Enhanced degradation of hydrocarbons in constructed wetlands aided with nutrients, surfactant, and aeration.

The use of constructed wetlands (CWs) is a promising approach for the remediation of hydrocarbon-polluted wastewater. The amendments of CWs with nutrients, surfactants, and aeration enhances the removal of pollutants from wastewater. The objective of the present study was to explore the effect of external stimulants, i.e., nutrients, surfactant, and aeration on hydrocarbons degradation potential of CWs. The CWs mesocosms were developed by the vegetation of Phragmites australis and amendments with nutrients (20 mg l-1 N, 2.6 mg l-1 P, and 16.4 mg l-1 K), surfactant Tween 20 (0.2%, v/v), and aeration (7 mg l-1) for the remediation of diesel-spiked water (2%, w/v). The comparative analysis showed that the addition of nutrients, surfactant, and aeration individually enhanced total petroleum hydrocarbons (TPHs) reduction, and maximum TPHs reduction (88.4%) was achieved after 60 days in the mesocosms amended with the combination of nutrients, surfactant, and aeration. Among different individual treatments, the aeration (alone) also played a pivotal role in TPHs reduction (61%). The least (12%) reduction in TPHs was achieved in the mesocosms supplied with surfactant only. This study revealed that the combined application of nutrients, surfactant, and aeration in CWs enhanced its hydrocarbons degradation performance.

The biodegradability of crude oil-polluted wastewater is not efficient. It is mainly due to the low bioavailability of hydrocarbons, and less amount of nutrients and dissolved oxygen in the wastewater. This study explores the importance of the amendments of nutrients, surfactant, and aeration on the enhanced performance of constructed wetlands (CWs) for the remediation of hydrocarbon-contaminated water. The application of nutrients, surfactant, and aeration in CWs not only enhanced hydrocarbon degradation and toxicity reduction but also improved plant growth.

Characterization of Hydrocarbon-Degrading Bacteria in Constructed Wetland Microcosms Used to Treat Crude Oil Polluted Water.

Ten plant species were grown in constructed wetlands (CWs) to remediate water containing 2% (w/v) crude oil. The plant species with better growth and biomass production were Typha latifolia and Cyperus laevigatus, and they were significantly correlated (R2 = 0.91) with hydrocarbon degradation. From T. latifolia and C. laevigatus, 33 hydrocarbon-degrading bacterial strains were isolated from the rhizosphere, and root and shoot interiors. More diversified bacteria were found in the rhizosphere and endosphere of C. laevigatus than those of T. latifolia. The predominant cultural hydrocarbon-degrading bacteria were shown to belong to the genera Pseudomonas, Acinetobacter and Bacillus. In addition to genes involved in hydrocarbon degradation, most of the bacteria displayed multiple plant growth promoting (PGP) activities. This study suggests the importance of selecting suitable bacterial strains with hydrocarbon degradation and PGP activities for improving the efficacy of CWs used in remediating water contaminated with crude oil.

In vitro toxicological assessment of iron oxide, aluminium oxide and copper nanoparticles in prokaryotic and eukaryotic cell types.

Metallic nanoparticles (NPs) have a variety of applications in different industries including pharmaceutical industry where these NPs are used mainly for image analysis and drug delivery. The increasing interest in nanotechnology is largely associated with undefined risks to the human health and to the environment. Therefore, in the present study cytotoxic and genotoxic effects of iron oxide, aluminium oxide and copper nanoparticles were evaluated using most commonly used assays i.e. Ames assay, in vitro cytotoxicity assay, micronucleus assay and comet assay. Cytotoxicity to bacterial cells was assessed in terms of colony forming units by using Escherichia coli (gram negative) and Bacillus subtilis (gram positive). Ames assay was carried out using two bacterial strains of Salmonella typhimurium TA98 and TA100. Genotoxicity of these NPs was evaluated following exposure to monkey kidney cell line, CHS-20. No cytotoxic and genotoxic effects were observed for iron oxide, and aluminium oxide NPs. Copper NPs were found mutagenic in TA98 and in TA100 and also found cytotoxic in dose dependent manner. Copper NPs induced significant (p < 0.01) increase in number of binucleated cells with micronuclei (96.6 ± 5.40) at the highest concentration (25 µg/mL). Copper NPs also induced DNA strand breaks at 10 µg/mL and oxidative DNA damage at 5 and 10 µg/mL. We consider these findings very useful in evaluating the genotoxic potential of NPs especially because of their increasing applications in human health and environment with limited knowledge of their toxicity and genotoxicity.