The replacement of synthetic surface-active compounds (SACs) by their microbial counterparts is carving out a niche for themselves in the field of bioremediation. However, the high cost of microbial products has limited their application at a realistic scale. In the current study, several hydrocarbon-degrading microorganisms were assayed as potential SAC producers in low-cost liquid media. Only the strain CC10, placed within the class Actinobacteria, was able to produce emulsifying molecules by using a combination of sugarcane vinasse or crude glycerol (as cheap carbon substrates) with urea or peptone (as nitrogen sources). The emulsifying activity of the supernatants and the stability of emulsions formed with motor oil depended on the carbon and nitrogen sources. However, the biodegradability of these metabolites was only associated with the carbon substrate, and it was always higher than the two tested synthetic surfactants, sodium dodecyl sulfate and Triton X-100. Also, a positive linear association between emulsifying and lipase activities of the CC10 supernatants was detected (r = 0.781; p = 0.219), with the maximum activities detected in the glycerol-peptone supernatant. Interestingly, this supernatant was able to emulsify different oily substrates, a property that could be used to increase the efficiency of the treatment of effluents with high fat content.

A unique test chamber system, which enables experiments with plants under highly controlled environmental conditions, was used to examine the pollutant removal efficiency of plants. For this purpose, the removal of two different volatile organic compounds (VOC) (toluene, 2-ethylhexanol) from the air by aerial plant parts of two common indoor plant species (Dieffenbachia maculata and Spathiphyllum wallisii) was monitored. While the control over environmental conditions (temperature, relative humidity, CO₂ content, and light condition) worked very well in all experiments, control experiments with the empty chamber revealed high losses of VOC, especially 2-ethylhexanol, over the test duration of 48 h. Nonetheless, compared to the empty chamber, a significantly stronger and more rapid decline in the toluene as well as in the 2-ethylhexanol concentrations was observed when plants were present in the chamber. Interestingly, almost the same VOC removal as by aerial plant parts could be achieved by potting soil without plants. A comparative literature survey revealed substantial heterogeneity in previous results concerning the VOC removal efficiency of plants. This can be mainly attributed to a high diversity in experimental setup. The experimental setup used in the current study offers an excellent opportunity to examine also plant physiological responses to pollutant exposure (or other stressors) under highly controlled conditions. For the analysis of VOC removal under typical indoor conditions, to obtain data for the assessment of realistic VOC removal efficiencies by plants in rooms and offices, a guideline would be helpful to achieve more coherent findings in this field of research.

The presence of urban surface pollutants washed off by stormwater is a growing concern due to their adverse effects on receiving water quality. The stormwater quality mitigation strategies, therefore, should be based on the knowledge of the distribution and source apportionment of pollutants on urban surfaces. This study showcases the distribution of particulate-associated PAHs as a function of surface characteristic. Samples were obtained from six sites in the city of Dresden, Germany, using a wet vacuum sample-taking method. Both surface load (mg/m²) and solid-phase concentration (mg/g) of PAHs were determined. Results show that the highest surface load of ∑₁₆PAHs was found at a natural stone-paved pedestrian path with 34.5 μg/m². By contrast, the highest solid-phase concentration occurred at a high traffic load road with 36 mg/kg. Through a combined qualitative diagnostic ratio and quantitative principal component analysis with stepwise multiple linear regression (PCA-MLR) source apportionment, two significant contributors to PAH at vehicular roads were primarily identified as pyrogenic and petrogenic sources; 81.6% of the PAH burden was ascribed to pyrogenic sources including vehicle emission, coal, and wood combustions; 18.4% was attributed to petrogenic sources, such as spilled engine oil and vehicular tire debris. To minimize the adverse influence of surface sediments adsorbed PAHs to the receiving waters via stormwater runoff, a surface pavement-based city street sweeping strategy could be planned and optimized to remove hazardous materials from the impervious urban surfaces.

Adsorption of hexavalent chromium (Cr(VI)) using pomelo peel activated biochar (PPAB) as a adsorbent was investigated. The characterization of the adsorbent was studied by Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and zeta potentials analysis. The results showed that the PPAB had a high microporous structure and the existence of organic compounds such as hemicellulose, cellulose, and lignin. Various parameters including initial Cr(VI) concentration, pH, and adsorbent dosage were studied. The results indicated that the adsorption process was pH dependent and maximum adsorption capacity of Cr(VI) was 57.637 mg/g at pH 2.0 and 35 °C with PPAB dosage of 0.05 g. The adsorption kinetics fitted well to the pseudo-second-order model and the correlation coefficients were greater than 0.999. The adsorption isotherm data could be better described with the Langmuir model, suggesting the homogeneous and monolayer adsorption. Moreover, the scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and Fourier transform infrared spectrum (FTIR) results showed that the surface of PPAB had plenty of developed pores after activation and the modification process was deemed to proceed between the O–H groups from pomelo peel and H₃PO₄ molecules. The main adsorption mechanism was attributed electrostatic interaction and ion exchange between the surface of PPAB and Cr(VI).

Microbiological activities are essential in the bioremediation of polluted soils. The enzymatic activities of microorganisms are usually used as a biological indicator of soil health. The aim of this work was to observe the catalase, acid phosphatase (AcP), and alkaline phosphatase (AlP) activities in soil that was amended with agro-industrial by-products and macronutrients during the process of total petroleum hydrocarbon (TPH) removal. To this end, microcosm tests were performed with soil and agro-industrial by-products ratios of 100:2:2, for soil:sugarcane bagasse pith:filter cake mud (SSF); 100:2, for both soil:sugarcane bagasse pith (SS); and for soil filter cake mud (SF). The macronutrients—carbon, nitrogen, and phosphorus—in the experimental treatments were adjusted to 100:10:1 with a solution of NH₄NO₃ and K₂HPO₄. The best TPH removal (51.4%) was obtained with SSF at 15 days. In addition, a significant correlation was observed between TPH removal and AlP as well as AcP (r = 0.74, p < 0.0001; r = 0.70, p < 0.0107, respectively). Fungi growth was also correlated with both AlP (r = 0.97, p < 0.0001) and AcP (r = 0.95, p < 0.0001) activities. Besides, bacterial and fungi growth showed a correlation with TPH (r = 0.86, p < 0.001; r = 0.77, p < 0.0034, respectively). It could be said that the agro-industrial by-products and macronutrients contributed to pollutant removal from the oil-polluted soil at relatively short amount of time. In addition, the enzymatic activities were increased after the treatment; in this study, the high sensitivity enzyme was AlP, and it could be used as an indirect indicator of oil pollutant removal.

Human health risks associated with the consumption of metal-contaminated fish over extended periods have become a concern particularly in Taiwan, where fish is consumed on a large scale. This study applied the interaction-based hazard index (HI) to assess the mixture health risks for fishers and non-fishers who consume the arsenic (As), copper (Cu), and zinc (Zn) contaminated milkfish from As-contaminated coastal areas in Taiwan, taking into account joint toxic actions and potential toxic interactions. We showed that the interactions of As–Zn and Cu–Zn were antagonistic, whereas As–Cu interaction was additive. We found that HI estimates without interactions considered were 1.3–1.6 times higher than interactive HIs. Probability distributions of HI estimates for non-fishers were less than 1, whereas all 97.5%-tile HI estimates for fishers were >1. Analytical results revealed that the level of inorganic As in milkfish was the main contributor to HIs, indicating a health risk posed to consumers of fish farmed in As-contaminated areas. However, we found that Zn supplementation could significantly decrease As-induced risk of hematological effect by activating a Zn-dependent enzyme. In order to improve the accuracy of health risk due to exposure to multiple metals, further toxicological data, regular environmental monitoring, dietary survey, and refinement approaches for interactive risk assessment are warranted.

In today’s world, remediation of the environmental pollutants including soil contaminations is among the main issues and concerns considered by environmental scientists. Vapor extraction method is an in situ method to clean up volatile and semi-volatile contaminants of soil especially in unsaturated areas. Thermal enhancement to extract vapors includes different technologies. Its purpose is to transfer heat to the subsurface of the soil to increase the vapor pressure of volatile organic compounds and, consequently, to increase the amount of extracted VOCs. In this study, modeling was done by using laboratory data after screening. Validation was also done with the help of an artificial neural network using the response surface methodology. After training and evaluating the model, it was found that this model determines the amount of contaminant removal rate according to available data and different temperatures by good measures. The correlation coefficient square was equal to 0.95 in the validation section by the neural network. This coefficient was equal to 0.99 in the original model. At the end, a contaminant removal formula for sandy soils has been presented. As a result, due to the proximity of the correlation coefficient to 1, this model can be used to predict the removal rate of thermal enhancement in the relevant circumstances with a slight error.

A strengthened constructed rapid infiltration (SCRI) system is a sewage treatment system derived from a constructed rapid infiltration (CRI) system. The SCRI tank structure primarily includes saturated and non-saturated layers. The degradation of the chemical oxygen demand (COD) and the conversion of ammonia nitrogen (NH₄⁺-N) are primarily performed in a non-saturated layer. To study the COD and NH₄⁺-N removal process in a non-saturated layer, two organic glass columns with a radius of 2.5 cm and a height of 70 cm were loaded with layers of soil from the Shunyi district of Beijing. The primary goal of this research is to quantify the removal effect factors and the relationship of the COD and NH₄⁺-N in the non-saturated layer. The SCRI system functioned successfully under a wetting-drying ratio of 1:5 with hydraulic loading at 1.0 m³/ (m²·d) for over 2 months. Our results show that the removal rate of NH₄⁺-N is approximately 69.11%, and the removal efficiency of COD is approximately 90.46%. The removal of COD is only slightly affected by pH, while the removal of NH₄⁺-N is greatly influenced by pH.

The effects of phosphate processing wastewater (PPWW) on heavy metal accumulation in a Mediterranean soil (Tunisia, North Africa) were investigated. Moreover, the residual toxicities of PPWW-irrigated soils extracts were assessed. Results showed that heavy metal accumulation was significantly higher in PPWW-irrigated soil extracts than in control soil. The heavy metal accumulation increased over time in treated soil samples and their average values followed the following order: Iron (Fe 252.72 mg l⁻¹) > Zinc (Zn 152.95 mg l⁻¹) > Lead (Pb 128.35 mg l⁻¹) > Copper (Cu 116.82 mg l⁻¹) > Cadmium (Cd 58.03 mg l⁻¹). The residual microtoxicity and phytotoxicity of the various treated soil samples extracts were evaluated by monitoring the bioluminescence inhibition (BI %) of Vibrio ficheri and the measurement of the germination indexes (GI %) of Lepidium sativum and Medicago sativa seeds. The results showed an important increase of residual toxicities of PPWW-treated soil extracts over time.

Current microbial source tracking methods heavily rely on the use of quantitative PCR (qPCR) assays to differentiate human and non-human sources of fecal contamination. However, traditional qPCR measures DNA from viable, viable but not culturable (VBNC), and dead cells, which may confound the use of this technique for detecting recent fecal contamination from waters receiving treated sewage effluent. In this study, fecal indicator bacteria (FIB), six host-associated markers, and two viability-based methods for rapid detection and assessment of fecal contamination were used in a microbial source tracking study to identify sources impairing water quality and sediments within the San Antonio de los Buenos watershed in Tijuana, Mexico. Horse- and gull-associated markers were detected in 4 and 8% of samples tested, respectively. The human- and dog-associated markers were positive in 74 and 63% of watershed samples and 92 and 75% of storm drain samples, respectively. Propidium monoazide (PMA) successfully inhibited amplification of DNA from dead cells in environmental creek waters that receive large volumes of treated wastewater effluent. Accordingly, PMA-qPCR measurements were more comparable to measurements made by culture-based methods (IDEXX). The covalently linked immunomagnetic separation/adenosine triphosphate (Cov-IMS/ATP) method showed a strong linear relationship to culture methods when compared to measurements made by the qPCR Entero1a assay. Both the PMA-qPCR and the Cov-IMS/ATP methods show promise for improved assessment of water quality and recent fecal contamination in sewage impacted waters, including areas receiving discharge from wastewater treatment plants, where measurement by qPCR does not effectively differentiate between DNA from live and dead cells. This study serves as an important positive control for non-point source pollution studies.