Fate and effect of naphthenic acids in biological systems

Naphthenic acids (NAs) are carboxylic acids found in crude oil and petroleum products. The objectives of the research presented here were to: a) assess the occurrence and fate of NAs in crude oil and refinery wastewater streams; b) evaluate the biotransformation potential and inhibitory effects of NAs under nitrifying, denitrifying and methanogenic/fermentative conditions; c) investigate the factors affecting NA biotransformation under aerobic conditions and the microbes involved; and d) assess the toxicity of individual model NAs using quantitative structure-activity relationships (QSAR) and examine the effect of structure on NA biotransformation potential. NAs are ubiquitous in refinery wastewater streams and the desalter brine was found to be the main source of NAs in refinery wastewater. A commercial NA mixture was not biodegraded under nitrate-reducing or methanogenic/fermentative conditions. NAs were degraded under aerobic conditions by an NA-enriched culture; however, a residual fraction was not degraded under all conditions studied. The results indicated that NAs are not inherently recalcitrant and the residual fraction was due to the individual NA concentrations being below the minimum substrate concentrations at which they are no longer degraded. A fraction of the NA mixture was completely mineralized to carbon dioxide, with the remaining portion biotransformed to more oxidized intermediates. Overall, the results indicated that NAs were degraded under aerobic conditions; however, biological treatment of NA-bearing wastewater will not completely remove NA concentrations and thus, biological treatment must be combined with physical/chemical treatment to achieve complete NA removal.PhDCommittee Chair: Spyros G. Pavlostathis; Committee Member: Ching-Hua Huang; Committee Member: Jim Spain; Committee Member: Sotira Yiacoumi; Committee Member: Sujit Banerje

Bollettino Sismico Italiano gennaio – aprile 2018

Nel primo quadrimestre 2018 si sono verificati in Italia cinque eventi di magnitudo superiore o uguale a 4.0, di cui nessuno di magnitudo superiore a 5.0. Due di essi, avvenuti il 4 (MW 4.0) e il 10 aprile (MW 4.6), hanno interessato la zona della sequenza dell’Italia centrale, in provincia di Macerata. Un terremoto di magnitudo MW 4.3 è avvenuto in provincia di Campobasso, il 25 aprile, ad una profondità di 29 km. Infine due terremoti profondi, avvenuti il 12 febbraio (ML 4.4, con profondità di 379 km) e il 7 marzo (ML 4.0, con profondità di 294 km), hanno interessato il Tirreno Meridionale, al largo della costa calabra.Istituto Nazionale di Geofisica e Vulcanologia - Dipartimento di Protezione CivilePublished4IT. Banche dat

Bollettino Sismico Italiano settembre – dicembre 2018

Gli analisti del BSI hanno revisionato tutti gli eventi di magnitudo M≥1.5, localizzati dal 1 settembre al 31 dicembre 2018. I parametri dei terremoti di magnitudo inferiore a tale soglia di revisione, sono quelli calcolati in tempo reale, nella sala di sorveglianza sismica di Roma.Istituto Nazionale di Geofisica e Vulcanologia - Dipartimento di Protezione CivilePublished4IT. Banche dat

Groundwater nitrate reduction in a simulated free water surface wetland system

Wetland-based treatment systems are often implemented as a method to remove unwanted substances from contaminated groundwater. Wetlands are effective due to the high biological activity that naturally takes place in the rhizosphere and soil. In support of a demonstration surface wetland system at a site in Columbus, Georgia, laboratory-scale wetland systems were designed to study the effect of different carbon sources and their biodegradability, COD:N ratio and temperature on the rate and extent of nitrate reduction of nitrate-bearing groundwater. Nitrate reducing bacteria are ubiquitous in surface and subsurface wetlands but a major limiting factor for these systems is carbon availability. Two major carbon sources were investigated in both continuous-flow and batch systems: a natural source, hay and a commercial source, MicroC GTM, a concentrated carbohydrate mix. Between these two carbon sources, the nitrate removal rate was not significantly different as long as sufficient biodegradable carbon was provided. The effect of both hydraulic retention time (HRT) and COD:N ratio on nitrate removal were investigated in continuous-flow systems. The specific nitrate removal rate in open to the atmosphere batch reactors was estimated at 0.55 mg N/mg biomass VSS-day. The effluent nitrate concentration in a continuous-flow system maintained with an HRT of 5 days at room temperature (22 to 23°C) was less than 3 mg nitrate-N/L. The COD:N ratio was kept at 6:1 for the majority of the experiments (approximately twice the theoretical requirement) to ensure sufficient carbon loading. Lower COD:N ratios of 5, 4, 3, 2, 1, and 0.5 were also investigated in the continuous-flow system and the minimum required carbon loading to achieve an effluent nitrate concentration below 10 mg N/L for an influent groundwater nitrate concentration between 65 and 70 mg N/L was determined to be 5:1 COD:N. The effect of temperature on the nitrate removal rate was also investigated at 22, 15, 10 and 5°C. As expected, the rate of nitrate reduction decreased with the decrease in temperature, especially below 10°C. Overall, the surface wetland is a feasible solution to treating nitrate-bearing groundwater even at relatively low ambient temperature values, provided that sufficient, biodegradable carbon is present.M.S.Committee Member: Pavlostathis, Spyros; Committee Member: Spain, Jim; Committee Member: Tezel, Ula

Fate and effect of naphthenic acids on the biological wastewater treatment processes in oil refineries

Issued as final reportConocoPhillips (Firm

Effect of Alkyl Side Chain Location and Cyclicity on the Aerobic Biotransformation of Naphthenic Acids

Aerobic biodegradation of naphthenic acids is of importance to the oil industry for the long-term management and environmental impact of process water and wastewater. The effect of structure, particularly the location of the alkyl side chain as well as cyclicity, on the aerobic biotransformation of 10 model naphthenic acids (NAs) was investigated. Using an aerobic, mixed culture, enriched with a commercial NA mixture (NA sodium salt; TCI Chemicals), batch biotransformation assays were conducted with individual model NAs, including eight 8-carbon isomers. It was shown that NAs with a quaternary carbon at the α- or β-position or a tertiary carbon at the β- and/or β′-position are recalcitrant or have limited biodegradability. In addition, branched NAs exhibited lag periods and lower degradation rates than nonbranched or simple cyclic NAs. Two NA isomers used in a closed bottle, aerobic biodegradation assay were mineralized, while 21 and 35% of the parent compound carbon was incorporated into the biomass. The NA biodegradation probability estimated by two widely used models (BIOWIN 2 and 6) and a recently developed model (OCHEM) was compared to the biodegradability of the 10 model NAs tested in this study as well as other related NAs. The biodegradation probability estimated by the OCHEM model agreed best with the experimental data and was best correlated with the measured NA biodegradation rate