Rafael Hernandez

Biodiesel production by in situ transesterification of municipal primary and secondary sludges

The potential of using municipal wastewater sludges as a lipid feedstock for biodiesel production was investigated. Primary and secondary sludge samples obtained from a municipal wastewater treatment plant in Tuscaloosa, AL were freeze-dried and subjected to an acid-catalyzed insitu transesterification process. Experiments were conducted to determine the effects of temperature, sulfuric acid concentration, and mass ratio of methanol to sludge on the yield of fatty acid methyl esters (FAMEs). Results indicated a significant interactive effect between temperature, acid concentration, and methanol to sludge mass ratio on the FAME yield for the insitu transesterification of primary sludge, while the FAME yield for secondary sludge was significantly affected by the independent effects of the three factors investigated. The maximum FAME yields were obtained at 75 degrees C, 5% (v/v) H(2)SO(4), and 12:1 methanol to sludge mass ratio and were 14.5% and 2.5% for primary and secondary sludge, respectively. Gas chromatography (GC) analysis of the FAMEs revealed a similar fatty acid composition for both primary and secondary sludge. An economic analysis estimated the cost of

The effect of glycerol as a sole and secondary substrate on the growth and fatty acid composition of Rhodotorula glutinis

3.23/gallon for a neat biodiesel obtained from this process at an assumed yield of 10% FAMEs/dry weight of sludge.

Effect of different C/N ratios on carotenoid and lipid production by Rhodotorula glutinis.

Rhodotorula glutinis is a yeast that produces copious quantities of lipids in the form of triacylglycerols (TAG) and can be used to make biodiesel via a transesterification process. The ester bonds in the TAG are broken leaving behind two products: fatty acid methyl esters and glycerol that could provide an inexpensive carbon source to grow oleaginous yeast R. glutinis. Described here are the effects of different growth substrates on TAG accumulation and fatty acids produced by R. glutinis. Yeast cultured 24h on medium containing dextrose, xylose, glycerol, dextrose and xylose, xylose and glycerol, or dextrose and glycerol accumulated 16, 12, 25, 10, 21, and 34% TAG on a dry weight basis, respectively. Lipids were extracted from R. glutinis culture and transesterified to form fatty acid methyl esters. The results show a difference in the degree of saturation for the carbon sources tested. Cells cultivated on glycerol alone had the highest degree of unsaturated fatty acids at 53% while xylose had the lowest at 25%. R. glutinis can be cultivated on all sugars tested as single carbon substrates or in mixtures. Glycerol may be used as secondary or primary carbon substrate.

Expert-based drug lists to measure anticholinergic burden: similar names, different results

Due to the increasing demand for sustainable biofuels, microbial oils as feedstock for the transesterification into biodiesel have gained scientific and commercial interest. Also, microbial carotenoids have a considerable market potential as natural colorants. The carbon to nitrogen (C/N) ratio of the respective cultivation media is one of the most important parameters that influence the production of microbial lipids and carotenoids. Thus, in the present experiment, the influence of different C/N ratios, initial glucose loadings, and ammonium concentrations of the cultivation medium on microbial cell growth and lipid and carotenoid production by the oleaginous red yeast Rhodotorula glutinis has been assessed. As a general trend, both lipid and carotenoid production increased at high C/N ratios. It was shown that not only the final C/N ratio but also the respectively applied initial carbon and nitrogen contents influenced the observed parameters. The lipid yield was not affected by different ammonium contents, while the carotenoid production significantly decreased both at low and high levels of ammonium supply. A glucose-based increase from C/N 70 to 120 did not lead to an increased lipid production, while carotenoid synthesis was positively affected. Generally, it can be asserted that lipid and carotenoid synthesis are stimulated at higher C/N ratios.

Comparing the performance of various advanced oxidation processes for treatment of acetone contaminated water

Background:  Scoring scales such as the Anticholinergic Drug Scale (ADS), the Anticholinergic Risk Scale (ARS), and the Anticholinergic Cognitive Burden Scale (ACB) provide an estimation of total anticholinergic burden. Not all the lists include the same drugs, and the points given for certain drugs differ among them. Whether these discrepancies present important differences in the estimation of anticholinergic burden for an individual patient is unknown. Therefore, the aim of this study is to assess agreement among the three scales.

Extractive-transesterification of algal lipids under microwave irradiation with hexane as solvent

Removal of low levels of organic pollutants can be quite challenging to many water treatment processes. Ketones, such as acetone, are often found in groundwaters and wastewaters at levels too low for supporting a bioreactor, yet since acetone is so soluble, it does not adsorb onto activated carbon very well, nor does it volatilize from water influent using air stripping. This study was undertaken to evaluate three advanced oxidation processes for their comparative ability to remove acetone from aqueous media. Optimization of the oxidation processes was attempted via adjustments of oxidizer inputs. The results indicated that all of the AOPs tested showed promise for removing acetone from water; however, ozonated systems undergoing UV photolysis achieved the highest rate and extent of treatment observed.

Lipid storage compounds in raw activated sludge microorganisms for biofuels and oleochemicals production

This study describes the use of microwaves (MW) for enhanced extractive-transesterification of algal lipids from dry algal biomass (Chlorella sp.). Two different single-step extractive-transesterification methods under MW irradiation were evaluated: (1) with ethanol as solvent/reactant and sodium hydroxide catalyst; and (2) with ethanol as reactant and hexane as solvent (sodium hydroxide catalyst). Biodiesel (fatty-acid-ethyl-esters, FAEE) yields from these two methods were compared with the conventional Bligh and Dyer (BD) method which followed a two-step extraction-transesterification process. The maximum lipid yields for MW, MW with hexane and BD methods were 20.1%, 20.1%, and 13.9%, respectively; while the FAEE conversion of the algal lipids were 96.2%, 94.3%, and 78.1%, respectively. The algae-biomass:ethanol molar ratio of 1:250-500 and 2.0-2.5% catalyst with reaction times around 6min were determined as optimum conditions for both methods. This study confers that the single-step non-conventional methods can contribute to higher algal lipid and FAEE yields.

Environmentally Friendly Supply Chain Planning and Design for Biodiesel Production via Wastewater Sludge

Activated sludge contains a microbial population responsible for the biological treatment of wastewater. This microbial population mostly consists of heterothrophic bacteria which utilize the organic content of the wastewater for growth, either as part of their cellular structures or as energy and carbon storage compounds. These compounds are mostly lipidic in nature and are or could be important raw materials for a multitude of applications in biofuel and oleochemical industries. In this study, a municipal activated sludge was analyzed for lipid storage compounds and other compound classes present in significant concentrations. Three extraction techniques, namely; Bligh & Dyer (applied on dried and partially dewatered samples) and accelerated solvent extractions, were initially investigated to identify the one resulting in the highest gravimetric and biodiesel yields. The highest yields were obtained using the Bligh & Dyer of partially dewatered sludge samples and thus, the extracts from this extraction technique were subjected to a series of analytical procedures such as precipitation, solid phase extraction, thin layer chromatography (TLC), gas chromatography with flame ionization detector (GC-FID) and gas chromatography-mass spectrometry (GC-MS) to characterize the major compound classes present. Results indicated that the major compounds in the samples were polyhydroxyalkanoates, wax esters, steryl esters, triacylglycerides, free fatty acids, free sterols and phospholipids. Hydrocarbons, diacylglycerides and monoacylglycerides were also detected. These compounds are either synthesized by microorganisms or from exogenous contributions. Regardless of the source of these compounds, their persistent presence in activated sludge offers another feedstock for a wide range of applications.

Single-step treatment of 2,4-dinitrotoluene via zero-valent metal reduction and chemical oxidation

This study presents mathematical models that capture the impact of different carbon-emission-related policies on the design of the biodiesel supply chain. These mathematical models identify locations and production capacities for biocrude production plants by exploring the trade-offs that exist between transportation costs, facility investments costs, and emissions. The mathematical models capture the dynamics of biomass supply and transportation costs during a predefined time horizon. We analyze the behavior of the chain under different regulatory policies such as carbon cap, carbon tax, carbon cap and trade, and carbon offset mechanisms. A number of observations are made about the impact of each policy on the supply chain performance. The models we developed are solved by using a commercial software GAMS/CPLEX. We use the state of Mississippi as the testing grounds for these models, and employ ArcGIS to visualize and validate the results from the optimization models.

Biocrude production by activated sludge microbial cultures using pulp and paper wastewaters as fermentation substrate

Many nitroaromatic compounds (NACs) are considered toxic and potential carcinogens. The purpose of this study was to develop an integrated reductive/oxidative process for treating NACs contaminated waters. The process consists of the combination of zero-valent iron and an ozonation based treatment technique. Corrosion promoters are added to the contaminated water to minimize passivation of the metallic species. Water contaminated with 2,4-dinitrotoluene (DNT) was treated with the integrated process using a recirculated batch reactor. It was demonstrated that addition of corrosion promoters to the contaminated water enhances the reduction of 2,4-DNT with zero-valent iron. The addition of corrosion promoters resulted in 62% decrease in 2,4-DNT concentration to 2,4-diaminotoluene. The data shows that iron reduced the 2,4-DNT and ozone oxidized these products resulting in a 73% removal of TOC and a 96% decrease in 2,4-DNT concentration.