International Journal of Environmental Science and Technology

The salinization process in agricultural soils is extensive and has a negative impact on ecosystems and economic activities. The effects and causes of salinity are multifactorial, which must be evaluated to value and propose alternatives for sustained and environmentally friendly recovery. This paper seeks to integrate updated and reliable information on biological research and evaluation methods where organisms are used to mobilize, metabolize or compartmentalize salts through bioremediation processes, for situations where anthropogenic activities contribute to accelerate the salinization processes in soils. It is emphasized in biological models where there are associations of plant growth-promoting rhizobacteria with halotolerant plants. Also, plant physiology is explained during the saline stress period; mobility, physical and chemical properties of ions related to salinity. Projections of oxidation mechanisms and genetic expression as resistance strategies in cells of halotolerant plants are addressed. The biochemical, phylogenetic relationship of molecular analyzes in associations between microorganisms of different genera with vegetative species is exposed. In addition, the application of biotechnological tools as a rapid and specific identification strategy. Finally, it is pointed out how statistical models are accompanied by biological bioremediation models to relate and select the response variables that explain and verify the results in a reliable way. Therefore, it is shown that bioremediation of saline soils can be achieved through synergy processes between the rhizosphere and the diversification of the native microbiota.

The gliding arc discharge, which is a source of nonthermal plasma, was used to enhance the biodegradation of crystal violet (CV), a triphenylmethane non-biodegradable organic dye. The determination of the biodegradability index, i.e., biochemical oxygen demand (BOD5)/chemical oxygen demand (COD) ratio, and the total organic carbon measurement were used to assess the biodegradability. For the biological treatment alone, a bacterial strain of Aeromonas hydrophila (8 × 108 CFU mL−1) bleached 42 % of CV solution (50 mg L−1) after 12-h incubation. The bleaching rate was enhanced by increasing the initial bacterial concentration; however, a drop in the bleaching rate was noted when CV concentration was increased. For the plasma process alone, a 15-min treatment resulted in a color removal of 49.7 %, at a mineralization rate of 12.2 %, thereby increasing the BOD5/COD ratio from 0.11 to 0.23. There was an increase in the bleaching rate in temporal post-discharge conditions (i.e., self-continuity of reaction after the discharge was switched off): For 2 h of temporal post-discharge reaction, the color removal of the 15-min plasma-pre-treated CV increased to 55 %. The disappearance of color during each treatment method followed the first-order kinetics. With regard to the combined plasma/biological treatment process, the 15-min plasma-pre-treated sample was bleached at 92 % by A. hydrophila after 2-h incubation and completely bleached for 6 h. Therefore, there is a positive synergism of bacterial and plasma treatments. This combined treatment is useful in reducing the energy involved in complete mineralization of wastewater containing non-biodegradable dyes.

This study aimed to evaluate the total concentration of polycyclic aromatic hydrocarbons in sediments of Iguassu River in Southern Brazil. Alongside the concentration, the amount of such compounds bioavailable was also evaluated. This is accomplished by comparing its total amount present in sediments and the amount extracted by n-butanol. The results showed that the total concentration of polycyclic aromatic hydrocarbons presented in sediment ranged from 4.49 to 58.75 μg/g. The total amount of polycyclic aromatic hydrocarbons extracted by n-butanol ranged from 1.22 to 17.07 μg/g. The use of n-butanol represents the mimetic conditions that hydrocarbons, derived from oil, could be taken up by organisms. Most of the hydrocarbons extracted by n-butanol were those with lower octanol–water partition constant, usually those with three and four rings. Compounds with more than four rings were extracted in lower or insignificant amounts. Even the hydrocarbons with lower molecular weight available may be degraded or eliminated by organisms, when accumulated. Estimating bioavailability of hydrocarbons represents what specific hydrocarbons could be available to be taken up by organisms.

This communication discusses styrene removal in air by positive and negative DC corona discharges. Experiments were performed with a wire-plate reactor and under a gas flow rate of 305 m3/h. In terms of averaged applied voltage and corona current, it is observed that the maximum negative corona current is always at least two times larger than the positive one at the same voltage level. At the same corona discharge energy density, however, the positive corona discharge produces around 2–6 times more ozone in comparison with the negative corona. For styrene removal, the positive corona processing is also around 2–6 times more effective than the negative corona. Humidity, an important and variable component of ambient air, affects the positive corona processing significantly. But it exerts a moderate effect on the negative corona. The differences between positive corona and negative corona discharges are attributed to their different discharge properties.

Nitrogen removal communities performing wastewater treatment consist of ammonia oxidisers, nitrite oxidisers, denitrifiers, and anammox bacteria, and the proportion and activity of particular microbial groups depend not only on the physiochemical parameters of the bioreactor, but also on the composition of the inoculum. Nitrifiers and denitrifiers usually dominate in conventional wastewater treatment systems due to the fact that nitrification and denitrification are the most commonly used nitrogen removal processes. However, from the economical point of view in case of wastewater with high ammonia concentrations, anammox-based technologies are desirable for their treatment. The disadvantage of such systems is slow anammox bacteria growth, which extends an effective technological start-up. Thus, in this study, a fast start-up of the anammox process supported with an anammox-rich inoculum was performed in a sequencing batch reactor (SBR). Using anammox inoculation of SBR laboratory system, the start-up can be fastened to 85 days with 84.5% of nitrogen removal efficacy. The spatial distribution of nitrogen removal bacteria analysed with fluorescent in situ hybridisation revealed that anammox and nitrifiers are located side by side in the flocs and the relative number of ammonia and nitrite oxidisers decreased after 85 days of the experiment.