied. The dry biomass was liquefied in water (slurry at 4 wt%) at 350 °C for 120 min. Results showed that the bio-crude contained aliphatic, aromatic, cyclic, oxygenated cyclic and aliphatic compounds containing N and O, with a bio-crude yield of between 10 and 16%. The best quality of bio-crude oil was produced from microalgae harvested and pretreated by ozone-flotation at 7 wt% HZSM-5. The increase in the bio-crude quality was a result of a lower nitrogen (3.2%), oxygen (4.8%) and sulfur (0.7%) content versus centrifuged (no catalyst) microalgae 4.6%, 7.9% and 1.6% respectively.

Laboratory-scale investigation on the role of microalgae towards a sustainable treatment of real municipal wastewater.

Engineered microalgal-bacteria consortia are an attractive solution towards a low-cost and sustainable wastewater treatment that does not rely on artificial mechanical aeration. In the research conducted for this study, a bench-scale photo-sequencing-batch reactor (PSBR) was operated without external aeration. A spontaneous consortium of microalgae and bacteria was developed in the PSBR at a concentration of 0.8-1.7 g TSS/L. The PSBR ensured removal efficiency of 85 ± 8% for chemical oxygen demand (COD) and 98 ± 2% for total Kjeldahl nitrogen (TKN). Nitrogen balance revealed that the main mechanisms for TKN removal was autotrophic nitrification, while N assimilation and denitrification accounted for 4% and 56%, respectively. The development of dense microalgae-bacteria bioflocs resulted in good settleability with average effluent concentration of 16 mgTSS/L. The ammonium removal rate was 2.9 mgN L-1 h-1, which corresponded to 2.4 mgN gTSS-1 h-1. Although this specific ammonium removal rate is similar to activated sludge, the volumetric rate is lower due to the limited total suspended solids (TSS) concentration (three times less than activated sludge). Therefore, the PSBR footprint appears less competitive than activated sludge. However, ammonium was completely removed without artificial aeration, resulting in a very cost-effective process. Only 50% of phosphorus was removed, suggesting that further research on P uptake is needed.

Experimental investigation of energy properties for Stigonematales sp. microalgae as potential biofuel feedstock

ABSTRACTMicroalgae has been considered potential biofuel source from the last decade owing to its versatile perspectives such as excellent capability of CO2 capture and sequestration, water treatment, prolific growth rate and enormous energy content. Thus, energy research on microalgae is being harnessed to mitigate CO2 and meet future energy demands. This study investigated the bioenergy potential of native blue-green microalgae consortium as initial energy research on microalgae in Brunei Darussalam. The local species of microalgae were assembled from rainwater drains, the species were identified as Stigonematales sp. and physical properties were characterised. Sundried biomass with moisture content ranging from 6.5% to 7.37% was measured to be used to determine the net and gross calorific value and they were 7.98 MJ/kg-8.57 MJ/kg and 8.70 MJ/kg-9.45 MJ/kg, respectively. Besides that, the hydrogen content, ash content, volatile matter, and bulk density were also experimented and they were 2.56%-3.15%, 43.6%-36.71%, 57–38%-63.29% and 661.2 kg/m3-673.07 kg/m3, respectively. Apart from experimental values, other physical bioenergy parameters were simulated and they were biomass characteristic index 61,822.29 kg/m3-62,341.3 kg/m3, energy density 5.27 GJ/m3-5.76G J/m3 and fuel value index 86.19–88.54. With these experimental results, microalgae manifested itself a potential source of biofuel feedstock for heat and electricity generation, a key tool to bring down the escalated atmospheric greenhouse gases and an alternation for fossil fuel.

Morphological responses to nitrogen stress deficiency of a new heterotrophic isolated strain of Ebro Delta microbial mats.

Microorganisms living in hypersaline microbial mats frequently form consortia under stressful and changing environmental conditions. In this paper, the heterotrophic strain DE2010 from a microalgae consortium (Scenedesmus sp. DE2009) from Ebro Delta microbial mats has been phenotypically and genotypically characterized and identified. In addition, changes in the morphology and biomass of this bacterium in response to nitrogen deficiency stress have been evaluated by correlative light and electron microscopy (CLEM) combining differential interference contrast (DIC) microscopy and transmission electron microscopy (TEM) and scanning electron microscopy (SEM). These isolated bacteria are chemoorganoheterotrophic, gram-negative, and strictly aerobic bacteria that use a variety of amino acids, organic acids, and carbohydrates as carbon and energy sources, and they grow optimally at 27°C in a pH range of 5 to 9 and tolerate salinity from 0 to 70‰ NaCl. The DNA-sequencing analysis of the 16S rRNA and nudC and fixH genes and the metabolic characterization highlight that strain DE2010 corresponds to the species Ochrobactrum anthropi. Cells are rod shaped, 1-3μm in length, and 0.5μm wide, but under deprived nitrogen conditions, cells are less abundant and become more round, reducing their length and area and, consequently, their biomass. An increase in the number of pleomorphic cells is observed in cultures grown without nitrogen using different optical and electron microscopy techniques. In addition, the amplification of the fixH gene confirms that Ochrobactrum anthropi DE2010 has the capacity to fix nitrogen, overcoming N2-limiting conditions through a nifH-independent mechanism that is still unidentified.

Effects of an Early Successional Biological Soil Crust from a Temperate Coastal Sand Dune (NE Germany) on Soil Elemental Stoichiometry and Phosphatase Activity

Early successional biological soil crusts (BSCs), a consortium of bacteria, cyanobacteria, and other microalgae, are one of the first settlement stages on temperate coastal sand dunes. In this study, we investigated the algal biomass (Chlorophyll a (Chl a)), algal (Calgal) and microbial carbon (Cmic), elemental stoichiometry (C:N:P), and acid and alkaline phosphatase activity (AcidPA and AlkPA) of two algae-dominated BSCs from a coastal white dune (northeast Germany, on the southwestern Baltic Sea) which differed in the exposure to wind forces. The dune sediment (DS) was generally low in total carbon (TC), nitrogen (TN), and phosphorus (TP). These elements, together with the soil organic matter (SOM)accumulated in the BSC layer and in the sediment underneath (crust sediment CS), leading to initial soil development. The more disturbed BSC (BSC1) exhibited lower algal and microbial biomass and lower Calgal/Cmic ratios than the undisturbed BSC (BSC2). The BSC1 accumulated more organic carbon (OC) than BSC2. However, the OC in the BSC2 was more effectively incorporated into Cmic than in the BSC1, as indicated by lower OC:Cmic ratios. The AcidPA (1.1-1.3μmolg-1DMh-1 or 147-178μgg-1DMh-1) and AlkPA (2.7-5.5μmolg-1DMh-1 or 372-764μgg-1DMh-1) were low in both BSCs. The PA, together with the elemental stoichiometry, indicated no P limitation of both BSCs but rather water limitation followed by N limitation for the algae community and a carbon limitation for the microbial community. Our results explain the observed distribution of early successional and more developed BSCs on the sand dune.

Dual-species cultivation of microalgae and yeast for enhanced biomass and microbial lipid production

Oleaginous microalgae and yeasts are well known as potential feedstocks for biofuels and other fatty acid-derived materials. Microalgae-yeast mixed culture has gained more attention recently for the improvement of microbial lipid production economically. In the present work, combinations of two Chlorella species with oleaginous yeast at different ratios by the mixed culture mode were evaluated for the improvement of biomass and lipid production. Yeast cells dominated in a dual-species cultivation system when co-cultivated with Chlorella vulgaris. Compared to the monoculture and other three studied consortia, the mixed culture of Chlorella pyrenoidosa and Rhodotorula glutinis with a ratio of 3:1 achieved maximum biomass concentration and lipid productivity. Further optimization of the C/N ratio in the medium was carried out using this consortium. At a C/N ratio of 64, biomass concentration and lipid yield reached 6.12 ± 0.31 and 2.48 ± 0.09 g L−1, respectively. The highest total fatty acid (TFA) productivity (175.64 ± 2.32 mg L−1 day−1) obtained in the mixed culture was twofold than that in the monoculture. Additionally, dissolved oxygen and pH were found to be adjusted synergistically in the mixed culture. These results demonstrated that an artificial consortium of microalgae and yeast is a promising approach for future applications in microbial lipid production.

Photosynthetic oxygenation for urine nitrification.

Human urine accounts for only a fraction of the sewage volume, but it contains the majority of valuable nutrient load in wastewater. In this study, synthetic urine was nitrified in a closed photo-bioreactor through photosynthetic oxygenation by means of a consortium of microalgae and nitrifying bacteria. In situ production of oxygen by photosynthetic organisms has the potential to reduce the energy costs linked to conventional aeration. This energy-efficient strategy results in stable urine for further nutrient recovery, while part of the nutrients are biologically recovered in the form of valuable biomass. In this study, urine was nitrified for the first time without conventional aeration at a maximum photosynthetic oxygenation rate of 160 mg O2 gVSS-1 d-1 (VSS: volatile suspended solids). A maximum volumetric nitrification rate of 67 mg N L-1 d-1 was achieved on 12% diluted synthetic urine. Chemical oxygen demand (COD) removal efficiencies were situated between 44% and 83% at a removal rate of 24 mg COD gVSS-1 d-1. After 180 days, microscopic observations revealed that Scenedesmus sp. was the dominant microalga. Overall, photosynthetic oxygenation for urine nitrification is promising as a highly electricity efficient approach for further nutrient recovery.

Evolution of real municipal wastewater treatment in photobioreactors and microalgae-bacteria consortia using real-time parameters

In the treatment of real municipal wastewater with photo-sequencing batch reactors (PSBR), operating strategies able to achieve high levels of pollutant removal, but reduce the hydraulic retention time (HRT), are imperative for making microalgae-bacteria consortia more competitive than conventional activated sludge systems. In regard to real-time monitoring, on-line probes like Dissolved Oxygen (DO), pH and oxidation–reduction potential (ORP) are cheap and reliable, but their exploitation has been largely overlooked in PSBRs. This paper proposes the use of DO, pH and ORP profiles to reveal the evolution of wastewater treatment in a PSBR treating real municipal wastewater with a mixed consortium of microalgae and bacteria. The PSBR ensured removal efficiency of 87 ± 5% for COD and 98 ± 2% for TKN without external aeration; indeed, photosynthesis was the only driver of the oxygen production. Considering the combined effects of photosynthetic oxygenation and microbial oxygen consumption, some practical information was gathered to understand the complex profiles of the on-line parameters. During dark and light phases, Zero-DO values, DO and pH raises, and their relative peaks were discussed to evaluate correctly the conclusion of the wastewater treatment and therefore to adjust the duration of the PSBR cycle. In particular: (1) two simultaneous “characteristic points”, “Ammonia valley” (pH profile) and “DO breakpoint” (DO profile), detected univocally the complete ammonium removal; (2) the absolute peaks of DO, pH and ORP at maximum irradiance revealed that wastewater treatment was complete and the cycle could be concluded. In this way, these characteristic points were exploited for the optimization of the PSBR cycle, which was concluded after 15–26 h, reducing the HRT by more than 45%.

Consortium of Higher Aquatic Plants and Microalgae Designed to Purify Sewage of Heavy Metal Ions

We selected higher aquatic plants (HAP) and microalgae possessing a high sorption capacity in respect to heavy metals to form a consortium designed to purify contaminated aquatic ecosystems. Accumulation of heavy metals Cd2+, Cu2+, Pb2+, and Zn2+ was investigated in plants Pistia stratiotes, Elodea canadensis, and Lemna minor and green microalgae Chlorella vulgaris ВВ-2, Ankistrodesmus sp. ВI-1, Chlamydomonas reinhardtii В-4, and Scеnеdеsmus quadricauda В-1. It was found that intense accumulation of metals occurs in cultures of HAP Pistia stratiotes and Elodea canadensis. These plants are macroconcentrators of zinc, lead, and copper and microconcentrators of cadmium. Out of the examined cultures of microalgae, effective bioaccumulators of heavy metals were C. vulgaris ВВ-2 and Ankistrodesmus sp. ВI-1. It was shown that heavy metals are selectively taken up from the medium in the series Zn2+ > Cu2+ > Cd2+ > Pb2+. In order to produce a consortium of higher aquatic plants and microalgae for purification of polluted aquatic ecosystems, we investigated interaction of HAP P. stratiotes and E. canadensis with microalgae C. vulgaris ВВ-2 and Ankistrodesmus sp. ВI-1 in the course of their cocultivation. Neutral relations were detected between the cells of microalgae C. vulgaris ВВ-2 and Ankistrodesmus sp. ВI-1 and HAP E. canadensis. At the same time, the cells of Ankistrodesmus sp. ВI-1 and HAP P. stratiotes formed a symbiosis. Microscopic examination showed numerous points where the cells of microalgae Ankistrodesmus sp. ВI-1 were attached to the roots of P. stratiotes plants. We tested an opportunity to employ the association between P. stratiotes and Ankistrodesmus sp. ВI-1 for purification of simulated wastewater polluted with heavy metal ions. This consortium proved to be capable of eliminating contaminants from the sewage, reducing their level in the sewage to standard values, and active accumulation of heavy metal ions.

The opportunities to use consortium of higher aquatic plants and microalgae in the treatment of polluted aquatic ecosystems

The opportunities to use consortium of higher aquatic plants and microalgae in the treatment of polluted aquatic ecosystems

Tunisian landfill leachate treatment using Chlorella sp.: effective factors and microalgae strain performance

The potential of the autoclaved Tunisian landfill leachate treatment using microalgae (Chlorella sp.) cultivation was investigated in this study. Landfill leachate was collected from Borj Chakir landfill, Tunisia. A full factorial experimental design 22 was proposed to study the effects of the incubation time and leachate ratio factors on the organic matter removal expressed in chemical oxygen demand (COD) and ammoniacal nitrogen (NH4─N) and on the biological response of Chlorella sp. expressed by the cell density and chlorophyll content. All experiments were batch runs at ambient temperature (25 ± 2 °C). The Chlorella sp. biomass and chlorophyll a concentrations of 1.2 and 5.32 mg L−1, respectively, were obtained with 10% leachate spike ratio. The obtained results showed that up to 90% of the ammoniacal nitrogen in landfill leachate was removed in 10% leachate ratio spiked medium with a residual concentration of 40 mg L−1. The maximum COD removal rate reached 60% within 13 days of incubation time indicating that microalgae consortium was quite effective for treating landfill leachate organic contaminants. Furthermore, with the 10% leachate ratio spiked medium, the maximum lipid productivity was 4.74 mg L−1 d−1. The present study provides valuable information for potential adaptation of microalgae culture and its contribution for the treatment of Tunisian landfill leachate.

Hydrolysis of microalgal biomass using ruminal microorganisms as a pretreatment to increase methane recovery

The use of ruminal fluid as a source of hydrolytic microorganisms for the pretreatment of a native consortium of microalgae (essentially Senedesmus) was investigated. The hydrolytic enzyme activity of the ruminal culture was first enriched in a bioreactor. Then, using the enriched culture, the effect of the microalgae to the ruminal fluid ratio (S/X) on the hydrolysis and subsequent production of methane was investigated. An S/X ratio of 0.5 showed the best hydrolysis efficiency (29%) reaching in a second stage process a methane yield of 193mL CH4g COD−1. The processing time (pretreatment plus methanization) was only 7days. The predominant ruminal hydrolytic bacteria selected in the enrichment were principally Clostridium, Proteocatella and Pseudomonas.

Ecotoxicological effects of enrofloxacin and its removal by monoculture of microalgal species and their consortium

Enrofloxacin (ENR), a fluoroquinolone antibiotic, has gained big scientific concern due to its ecotoxicity on aquatic microbiota. The ecotoxicity and removal of ENR by five individual microalgae species and their consortium were studied to correlate the behavior and interaction of ENR in natural systems. The individual microalgal species (Scenedesmus obliquus, Chlamydomonas mexicana, Chlorella vulgaris, Ourococcus multisporus, Micractinium resseri) and their consortium could withstand high doses of ENR (≤1 mg L-1). Growth inhibition (68–81%) of the individual microalgae species and their consortium was observed in ENR (100 mg L-1) compared to control after 11 days of cultivation. The calculated 96 h EC50 of ENR for individual microalgae species and microalgae consortium was 9.6–15.0 mg ENR L−1. All the microalgae could recover from the toxicity of high concentrations of ENR during cultivation. The biochemical characteristics (total chlorophyll, carotenoid, and malondialdehyde) were significantly influenced by ENR (1–100 mg L-1) stress. The individual microalgae species and microalgae consortium removed 18–26% ENR at day 11. Although the microalgae consortium showed a higher sensitivity (with lower EC50) toward ENR than the individual microalgae species, the removal efficiency of ENR by the constructed microalgae consortium was comparable to that of the most effective microalgal species.

Cultivation and selection of cyanobacteria in a closed photobioreactor used for secondary effluent and digestate treatment

The main objective of this study was to select and grow wastewater-borne cyanobacteria in a closed photobioreactor (PBR) inoculated with a mixed consortium of microalgae. The 30L PBR was fed with a mixture of urban secondary effluent and digestate, and operated in semi-continuous mode. Based on the nutrients variation of the influent, three different periods were distinguished during one year of operation. Results showed that total inorganic nitrogen (TIN), inorganic phosphorus concentration (PO43−), phosphorus volumetric load (LV-P) and carbon limited/non-limited conditions leaded to different species composition, nutrients removal and biomass production in the culture. High TIN/PO43− concentrations in the influent (36mg N L−1/3mg P L−1), carbon limitation and an average LV-P of 0.35mg P L−1d−1 were negatively related to cyanobacteria dominance and nutrients removal. On the contrary, cyanobacteria predominance over green algae and the highest microbial biomass production (averaging 0.084g Volatile Suspended Solids (VSS) L−1d−1) were reached under TIN/PO43− concentrations of 21mg N L−1/2mg P L−1, no carbon limitation and an average LV-P of 0.23mg P-PO43− L−1d−1. However, although cyanobacteria predominance was also favored with a LV-P 0.15mg L−1d−1, biomass production was negatively affected due to a P limitation in the culture, resulting in a biomass production of 0.0.39g VSS L−1d−1. This study shows that the dominance of cyanobacteria in a microalgal cyanobacterial community in an agitated PBR using wastewater as nutrient source can be obtained and maintained for 234days. These data can also be applied in future biotechnology applications to optimize and enhance the production of added value products by cyanobacteria in wastewater treatment systems.

Microalgal Cultivation in Secondary Effluent: Recent Developments and Future Work.

Eutrophication of water catchments and the greenhouse effect are major challenges in developing the global economy in the near future. Secondary effluents, containing high amounts of nitrogen and phosphorus, need further treatment before being discharged into receiving water bodies. At the same time, new environmentally friendly energy sources need to be developed. Integrating microalgal cultivation for the production of biodiesel feedstock with the treatment of secondary effluent is one way of addressing both issues. This article provides a comprehensive review of the latest progress in microalgal cultivation in secondary effluent to remove pollutants and accumulate lipids. Researchers have discovered that microalgae remove nitrogen and phosphorus effectively from secondary effluent, accumulating biomass and lipids in the process. Immobilization of appropriate microalgae, and establishing a consortium of microalgae and/or bacteria, were both found to be feasible ways to enhance pollutant removal and lipid production. Demonstrations of pilot-scale microalgal cultures in secondary effluent have also taken place. However there is still much work to be done in improving pollutants removal, biomass production, and lipid accumulation in secondary effluent. This includes screening microalgae, constructing the consortium, making use of flue gas and nitrogen, developing technologies related to microalgal harvesting, and using lipid-extracted algal residues (LEA).

Enhanced microalgal biomass and lipid production from a consortium of indigenous microalgae and bacteria present in municipal wastewater under gradually mixotrophic culture conditions

The goal of this study was to investigate the influences of gradually mixotrophic culture conditions on microalgal biomass and lipid production by a consortium of indigenous microalgae and bacteria present in raw municipal wastewater. Lab-scale photobioreactors containing the consortium were operated in repeated batch mode. Initial cultivation (phase I) was performed using only the municipal wastewater, then 10% and 25% of the reactor volumes were replaced with the effluent from a sewage sludge fermentation system producing volatile fatty acids (SSFV) at the beginnings of phase II and phase III, respectively. The highest biomass productivity (117.1±2.7mg/L/d) was attained during phase II, but the lipid productivity (17.2±0.2mg/L/d) was attained during phase III. The increase in the effluent from the SSFV influenced microalgal diversity with a preference for Chlorella sp., but bacterial diversity increased significantly during phase III.

Biohydrogen and methane production via a two-step process using an acid pretreated native microalgae consortium

A native microalgae consortium treated under thermal-acidic hydrolysis was used to produce hydrogen and methane in a two-step sequential process. Different acid concentrations were tested, generating hydrogen and methane yields of up to 45mLH2gVS−1 and 432mLCH4gVS−1, respectively. The hydrogen production step solubilized the particulate COD (chemical oxygen demand) up to 30%, creating considerable amounts of volatile fatty acids (up to 10gCODL−1). It was observed that lower acid concentration presented higher hydrogen and methane production potential. The results revealed that thermal acid hydrolysis of a native microalgae consortium is a simple but effective strategy for producing hydrogen and methane in the sequential process. In addition to COD removal (50–70%), this method resulted in an energy recovery of up to 15.9kJ per g of volatile solids of microalgae biomass, one of the highest reported.

Enhancing the Removal of Highly Concentrated CO2 Through Synergism between Microalgae Consortium and Nutrient Ratio in Photobioreactor

This research was carried out by developing the carbon capture and storage (CCS) technology to determine the synergism between microalgae consortium and the optimum nutrient ratio as an effort to obtain higher CO 2 removal efficiency and CO 2 utilization efficiency. The microalgae consortium consisting of Chlorella sp., Scenedesmus sp. and Ankistrodesmus sp. have been selected previously as potential candidates for Microbial Carbon Capture and Storage (MCCS) agent and already cultured continuously in PHM (Provasoli Haematococcus Media) artificial medium, in vertical column photobioreactor. Pure CO 2 gas at a high concentration of 10% (v/v) flowed from the bottom of vertical column photobioreactor continuously with optimum flow rate of 5 L.min -1 . A growth medium (PHM) containing artificial nutrients was flowed continuously at flow rate 7L.day -1 and detention time 3.8 days. Four fluorescent lamps were positioned outside the photo-bioreactor to obtain light intensity of 4000 lux, set for 16 hours light exposure and 8 hours dark, with operating temperature 30°C maintained during the study. Three compositional variations of microalgae consortium were used. They are as follows; Ch : Sc : An = 1: 1: 1; Ch : Sc = 1: 1; and Ch : An = 1: 1, where Ch, Sc, and An were Chlorella sp., Scenedesmus obliquus and Ankistrodesmus sp., respectively. The following variations of nutrient composition were used; C: N: P = 100: 10: 1, C: N: P = 100: 50: 1 and C: N: P = 100: 25: 1. The C, N, and P sources were CO 2 (inorganic), KNO 3 , and KH 2 PO 4 , respectively. This study proves that synergism between the types making up the consortium also determined the ability to utilize inorganic carbon source. Without the presence of Ankistrodesmus sp., synergism between Scenedesmus obliquus and Chlorella sp. showed twice higher CO 2 utilization efficiency in comparison to the synergism between Ankistrodesmus sp and Chlorella sp. Increased nitrogen concentration in medium increased the growth of Chlorella sp and Scenedesmus obliquus as a consortium, the CO 2 removal efficiency, the CO 2 utilization efficiency and the Carbon Uptake Rate. The nutrient ratios C:N:P of 100:50:1 could increase CO 2 utilization efficiency upto 50% higher than the C:N:P of 100:10:1.

Assessment of microalgae and nitrifiers activity in a consortium in a continuous operation and the effect of oxygen depletion

Background: Industrial wastewaters with a high content of nitrogen are a relevant environmental problem. Currently, treatments to remove nitrogen are not efficient, so is necessary to develop alternative methods. The objective of this study is to investigate a consortium of microalgae - nitrifying, that due to the symbiosis between them could be an interesting alternative. Results: In this study, it was possible to obtain a consortium of nitrifying bacteria (NB) and microalgae (MA) capable of operating with low requirements of dissolved oxygen, using aerobic sludge from wastewater treatment plants. During the operation, this consortium presents removal percentages above 98% of ammonia, even at concentrations of DO of 0.5 mg O 2 L -1 . It is estimated that the removal was caused both by the action of nitrifying bacteria and microalgae. It was determined that approximately 60% of the ammonia feed was oxidized to nitrate by nitrifying bacteria, while the algae assimilated 40% of the nitrogen feed at steady state. A methodology for measuring the specific activities of nitrifying bacteria and microalgae by comparing the rates in the variation inorganic nitrogen compounds was established with satisfactory results. An average specific activity of 0.05 and 0.02 g NH 4 + gVSS -1 d -1 for nitrifying bacteria and microalgae was determined, respectively. Conclusions: The consortium it can be obtained in a single continuous operation, and has a high capacity for nitrogen removal with low oxygen content. The consortium could prove to be a more economical method compared to traditional. Normal 0 21 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabla normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:Calibri,sans-serif; mso-ansi-language:EN-US; mso-fareast-language:EN-US;}