Investigation of carbon steel corrosion by oilfield nitrate- and sulfate-reducing prokaryotes consortia in a hypersaline environment.

Microbiologically influenced corrosion (MIC) behavior of the AISI 1020 carbon steel caused by consortia of nitrate-reducing prokaryotes (NRP) and sulfate-reducing prokaryotes (SRP) was investigated separately in hypersaline seawater conditions. Microbiological analysis, surface images, characterization of corrosion products, weight loss, and electrochemical measurements were employed to monitor the corrosion process for 10 days at 40 °C. Compared to abiotic corrosion (control), the extent of corrosion was more aggravated in the conditions with microbial consortia. It corroborates the critical role of microbial activity in corrosion processes in natural and industrial environments since microorganisms are widely spread. Corrosion rates obtained from Tafel extrapolation were statically equal for both microbial consortia (0.093 ± 0.009 mm.y-1); however, the maximum pit depth on the steel surface subjected to NRP-MIC was about 25% deeper (48.5 µm) than that caused by SRP-MIC (32.6 µm). In contrast, SRP activity almost doubled the number of pits on the steel surface (2.7 × 104 ± 4.1 × 103 pits.m-2), resulting in more weight loss than NRP activity. In addition, SRP cells formed nanowires to support direct electron uptake from steel oxidation. This research contributes to the understanding of steel corrosion mechanisms in hypersaline environments with the prevalence of NRP or SRP, as oil reservoirs undergo nitrate injection treatments.

Simultaneous removal of organic matter and nitrogen compounds from landfill leachate by aerobic granular sludge.

This study aimed at investigating the treatment of landfill leachate using the aerobic granular sludge process in a lab-scale sequential batch reactor (SBR-AGS). The leachate from a giant sanitary landfill localized in the State of São Paulo (Brazil) exhibited high concentration of organic matter (COD 5,300 ± 78 mg L-1) and total nitrogen (TKN 2,630 ± 355 mg L-1). Comparatively, the leachate was added to wastewater in three different volumetric ratios (5, 10 and 20%) and the mixtures were characterized over treatment. The results indicated that there were no significant changes in the behaviour of the biological process even at the highest leachate ratio. The granulation of the aerobic sludge occurred after 90 days of operation and the granules had a diameter of 485-1585 µm. SBR-AGS exhibited removal efficiency of 87-89% for organic matter and at least 98% for total nitrogen, regardless of the leachate ratio. The treated effluent that received 20% of leachate showed 2.7 mg L-1 ammonia and 1.1 mg L-1 nitrate. This study shows that SBR-AGS was able to form large granules, thus promoting a simultaneous nitrification and denitrification (SND) process. We highlighted that SND occurred in low dissolved oxygen concentrations (< 1.5 mg L-1) for 120 days, without compromising aerobic granule integrity. These results suggest that the aerobic granular sludge process is a promising alternative for the co-treatment of landfill leachate and domestic wastewater under tropical climate conditions and its use should be encouraged.

Generation, characterization and reuse of solid wastes from a biodiesel production plant.

The aim of this study was to identify and characterize industrial solid wastes generated by a biodiesel production plant in Brazil, as well as to present strategies for the management of these materials. This plant produces every year around 100,000tons of biodiesel from vegetable oils and animal fats. The methodology of the study included technical visits, interviews with the operational and environmental management staff as well as analysis of documents, reports and computerized data systems. An approach to reduce the generation of hazardous waste was investigated. It was take into account the amount of raw material that was processed, reduction of landfill disposal, and the maximization of the their recycling and reuse. The study also identified the sources of waste generation and accordingly prepared an evaluation matrix to determine the types of waste with the higher potential for minimization. The most important residue of the process was the filter material impregnated with oil and biodiesel, requiring, therefore, measures for its minimization. The use of these residues in the production of ceramic artefacts (light bricks) was considered to be very promising, since no significant effect on the physico-chemical and mechanical properties of the artefacts produced was observed. Phytotoxicity test using seeds of Lactuva sativa (lettuce), Brassica juncea (mustard), Abelmoschus esculentus (okra), Chrysanthemum leucanthemum (daisy), Dendranthema grandiflorum (chrysanthemum) and Allium porrum (leek) were carried out. The results clearly show incorporation of the waste material into bricks did not influence relative germination and relative root elongation in comparison to control tests.