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Knowledge and Confidence Level Among Emergency Healthcare Workers in Airway Management and Resuscitation of Suspected COVID-19 Patients: A Cross Sectional Study in Malaysia

Abd Samat AH, Isa MH, Sabardin DM, Jamal SM, Jaafar MJ, Hamzah FA, et al.

Ann Acad Med Singap, 2020 Sep;49(9):643-651.
PMID: 33241252

INTRODUCTION: This study aims to evaluate the knowledge and confidence of emergency healthcare workers (EHCW) in facing the COVID-19 pandemic.
MATERIALS AND METHODS: A cross-sectional online study using a validated questionnaire was distributed to doctors (MD), assistant medical officers (AMO), and staff nurses (SN) at an urban tertiary Emergency Department. It comprised of 40 knowledge and 10 confidence-level questions related to resuscitation and airway management steps.
RESULTS: A total of 135 from 167 eligible EHCW were enrolled. 68.9% (n = 93) had high knowledge while 53.3% (n = 72) possessed high confidence level. Overall knowledge mean score was 32.96/40 (SD = 3.63) between MD (33.88±3.09), AMO (32.28±4.03), and SN (32.00±3.60), P= 0.025. EHCWs with a length of service (LOS) between 4-10 years had the highest knowledge compared to those with LOS <4-year (33.71±3.39 versus 31.21±3.19 P = 0.002). Airway-related knowledge was significantly different between the designations and LOS (P = 0.002 and P = 0.003, respectively). Overall, EHCW confidence level against LOS showed significant difference [F (2, 132) = 5.46, P = 0.005] with longer LOS showing better confidence. MD showed the highest confidence compared to AMO and SN (3.67±0.69, 3.53±0.68, 3.26±0.64) P = 0.049. The majority EHCW were confident in performing high-quality chest-compression, and handling of Personal Protective Equipment but less than half were confident in resuscitating, leading the resuscitation, managing the airway or being successful in first intubation attempt.
CONCLUSIONS: EHCW possessed good knowledge in airway and resuscitation of COVID-19 patients, but differed between designations and LOS. A longer LOS was associated with better confidence, but there were some aspects in airway management and resuscitation that needed improvement.
Enhancing the hydrophobicity of mangrove bark by esterification for oil adsorption

Asadpour R, Sapari NB, Isa MH, Orji KU

Water Sci Technol, 2014 10 18;70(7):1220-8.
PMID: 25325547 DOI: 10.2166/wst.2014.355

Oil spills generally cause worldwide concern due to their detrimental effects on the environment and the economy. An assortment of commercial systems has been developed to control these spills, including the use of agricultural wastes as sorbents. This work deals with raw and modified mangrove barks (Rhizophora apiculata), an industrial lignocellulosic waste, as a low cost adsorbent for oil-product-spill cleanup in the aquatic environment. Mangrove bark was modified using fatty acids (oleic acid and palmitic acid) to improve its adsorption capacity. The oil sorption capacity of the modified bark was studied and compared with that of the raw bark. Kinetic tests were conducted with a series of contact times. The influence of particle size, oil dosage, pH and temperature on oil sorption capacity was investigated. The results showed that oleic acid treated bark has a higher sorption capacity (2,860.00 ± 2.00 mg/g) than untreated bark for Tapis crude oil. A correlation between surface functional groups, morphology and surface area of the adsorbent was studied by Fourier transform infrared spectrum, field emission scanning electron microscopy images and Brunauer-Emmett-Teller analysis. Isotherm study was conducted using the Langmuir and Freundlich isotherm models. The result showed that adsorption of crude oil on treated mangrove bark could be best described by the Langmuir model.
Acetylation of oil palm empty fruit bunch fiber as an adsorbent for removal of crude oil

Asadpour R, Sapari NB, Isa MH, Kakooei S

Environ Sci Pollut Res Int, 2016 Jun;23(12):11740-50.
PMID: 26944428 DOI: 10.1007/s11356-016-6349-2

Removal of oil spillage from the environment is a global concern. Various methods, including the use of fibers as sorbents, have been developed for oil spill control. Oil palm empty fruit bunch (OPEFB) fiber is a plant biomass that may be acetylated by acetic anhydride using N-bromosuccinimide (NBS) as a catalyst; here, the extent of acetylation may be calculated in terms of weight percent gain (WPG). The modified fiber was used to remove Tapis and Arabian crude oils. The optimum time, temperature, and catalyst concentration were 4 h, 120 °C, and 3 %, respectively, and these parameters could achieve an 11.49 % increase in WPG. The optimized parameters improved the adsorption capacity of OPEFB fibers for crude oil removal. The acetylated OPEFB fibers were characterized by using Fourier transform infrared spectroscopy and field emission scanning electron microscopy to observe the functional groups available and morphology. Kinetic and isotherm studies were conducted using different contact times and oil/water ratios. The rate of oil sorption onto the OPEFB fibers can be adequately described by the pseudo-second-order equation. Adsorption studies revealed that adsorption of crude oil on treated OPEFB fiber could be best described by the Langmuir isotherm model.
Landfill leachate treatment by electrochemical oxidation

Bashir MJ, Isa MH, Kutty SR, Awang ZB, Aziz HA, Mohajeri S, et al.

Waste Manag, 2009 Sep;29(9):2534-41.
PMID: 19523802 DOI: 10.1016/j.wasman.2009.05.004

This study investigated the electrochemical oxidation of stabilized leachate from Pulau Burung semi-aerobic sanitary landfill by conducting laboratory experiments with sodium sulfate Na(2)SO(4) (as electrolyte) and graphite carbon electrodes. The control parameters were influent COD, current density and reaction time, while the responses were BOD removal, COD removal, BOD:COD ratio, color and pH. Na(2)SO(4) concentration was 1 g/L. Experiments were conducted based on a three-level factorial design and response surface methodology (RSM) was used to analyze the results. The optimum conditions were obtained as 1414 mg/L influent COD concentration, 79.9 mA/cm(2) current density and 4 h reaction time. This resulted in 70% BOD removal, 68% COD removal, 84% color removal, 0.04 BOD/COD ratio and 9.1 pH. Electrochemical treatment using graphite carbon electrode was found to be effective in BOD, COD and color removal but was not effective in increasing the BOD/COD ratio or enhancing biodegradability of the leachate. The color intensity of the treated samples increased at low influent COD and high current density due to corrosion of electrode material.
Application of response surface methodology (RSM) to optimize coagulation-flocculation treatment of leachate using poly-aluminum chloride (PAC) and alum

Ghafari S, Aziz HA, Isa MH, Zinatizadeh AA

J Hazard Mater, 2009 Apr 30;163(2-3):650-6.
PMID: 18771848 DOI: 10.1016/j.jhazmat.2008.07.090

Coagulation-flocculation is a relatively simple physical-chemical technique in treatment of old and stabilized leachate which has been practiced using a variety of conventional coagulants. Polymeric forms of metal coagulants which are increasingly applied in water treatment are not well documented in leachate treatment. In this research, capability of poly-aluminum chloride (PAC) in the treatment of stabilized leachate from Pulau Burung Landfill Site (PBLS), Penang, Malaysia was studied. The removal efficiencies for chemical oxygen demand (COD), turbidity, color and total suspended solid (TSS) obtained using PAC were compared with those obtained using alum as a conventional coagulant. Central composite design (CCD) and response surface method (RSM) were applied to optimize the operating variables viz. coagulant dosage and pH. Quadratic models developed for the four responses (COD, turbidity, color and TSS) studied indicated the optimum conditions to be PAC dosage of 2g/L at pH 7.5 and alum dosage of 9.5 g/L at pH 7. The experimental data and model predictions agreed well. COD, turbidity, color and TSS removal efficiencies of 43.1, 94.0, 90.7, and 92.2% for PAC, and 62.8, 88.4, 86.4, and 90.1% for alum were demonstrated.
Enhancement of anaerobic digestibility of waste activated sludge using photo-Fenton pretreatment

Heng GC, Isa MH, Lim JW, Ho YC, Zinatizadeh AAL

Environ Sci Pollut Res Int, 2017 Dec;24(35):27113-27124.
PMID: 28963706 DOI: 10.1007/s11356-017-0287-5

Biological treatments, such as activated sludge process, are common methods to treat municipal and industrial wastewaters. However, they produce huge amounts of waste activated sludge (WAS). The excess sludge treatment and disposal are a challenge for wastewater treatment plants due to economic, environmental, and regulatory factors. In this study, photo-Fenton pretreatment (oxidation using hydrogen peroxide and iron catalyst aided with UV light) was optimized using response surface methodology (RSM) and central composite design (CCD) to determine the effects of three operating parameters (H2O2 dosage, H2O2/Fe2+ molar ratio, and irradiation time) on disintegration and dewaterability of WAS. MLVSS removal, capillary suction time (CST) reduction, sCOD, and EPS were obtained as 70%, 25%, 12,000 mg/L, and 500 mg/L, respectively, at the optimal conditions, i.e., 725 g H2O2/kg TS, H2O2/Fe2+ molar ratio 80, and irradiation time 40 min. Two batch-fed completely mixed mesophilic anaerobic digesters were then operated at 15-day solid retention time (SRT) and 37 ± 0.5 °C to compare the digestibility of untreated and photo-Fenton pretreated sludge in terms of volatile solids (VS) reduction, COD removal, and biogas production at steady-state operations. Photo-Fenton pretreatment followed by anaerobic digestion of WAS was very effective and yielded 75.7% total VS reduction, 81.5% COD removal, and 0.29-0.31 m3/kg VSfed·d biogas production rate, compared to 40.7% total VS solid reduction, 54.7% COD removal, and 0.12-0.17 m3/kg VSfed·d biogas production rate for control. Thus, photo-Fenton can be a useful pretreatment step in sludge management.
Physico-chemical method for ammonia removal from synthetic wastewater using limestone and GAC in batch and column studies

Hussain S, Aziz HA, Isa MH, Adlan MN, Asaari FA

Bioresour Technol, 2007 Mar;98(4):874-80.
PMID: 16716587

The purpose of the present study was to examine the removal of ammoniacal nitrogen (NH4-N) from synthetic wastewater using limestone (LS) and granular activated carbon (GAC) mixture as low cost adsorbent. In batch study, optimum shaking and settling times were 150 and 120 min, respectively. The LS-GAC mixture ratio of 25:15 removed about 58% NH4-N. The smaller particle size of medium yielded higher adsorption capacity. The equilibrium adsorption data followed the Freundlich isotherm (R2 > 0.98) but it showed weak bond. Adsorption kinetics were well described by the pseudo second-order rate model (R2 > 0.93). The upflow column showed that higher flow rate and initial concentration resulted in shorter column saturation time. The study showed that the usage of GAC could be reduced by combining GAC with LS for the removal of NH4-N from wastewater; thus reducing the cost of treatment.
Removal of chromium (VI) from aqueous solution using treated oil palm fibre

Isa MH, Ibrahim N, Aziz HA, Adlan MN, Sabiani NH, Zinatizadeh AA, et al.

J Hazard Mater, 2008 Apr 1;152(2):662-8.
PMID: 17714862

This study proposed an oil palm by-product as a low-cost adsorbent for the removal of hexavalent chromium [Cr (VI)] from aqueous solution. Adsorption of Cr (VI) by sulphuric acid and heat-treated oil palm fibre was conducted using batch tests. The influence of pH, contact time, initial chromium concentration and adsorbent dosage on the removal of Cr (VI) from the solutions was investigated. The optimum initial pH for maximum uptake of Cr (VI) from aqueous solution was found to be 1.5. The removal efficiency was found to correlate with the initial Cr (VI) concentration, adsorbent dosage as well as the contact time between Cr (VI) and the adsorbent. The adsorption kinetics tested with pseudo first order and pseudo second order models yielded high R(2) values from 0.9254 to 0.9870 and from 0.9936 to 0.9998, respectively. The analysis of variance (ANOVA) showed significant difference between the R(2) values of the two models at 99% confidence level. The Freundlich isotherm (R(2)=0.8778) described Cr (VI) adsorption slightly better than the Langmuir isotherm (R(2)=0.8715). Difficulty in desorption of Cr (VI) suggests the suitability of treated oil palm fibre as a single-use adsorbent for Cr (VI) removal from aqueous solution.
Solid waste collection and recycling in Nibong Tebal, Penang, Malaysia: a case study

Isa MH, Asaari FA, Ramli NA, Ahmad S, Siew TS

Waste Manag Res, 2005 Dec;23(6):565-70.
PMID: 16379126

The implementation of a suitable solid waste management programme with appropriate methods of recycling as an inherent element is vital to the alleviation of the problems associated with solid waste generation, handling and disposal, environmental conservation, public hygiene, etc. The present work is a case study on solid waste collection and recycling practices in Nibong Tebal town, Penang, Malaysia. The amount and types of domestic waste generated, household participation in recycling, identification of existing problems related to the implementation of the recycling programme, etc. formed the basis of this study. Surveys (interviews/questionnaires) and on-site observations were conducted to gather information on the solid waste collection and recycling practice of the residents. A focus group of 60 individuals was selected and their response to a questionnaire, prepared according to a Likert scale, was obtained and analysed. The majority of the respondents expressed concerns about recycling and wanted more to be done in this regard. Illegal collection, aesthetically displeasing sites and a lack of public awareness were problems of major concern. Issues related to inadequate funding and manpower as well as end market are also addressed and suggestions made.
Boron removal by electrocoagulation and recovery

Isa MH, Ezechi EH, Ahmed Z, Magram SF, Kutty SR

Water Res, 2014 Mar 15;51:113-23.
PMID: 24412846 DOI: 10.1016/j.watres.2013.12.024

This work investigated the removal of boron from wastewater and its recovery by electrocoagulation and hydrothermal mineralization methods respectively. The experimental design was developed using Box-Behnken Model. An initial study was performed based on four preselected variables (pH, current density, concentration and time) using synthetic wastewater. Response surface methodology (RSM) was used to evaluate the effect of process variables and their interaction on boron removal. The optimum conditions were obtained as pH 6.3, current density 17.4 mA/cm(2), and time 89 min. At these applied optimum conditions, 99.7% boron removal from an initial concentration of 10.4 mg/L was achieved. The process was effectively optimized by RSM with a desirability value of 1.0. The results showed that boron removal efficiency enhanced with increase in current density and treatment time. Removal efficiency also increased when pH was increased from 4 to 7 and subsequently decreased at pH 10. Adsorption kinetics study revealed that the reaction followed pseudo second order kinetic model; evidenced by high correlation and goodness of fit. Thermodynamics study showed that mechanism of boron adsorption was chemisorption and the reaction was endothermic in nature. Furthermore, the adsorption process was spontaneous as indicated by negative values of the adsorption free energy. Treatment of real produced water using electrocoagulation resulted in 98% boron removal. The hydrothermal mineralization study showed that borate minerals (Inyoite, Takadaite and Nifontovite) can be recovered as recyclable precipitate from electrocoagulation flocs of produced water.
Fulltext The Effectiveness of Self-Instructional Video vs. Classroom Teaching Method on Focused Assessment With Sonography in Trauma Among House Officers in University Hospital

Isa MH, Lim K, Jaafar MJ, Mohd Saiboon I

Front Surg, 2021;8:698774.
PMID: 34485373 DOI: 10.3389/fsurg.2021.698774

Background: The aim of this study was to compare the effectiveness of self-instructional-video (SIV) and classroom training method (CTM) in learning Focus-Assessment with Sonography-in-Trauma (FAST) among house officers (HO). Method: A randomized controlled study involving house officers working in the university hospital in Malaysia was conducted where participants were randomized into SIV group (intervention) and CTM group (control). Each group had to undergo a 4 h hands-on training. The intervention group has undergone self-training using the video material without any facilitation while the control group received lecture and hands-on training with facilitators. Participants' performance was assessed using a validated Objective Structured Clinical Examination checklist for landmark identification and interpretation of images generated. Learning preference and confidence level were also assessed. Result: A total of 33 HO were enrolled in this study. Marks obtained in image acquisition by the intervention and control were 25.3 (SD = 5.3) and 25.6 (SD = 2.3) p > 0.05, respectively. While in image interpretation, the mean score for the intervention and control group was 10.3 (SD 1.7) and 9.8 (SD = 1.7) p > 0.05, respectively. Overall performance assessment, showed the intervention group obtained 35.6 (SD = 5.9) compared to control 35.3 (SD = 3.4), p > 0.05. Based on pre-specified determinant these scores difference falls within the 10% of non-inferiority margin. The absolute difference between both groups was 0.3 (CI = -3.75 to 3.21, p = 0.871), which proves non-inferiority but not superiority. In terms of learning preference and confidence to perform FAST, most of the participants preferred the control group approach. Conclusion: The SIV method is as effective as the CTM for learning FAST among the house officers and served as an alternative to classroom teaching. However, this technique needs improvement in promoting their confidence and preference. Perhaps incorporating a feedback session after going through the SIV would improve the confidence.
Improved anaerobic digestion of palm oil mill effluent and biogas production by ultrasonication pretreatment

Isa MH, Wong LP, Bashir MJK, Shafiq N, Kutty SRM, Farooqi IH, et al.

Sci Total Environ, 2020 Jun 20;722:137833.
PMID: 32199372 DOI: 10.1016/j.scitotenv.2020.137833

Palm oil mill effluent (POME) is a highly polluted wastewater that consists of a high organic content of 4-5% total solids; a potential renewable energy source. A waste to energy study was conducted to improve biogas production using POME as substrate by ultrasonication pretreatment at mesophilic temperatures. The effect of temperature on the specific growth rate of anaerobes and methanogenic activity was investigated. Five sets of assays were carried out at operating temperatures between 25 °C and 45 °C. Each set consisted of two experiments using identical anaerobic sequencing batch reactors (AnSBR); fed with raw POME (control) and sonicated POME, respectively. The ultrasonication was set at 16.2 min ultrasonication time and 0.88 W mL-1 ultrasonication density with substrate total solids concentration of 6% (w/v). At 25 °C, biogas production rate and organic matter removal exhibited lowest values for both reactors. The maximum organic degradation was 96% from AnSBR operated at 30 °C fed with sonicated POME and 91% from AnSBR operated at 35 °C fed with unsonicated POME. In addition, the methane yield from AnSBR operated at 30 °C was enhanced by 21.5% after ultrasonication pretreatment. A few normality tests and a t-test were carried out. Both tests indicated that the residuals of the experimental data were normality distributed with mean equals to zero. The results demonstrated that ultrasonication treatment was a promising pretreatment to positively affect the organic degradation and biogas production rates at 30-35 °C.
Anaerobic treatment of ultrasound pretreated palm oil mill effluent (POME): microbial diversity and enhancement of biogas production

Isa MH, Bashir MJK, Wong LP

Environ Sci Pollut Res Int, 2022 Jun;29(29):44779-44793.
PMID: 35138542 DOI: 10.1007/s11356-022-19022-3

In this study, palm oil mill effluent (POME) treated by ultrasonication at optimum conditions (sonication power: 0.88 W/mL, sonication duration: 16.2 min and total solids: 6% w/v) obtained from a previous study was anaerobically digested at different hydraulic retention times (HRTs). The reactor biomass was subjected to metagenomic study to investigate the impact on the anaerobic community dynamics. Experiments were conducted in two 5 L continuously stirred fill-and-draw reactors R1 and R2 operated at 30 ± 2 °C. Reactor R1 serving as control reactor was fed with unsonicated POME with HRT of 15 and 20 days (R1-15 and R1-20), whereas reactor R2 was fed with sonicated POME with the same HRTs (R2-15 and R2-20). The most distinct archaea community shift was observed among Methanosaeta (R1-15: 26.6%, R2-15: 34.4%) and Methanobacterium (R1-15: 7.4%, R2-15: 3.2%). The genus Methanosaeta was identified from all reactors with the highest abundance from the reactors R2. Mean daily biogas production was 6.79 L from R2-15 and 4.5 L from R1-15, with relative methane gas abundance of 85% and 73%, respectively. Knowledge of anaerobic community dynamics allows process optimization for maximum biogas production.
Fulltext Modeling of Cu(II) Adsorption from an Aqueous Solution Using an Artificial Neural Network (ANN)

Khan T, Binti Abd Manan TS, Isa MH, Ghanim AAJ, Beddu S, Jusoh H, et al.

Molecules, 2020 Jul 17;25(14).
PMID: 32708928 DOI: 10.3390/molecules25143263

This research optimized the adsorption performance of rice husk char (RHC4) for copper (Cu(II)) from an aqueous solution. Various physicochemical analyses such as Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FESEM), carbon, hydrogen, nitrogen, and sulfur (CHNS) analysis, Brunauer-Emmett-Teller (BET) surface area analysis, bulk density (g/mL), ash content (%), pH, and pHZPC were performed to determine the characteristics of RHC4. The effects of operating variables such as the influences of aqueous pH, contact time, Cu(II) concentration, and doses of RHC4 on adsorption were studied. The maximum adsorption was achieved at 120 min of contact time, pH 6, and at 8 g/L of RHC4 dose. The prediction of percentage Cu(II) adsorption was investigated via an artificial neural network (ANN). The Fletcher-Reeves conjugate gradient backpropagation (BP) algorithm was the best fit among all of the tested algorithms (mean squared error (MSE) of 3.84 and R2 of 0.989). The pseudo-second-order kinetic model fitted well with the experimental data, thus indicating chemical adsorption. The intraparticle analysis showed that the adsorption process proceeded by boundary layer adsorption initially and by intraparticle diffusion at the later stage. The Langmuir and Freundlich isotherm models interpreted well the adsorption capacity and intensity. The thermodynamic parameters indicated that the adsorption of Cu(II) by RHC4 was spontaneous. The RHC4 adsorption capacity is comparable to other agricultural material-based adsorbents, making RHC4 competent for Cu(II) removal from wastewater.
Fulltext Strength enhancement of concrete using incinerated agricultural waste as supplementary cement materials

Manan TSBA, Kamal NLM, Beddu S, Khan T, Mohamad D, Syamsir A, et al.

Sci Rep, 2021 06 16;11(1):12722.
PMID: 34135374 DOI: 10.1038/s41598-021-92017-1

The potassium (K) and sodium (Na) elements in banana are needed for hydration reaction that can enhance the strength properties of concrete. This research aims (a) to determine the material engineering properties of banana skin ash (BSA) and concrete containing BSA, (b) to measure the strength enhancement of concrete due to BSA, and (c) to identify optimal application of BSA as supplementary cement materials (SCM) in concrete. The BSA characterization were assessed through X-ray fluorescence (XRF) and Blaine's air permeability. The workability, compressive strength, and microstructures of concrete containing BSA were analysed using slump test, universal testing machine (UTM) and scanning electron microscope (SEM). A total of 15 oxides and 19 non-oxides elements were identified in BSA with K (43.1%) the highest and Na was not detected. At 20 g of mass, the BSA had a higher bulk density (198.43 ± 0.00 cm3) than ordinary Portland cement (OPC) (36.32 ± 0.00 cm3) indicating availability of large surface area for water absorption. The concrete workability was reduced with the presence of BSA (0% BSA: > 100 mm, 1% BSA: 19 ± 1.0 mm, 2%: 15 ± 0.0 mm, 3% BSA: 10 ± 0.0 mm). The compressive strength increased with the number of curing days. The concrete microstructures were improved; interfacial transition zones (ITZ) decreased with an increase of BSA. The optimal percentage of BSA obtained was at 1.25%. The established model showed significant model terms (Sum of Squares = 260.60, F value = 69.84) with probability of 0.01% for the F-value to occur due to noise. The established model is useful for application in construction industries.
Ex-situ bioremediation of crude oil in soil, a comparative kinetic analysis

Mohajeri L, Aziz HA, Isa MH, Zahed MA, Mohajeri S

Bull Environ Contam Toxicol, 2010 Jul;85(1):54-8.
PMID: 20577869 DOI: 10.1007/s00128-010-0058-1

Weathered crude oil (WCO) removals in shoreline sediment samples were monitored for 60 days in bioremediation experimentation. Experimental modeling was carried out using statistical design of experiments. At optimum conditions maximum of 83.13, 78.06 and 69.92% WCO removals were observed for 2, 16 and 30 g/kg initial oil concentrations, respectively. Significant variations in the crude oil degradation pattern were observed with respect to oil, nutrient and microorganism contents. Crude oil bioremediation were successfully described by a first-order kinetic model. The study indicated that the rate of hydrocarbon biodegradation increased with decrease of crude oil concentrations.
A statistical experiment design approach for optimizing biodegradation of weathered crude oil in coastal sediments

Mohajeri L, Aziz HA, Isa MH, Zahed MA

Bioresour Technol, 2010 Feb;101(3):893-900.
PMID: 19773160 DOI: 10.1016/j.biortech.2009.09.013

This work studied the bioremediation of weathered crude oil (WCO) in coastal sediment samples using central composite face centered design (CCFD) under response surface methodology (RSM). Initial oil concentration, biomass, nitrogen and phosphorus concentrations were used as independent variables (factors) and oil removal as dependent variable (response) in a 60 days trial. A statistically significant model for WCO removal was obtained. The coefficient of determination (R(2)=0.9732) and probability value (P<0.0001) demonstrated significance for the regression model. Numerical optimization based on desirability function were carried out for initial oil concentration of 2, 16 and 30 g per kg sediment and 83.13, 78.06 and 69.92 per cent removal were observed respectively, compare to 77.13, 74.17 and 69.87 per cent removal for un-optimized results.
Multiple responses analysis and modeling of Fenton process for treatment of high strength landfill leachate

Mohajeri S, Aziz HA, Zahed MA, Mohajeri L, Bashir MJ, Aziz SQ, et al.

Water Sci Technol, 2011;64(8):1652-60.
PMID: 22335108

Landfill leachate is one of the most recalcitrant wastes for biotreatment and can be considered a potential source of contamination to surface and groundwater ecosystems. In the present study, Fenton oxidation was employed for degradation of stabilized landfill leachate. Response surface methodology was applied to analyze, model and optimize the process parameters, i.e. pH and reaction time as well as the initial concentrations of hydrogen peroxide and ferrous ion. Analysis of variance showed that good coefficients of determination were obtained (R2 > 0.99), thus ensuring satisfactory agreement of the second-order regression model with the experimental data. The results indicated that, pH and its quadratic effects were the main factors influencing Fenton oxidation. Furthermore, antagonistic effects between pH and other variables were observed. The optimum H2O2 concentration, Fe(II) concentration, pH and reaction time were 0.033 mol/L, 0.011 mol/L, 3 and 145 min, respectively, with 58.3% COD, 79.0% color and 82.1% iron removals.
Influence of Fenton reagent oxidation on mineralization and decolorization of municipal landfill leachate

Mohajeri S, Aziz HA, Isa MH, Bashir MJ, Mohajeri L, Adlan MN

J Environ Sci Health A Tox Hazard Subst Environ Eng, 2010;45(6):692-8.
PMID: 20390917 DOI: 10.1080/10934521003648883

This study evaluated the effectiveness of Fenton's technique for the treatment of semi-aerobic landfill leachate collected from Pulau Burung Landfill Site (PBLS), Penang, Malaysia. The Fe2+ or Fe3+ as catalyst and H2O2 as oxidizing agent are commonly used for the classical Fenton's reaction. In present study, the effect of operating conditions such as pH, reaction time, molar ratio, agitation rate, feeding mode and Fenton reagent concentrations which are important parameters that affect the removal efficiencies of Fenton method were investigated. Under the most favorable conditions, the highest removals of 58.1 and 78.3% were observed for COD and color, respectively. In general, the best operating conditions were pH = 3, Fe = 560 mg L(-1), H2O2 = 1020 mg L(-1), H2O2/Fe2+ molar ratio = 3, agitation rate = 400 rpm and reaction time = 120 minutes. The results highlighted that stepwise addition of Fenton's reagent was more effective than adding the entire volume in a single step. Excessive hydrogen peroxide and iron have shown scavenging effects on hydroxyl radicals and reduced degradation of refractory organics in the landfill leachate.
Statistical optimization of process parameters for landfill leachate treatment using electro-Fenton technique

Mohajeri S, Aziz HA, Isa MH, Zahed MA, Adlan MN

J Hazard Mater, 2010 Apr 15;176(1-3):749-58.
PMID: 20022166 DOI: 10.1016/j.jhazmat.2009.11.099

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.

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