Response surface methodology (RSM) was employed to optimize nitrogen and phosphorus concentrations for removal of n-alkanes from crude oil contaminated seawater samples in batch reactors. Erlenmeyer flasks were used as bioreactors; each containing 250 mL dispersed crude oil contaminated seawater, indigenous acclimatized microorganism and different amounts of nitrogen and phosphorus based on central composite design (CCD). Samples were extracted and analyzed according to US-EPA protocols using a gas chromatograph. During 28 days of bioremediation, a maximum of 95% total aliphatic hydrocarbons removal was observed. The obtained Model F-value of 267.73 and probability F<0.0001 implied the model was significant. Numerical condition optimization via a quadratic model, predicted 98% n-alkanes removal for a 20-day laboratory bioremediation trial using nitrogen and phosphorus concentrations of 13.62 and 1.39 mg/L, respectively. In actual experiments, 95% removal was observed under these conditions.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
Mature landfill leachate is typically non-biodegradable and contains high concentration of refractory organics. The aim of this research was to optimize operating parameters in electro-Fenton process, for the removal of recalcitrant organics from semi-aerobic landfill leachate using response surface methodology (RSM). Effectiveness of important process parameters H(2)O(2)/Fe(2+) molar ratio, current density, pH and reaction time were determined, optimized and modeled successfully. Significant quadratic polynomial models were obtained (R(2)=0.9972 and 0.9984 for COD and color removals, respectively). Numerical optimization based on desirability function were employed; in a 43 min trial 94.07% of COD and 95.83% of color were removed at pH 3 and H(2)O(2)/Fe(2+) molar ratio 1, while current density was 49 mA/cm(2). The results indicate that E-Fenton process was an effective technology for semi-aerobic landfill leachate treatment.
Matched MeSH terms: Environmental Restoration and Remediation/methods
A central composite design (CCD) was employed to optimize the biosorption of Pb(II) ions onto immobilized cells of Pycnoporus sanguineus. The independent variables were initial Pb(II) concentration, pH and biomass loading. The combined effects of these variables were analyzed by response surface methodology (RSM) using quadratic model for predicting the optimum point. Under these conditions the model predicted a maximum of 97.7% of Pb(II) ions removal at pH 4, 200mg/L of initial Pb(II) concentration with 10g/L of biosorbent. The experimental values are in good agreement with predicted values within +0.10 to +0.81% error.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
The degradation potential and ligninolytic enzyme production of two isolated Panus tigrinus strains (M609RQY and M109RQY) were evaluated in this study. These strains were grown on three selected abundant agro-industrial wastes (rice straw; rice husk and cassava peel) under solid-state fermentation conditions. Degradation potential was determined by analyzing the chemical composition of the selected substrates before and after fermentation along with ligninolytic enzyme production. The strain M609RQY led to the highest lignin degradation of 40.81% on cassava peel, 11.25% on rice husk and 67.96% on rice straw. Both strains significantly increased the protein content of cassava peel. Rice husk stimulated maximum laccase (2556 U/L) and lignin peroxidase (24 U/L) production by the strains M109RQY and M609RQY, respectively. Furthermore, cassava peel stimulated maximum manganese-dependent peroxidase (141 U/L) production by the strain M109RQY. The de-lignified rice straw and the nutritionally-improved cassava peel could serve as potential animal feed supplements.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
This study investigated the capability of a biosurfactant produced by a novel strain of Bacillus salmalaya to enhance the biodegradation rates and bioavailability of organic contaminants. The biosurfactant produced by cultured strain 139SI showed high physicochemical properties and surface activity in the selected medium. The biosurfactant exhibited a high emulsification index and a positive result in the drop collapse test, with the results demonstrating the wetting activity of the biosurfactant and its potential to produce surface-active molecules. Strain 139SI can significantly reduce the surface tension (ST) from 70.5 to 27 mN/m, with a critical micelle concentration of 0.4%. Moreover, lubricating oil at 2% (v/v) was degraded on Day 20 (71.5). Furthermore, the biosurfactant demonstrated high stability at different ranges of salinity, pH, and temperature. Overall, the results indicated the potential use of B. salmalaya 139SI in environmental remediation processes.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
This study was carried out to evaluate the efficiency of Guar gum in removing Persistent Organic Pollutants (POPs), viz. phenol,2,4-bis(1,1-dimethylethyl) and bis(2-ethylhexyl) phthalate (DEHP), from farm effluent. The removal efficiency was compared with alum. The results indicated that 4.0 mg L(-1) of Guar gum at pH 7 could remove 99.70% and 99.99% of phenol,2,4-bis(1,1-dimethylethyl) and DEHP, respectively. Box Behnken design was used for optimization of the operating parameters for optimal POPs removal. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) spectroscopy studies were conducted on the flocs. SEM micrographs showed numerous void spaces in the flocs produced by Guar gum as opposed to those produced by alum. This indicated why Guar gum was more effective in capturing and removal of suspended particles and POPs as compared to alum. FTIR spectra indicated a shift in the bonding of functional groups in the flocs produced by Guar gum as compared to raw Guar gum powder signifying chemical attachment of the organics present in the effluent to the coagulant resulting in their removal. Guar gum is highly recommended as a substitute to chemical coagulant in treating POPs due to its non-toxic and biodegradable characteristics.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
Deep eutectic solvents (DESs) are a class of green solvents analogous to ionic liquids, but less costly and easier to prepare. The objective of this study is to remove lead (Pb) from a contaminated soil by using polyol based DESs mixed with a natural surfactant saponin for the first time. The DESs used in this study were prepared by mixing a quaternary ammonium salt choline chloride with polyols e.g. glycerol and ethylene glycol. A natural surfactant saponin obtained from soapnut fruit pericarp, was mixed with DESs to boost their efficiency. The DESs on their own did not perform satisfactory due to higher pH; however, they improved the performance of soapnut by up to 100%. Pb removal from contaminated soil using mixture of 40% DES-Gly and 1% saponin and mixture of 10% DES-Gly and 2% saponin were above 72% XRD and SEM studies did not detect any major corrosion in the soil texture. The environmental friendliness of both DESs and saponin and their affordable costs merit thorough investigation of their potential as soil washing agents.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
Water pollution is a global problem. During current study, ammonia, phosphate, phenol, and copper(II) were removed from aqueous solution by subsurface and surface flow constructed wetland. In current investigation, distilled water was polluted with four contaminants including ammonia, phosphate, copper (Cu), and phenol. Response surface methodology and central composite design were applied to optimize pollutant removal during treatment by subsurface flow constructed wetland (SSFCW). Contact time (12 to 80 h) and initial pollutant concentration (20 to 85 mg/L) were selected as independent factors; some upper and lower ranges were also monitored for accuracy. In SSFCW, water hyacinth transplanted in two substrate layers, namely zeolite and cockle shell. SSFCW removed 87.7, 81.4, 74.7, and 54.9% of ammonia, phosphate, Cu, and phenol, respectively, at optimum contact time (64.5 h) and initial pollutant concentration (69.2 mg/L). Aqueous solution was moved to a surface flow constructed wetland (SFCW) after treating via SSFCW at optimum conditions. In SFCW, Typha was transplanted to a fixed powdered substrate layer, including bentonite, zeolite, and cockle shell. SFCW could develop performance of this combined system and could improve elimination efficacy of the four contaminants to 99.99%. So this combined CW showed a good performance in removing pollutants. Graphical abstract Wetlands arrangement for treating aqueous solution in current study.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
The application of chemical dispersants in marine oil spill remediation is comprehensively reported across the globe. But, the augmented toxicity and poor biodegradability of reported chemical dispersants have created necessity for their replacement with the bio-based green dispersants. Therefore, in the present study, we have synthesized five ionic liquids (ILs) namely 1-butyl-3-methylimidazolium lauroylsarcosinate, 1,1'-(1,4-butanediyl)bis(1-H-pyrrolidinium) dodecylbenzenesulfonate, tetrabutylammonium citrate, tetrabutylammonium polyphosphate and tetrabutylammonium ethoxylate oleyl ether glycolate, and formulated a water based ILs dispersant combining the synthesized ILs at specified compositions. The effectiveness of formulated ILs dispersant was found between 70.75% and 94.71% for the dispersion of various crude oils ranging from light to heavy. Further, the acute toxicity tests against zebra fish and grouper fish have revealed the practically non-toxic behaviour of formulated ILs dispersant with LC50 value greater than 100 ppm after 96 h. In addition, the formulated ILs dispersant has provided excellent biodegradability throughout the test period. Overall, the formulated new ILs dispersant is deemed to facilitate environmentally benign oil spill remediation and could effectively substitute the use of hazardous chemical dispersants in immediate future.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
Electrokinetic process has emerged as an important tool for remediating heavy metal-contaminated soil. The process can concentrate heavy metals into smaller soil volume even in the absence of hydraulic flow. This makes it an attractive soil pre-treatment method before other remediation techniques are applied such that the chemical consumption in the latter stage can be reduced. The present study evaluates the feasibility of electrokinetic process in concentrating lead (Pb) and chromium (Cr) in a co-contaminated soil using different types of wetting agents, namely 0.01 M NaNO3, 0.1 M citric acid and 0.1 M EDTA. The data obtained showed that NaNO3 and citric acid resulted in poor Pb electromigration in this study. As for Cr migration, these agents were also found to give lower electromigration rate especially at low pH region as a result of Cr(VI) adsorption and possible reduction into Cr(III). In contrast, EDTA emerged as the best wetting agent in this study as it formed water-soluble anionic complexes with both Pb and Cr. This provided effective one-way electromigration towards the anode for both ions, and they were accumulated into smaller soil volume with an enrichment ratio of 1.55-1.82. A further study on the application of approaching cathode in EDTA test showed that soil alkalisation was achieved, but this did not provide significant enhancement on electromigration for Pb and Cr. Nevertheless, the power consumption for electrokinetic process was decreased by 22.5%.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
Titanium dioxide (TiO2) has been considered a useful material for the treatment of wastewater due to its non-toxic character, chemical stability and excellent electrical and optical properties which contribute in its wide range of applications, particularly in environmental remediation technology. However, the wide band gap of TiO2 photocatalyst (anatase phase, 3.20 eV) limits its photocatalytic activity to the ultraviolet region of light. Besides that, the electron-hole pair recombination has been found to reduce the efficiency of the photocatalyst. To overcome these problems, tailoring of TiO2 surface with rare earth metals to improve its surface, optical and photocatalytic properties has been investigated by many researchers. The surface modifications with rare earth metals proved to enhance the efficiency of TiO2 photocatalyts by way of reducing the band gap by shifting the working wavelength to the visible region and inhibiting the anatase-to-rutile phase transformations. This review paper summarises the attempts on modification of TiO2 using rare earth metals describing their effect on the photocatalytic activities of the modified TiO2 photocatalyst.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
Tropical forest ecosystems are facing unprecedented levels of degradation, severely compromising habitat suitability for wildlife. Despite the fundamental role biodiversity plays in forest regeneration, identifying and prioritizing degraded forests for restoration or conservation, based on their wildlife value, remains a significant challenge. Efforts to characterize habitat selection are also weakened by simple classifications of human-modified tropical forests as intact vs. degraded, which ignore the influence that three-dimensional (3D) forest structure may have on species distributions. Here, we develop a framework to identify conservation and restoration opportunities across logged forests in Borneo. We couple high-resolution airborne light detection and ranging (LiDAR) and camera trap data to characterize the response of a tropical mammal community to changes in 3D forest structure across a degradation gradient. Mammals were most responsive to covariates that accounted explicitly for the vertical and horizontal characteristics of the forest and actively selected structurally complex environments comprising tall canopies, increased plant area index throughout the vertical column, and the availability of a greater diversity of niches. We show that mammals are sensitive to structural simplification through disturbance, emphasizing the importance of maintaining and enhancing structurally intact forests. By calculating occurrence thresholds of species in response to forest structural change, we identify areas of degraded forest that would provide maximum benefit for multiple high-conservation value species if restored. The study demonstrates the advantages of using LiDAR to map forest structure, rather than relying on overly simplistic classifications of human-modified tropical forests, for prioritizing regions for restoration.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
In phytoremediation of co-contaminated soil, the simultaneous and efficient remediation of multiple pollutants is a major challenge rather than the removal of pollutants. A laboratory-scale experiment was conducted to investigate the effect of 5% addition of each of three different organic waste amendments (tea leaves, soy cake, and potato skin) to enhance the phytoaccumulation of lead (60 mg kg(-1)) and diesel fuel (25,000 mg kg(-1)) in co-contaminated soil by Dracaena reflexa Lam for a period of 180 day. The highest rate of oil degradation was recorded in co-contaminated soil planted with D. reflexa and amended with soy cake (75%), followed by potato skin (52.8%) and tea leaves (50.6%). Although plants did not accumulate hydrocarbon from the contaminated soil, significant bioaccumulation of lead in the roots and stems of D. reflexa was observed. At the end of 180 days, 16.7 and 9.8 mg kg(-1) of lead in the stems and roots of D. reflexa were recorded, respectively, for the treatment with tea leaves. These findings demonstrate the potential of organic waste amendments in enhancing phytoremediation of oil and bioaccumulation of lead.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
The Proposed New Environmental Quality (Clean Air) Regulation 201X (Draft), which replaces the Malaysia Environmental Quality (Clean Air) 1978, specifies limits to additional pollutants from power generation using fossil fuel. The new pollutants include Hg, HCl, and HF with limits of 0.03, 100, and 15 mg/N-m3 at 6% O2, respectively. These pollutants are normally present in very small concentrations (known as trace elements [TEs]), and hence are often neglected in environmental air quality monitoring in Malaysia. Following the enactment of the new regulation, it is now imperative to understand the TEs behavior and to assess the capability of the existing abatement technologies to comply with the new emission limits. This paper presents the comparison of TEs behavior of the most volatile (Hg, Cl, F) and less volatile (As, Be, Cd, Cr, Ni, Se, Pb) elements in subbituminous and bituminous coal and coal combustion products (CCP) (i.e., fly ash and bottom ash) from separate firing of subbituminous and bituminous coal in a coal-fired power plant in Malaysia. The effect of air pollution control devices configuration in removal of TEs was also investigated to evaluate the effectiveness of abatement technologies used in the plant. This study showed that subbituminous and bituminous coals and their CCPs have different TEs behavior. It is speculated that ash content could be a factor for such diverse behavior In addition, the type of coal and the concentrations of TEs in feed coal were to some extent influenced by the emission of TEs in flue gas. The electrostatic precipitator (ESP) and seawater flue gas desulfurization (FGD) used in the studied coal-fired power plant were found effective in removing TEs in particulate and vapor form, respectively, as well as complying with the new specified emission limits. Implications: Coals used by power plants in Peninsular Malaysia come from the same supplier (Tenaga Nasional Berhad Fuel Services), which is a subsidiary of the Malaysia electricity provider (Tenaga Nasional Berhad). Therefore, this study on trace elements behavior in a coal-fired power plant in Malaysia could represent emission from other plants in Peninsular Malaysia. By adhering to the current coal specifications and installation of electrostatic precipitator (ESP) and flue gas desulfurization, the plants could comply with the limits specified in the Malaysian Department of Environment (DOE) Scheduled Waste Guideline for bottom ash and fly ash and the Proposed New Environmental Quality (Clean Air) Regulation 201X (Draft).
Matched MeSH terms: Environmental Restoration and Remediation/methods*
In the work presented here, photocatalytic systems using TiO2 and ZnO suspensions were utilized to evaluate the degradation of resorcinol (ReOH). The effects of catalyst concentration and solution pH were investigated and optimized using multivariate analysis based on response surface methodology. The results indicated that ZnO showed greater degradation and mineralization activities compared to TiO2 under optimized conditions. Using certain radical scavengers, a positive hole, together with the participation of hydroxyl radicals, were the oxidative species responsible for ReOH degradation on TiO2 whereas, the ZnO photocatalysis occurred principally via hydroxyl radicals. Some hitherto unreported pathway intermediates of ReOH degradation were identified using gas chromatography-mass spectrometry. A tentative reaction mechanism for the formation of these intermediates was proposed. Moreover, the figure-of-merit electrical energy per order was employed to estimate the electrical energy consumption.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
Polycyclic aromatic hydrocarbons (PAHs) in soil have been recognised as a serious health and environmental issue due to their carcinogenic, mutagenic and teratogenic properties. One of the commonly employed soil remediation techniques to clean up such contamination is soil washing or solvent extraction. The main factor which governs the efficiency of this process is the solubility of PAHs in the extraction agent. Past field-scale soil washing treatments for PAH-contaminated soil have mainly employed organic solvents or water which is either toxic and costly or inefficient in removing higher molecular weight PAHs. Thus, the present article aims to provide a review and discussion of the alternative extraction agents that have been studied, including surfactants, biosurfactants, microemulsions, natural surfactants, cyclodextrins, vegetable oil and solution with solid phase particles. These extraction agents have been found to remove PAHs from soil at percentages ranging from 47 to 100% for various PAHs.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
This paper aims to review the applications of Fenton based treatments specifically for polycyclic aromatic hydrocarbons-contaminated soils. An overview of the background and principles of Fenton treatment catalysed by both homogenous (conventional and modified Fenton) and heterogeneous (Fenton-like) catalysts is firstly presented. Laboratory and field soil remediation studies are then discussed in terms of efficiency, kinetics and associated factors. Four main scopes of integrated Fenton treatments, i.e. physical-Fenton, biological-Fenton, electro-Fenton and photo-Fenton are also reviewed in this paper. For each of these integrated remediation technologies, the theoretical background and mechanisms are detailed alongside with achievable removal efficiencies for polycyclic aromatic hydrocarbons in contaminated soils compared to sole Fenton treatment. Finally, the environmental impacts of Fenton based soil treatments are documented and discussed.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
To date, little information is known about the operation of the enhanced biological phosphorus removal (EBPR) process in tropical climates. Along with the global concerns on nutrient pollution and the increasing array of local regulatory requirements, the applicability and compliance accountability of the EBPR process for sewage treatment in tropical climates is being evaluated. A sequencing batch reactor (SBR) inoculated with seed sludge from a conventional activated sludge (CAS) process was successfully acclimatized to EBPR conditions at 28 °C after 13 days' operation. Enrichment of Candidatus Accumulibacter phosphatis in the SBR was confirmed through fluorescence in situ hybridization (FISH). The effects of operational pH and influent C:P ratio on EBPR were then investigated. At pH 7 or pH 8, phosphorus removal rates of the EBPR processes were relatively higher when operated at C:P ratio of 3 than C:P ratio of 10, with 0.019-0.020 and 0.011-0.012 g-P/g-MLVSS•day respectively. One-year operation of the 28 °C EBPR process at C:P ratio of 3 and pH 8 demonstrated stable phosphorus removal rate of 0.020 ± 0.003 g-P/g-MLVSS•day, corresponding to effluent with phosphorus concentration <0.5 mg/L. This study provides the first evidence on good EBPR activity at relatively high temperature, indicating its applicability in a tropical climate.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
Artificial neural networks (ANNs) have been widely used to solve the problems because of their reliable, robust, and salient characteristics in capturing the nonlinear relationships between variables in complex systems. In this study, ANN was applied for modeling of Chemical Oxygen Demand (COD) and biodegradable organic matter (BOD) removal from palm oil mill secondary effluent (POMSE) by vetiver system. The independent variable, including POMSE concentration, vetiver slips density, and removal time, has been considered as input parameters to optimize the network, while the removal percentage of COD and BOD were selected as output. To determine the number of hidden layer nodes, the root mean squared error of testing set was minimized, and the topologies of the algorithms were compared by coefficient of determination and absolute average deviation. The comparison indicated that the quick propagation (QP) algorithm had minimum root mean squared error and absolute average deviation, and maximum coefficient of determination. The importance values of the variables was included vetiver slips density with 42.41%, time with 29.8%, and the POMSE concentration with 27.79%, which showed none of them, is negligible. Results show that the ANN has great potential ability in prediction of COD and BOD removal from POMSE with residual standard error (RSE) of less than 0.45%.
Matched MeSH terms: Environmental Restoration and Remediation/methods*
Pristine chitosan beads were modified with sulfur (S)-containing functional groups to produce thiolated chitosan beads (ETB), thereby increasing S donor ligands and crosslinks. The effect of temperature, heating time, carbon disulfide (CS2)/chitosan ratio, and pH on total S content of ETB was examined using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The total S content of ETB increased with increasing CS2/chitosan ratio and decreased with decreasing pH and increasing temperature (>60 °C) and heating time (at 60 °C). Spectroscopic analyses revealed the presence of thiol (-SH)/thione, disulfide (-S-S-), and sulfonate groups in ETB. The thiolation mechanism involves decomposition of dithiocarbamate groups, thereby forming thiourea crosslinks and trithiocarbonate, resulting in -SH oxidation to produce -S-S- crosslinks. The partially formed ETB crosslinks contribute to its acid stability and are thermodynamically feasible in adsorbing Cd and Cu. The S-containing functional groups added to chitinous wastes act as sorbents for metal remediation from acidic environments.
Matched MeSH terms: Environmental Restoration and Remediation/methods*