• Energy Research

10.1016/j.renene.2014.10.019 Isochrysis galbana and Selenastrum capricornutum, marine and freshwater microalgae species respectively,were co-digested with sewage sludge under mesophilic and thermophilic conditions. The substrates and the temperatures significantly influenced biogas production. Under mesophilic conditions, the sewage sludge digestion produced 451 ± 12 mLBiogas/gSV. Furthermore, all digesters were fed with I. galbana, or mixed with sludge, resulting in an average of 440 ± 25 mLBiogas/gSV. On the contrary, S. capricornutum produced 271 ± 6 mLBiogas/gSV and in the mixtures containing sludge produced intermediate values between sludge and microalgae production. Under thermophilic conditions, the sewage sludge digestion achieved yet the highest biogas yield, 566 ± 5 mLBiogas/gSV. During co-digestion, biogas production decreased when the microalgae content increased, and for I. galbana and for S. capricornutum it reached minimum values, 261 ± 11 and 185 ± 7 mLBiogas/gSV, respectively. However, no evidence of inhibition was found and the low yields were attributed to microalgae species characteristics. The methane content in biogas showed similar values, independently from the digested substrate, although this increased by approximately 5% under thermophilic condition.

Advance oxidation process was employed as a pretreatment of industrial wastewater. For this purpose, the use of heavy metals as a catalyst is necessary but also complicated because homogeneous catalysts are difficult to recover after reaction process. The heterogenization of Cu(II) ions was proposed by taking advantage of the adsorptive characteristics of polymeric matrices. Crosslinked poly(4‐vinylpyridine) of 2 and 25% and poly(D‐glucosamine) were tested as supports of copper. Adsorption was employed to heterogenize Cu(II) by considering the influences of pH and temperature on the process. The catalysts were evaluated by their metal content, catalytic behavior for the oxidation of phenol and leaching degree after reaction. Poly(4‐vinylpyridine) 2% was the best material for Cu(II) immobilization with an adsorption capacity of 90 mg g−1. Afterward, poly(4‐vinylpyridine) 2%, Cu(II) achieved 64% of phenol conversion, which represents a favorable result for the oxidation of phenol as the model of industrial wastewater pretreatments. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 269‐278, 2013

Production of biodiesel from sewage sludge lipids was catalysed by six different Brønsted acidic imida-zolium and long chain ammonium ionic liquids; both with an alkane sulfonic acid group and with differentanions. Among the ionic liquid tested, 4-(3-methylimidazolium) butanesulfonic acid trifluoromethane-sulfonate, [mimC4SO3H][SO3CF3], was selected as the best catalyst due to its high catalytic performanceand purer biodiesel obtained than the equivalent ammonium ionic liquid, 4-(trihexylammonium) butane-sulfonic acid trifluoromethanesulfonate, [N666(C4SO3H)][SO3CF3]. The influence of different reactionvariables on the biodiesel yield was studied using [mimC4SO3H][SO3CF3] as a catalyst. The yield of fattyacid methyl esters (biodiesel) reached 90% (based on saponifiable lipids) under the following optimisedconditions: 10:1 molar ratio of methanol to saponifiable lipids, 7 wt% ionic liquid catalyst (wt%, based onlipids), 100◦C and 5 h. In addition, the ionic liquid has a good reusability and can be easily separated fromthe biodiesel. These acidic ionic liquids were found to be efficient catalysts for the synthesis of biodieselfrom low-cost and non-edible feedstock like sewage sludge lipids. doi: 10.1016/j.apcatb.2015.08.039

Municipal sludge from wastewater treatment plants is a promising lipid feedstock for biodiesel production as it contains a significant amount of lipids. However, the energy necessary to remove its high water content is a major inconvenience for scaling up because of the high associated cost. In addition, the expensive conventional sludge drying methods are not effective enough for lipid recovery, thus reducing the potential biodiesel production. This study explores an alternative method, the direct sequential liquid-liquid extraction, which was performed in a batch mixer-settler reactor at room temperature, using hexane as a solvent, after previous sludge acidification showed significant increase in the lipid efficiency. The optimisation study demonstrated that, after three stages, 91% of lipid from primary sludge was recovered. The optimised extraction gave slightly higher lipid (27%, dry sludge) than the standard method (25%, dry sludge), supporting the suitability of the proposed process. Finally, this work demonstrates that the residual lipid-extracted sludge is still a good feedstock for energy production via anaerobic digestion. Anyway, the economic and environmental aspects of biodiesel production from sewage sludge could be improved. (C) 2014 Elsevier B.V. All rights reserved. Peer Reviewed

Biodiesel expansion is currently limited due to high raw material costs for its production. The potential of using sludge from municipal wastewater treatment plants as an alternative lipid feedstock for biodiesel production was investigated. Experiments were conducted to evaluate the suitability of four different types of wastewater sludges for biodiesel production. Lipids were extracted from primary, secondary, blended and stabilized sludge in a Soxhlet extractor, using hexane as a solvent. Finally, the lipids were converted by acid catalysis transesterification into their corresponding fatty acid methyl esters (FAMEs) - biodiesel. Results indicated that among four sludge tested, primary sludge achieved the greatest lipids and biodiesel yields. The amount of extracted lipids for primary sludge was 25.3% compared to 21.9%, 10.1% and 9.1% (dry wt) for blended, stabilized and secondary sludge, respectively. The FAMEs yields obtained in this study were 13.9%, 10.9%, 2.9% and 1% (dry wt) for primary, blended, secondary and stabilized sludge, respectively. The estimation of annual biodiesel production based on the sludge generated in WWTP of Reus was evaluated, showing that primary sludge consists of 87% of the total biodiesel among the wastewater sludges. Gas chromatography analysis of the FAMEs revealed a similar fatty acids composition for all sludge tested with a predominance of palmitic acid, stearic acid, oleic acid and linoleic acid. Comparison of sludge fatty acid profile with common biodiesel feedstocks showed their suitability for the production of biodiesel. http://dx.doi.org/10.1016/j.proeng.2012.07.456

Biodiesel production is currently limited due to high raw material costs. The potential of using sludge from municipal wastewater treatment plants as an alternative lipid feedstock was investigated. Four different types of sludge (primary, secondary, blended and stabilised) were tested in lipid extraction by Soxhlet using hexane, and biodiesel production by acid catalysis. To improve the extraction efficiency, the influence of pre-treatment methods (ultrasonic and mechanical disintegration) and duration of these treatments were investigated. Finally, the effect of sludge acidification with concentrated HCl was also evaluated. The pre-treatment methods did not increase significantly the amount of extracted lipid as well as biodiesel yield. Previous sludge acidification showed lower yield of lipids from primary, secondary and blended sludge. However, the amount of saponifiable lipids was higher, giving the overall biodiesel yield almost unchanged. Among the four sludges tested, primary sludge achieved the greatest lipid and biodiesel yields, 27% and 19% respectively, on the basis of dry sludge. The highest biodiesel yields obtained from blended, secondary and stabilised sludge amounted to 15%, 4% and 2% respectively, on the basis of dry sludge. No significant influence of the pre-treatments and acidification on the fatty acid composition was found. At least 8 fatty acids were determined, with a predominance of palmitic (C16:0), stearic (C18:0) and oleic acid (C18:1). The comparison of sludge fatty acids profile with common biodiesel feedstocks showed suitability of WWTP sludge for production of biodiesel. Peer Reviewed