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Landfills are one of the main point sources of groundwater pollution. This research mainly aims to assess the risk of nitrate transport from the unlined landfill to subsurface layers and groundwater using experimental results and the SESOIL model. Samples from 12 groundwater wells downstream of the landfill were collected and analyzed in 2008, 21 years after the landfill construction. The average concentration in the wells was 54 mg/L, slightly higher than the World Health Organization ( 50 mg/L) standards. SESOIL model was used to predict the concentration at the bottom of the unsaturated zone. Results indicated that the current mean concentration at the bottom of the unsaturated zone is 75 mg/L. the model predicted that the level of NO3 will increased up to 325 mg/L within 30 years. Accordingly, the concentration in groundwater wells near the landfill area is expected to gradually increase with time. Although the current risk associated with the level might not be harm to adults, however, it might pose severe risks to both adults and infants in the near future due to leaching. Urgent mitigation measures such as final cell cover (cap), lining system and vertical expansion should be considered at the landfill to protect the public health in the area. [ABSTRACT FROM AUTHOR]

The major drawback of the wide applicability of biodiesel is its price compared to the conventional petro-diesel. The feedstock and the applied catalyst in the transesterification reaction are the main contributor for the overall cost of the biodiesel production. Thus, this study summarizes the optimization of a batch transesterification reaction of used domestic waste oil (UDWO) with methanol using CaO, which can be easily prepared from different cheap and readily available natural sources. Quadratic model equations were elucidated describing the effect of methanol:oil molar ratio, CaO concentration wt.%, reaction temperature °C, reaction time h, and mixing rate rpm on biodiesel yield and conversion percentage. The optimum operating conditions were found to be competitive with those of the high-cost immobilized enzyme Novozym435. An overall acceptable agreement was achieved between the produced biodiesel, its blends with petro-diesel and the available commercial petro-diesel, and the international fuel standards. A precise and reliable logarithmic mathematical model was predicted correlating the production of pure high-quality biodiesel yield with the conversion percentage which were measured based on the fatty acid methylester content and decrease in viscosity, respectively. [ABSTRACT FROM AUTHOR]

In this study, response surface methodology based on face center composite – 1/2 factorial fraction design (FCCD) of experiments was employed to optimize the batch transesterification process of waste cooking oil as one of the most abundant and readily available domestic wastes with methanol using immobilizedCandida antarcticalipase (Novozym435) to maximize the production of high-purity biodiesel. Statistically significant second-order quadratic model equations (p< 0.0001) were elucidated through multiple regression analysis to describe the interrelationships between response of interest (biodiesel yield wt% and % conversion, i.e. the transesterification efficiency) and five independent variables (methanol:oil molar ratio, enzyme concentration wt%, reaction temperature °C, reaction time h, and mixing rate rpm). The statistical significance of the effect of these variables (factors) and their interactions on the transesterification efficiency was evaluated and the validity of the predicted models was confirmed. The optimum operating conditions were found to be: 3.63:1 M:O, 8.94 wt% Novozym435, 45.23°C, 2.76 h, and 535.84 rpm. This produced 97 wt% biodiesel yield with % conversion of ≈ 91.79%. An overall acceptable agreement was achieved between the produced biodiesel fuel properties at the aforementioned optimal operating conditions and the Egyptian petrodiesel and international biodiesel standards. [ABSTRACT FROM AUTHOR]

This work illustrates a comparative study on the applicability of the natural calcium oxide (CaO) prepared from waste eggshells and chemical CaO as basic heterogeneous catalyst in the transesterification of waste cooking oil (WCO) with methanol for production of biodiesel. Response surface methodology (RSM) based on D-optimal design of experiments was employed to study the significance and interactive effect of methanol-to-oil (M:O) molar ratio, catalyst concentration, reaction time, and mixing rate on biodiesel yield. Second-order quadratic model equations were obtained describing the interrelationships between dependent and independent variables to maximize the response variable (biodiesel yield) and the validity of the predicted models were confirmed. The activity of the produced natural biocatalyst was comparable to that of chemical CaO, producing high yield of biodiesel ≈91 and 98% at 8.57:1 M:O, 3.99 catalyst wt%, 31 min reaction time, and 398.88 rpm mixing rate at 60°C, respectively. Fuel properties of the produced biodiesel were measured and compared with those of Egyptian petro-diesel and international biodiesel standards. The overall biodiesel characteristics either prepared using natural or chemical CaO were comparable and acceptable, encouraging the application of CaO prepared from waste eggshells for production of biodiesel as an efficient, environmentally friendly, sustainable, and low cost heterogeneous catalyst. [ABSTRACT FROM PUBLISHER]

The objective of this study was to investigate the performance of employing Fenton's reagent in the advanced oxidation of ozone to treat stabilized landfill leachate in an ozone reactor. A central composite design (CCD) with response surface methodology (RSM) was applied to evaluate the relationships between operating variables, such as ozone and Fenton dosage, pH, and reaction time, to identify the optimum operating conditions. Quadratic models for the following four responses proved to be significant with very low probabilities (<0.0001): chemical oxygen demand (COD), color, NH3–N, and ozone consumption (OC). The obtained optimum conditions included a reaction time of 90 min, 30 g/m3ozone, 0.01 mol/LH2O2,0.02 mol/L Fe2+, and pH 5. COD, color, and NH3–N removal rates of 79%, 100%, and 20%, respectively, and 0.18 kg O3/kg COD OC were obtained. The predictions correspond well with experimental results (COD, color, and NH3–N removal rates of 78%, 98.5%, and 19%, respectively, and 0.29 kg O3/kg COD OC). This method reduces the treatment time and improves the treatment efficiency relative to a previously published method that used Fenton's reagent prior to ozonation. [ABSTRACT FROM AUTHOR]