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Oil leakage, which is inevitable in the process of extraction, processing, transportation and storage, seriously undermines the soil and groundwater environment. Surfactants can facilitate the migration and solution of oil contaminants from nonaqueous phase liquid (NAPL) or solid phase to water by reducing the (air/water) surface tension, (oil/water) interfacial tension and micellar solubilization. They can effectively enhance the hydrodynamic driven remediation technologies by improving the contact efficiency of contaminants and liquid remediation agents or microorganism, and have been widely used to enhance the remediation of oil-contaminated sites. This paper summarizes the characteristics of different types of surfactants such as nonionic, anionic, biological and mixed surfactants, their enhancements to the remediation of oil-contaminated soil and groundwater, and examines the factors influencing surfactant performance. The causes of tailing and rebound effects and the role of surfactants in suppressing them are also discussed. Laboratory researches and actual site remediation practices have shown that various types of surfactants offer diverse options. Biosurfactants and mixed surfactants are superior and worth attention among the surfactants. Using surfactant foams, adding shear-thinning polymers, and combining surfactants with in-situ chemical oxidation are effective ways to resolve tailing and rebound effects. The adsorption of surfactants on soils and aquifer sediments decreases remediation efficiency and may cause secondary pollution, Therefore the adsorption loss should be noticed and minimized.

Dissolved organic matter (DOM) is the most active fraction of compost organic matter. The presence of the redox-active functional groups in DOM allows it to act an electron shuttle to promote the electron transfer between microorganisms and terminal electron acceptors. In this study, the electron transfer capacities (ETCs) of compost DOM samples at eight different composting stages were determined by electrochemical method. 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and Diquat dibro-mide monohydrate (DQ) were used to measured electron donating capacity (EDC) and electron accepting capacity (EAC) at working voltage 0.61 V/–0.49 V, respectively. The evolution characteristics of the chemical structures and components were analyzed by combining the three-dimensional fluorescence spectra, Fourier transform infrared (FTIR) spectra and elemental analysis. The results showed that the EDC of DOM increased from 16.850 μmol e− (g C)−1 to 22.077 μmol e− (g C)−1, The EAC decreased from 1.866 μmol e− (g C)−1 to 1.779 μmol e− (g C)−1. The results of three-dimensional fluorescence spectroscopy showed that the relative contents of humic-like and protein-like components gradually increased and decreased, respectively, during the composting process. The humuc-like components were the main contributor for the ETC of DOM. FTIR spectra showed that there was no significant change in the hydroxyl and carboxyl group contents of DOM during composting, suggesting no contribution of these function groups to the ETC of DOM. The elemental analysis showed that the content of oxygen in the DOM increased during the composting process, while the sulfur-containing group might be dominated contributor for its ETC.

Dissolved organic matter (DOM) in wastewater treatment plant (WWTP) effluent threats aquatic environment and challenges engineered aquatic systems. In order to predict its environmental risk and guide the selection of suitable strategy and technology, understanding the removal efficiency and the fate of DOM along the treatment is helpful. Herein, to qualitatively and quantitatively estimate the composition of DOM in a full-scale WWTP in northern China, a combined approach of chromatography and spectroscopy was employed, and the contribution of size-dependent substructure to the global feature of DOM was discussed simultaneously. The results suggest that the WWTP could remove the free proteins of low molecular size by physical treatment with removal ratios of 46.4% and 41.0% for tyrosine and tryptophan, respectively, whereas humic-like and humic-protein complex accumulate in the effluent of treatment with a ratio of 40.6%. Biotreatment is of importance for changing the proportion of different types of DOM, especially for anaerobic tank and the anoxic tank, which results in the increase of humification. Size exclusive chromatography (SEC) coupled with multi emission maps identifies six DOM substructures. Two protein-like DOM were removed by the WWTP, except the composition with the molecular weight ranging from 0.75 to 0.25 kDa, whereas humic-like DOM with whole size range accumulated to varying extent. The standard deviation analysis states that the structure variation of bulk DOM in the WWTP is primarily contributed by the decrease of small-sized proteins and the increase of humic-like DOM. This study presents insight into the fate and behavior of DOM components during the full-scale WWTP treatment and provides guidelines for altering DOM-treating technologies. Besides, innovative strategies suggest using DOM as a resource based on the critical review of previous research.

Powder activators are difficult to recycle in the peroxydisulfate (PDS) activation process, increasing the secondary pollution risk. In contrast, granular activators facilitate recycling, but with a weak PDS activation capability. Aiming at these limitations, a granular visible-light-driven photocatalyst (MoS2/rGO/WO3, MRW) with a diameter of 2.5 mm was synthesized. In the presence of 0.125 mM PDS and 2.5 g L−1 granular MRW, 79.67% carbamazepine was removed within 20 min under visible-light irradiation, exhibiting a rapid degradation capability. The degradation efficiency was maintained at 70% during the cycling experiment, exhibiting a good stability of the granular MRW. Only 20 μg L−1 tungsten was detected in the solution after a 10-hour dissolved-release experiment, demonstrating a low risk for secondary pollution. The cooperative catalytic degradation was mainly attributed to OH and SO4 −. Eleven intermediates were identified and the corresponding degradation pathways were proposed. The good degradation performance of granular MRW makes it a promising wastewater treatment technology for future use.

To study the influence of long-term pesticide application on the distribution of organochlorine pesticides (OCPs) in the soil-groundwater system, 19 soil samples and 19 groundwater samples were collected from agricultural area with long-term pesticide application history in Northern China. Results showed that the composition of OCPs changed significantly from soil to groundwater. For example, ∑DDT, ∑HCH, and ∑heptachlor had high levels in the soil and low levels in the groundwater; in contrast, endrin had low level in the soil and high level in the groundwater. Further study showed that OCP distribution in the soil was significantly influenced by its residue time, soil organic carbon level, and small soil particle contents (i.d.

Soil and groundwater samples were collected from paddy fields in the middle reaches of the Yangtze River Basin to study the occurrence and the risks associated with organochlorine pesticides (OCPs) and organophosphorus pesticides (OPPs) in soil and groundwater. Results showed that OCPs and OPPs were widely distributed throughout the study area. The levels of OCPs and OPPs in the soil were much lower than those specified by soil quality standards. However, the levels of four OCPs (heptachlors, aldrin, dieldrin, and γ-hexachlorocyclohexane) in groundwater were higher than those permitted by drinking water standards. The health risk assessment method suggested by the US Environment Protection Agency was used to evaluate the regional risks from selected pesticides. Results showed that there were low health risks from OCPs and OPPs in soil at the regional scale, but high risks from heptachlor, aldrin, and endrin in groundwater, suggesting an urgent need for groundwater protection. There are widespread concerns on dichlorodiphenyltrichloroethane and hexachlorocyclohexane, but little focus on other pesticides in China. However, our results suggest that the presence of, and risks from, other pesticides in groundwater should be a focus from the region aspect.