A. A. Alazba

A Review of Removal of Pollutants from Water/Wastewater Using Different Types of Nanomaterials

The rapidly increasing population, depleting water resources, and climate change resulting in prolonged droughts and floods have rendered drinking water a competitive resource in many parts of the world. The development of cost-effective and stable materials and methods for providing the fresh water in adequate amounts is the need of the water industry. Traditional water/wastewater treatment technologies remain ineffective for providing adequate safe water due to increasing demand of water coupled with stringent health guidelines and emerging contaminants. Nanotechnology-based multifunctional and highly efficient processes are providing affordable solutions to water/wastewater treatments that do not rely on large infrastructures or centralized systems. The aim of the present study is to review the possible applications of the nanoparticles/fibers for the removal of pollutants from water/wastewater. The paper will briefly overview the availability and practice of different nanomaterials (particles or fibers) for removal of viruses, inorganic solutes, heavy metals, metal ions, complex organic compounds, natural organic matter, nitrate, and other pollutants present in surface water, ground water, and/or industrial water. Finally, recommendations are made based on the current practices of nanotechnology applications in water industry for a stand-alone water purification unit for removing all types of contaminants from wastewater.

Photocatalysis and Bandgap Engineering Using ZnO Nanocomposites

Nanocomposites have a great potential to work as efficient, multifunctional materials for energy conversion and photoelectrochemical reactions. Nanocomposites may reveal more improved photocatalysis by implying the improvements of their electronic and structural properties than pure photocatalyst. This paper presents the recent work carried out on photoelectrochemical reactions using the composite materials of ZnO with CdS, ZnO with SnO2, ZnO with TiO2, ZnO with Ag2S, and ZnO with graphene and graphene oxide. The photocatalytic efficiency mainly depends upon the light harvesting span of a material, lifetime of photogenerated electron-hole pair, and reactive sites available in the photocatalyst. We reviewed the UV-Vis absorption spectrum of nanocomposite and photodegradation reported by the same material and how photodegradation depends upon the factors described above. Finally the improvement in the absorption band edge of nanocomposite material is discussed.

Comparison of ANN, MVR, and SWR models for computing thermal efficiency of a solar still

ABSTRACT In this paper, the viability of modeling the instantaneous thermal efficiency (ηith) of a solar still was determined using meteorological and operational data with an artificial neural network (ANN), multivariate regression (MVR), and stepwise regression (SWR). This study used meteorological and operational variables to hypothesize the effect of solar still performance. In the ANN model, nine variables were used as input parameters: Julian day, ambient temperature, relative humidity, wind speed, solar radiation, feed water temperature, brine water temperature, total dissolved solids of feed water, and total dissolved solids of brine water. The ηith was represented by one node in the output layer. The same parameters were used in the MVR and SWR models. The advantages and disadvantages were discussed to provide different points of view for the models. The performance evaluation criteria indicated that the ANN model was better than the MVR and SWR models. The mean coefficient of determination for the ANN model was about 13% and14% more accurate than those of the MVR and SWR models, respectively. In addition, the mean root mean square error values of 6.534% and 6.589% for the MVR and SWR models, respectively, were almost double that of the mean values for the ANN model. Although both MVR and SWR models provided similar results, those for the MVR were comparatively better. The relative errors of predicted ηith values for the ANN model were mostly in the vicinity of ±10%. Consequently, the use of the ANN model is preferred, due to its high precision in predicting ηith compared to the MVR and SWR models. This study should be extremely beneficial to those coping with the design of solar stills.

Soil Erosion Control and Moisture Conservation of Arid Lands with Stone Cover

Soil moisture conservation and combating soil erosion on agricultural fields are the highest priorities for crop production in arid lands. In this research, the effect of land application of rock fragments on runoff, soil loss, and vegetative cover on a silt loam soil has been tested under natural rainfall conditions. Field plots of 2 m wide by 10 m long were prepared in two locations with a deposit installed at the downstream end of the plots to collect runoff and sediments after each storm during the 2004/2005 winter season. Three treatments were used in the experiments in duplicates including plots covered with 5% and 15% stone and a control. Experimental results showed that rock fragments were highly effective in reducing runoff and soil loss. Runoff depth from plots covered with rock fragments at a rate of 5% and 15% was reduced by 17% and 30% compared to the control, respectively. The corresponding reductions in soil loss for both stone treatment levels were as high as 35% and 53%, respectively. The average soil moisture measured at the center of the plots during the entire season was always higher for stone treated plots and increased with stone coverage percentage compared to control. Consequently, vegetative cover was higher in the plots with 5% rock fragments cover. For higher stone coverage of 15%, rock fragments occupy more soil surface area and, therefore, reduce the space available for vegetation.

Comparison between gene expression programming and traditional models for estimating evapotranspiration under hyper arid Conditions

Gene Expression Programming (GEP) was used to develop new mathematical equations for estimating daily reference evapotranspiration (ETref) for the Kingdom of Saudi Arabia. The daily climatic variables were collected by 13 meteorological stations from 1980 to 2010. The GEP models were trained on 65% of the climatic data and tested using the remaining 35%. The generalised Penman-Monteith model was used as a reference target for evapotranspiration (ET) values, with hc varies from 5 to 105 cm with increment of a centimetre. Eight GEP models have been compared with four locally calibrated traditional models (Hargreaves-Samani, Irmak, Jensen-Haise and Kimberly-Penman). The results showed that the statistical performance criteria values such as determination coefficients (R2) ranged from as low as 64.4% for GEP-MOD1, where the only parameters included (maximum, minimum, and mean temperature and crop height), to as high as 95.5% for GEP-MOD8 with which all climatic parameters included (maximum, minimum and mean temperature; maximum, minimum and mean humidity; solar radiation; wind speed; and crop height). Moreover, an interesting founded result is that the solar radiation has almost no effect on ETref under the hyper arid conditions. In contrast, the wind speed and plant height have a great positive impact in increasing the accuracy of calculating ETref. Furthermore, eight GEP models have obtained better results than the locally calibrated traditional ETref equations.

Synergistic effect of nano-sized mackinawite with cyano-cobalamin in cement slurries for reductive dechlorination of tetrachloroethylene

Experiments were conducted to investigate the reductive dechlorination of tetrachloroethylene (PCE) by nano-Mackinawite (nFeS) with cyano-cobalamin (Cbl(III)) in cement slurries. Almost complete degradation of PCE by nFeS-Cbl(III) was observed in cement slurries in 5 h and its degradation kinetics (k(obs-PCE)=0.57 h(-1)) was 6-times faster than that of nFeS-Cbl(III) without the cement slurries. PCE was finally transformed to non-chlorinated organic compounds such as ethylene, acetylene, and C3-C4 hydrocarbons by nFeS-Cbl(III) in cement slurries. X-ray photoelectron spectroscopy and PCE degradation by cement components (SiO2, Al2O3, and CaO) revealed that both the reduced Co species in Cbl(III) and the presence of Ca in cement played an important role for the enhanced reductive dechlorination of PCE. The increase in the concentration of Cbl(III) (0.005-0.1 mM), cement ratio (0.05-0.2), and suspension pH (11.5-13.5) accelerated the PCE degradation kinetics by providing more favorable environments for the production of reactive Ca species and reduction of Co species. We also observed that the degradation efficiency of PCE by nFeS-Cbl(III)-cement lasted even at high concentration of PCE. The experimental results obtained from this study could provide fundamental knowledge of redox interactions among nFeS, Cbl(III), and cement, which could significantly enhance reductive dechlorination of chlorinated organics in contaminated natural and engineered environments.

Evapotranspiration models assessment under hyper-arid environment

In this study, we develop more accurate hyper-arid evapotranspiration (ET) models to help improve irrigation water conservation. We examine five ET models (one combination model, three radiation-based models, and one temperature-based model) under hyper-arid condition at three center-pivot fields in the Kingdom of Saudi Arabia. These models were evaluated and calibrated for the alfalfa crop of 2010 and validated for the wheat and potato crops of 2011. The FAO-56 Penman–Monteith (PM) was the most accurate ET model for estimating crop water irrigation needs. The Turc and the Makkink solar radiation-based ET models provided the least accurate estimates even after calibration, while the calibrated Hargreaves–Samani temperature-based model provided the second most accurate estimates for irrigation scheduling in hyper-arid environments. Unlike the FAO-56 PM model, Hargreaves–Samani does not require wind speed or relative humidity data. The most sensitive parameter for this model is air temperature, which is readily available at most sites. The Priestley–Taylor model is highly sensitive to solar radiation data that may not be locally available. The main drawback of the FAO-56 PM model is that it requires extensive list of meteorological data. Weather forecasts are often limited to air temperature data that limit the use of the FAO-56 PM model for irrigation scheduling compared to the calibrated Hargreaves–Samani model.

Effect of the irrigation frequency and quality on yield, growth and water productivity of maize crops

A research study was conducted to examine the crop responses of maize under two irrigation systems, i.e. raised bed and high-efficiency irrigation system (HEIS; drip irrigation) systems, with three irrigation frequencies and three levels of irrigation water quality. The trial was carried out in a completely randomised design mode with triple replication of each treatment. The raised bed irrigation system demonstrated better performance in terms of crop parameters: plant height, biological yield and grain yield for the raised bed system were recorded as 1, 5 and 21%, respectively, higher than the drip irrigation system. Field measurements for the HEIS showed that the biological yield, grain yield and harvest index were quadratically correlated with the frequency of irrigation. Better results were obtained for plots irrigated every 2 or 6 days than for those irrigated every 4 days. Good-quality water raised plant biological yield by 12% and grain yield by 14.85%. The irrigation frequency had a clear-cut eff...

Cost-effective and sustainable solutions to enhance the solar disinfection efficiency improving the microbiological quality of rooftop-harvested rainwater

AbstractThis paper investigates the efficiency of solar-based disinfection methods for improving the microbial quality of rooftop-harvested rainwater. Bacteriological water quality indicators including total and fecal coliforms, Escherichia coli, and Heterotrophic Plate Count were examined under different sunlight radiations. The efficiency of simple solar disinfection (SODIS) was enhanced at low pH values of the exposed rainwater. To enhance the concentrating effects of radiations, solar collector disinfection (SOCODIS) system was used. In addition, very simple and cost-effective techniques were employed to enhance the disinfection efficiency. This includes the wrapping of polyethylene terephthalate bottles with heat-resistant plastic bags to enhance the thermal/synergistic effects of radiations and the addition of natural acids (lemon/vinegar) for getting a low pH value of the rainwater in a natural way. Both simple SODIS and SOCODIS systems remained ineffective even under strong radiations and the best...

Comparison of mixed distribution with EV1 and GEV components for analyzing hydrologic data containing outlier

An outlier is a very large or very small value that does not follow the general trend of a given data set. Outliers in rainfall data cause uncertainty in water engineering studies and estimated design events. As such, an additional mathematical tool for dealing with outliers is needed. One of the main issues in hydrologic frequency analysis is the problem of mixed distributions or multiple populations in hydrologic time series. Univariate probability distributions are unsuitable for data sets with outliers, therefore three mixed distributions (mixed Gumbel, mixed GEV, EV1–GEV) were used in this paper. The mixed Gumbel distribution was found to be the best distribution to fit to the 24-h annual maximum rainfall data at all of the rainfall gauging stations used in this study, on the basis of the minimum standard error of fit.