In Situ Aerobic Bioremediation of Sediments Polluted with Petroleum Hydrocarbons: A Critical Review

Oil pollution has been a worldwide concern especially in environments where treatment is quite difficult to apply. Marine polluted sediments, in particular, constitute one of the most recalcitrant environments for bioremediation and are often the final repository of petroleum contaminants, as a result of runoff and deposition. Aerobic hydrocarbon degraders present in the sediments are tackling the pollution under oxygen-limited or oxygen-depleted conditions. Research has focused on new ways to enhance bioremediation under anoxic conditions, however aerobic bioremediation is faster, and hence more effort should be made to sustain oxygen concentration levels. In this review, the different bioremediation techniques used for the decontamination of marine sediments are briefly discussed, and focus is primarily given to the different oxygenation methods used for enhancing aerobic bioremediation and the aeration methods that are suitable for in situ application, as well as state of the art technologies that make in situ aeration an appealing approach. Based on the technologies analyzed, suggestions are made for sediment bioremediation techniques in different marine environments.

Large-scale Application of Klozur® CR for the Treatment of an Aquifer Contaminated with Heavy Hydrocarbons and MTBE in Southern Italy

Klozur® CR is a combined remedy treatment technology consisting of Klozur® SP and PermeOx® Ultra. Klozur CR is a single, all-in-one formulated product that can be readily applied to either source areas or plumes with mixed petroleum and chlorinated solvents contamination. Klozur CR destroys contaminants in soil and groundwater by promoting three modes of action: Klozur activated persulfate chemical oxidation, aerobic bioremediation and anaerobic bioremediation. This technology was successfully applied to a site in southern Italy, contaminated by the storage and sale of fuels. The groundwater was contaminated by heavy chain hydrocarbons (TPH> 2500 μg / l) and MTBE (> 150 μg / l) in proximity to the reservoir park. During the site maintenance activities, the qualitative status of adjacent coastal waters was also verified, which, however, were found to be compliant. Previously the site used a pump and treat system, but it was unable to achieve remedial goals. Klozur CR was injected and within 4 months, the concentrations of the contaminants were found to have reached the remedial goals. In addition, monitoring data also confirmed enhanced ISCO conditions and enhanced aerobic bioremediation were present at the site.

Laboratory tests for aerobic bioremediation of the contaminated sites in the Czech Republic

Laboratory-scale testing methods applicable to evaluation of contaminated subsurface microbial communities are discussed in relation to their potential in supporting effective site bioremediation. Both culture-dependent and culture-independent techniques are considered here with special emphasis on their capacity to contribute to bioremediation system design, in optimal cases by providing information on contaminant degradation rates. In this regard, microbial soil respiration tests seem to be the most useful tool since microbial soil respiration is a sensitive and easily measurable parameter for determination of metabolic activity within the sample and is closely related to other microbial parameters such as microbial biomass.

Kinetics and Optimization by Response Surface Methodology of Aerobic Bioremediation. Geoelectrical Parameter Monitoring

This study aimed to investigate the kinetics of an aerobic bioremediation process of diesel oil removal by indigenous microorganisms, and to define the optimal operative conditions by means of response surface methodology. This was carried out by setting up a series of microcosms (200 g of soil), polluted with the same diesel oil concentration (70 g·kg−1 of soil), but with different water contents (u%) and carbon to nitrogen (C/N) ratios. The process was monitored by: (1) residual diesel oil concentration, to measure the removal efficiency, and (2) fluorescein production, to check the microbial activity. These two parameters were the objective variables used for the analysis of variance (ANOVA) and response surface methodology (RSM). The results allowed the interactions between u% and C/N to be defined and the optimal range to be adopted for each. The process kinetics was modeled with first- and second-order reaction rates; slightly better results were achieved for the second-order model in terms of parameter variability. Biological processes like degradation may have effects on dielectric properties of soil; an open-ended coaxial cable was used to measure the dielectric permittivity of microcosm matrices at the start and after 130 days of bioremediation. The evolution of the real and the imaginary components of dielectric permittivity provided results that supported the evidence of a biodegradation process in progress.

Sustainable remediation of antibacterials, metals and DNA

The global antibacterial crisis requires urgent attention from environmental engineering and bioengineering. Here, unit operation efficiencies are assessed, in a novel water treatment train capable of remediating antibacterials, metals and DNA. This technological cycle relies on bioremediation, high temperature and pressure. The analyses used 14C-respirometry, spectrometry, and a set of molecular analyses. Multiresistant bacteria hold antibacterial resistance genes (ARGs); they were harnessed for bioremediation of pollutant mixtures. Treatment efficiencies were 25-71% for 8-days aerobic metal reduction and removal (CrVI: 255, Cd: 0.65, and Pb: 0.65 mg L-1 initial concentrations); 34.8% erythromycin (ERY) 20-days biodegradation (from 750 mg L-1). The anaerobic digestion (AD) bioremediated mixed antibacterials (65-73% in 60 days from initial 100 mg L-1). However, high concentrations of mixed antibacterials (SMX+ERY) induced stronger inhibition of enzymatic activity, higher sensitivity of bacteria and acetoclastic methanogens, and higher diversity of ARGs. ARGs justified complete DNA degradation (60°C at 5.8 kPa for 10 min). The suggested coupling sequence of operations was metal then antibacterial aerobic bioremediation (as pre-treatments to anaerobic digestion), anaerobic bioremediation (also yielding biomethane as heat source), recirculation of ARGs in situ, and thermal-barometric DNA degradation.