Presence Of Organic Carbon Source Research Articles

Wastewater treatment optimization utilizing polyvinyl alcohol cryogel immobilized microalgae for nutrient removal

This study investigated the use of polyvinyl alcohol (PVA) cryogels to immobilize microalgae for wastewater treatment. Chlorella sorokiniana was successfully entrapped in PVA cryogels via repeated freeze/thaw cycles. The nutrient removal efficiency of these cryogels was tested in a continuously stirred photobioreactor under varying conditions, both with and without the addition of an organic carbon source (sodium acetate). The presence of organic carbon significantly enhanced nutrient removal. Specifically, PVA cryogels with immobilized C. sorokiniana achieved 100% nitrogen removal and 97.2% phosphorus removal under mixotrophic conditions. Furthermore, the maximum nutrient removal capacities of the PVA cryogels were found to be 0.033 mg-N/cube·day for nitrogen and 0.0047 mg-P/cube·day for phosphorus. As the inorganic carbon (bicarbonate) concentration increased from 5 to 100 mg/L, the N/P ratio rose from 6 to 8, with a higher N/P ratio of 10 observed when nitrate nitrogen was used as the nitrogen source, compared to ammonia nitrogen, at 100 mg/L bicarbonate. This study offers an effective method for using microalgae immobilized in PVA cryogels for wastewater treatment. The findings highlight the potential for PVA cryogels to significantly improve nutrient removal efficiency, particularly in the presence of organic carbon sources, thereby enhancing bioreactor performance. High nitrogen and phosphorus removal efficiencies can help reduce eutrophication in water bodies, protect aquatic ecosystems, and enable nutrient recovery and reuse, supporting a circular economy in wastewater treatment practices.

Heterotrophic soil respiration and carbon cycling in geochemically distinct African tropical forest soils

Abstract. Heterotrophic soil respiration is an important component of the global terrestrial carbon (C) cycle, driven by environmental factors acting from local to continental scales. For tropical Africa, these factors and their interactions remain largely unknown. Here, using samples collected along topographic and geochemical gradients in the East African Rift Valley, we study how soil chemistry and fertility drive soil respiration of soils developed from different parent materials even after many millennia of weathering. To address the drivers of soil respiration, we incubated soils from three regions with contrasting geochemistry (mafic, felsic and mixed sediment) sampled along slope gradients. For three soil depths, we measured the potential maximum heterotrophic respiration under stable environmental conditions and the radiocarbon content (Δ14C) of the bulk soil and respired CO2. Our study shows that soil fertility conditions are the main determinant of C stability in tropical forest soils. We found that soil microorganisms were able to mineralize soil C from a variety of sources and with variable C quality under laboratory conditions representative of tropical topsoil. However, in the presence of organic carbon sources of poor quality or the presence of strong mineral-related C stabilization, microorganisms tend to discriminate against these energy sources in favour of more accessible forms of soil organic matter, resulting in a slower rate of C cycling. Furthermore, despite similarities in climate and vegetation, soil respiration showed distinct patterns with soil depth and parent material geochemistry. The topographic origin of our samples was not a main determinant of the observed respiration rates and Δ14C. In situ, however, soil hydrological conditions likely influence soil C stability by inhibiting decomposition in valley subsoils. Our results demonstrate that, even in deeply weathered tropical soils, parent material has a long-lasting effect on soil chemistry that can influence and control microbial activity, the size of subsoil C stocks and the turnover of C in soil. Soil parent material and its control on soil chemistry need to be taken into account to understand and predict C stabilization and rates of C cycling in tropical forest soils.

Evaluation of the potential of Chlorella sp. HS2, an algal isolate from a tidal rock pool, as an industrial algal crop under a wide range of abiotic conditions

While the screening and development of robust algal crops have mostly focused on determining strains that exhibit the highest possible yields of biomass or desirable biomolecules, these criteria do not necessarily lead to finding algal strains with high tolerance to varying outdoor cultivation conditions. Herein, we report Chlorella sp. HS2 isolated from a tidal rock pool nearby a local coastal waterfall that presumably experienced fluctuations in salinity, pH, and temperature. Compared to two reference strains, Chlorella sp. HS2 exhibited relatively high tolerance to a wide range of salinity (0–5% (w/v) of supplemental NaCl), pH (3.0–10.5), and temperature (14–46 °C) with substantially high biomass accumulation. While the supplementation of either gaseous CO2 or sodium bicarbonate enhanced algal growth, the mixotrophic and heterotrophic cultivations of Chlorella sp. HS2 further indicated its propensity to grow favorably under the presence of organic carbon sources. Subsequent PBR cultivation of Chlorella sp. HS2 under optimal light and/or temperature conditions suggested the highest specific growth rate during mixotrophy, while the analyses of the harvested biomass identified palmitate, oleate, and linoleate as major fatty acid methyl esters, and lutein and s-carotene as predominant carotenoids. Substantially, high growth rates of Chlorella sp. HS2 under a wide range of abiotic conditions and different trophic modes with favorable biochemical composition thus strongly support our algal isolate as a robust and reliable algal crop that can be deployed to achieve high production of commercially important biomolecules and to incorporate simultaneous treatment of wastewater or CO2-replete flue gas into algal cultivation.

Nitrogen Removal Performance of ANAMMOX with Different Organic Carbon Sources

Anaerobic ammonium oxidation (ANAMMOX) has been regarded as an efficient process to treat high-strength wastewater without organic carbon source. To investigate the nitrogen removal performance of ANAMMOX in the presence of organic carbon source can broaden its application in organic wastewater treatment. In this work, an anaerobic sequencing batch reactor (ASBR) was used to study the effect of organic carbon source on ANAMMOX process. The experimental results indicated that the activity of anaerobic ammonia oxidizing bacteria (AAOB) decreased by 84.2% when 200 mg·L-1 COD of glucose was added. When sodium acetate was added, the activity of AAOB was affected little. Besides, it even promoted the activity with COD less than 120 mg·L-1. The effect of sucrose on ANAMMOX process was similar to that of sodium acetate and the maximum specific ANAMMOX activity (SAA) increased by 25.0% with 80 mg·L-1 COD. When citric acid was added, the maximum SAA peaked with 80 mg·L-1 COD. The order of ANAMMOX promotion resulted from organic carbon source was sucrose, sodium acetate, citric acid and glucose. With addition of organic carbon source, nitrate could also be removed through the synergy of ANAMMOX and denitrification, and the total nitrogen removal efficiency increased.

Effect of carbon source on nitrogen removal in anaerobic ammonium oxidation (anammox) process

Anaerobic ammonium oxidation (anammox) has been regarded as an efficient process to treat high-strength wastewater without organic carbon source. To investigate nitrogen removal performance of anammox in presence of organic carbon source can broaden its application on organic wastewater treatment. In this work, effect of carbon source on anammox process was explored. Operating temperature was set at 35±1°C. Influent pH and hydraulic retention time were 7.5 and 6h, respectively. Effluent [Formula: see text] was affected little with COD no more than 480mg/L. Independent of carbon source content, nitrite removal rate was around 99%. The variation of [Formula: see text] lagged behind [Formula: see text] at high COD content, and pH could be used as an indicator for [Formula: see text] removal. Specific anammox activity dropped from 0.39 to 0.19 [Formula: see text] at COD=720mg/L. The remodified logistic model was quite appropriate for describing the nitrogen removal kinetics and predicting the performance of anammox process in presence of carbon source.

Addition of Fe2+ increase nitrate removal in vertical subsurface flow constructed wetlands

Fe2+ can assist in the process of denitrification as electron donor to enhance nitrogen removal in constructed wetlands (CWs). In this study, Fe2+ was added to the influent of CWs aiming to investigate the effects of external Fe2+ addition on denitrification efficiency at different carbon/nitrogen (C/N). Community-level physiological profile (CLPP) was assessed according to substrate utilization patterns with Biolog Eco Plates™. Results showed that external Fe2+ remarkably improved the capability of denitrification in constructed wetlands. Nitrate removal rate was largely increased after the addition of 30mg/L Fe2+ to the CWs reactor for a 2-day hydraulic retention time (HRT) at the presence of organic carbon source with low C/N ratio of 2. In reactor without adding organic carbon source, Fe(II)–Fe(III) cycle reaction could not be completed, thus forming hydroxide precipitation leading to low effluent Fe2+ and total iron. However, the enhancement of Fe2+ on denitrification was not obvious at high C/N of 6 and 4 in that organic carbon acted as dominant electron donor in participating denitrification processes. Substrate microbial community structure and diversity in CWs were influenced by organic carbon source and Fe2+. The Shannon, Pielou and Simpson indices in the CWs with external Fe2+ were higher than the control. Principal component analysis (PCA) showed that the CLPPs in constructed wetlands of different influents were significantly different. The constructed wetlands with added organic carbon sources and Fe2+ were grouped together, while the wetlands with the low C/N and the wetlands with high C/N were detached.

Establishment of cell suspension culture in Marchantia linearis Lehm & Lindenb. for the optimum production of flavonoids.

Bryophytes are the second largest group in the plant kingdom, but studies conducted to better understand their chemical composition are limited and scattered. Axenically grown bryophytes expressed potential in biotechnological processes. The present study was designed to investigate the in vitro cell growth, culture parameters and their effect on flavonoid synthesis. Chlorophyll-containing callus cells of Marchantia linearis Lehm & Lindenb. is able to grow under low light in the presence of organic carbon source and retain the ability to produce flavonoids. Highest flavonoid production was achieved using 2,4-dichlorophenoxyacetic acid as growth hormone. Inoculum size, light intensity, organic carbon source and cations are the culture parameters affecting flavonoid productivity. Maximum flavonoid productivity is observed under low light intensity, with a photon flux density ca. 20 μmol/m2/s. Optimal inoculum size and glucose concentration for flavonoid production are 10–14 and 2–3 %, respectively. Cations like ferrous trigger flavonoid synthesis by increasing its intracellular concentrations. Flavonoid production in the cell culture is shown to be significantly growth related. Osmotic stress is ineffective in triggering flavonoid synthesis. Methyl jasmonate and 2-(2-fluoro-6-nitrobenzylsulfanyl) pyridine-4-carbothioamide elicitors showed positive effect on intracellular flavonoid content in cultured cells. Using the standard plot of quercetin (y = 0.0148x, R2 = 0.975), the flavonoid contents of in vitro samples were found ranging from 4.0 to 17.7 mg quercetin equivalent/g tissue. Flavonoids are fractionated by HPLC-PAD revealed the presence of quercetin (182.5 μg/g), luteolin (464.5 μg/g) and apigenin (297.5 μg/g). Further studies are warranted to analyze the therapeutic potentiality of the flavonoids in the liverwort.

Isolation, identification and application of novel bacterial consortium TJ-1 for the decolourization of structurally different azo dyes

A novel bacterial consortium (TJ-1), which could decolorize Acid Orange 7 (AO7) and manyother azo dyes, was developed. In TJ-1 three bacterial strains were identified as Aeromonas caviae, Proteus mirabilis and Rhodococcus globerulus by 16S rRNA gene sequence analysis. AO7 decolorization was significantly higher with the use of consortium as compared to the use of individual strains, indicating complementary interactions among these strains. AO7 decolorization was observed under microaerophilic condition in the presence of organic carbon source. Either yeast extract (YE) alone or a combination of YE and glucose resulted in much higher decolorization of AO7 as compared to glucose alone, peptone or starch. Kinetic studies with different initial AO7 concentrations showed that more than 90% decolorization could be achieved even at 200mg/l within 16h. Fed-batch studies showed that AO7 decolorization required 10h during the first cycle and 5h in the second and third cycles, showing that bacterial cells could be used for multiple cycles. The consortium also decolorized fifteen other azo dyes individually as well as a simulated wastewater containing a mixture of all the sixteen azo dyes, thus, conferring the possibility of application of TJ-1 for the treatment of industrial wastewaters.

Natural attenuation of chlorinated solvent plumes at Texas dry cleaners

AbstractDry cleaners are the largest users of perchloroethene (PCE) solvents in the United States. Releases from dry cleaners to soil and groundwater, however, remain largely unstudied. This article presents a database of 137 chlorinated solvent plumes at dry cleaners in Texas. The data indicate that PCE plumes are generally shorter in extent than those from industrial sites. Degradation products were observed at more than 80 percent of the sites with groundwater contamination. Calculated attenuation rates are on the order of one‐to‐three‐year half‐lives for PCE and its degradation products. The estimated cleanup timeframe for calculated attenuation rates is < 50 years. More research is needed to understand the presence of organic carbon sources at dry cleaners and its implications for natural attenuation. © 2004 Wiley Periodicals, Inc.

The transformation of inorganic sulfur compounds and the assimilation of organic and inorganic carbon by the sulfur disproportionating bacterium Desulfocapsa sulfoexigens

The physiology of the sulfur disproportionator Desulfocapsa sulfoexigens was investigated in batch cultures and in a pH-regulated continuously flushed fermentor system. It was shown that a sulphide scavanger in the form of ferric iron was not obligatory and that the control of pH allowed production of more biomass than was possible in carbonate buffered but unregulated batch cultures. Small amounts of sulphite were produced during disproportionation of elemental sulfur and thiosulphate. In addition, it was shown that in the presence of hydrogen, a respiratory type of process is favored before the disproportionation of sulphite, thiosulphate and elemental sulfur. Sulphate reduction was not observed. D. sulfoexigens assimilated inorganic carbon even in the presence of organic carbon sources. Inorganic carbon assimilation was probably catalyzed by the reverse CO-dehydrogenase pathway, which was supported by the constitutive expression of the gene encoding CO-dehydrogenase in cultures grown in the presence of acetate and by the high carbon fractionation values that are indicative of this pathway.

Growth aspects of the marine microalga Nannochloropsis gaditana

Nannochloropsis is well appreciated in aquaculture due to its nutritional value and the ability to produce valuable chemical compounds, such as pigments (zeaxanthin, astaxanthin…) and polyunsaturated fatty acids (EPA). Commercial exploitation needs high cell densities but the low growth rate and the small size of cells are practical difficulties. To increase biomass concentration the positive effect of several factors was evident: (i) pH≈8 control (with dilute Tris–HCl buffer); (ii) the continuous illumination (no evidence of photo-inhibition was observed); (iii) a quite large temperature range (25±5 °C); (iv) the presence of organic carbon source (with the danger of contamination); (v) the presence of urea as an additional nitrogen source (10 mM); (vi) a small air flow rate with large bubbles can be more efficient for CO 2 mass transfer (associated to reduced shearing).

The anaerobic degradation of endosulfan by indigenous microorganisms from low-oxygen soils and sediments

Indigenous mixed populations of anaerobic microorganisms from an irrigation tailwater drain and submerged agricultural chemical waste pit readily biodegraded the major isomer of endosulfan (endosulfan I). Endosulfan I was biodegraded to endosulfan diol, a low toxicity degradation product, in the presence of organic carbon sources under anaerobic, methanogenic conditions. While there was extensive degradation (>85%) over the 30 days, there was no significant enhancement of degradation from enriched inocula. This study demonstrates that endosulfan I has the potential to be biodegraded in sediments, in the absence of enriched microorganisms. This is of particular importance since such sediments are prevalent in cotton-growing areas and are typically contaminated with endosulfan residues. The importance of minimizing non-biological losses has also been highlighted as a critical issue in determining anaerobic biodegradation potential. Seals for such incubation vessels must be both oxygen and pollutant impermeable. Teflon-lined butyl rubber provides such a seal because of its resistance to the absorption of volatiles and in preventing volatilization. Moreover, including a 100 mM phosphate buffer in the anaerobic media has reduced non-biological losses from chemical hydrolysis, allowing biodegradation to be assessed.