Tremendous surge in the industrialization and infrastructure development worldwide have led to a significant rise in environmental pollutants in the last 2–3 decades. Pollutants in the natural environment consist of highly diversified and complex mixtures. A single biomarker cannot be used to assess a complete identification of environmental pollutants. In this context, it is highly recommended by environmental scientists to evaluate a set of complementary biomarkers for the complete assessment of toxic burden of complex environmental pollutants in the exposed organisms. Moreover, a multiple biomarker approach for the stress assessment is believed to have high sensitivity and could be done in comparatively lesser measuring time. The present article focuses on the viability of usage of xenobiotic detoxification enzymes viz. phase I and II as the toxicity biomarkers. As far as our knowledge goes, we are for the first time reporting phase I and phase II enzymes together as potential toxicity biomarkers in a single article.

The ability of untreated and acid-treated biomass from Pistia stratiotes (PL and APL, respectively) and Eichhornia crassipes (ELS and AELS, respectively) to remove color from anaerobically digested sugar cane stillage (ADS) was investigated. The effects of pH (3–8), particle size (< 0.75, 0.75–1, 1–4 mm), and biomass concentration (5–15 g/L) on decolorization of ADS were assessed using untreated biomass. After acid modification of biomass (acid-treated), the effects of pH (3–8), biomass concentration (6–10 g/L), time (20–480 min), and ADS dilution (non-diluted, 1:2, 1:10, 1:20) on color removal from ADS were evaluated. Scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR) analyses were also performed. A clear effect of particle size on ADS decolorization was found (21.04 ± 0.75 and 27.87 ± 0.30 % for 0.75–1 and <0.75 mm, respectively, for ELS; 31.65 ± 0.23 and 37.82 ± 0.53 for 1–4 and 0.75–1 mm, respectively, for PL). Decolorization also increased when the untreated biomass concentration was higher (15.41 ± 0.3 and 27.89 ± 0.2 % for 5 and 10 g/L, respectively, for ELS; 15.61 ± 0.11 and 33.06 ± 1.09 % for 5 and 10 g/L, respectively, for PL). The use of acid-treated biomass enhanced the effect of pH on color removal (48.30 ± 1.27 and 12.96 ± 0.27 % for pH of 3 and 7, respectively, for AELS; 47.11 ± 1.72 and 6.62 ± 0.21 % for pH of 3 and 7, respectively, for APL). The highest rate of color removal obtained using acid-treated biomass was 55.58 ± 1.82 and 56 ± 0.77 % for AELS and APL, respectively. The FTIR spectra analysis suggested the electrostatic attraction between protonated carboxylic groups on biomass and anionic colored compounds as being one of the adsorption mechanisms for ADS decolorization. The use of dry biomass from invasive macrophytes is an effective alternative for color removal from ADS.

The sorption behavior of cobalt by a sodium-modified zeolite-rich tuff was investigated using cobalt solutions prepared with water from the cooling system of a nuclear reactor. The sorption kinetics shows that the equilibrium was reached in less than 20 h. The isotherms showed that the sorption capacity of the sodium-modified zeolite-rich tuff for cobalt was 20.73 mg/g at 60 °C. The pH affects the sorption capacity of the sodium-modified zeolite-rich tuff for cobalt. The sorption capacity of the sodium-modified zeolite-rich tuff for cobalt was higher using nuclear purity water than water from other aqueous matrices.

Bioflocculation occurs in both engineered and natural systems and plays an important role in several water treatment processes as well as in pathogen transport and survival. In this study, bioflocculation was simulated in the laboratory to allow for well-controlled experiments. Escherichia coli and latex particles of varying sizes (3.2, 11 and 25 μm) were spiked into a buffer solution and were bioflocculated by adding alginate and varying amounts of calcium (0, 5, 10 and 15 mM). The extent of flocculation was determined by the calcium concentration, and the floc structure was modified by varying the particle size. The bioflocculation process was monitored with a dynamic particle analyzer, and the flocs formed were analyzed with respect to size, shape and porosity parameters. Larger flocs were observed to have a more heterogeneous structure with higher variation in shape and porosity compared to smaller flocs. Circularity and porosity parameters were shown to be strongly correlated with the calcium concentration. In addition, ultraviolet (UV) irradiation experiments were performed on flocculated and non-flocculated samples, and the inactivation data were assessed in light of floc characteristics determined with the particle analyzer.

A novel alginate–montmorillonite biopolymer-clay composite bead formulation for water defluoridation was developed in this study. Montmorillonite was dispersed alginate solution, and the mixture was cross-linked in an aqueous solution of aluminum(III). The resulting cross-linked beads were characterized using FTIR, SEM, and mechanical measurements. In order to reveal the defluoridation capacity of the beads, batch adsorption experiments were carried out. Optimum conditions and effect of competing ions were investigated. Experimental data were modeled using several isothermal, kinetic, and thermodynamic models. Maximum Langmuir adsorption capacity was reached as 31.0 mg g⁻¹at 25 °C. It is also found that the adsorption is physical in nature and follows the Elovich kinetic model, and the fluoride removal efficiency is not affected by the presence of most competing anions. The results show that aluminum alginate–montmorillonite composite beads can be used as effective and natural sorbents for fluoride removal from water.

Previous studies with bioindicator organisms have used somatic length distributions, i.e., population structure, to understand the effects of management, environment, or a potential contaminant on populations. We describe a statistical approach to separate somatic length classes of Folsomia candida juveniles as an endpoint for the assessment of changes in population structure. Reproduction-survival bioassays were carried out with five different biochars applied at increasing concentrations. Multi-Gaussian models parameterized juvenile size class cohorts, and the biomass of each size class cohort was estimated. Population structure was modified by both material type as well as concentration. Both biomass and population structure were sensitive to effects not reflected in juvenile number, the classic endpoint. Treatments with more size classes and larger individuals were taken to represent favorable conditions, and less size classes and smaller individuals indicated less favorable conditions. This extension of the standardized test provided additional information about the demography of the population.

This study evaluated the behavior of a sequencing batch reactor (SBR) at laboratory-scale in removing the emerging contaminants, ibuprofen (IBP) and methylparaben (MPB), at different concentrations. Individual experiments were carried out for each pollutant and they were divided into six stages of operation, which included starting, load variation, and interim periods of system stabilization. The treated wastewater was synthetic, and it included the pollutions MPB or IBP, glucose as a co-substrate, macronutrients, and micronutrients. The inoculum used to start the reactor was an aerobic sludge from an SBR system used in the treatment of domestic wastewater, which presented with high-content organic material and featured good sedimentation characteristics. The removal percentages of the two compounds at concentrations of 300, 500, and 1000 μg/L were not similar. For MPB, high removal percentages (>96 %) were obtained, while for IBP, decreasing removal percentages were found with increases in analyte concentration, exhibiting average values of 51 ± 15.3, 26 ± 16.6, and 16 ± 5.4 %. Following the removal of IBP, this behavior showed pronounced effects in biomass inhibition during exposure to high concentrations of the pollutant.

Nitrogen significantly regulated (p < 0.05) the effects of spiramycin on the growth and antioxidant responses of Microcystis aeruginosa as well as the biodegradation of spiramycin by M. aeruginosa during a 7-day exposure test. At a nitrogen level of 0.5 mg L⁻¹, the activities of superoxide dismutase and catalase were stimulated by 100–400 ng L⁻¹of spiramycin to protect algal cells from oxidative damage, resulting in alleviated toxicity of spiramycin and low malondialdehyde content in M. aeruginosa. The catalase activity was inhibited by 400 ng L⁻¹of spiramycin at higher nitrogen levels of 5–50 mg L⁻¹, leading to significant growth inhibition (p < 0.05) and higher malondialdehyde content through accumulation of hydrogen peroxide. Stimulated glutathione content and glutathione S-transferase activity were coupled to the biodegradation of spiramycin in M. aeruginosa. The 7-day biodegradation percentage of spiramycin varied from 8.9 to 29.6 %, which was enhanced by increased nitrogen concentration and decreased spiramycin concentration. Due to the regulation of algal growth, the toxicity of M. aeruginosa were significantly enhanced (p < 0.05) by 100 ng L⁻¹of spiramycin at a nitrogen concentration of 0.5 mg L⁻¹while significantly reduced (p < 0.05) by 400 ng L⁻¹of spiramycin at nitrogen levels of 5–50 mg L⁻¹, according to the luminescent bacteria test. Low concentration of coexisting spiramycin contaminant should be considered during the control of M. aeruginosa bloom, especially under nitrogen deficient condition.

As a biopolymer-modified building block, a poly-dopamine layer can be utilized with a wide range of inorganic and organic materials for an adsorptive and microbial remediation. In this study, dopamine (DOPA) was used as a structural platform to bind silver onto the surface of kapok fibers, and a composite of surface-modified kapok fibers coated with DOPA along with silver were successfully manufactured. After a silver-coating process, a very strong antibacterial property was exhibited against Staphylococcus aureus with a high antibacterial efficiency, over 99 %, which could last for 48 h in peptone water. Enumeration determination was carried out in a spread plate method. For a comparative study, the antibacterial activity of raw kapok fibers and chemically enhanced kapok fibers with DOPA and silver was also evaluated. The results indicated that the chemically enhanced kapok fibers were very useful in controlling a microbial activity on a surface environment.