Despite the known high toxicity of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs, or dioxins), there are few case studies of PCDD/Fs contamination in sediment and there remains much to ...learn regarding their ecological impact. In this study, we performed an environmental risk assessment of a brine water storage pond near a chemical plant with high PCDD/Fs pollution potential before and after corrective actions. We found PCDD/F accumulation in the pond's fish and crab from the brine water storage pond, and the PCDD/Fs concentrations in biota higher than Taiwan's food safety standard (3.5 pg-TEQ/g). Furthermore, we found a high degree of pollution using different indices, including contamination factor (CF), modified degree of contamination (mCd), and pollution index (PI), in the pond's sediment. Before corrective actions, we also found high risk in the PCDD/F contamination in the sediment using various biological risk indices, including potential ecological risk index (RI) and risk quotient (RQ). After the corrective actions, including institutional/engineering control and remediation, the CF, mCd, and PI had decreased by 20–41 % and RI and RQ by 41–56 %. In addition, despite the slight reduction of pollution and risk index values in the whole pond, significant reduction was observed in the sediment of highly polluted area A owing to the lower disturbing suction dredging. In conclusion, the corrective actions used in this study helped decrease the pollution and ecological risk associated with this site's PCDD/Fs polluted sediment to some extent, suggesting that contamination and risk could be reduced to acceptable levels if these corrective actions are continued.
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•High PCDD/F accumulation in sediment and biota in the study area was observed.•PCDD/F concentrations and pollution indices were reduced after corrective actions.•Ecological risk of PCDD/Fs in sediment was declined after corrective actions•Implementation of corrective actions could help mitigate PCDD/F pollution.
The global rise in industrialization and vehicularization has led to the increasing trend in the use of different crude oil types. Among these mobil oil has major application in automobiles and ...different machines. The combustion of mobil oil renders a non-usable form that ultimately enters the environment thereby causing problems to environmental health. The aliphatic and aromatic hydrocarbon fraction of mobil oil has serious human and environmental health hazards. These components upon interaction with soil affect its fertility and microbial diversity. The recent advancement in the omics approach viz. metagenomics, metatranscriptomics and metaproteomics has led to increased efficiency for the use of microbial based remediation strategy. Additionally, the use of biosurfactants further aids in increasing the bioavailability and thus biodegradation of crude oil constituents. The combination of more than one approach could serve as an effective tool for efficient reduction of oil contamination from diverse ecosystems. To the best of our knowledge only a few publications on mobil oil have been published in the last decade. This systematic review could be extremely useful in designing a micro-bioremediation strategy for aquatic and terrestrial ecosystems contaminated with mobil oil or petroleum hydrocarbons that is both efficient and feasible. The state-of-art information and future research directions have been discussed to address the issue efficiently.
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•Mobil oil waste contains aliphatic and aromatic hydrocarbons.•Microbial aided degradation is effective for combating hydrocarbon pollution.•Meta-omics approach aids in the identification of robust microbial strains.•Biosurfactants addition increases the biodegradation of mobil oil.
The applications of forward osmosis (FO) have been hindered because of the lack of an optimal draw solution. The reverse salt flux from the draw solution not only reduces the water flux but also ...increases the cost of draw solute replenishment. Therefore, in this study, Tergitol NP7 and NP9 with a long straight carbon chain and low critical micelle concentration (CMC) were coupled with highly charged ethylenediaminetetraacetic acid (EDTA) as an innovative draw solution to minimize reverse salt diffusion in FO for the first time. The results showed that the lowest reverse salt flux of 0.067 GMH was observed when 0.1M EDTA-2Na coupled with 15mM NP7 was used as a draw solution and deionized water was used as a feed solution in FO mode (active layer facing with the feed solution). This is due to the hydrophobic interaction between the tails of NP7 and the FO membrane, thus creating layers on the membrane surface and constricting the FO membrane pores. Moreover, 1M EDTA-2Na coupled with 15mM NP7 is promising as an optimal draw solution for brackish water and sea water desalination. Average water fluxes of 7.68, 6.78, and 5.95 LMH were achieved when brackish water was used as a feed solution (5, 10, and 20g/L NaCl), and an average water flux of 3.81 LMH was achieved when sea water was used as a feed solution (35g/L NaCl). The diluted draw solution was recovered using a nanofiltration (NF-TS80) membrane with a high efficiency of 95% because of the high charge and large size of the draw solution.
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•NP surfactant coupled with highly charged EDTA could minimize salt leakage.•Reverse salt flux of the novel DS was 3 times lower than that of EDTA-2Na only.•Interaction between tails of NP with FO membrane constricted membrane pore.•Approximately 95% recovery of draw solute achieved by using NF-TS80 membrane
There is a global need to develop low-cost technologies to remove arsenic from water for individual household water supply. In this study, a purified and enriched waste material (treated magnetite ...waste, TMW) from the Trai Cau's iron ore mine in the Thai Nguyen Province in Vietnam was examined for its capacity to remove arsenic. The treatment system was packed with TMW that consisted of 75% of ferrous-ferric oxide (Fe(3)O(4)) and had a large surface area of 89.7 m(2)/g. The experiments were conducted at a filtration rate of 0.05 m/h to treat groundwater with an arsenic concentration of 380 microg/L and iron, manganese and phosphate concentrations of 2.07 mg/L, 0.093 mg/L and 1.6 mg/L respectively. The batch experimental results show that this new material was able to absorb up to 0.74 mg arsenic/g. The results also indicated that the treatment system removed more than 90% arsenic giving an effluent with an arsenic concentration of less than 30 microg/L while achieving a removal efficiency of about 80% for Mn(2 + ) and PO(4) (3-). This could be a promising and cost-effective new material for capturing arsenic as well as other metals from groundwater.
Novel phycosphere associated bacteria processes are being regarded as a potential and cost-effective strategy for controlling anthropogenic contaminants in wastewater treatment. However, the ...underlying concern with the process is its vulnerability to improper organic or nutrient intake. This study established a synergistic interaction between microalgae and activated sludge in a three-photobioreactor system (without external aeration) to understand how pollutants could be mitigated whilst simultaneously yielding biomass under different C/N ratios of 1:1, 5:1 and 10:1. The result showed that the superior biomass productivity was facilitated at a C/N ratio of 5:1 (106 mg L−1 d−1), and the high degradation rate constants (kCOD = 0.25 d−1, kTN = 0.29 d−1, kTP = 0.35 d−1) was approximated using a first-order kinetic model. The removal of pollutants was remarkably high, exceeding 90% (COD), 93% (TN), and 96% (TP). Nevertheless, the C/N ratio of 1:1 resulted in a threefold drop in biomass-specific growth rate (μ = 0.07 d−1). Microalgal assimilation, followed by bacterial denitrification, is the major pathway of removing total nitrogen when the C/N ratio exceeds 5:1. Activated sludge plays an important role in improving microalgae tolerance to high concentration of ammonia nitrogen and boosting nitrification (light phase) and denitrification (dark phase). The use of phycosphere associated bacteria could be a promising strategy for controlling nutrients pollution and other environmental considerations in wastewater.
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•The reduction of COD, TN and TP fitted with the first-order degradation model.•COD removal remained stable in co-culture under different C/N ratios.•C/N ratio of 5:1 possessed a high rate of pollutant degradation and biomass growth.•Activated sludge boosts microalgae tolerance to NH4+-N up to 300 mg L−1.•Assimilation and denitrification reduced total nitrogen when the C/N ratio increased.
Sludge serves as an alternative to traditional sources of phosphorus. However, the low phosphorus bioavailability limits its utilization. In this study, different oxidation treatments based on ...permanganate-ferric chloride (Mn(VII)-Fe(III)) catalysis were employed to improve the phosphorus bioavailability of sludge. The phosphorus bioavailability was evaluated using sequential extraction. Comparative experiments showed that the group of Mn(VII)-Fe(III)/peroxydisulfate (PDS) was more effective than Mn(VII)-Fe(III)/sodium percarbonate (SPC) and Mn(VII)-Fe(III)/hydrogen peroxide (H2O2) in increasing the phosphorus bioavailability of sludge. The extracellular polymeric substances (EPS) of sludge were disintegrated under the oxidative treatment through destructing the bonds of CH and OH, leading to the release of phosphorus. Meanwhile, the bond of O=P=O was broken down, which caused the degradation of organic phosphorus into inorganic phosphorus. This process reduced the amount of residual phosphorus and insoluble phosphorus in sludge, as well as increased the amount of phosphates. Some of the phosphate was deposited in sludge solid phase due to the adsorption of MnOx and FeOx. Phosphates combined with added and released Fe ions to form FeP complex enhanced the phosphorus bioavailability. The stronger destruction on O=P=O and higher disintegration on EPS promoted the achievement of better enhancement of phosphorus bioavailability under Mn(VII)-Fe(III)/PDS treatment. Furthermore, three types of oxidation treatments based on Mn(VII)-Fe(III) have all been shown to improve heavy metals leaching and reduce sludge dewaterability. Therefore, oxidation methods based on Mn(VII)-Fe(III) have excellent effects on the resourcefulness, harmlessness and minimization of sludge. This work provides ideas for selecting more practical sludge conditioning methods in engineering.
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•Oxidation treatments improved the phosphorus bioavailability of sludge•Phosphorus was released by destroying EPS structure under oxidation treatments•The O=P=O bond of organic phosphorus was effectively destroyed•Phosphorus was deposited by adsorption and binding of Mn and Fe
In this study, ultrasonic-assisted liquid-phase stripping and hydrothermal synthesis were used to prepare the two structural types of MoS2 nanosheets, namely u-MoS2 and h-MoS2, respectively. The ...u-MoS2 and h-MoS2 were characterized by various techniques, and the profound relationship between the structure and preparation method was also identified. Results indicated that adsorptions of Pb2＋ onto both u-MoS2 and h-MoS2 nanosheets reached equilibrium after 30 min at higher rates. The removal efficiencies of Pb2＋ by h-MoS2 and u-MoS2 nanosheets were 98.4% and 20.6% under the condition of low dosage (60 mg/L). The Pb2＋ by h-MoS2 adsorption fitted well to the Langmuir adsorption isotherm with the adsorption capacity of 174.0 mg/g while the Pb2＋ adsorption by u-MoS2 fitted well to the Freundlich isotherm (n=1). The obvious discrepancy suggested that the adsorption performance was directly associated with their structural properties, which were induced by two different synthesis methods. Based on these results, the effects of operational parameters (pH, dosage and existing ions) on Pb2＋ adsorption using h-MoS2 were further investigated. The dosage greatly affected the adsorption capacity and removal efficiency, while pH and coexisting ions had small effects on adsorption performance. In short, this study could help to better understand the role of MoS2 nanosheets’ structures obtained by different preparation methods for adsorption of heavy metal ions in aqueous solution.
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•h-MoS2 nanosheets prepared by hydrothermal synthesis was suitable for adsorption of Pb2+.•Structural defects, interlayer spacing and phase played essential roles in Pb2+ adsorption.•Preparation method steps, structure and adsorption performance are closed relation.
The mechanism for perchlorate reduction was investigated using thiosulfate-driven (T-driven) perchlorate reduction bacteria. The influences of various environmental conditions on perchlorate ...reduction, including pH, temperature and electron acceptors were examined. The maximum perchlorate removal rate was observed at pH 7.5 and 40 °C. Perchlorate reduction was delayed due to the coexistence of perchlorate-chlorate and perchlorate-nitrate. The mechanism of the T-driven perchlorate reduction electron transport chain (ETC) was also investigated by utilizing different inhibitors. The results were as follows: firstly, the NADH dehydrogenase was not involved in the ETC; secondly, the FAD dehydrogenase and quinone loop participated in the ETC; and thirdly, cytochrome oxidase was the main pathway in the ETC. Meanwhile, microbial consortium structure analysis indicated that Sulfurovum which can oxidize sulfur compounds coupled to the reduction of nitrate or perchlorate was the primary bacterium in the T-driven and sulfur-driven consortium. This study generates a better understanding of the mechanism of T-driven perchlorate reduction.
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•The optimum temperature 40 °C, pH 7.5 was obtained for perchlorate reduction.•Perchlorate reduction was delayed in presence of NO3− and ClO3−.•Complex I was not involved in electron transport process of T-driven ClO4− reduction.•Sulfurovum was the main bacterium in T-driven and S-driven consortium.
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•A new activated primary tank (APT) was developed to recover carbon source from sludge.•APT was beneficial for the breeding of fermentative bacteria and maximised VFAs ...yield.•Mechanical elutriation significantly promoted the release of fermentation products.•APT was applied in a sewage treatment plant and recovered carbon source successfully.
A novel activated primary tank process (APT) was developed for recovering carbon source by fermentation and elutriation of primary sludge. The effects of solids retention time (SRT), elutriation intensity (G) and return sludge ratio (RSR) on this recovery were evaluated in a pilot scale reactor. Results indicated that SRT significantly influenced carbon source recovery, and mechanical elutriation could promote soluble COD (SCOD) and VFA yields. The optimal conditions of APT were SRT=5d, G=152s−1 and RSR=10%, SCOD and VFA production were 57.0mg/L and 21.7mg/L. Particulate organic matter in sludge was converted into SCOD and VFAs as fermentative bacteria were significantly enriched in APT. Moreover, the APT process was applied in a wastewater treatment plant to solve the problem of insufficient carbon source. The outcomes demonstrated that influent SCOD of biological tank increased by 31.1%, which improved the efficiency of removing nitrogen and phosphorus.
At present, the application of sewage treatment technologies is restricted by high sulfate concentrations. In the present work, the sulfate removal was biologically treated using an upflow anaerobic ...sludge blanket (UASB) in the absence/presence of light. First, the start-up of UASB for the sulfate removal was studied in terms of COD degradation, sulfate removal, and effluent pH. Second, the impacts of different operation parameters (i.e., COD/SO
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ratio, temperature and illumination time) on the UASB performance were explored. Third, the properties of sludge derived from the UASB at different time were analyzed. Results show that after 28 days of start-up, the COD removal efficiencies in both the photoreactor and non-photoreactor could reach a range of 85–90% while such reactors could achieve > 90% of sulfate being removed. Besides, higher illumination time could facilitate the removal of pollutants in the photoreactor. To sum up, the present study can provide technical support for the clean removal of sulfate from wastewater using photoreactors.
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