1. Introduction and Overview. 2. Detecting Influential Observations and Outliers. 3. Detecting and Assessing Collinearity. 4. Applications and Remedies. 5. Research Issues and Directions for Extensions. Bibliography. Author Index. Subject Index.

Regression Diagnostics: Identifying Influential Data and Sources of Collinearity

Lignocelluloses are often a major or sometimes the sole components of different waste streams from various industries, forestry, agriculture and municipalities. Hydrolysis of these materials is the first step for either digestion to biogas (methane) or fermentation to ethanol. However, enzymatic hydrolysis of lignocelluloses with no pretreatment is usually not so effective because of high stability of the materials to enzymatic or bacterial attacks. The present work is dedicated to reviewing the methods that have been studied for pretreatment of lignocellulosic wastes for conversion to ethanol or biogas. Effective parameters in pretreatment of lignocelluloses, such as crystallinity, accessible surface area, and protection by lignin and hemicellulose are described first. Then, several pretreatment methods are discussed and their effects on improvement in ethanol and/or biogas production are described. They include milling, irradiation, microwave, steam explosion, ammonia fiber explosion (AFEX), supercritical CO2 and its explosion, alkaline hydrolysis, liquid hot-water pretreatment, organosolv processes, wet oxidation, ozonolysis, dilute- and concentrated-acid hydrolyses, and biological pretreatments.

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Pretreatment of lignocellulosic wastes to improve ethanol and biogas production: a review.

Trends in bioconversion of lignocellulose: Biofuels, platform chemicals & biorefinery concept

Although of limited metabolic diversity, methanogenic archaea or methanogens possess great phylogenetic and ecological diversity. Only three types of methanogenic pathways are known: CO(2)-reduction, methyl-group reduction, and the aceticlastic reaction. Cultured methanogens are grouped into five orders based upon their phylogeny and phenotypic properties. In addition, uncultured methanogens that may represent new orders are present in many environments. The ecology of methanogens highlights their complex interactions with other anaerobes and the physical and chemical factors controlling their function.

Metabolic, phylogenetic, and ecological diversity of the methanogenic archaea.

Advances in enhanced biological phosphorus removal: from micro to macro scale.

Methanosarcina species with a high maximum specific growth rate (mumax) and high half-saturation coefficient (KS) and Methanosaeta species with a low mumax and low KS are the only known aceticlastic methanogens. Because of Methanosaeta's low KS, the low acetate concentrations in conventional, mesophilic anaerobic digestion yield Methanosaeta dominance. However, Methanosarcina absorbs increases in acetate more efficiently and thus promotes more stable digestion. This paper tests the hypothesis that decreasing digester feeding frequencies can increase Methanosarcina predominance. Two acetate-fed reactors were established at a 17-day solids retention time. One reactor was fed hourly, and one was fed once daily. Microscopic and molecular methods were used to verify that the hourly fed reactor enriched for Methanosaeta, while the daily fed reactor enriched for Methanosarcina. Growth and substrate-use kinetics were measured for each reactor. A digester overload condition was simulated, and the Methanosarcina-enriched reactor was found to perform better than the Methanosaeta-enriched reactor. These findings indicate that Methanosarcina dominance can be achieved with infrequent feedings, leading to more stable digestion.

https://www.jstor.org/stable/info/25053536

Growth kinetics and competition between Methanosarcina and Methanosaeta in mesophilic anaerobic digestion.

A methanogenic fluidized bed reactor (FBR) fed with lactate and tetrachloroethene (PCE) was operated for 14 months to study the effect of electron donor and PCE loading on chloroethene dechlorination rates. Lactate was fed continu ously at 200 mg/L (2.2 mmol/L), and the influent PCE feed concentration was increased stepwise from 3.5 to 160 μmol/L. Vinyl chloride (VC) and ethene accounted for 80% and 20%, respectively, of the PCE dechlorination. Batch tests with various electron donors showed that H2, propionate, and lactate supported dechlorination of PCE, trichloroethene (TCE), cis-dichloroethene (c-DCE), and VC, whereas no dechlorination was observed with acetate or in the absence of an electron donor. Different short-term steady H2 concentrations were obtained by adjusting the FBR influent lactate feed concentration, and the effect of H2 concentra tion on the rate of chloroethene dechlorination was determined. Dechlorination rates for PCE, TCE, c-DCE, and VC showed a Michaelis−Menten relationship with ...

Effect of Hydrogen on Reductive Dechlorination of Chlorinated Ethenes

Impacts of trace concentrations of estrogens on aquatic ecosystems are a serious environmental concern, with their primary source being wastewater treatment facility effluents. Increased removal of 17α-ethinylestradiol (EE2) has been reported for activated sludge treatment with long enough solids retention time for nitrification. Previous work based on batch tests with Nitrosomonas europaea and nitrifying activated sludge at high EE2 concentrations (>300 000 ng/L) and high NH4—N concentrations (>200 mg/L) has led to the hypothesis that ammonia oxidizing bacteria cometabolically degrade EE2. This work investigated EE2 transformation with N. europaea and Nitrosospira multiformis at environmentally relevant EE2 concentrations and LC-MS-MS to observe transformation products. Degradation of EE2 was not observed in batch tests with no NH4—N addition or with 10 mg/L NH4—N fed daily. At increased NH4−N concentrations (200−500 mg/L) EE2 transformation was observed, but the only detected products were nitrated EE2....

17α-ethinylestradiol Transformation via Abiotic Nitration in the Presence of Ammonia Oxidizing Bacteria

Microbial community adaptation influences long-chain fatty acid conversion during anaerobic codigestion of fats, oils, and grease with municipal sludge.

H. David Stensel

Papers

Growth kinetics and competition between Methanosarcina and Methanosaeta in mesophilic anaerobic digestion.

Effect of Hydrogen on Reductive Dechlorination of Chlorinated Ethenes

17α-ethinylestradiol Transformation via Abiotic Nitration in the Presence of Ammonia Oxidizing Bacteria

Microbial community adaptation influences long-chain fatty acid conversion during anaerobic codigestion of fats, oils, and grease with municipal sludge.

Biodegradation of polyaromatic hydrocarbons by marine bacteria: effect of solid phase on degradation kinetics