Pakistan experiences extreme flood events almost every year during the monsoon season. Recently, flood events have become more disastrous as their frequency and magnitude have increased due to ...climate change. This situation is further worsened due to the limited capacity of existing water reservoirs and their ability to absorb and mitigate peak floods. Thus, the simulation of stream flows using projected data from climate models is essential to assess flood events and proper water resource management in the country. This study investigates the future floods (in near future and far future periods) using the integrated flood analysis system (IFAS) model under the RCP2.6, RCP4.5, and RCP8.5 climate change scenarios. Downscaled and bias corrected climatic data of six general circulation models and their ensemble were used in this study. The IFAS model simulated the stream flow efficiently (R2 = 0.86–0.93 and Nash–Sutcliffe efficiency = 0.72–0.92) in the Jhelum River basin (JRB), Kabul River basin (KRB), and upper Indus River basin (UIRB) during the calibration and validation periods. The simulation results of the model showed significant impact of projected climate change on stream flows that will cause the mean monthly stream flow in the JRB to be lower, while that of the KRB and UIRB to be higher than that of the historical period. The highest flow months are expected to shift from May–June (Jhelum basin) and June–July (Kabul basin) to April–May with no changes in the UIRB. Higher frequencies of low to medium floods are projected in the KRB and UIRB, while the JRB expects fewer flood events. Based on the results from the IFAS model, it is concluded that stream flow in the study area will increase with several flood events.
Microalgae technology is a viable solution for environmental conservation (carbon capture and wastewater treatment) and energy production. However, the nutrient cost, slow-kinetics, and low ...biosorption capacity of microalgae hindered its application. To overcome them, algal-biochar (BC) can be integrated with microalgae to treat textile wastewater (TWW) due to its low cost, its ability to rapidly adsorb pollutants, and its ability to serve as a nutrient source for microalgal-growth to capture CO
2
and biodiesel production.
Chlorella vulgaris
(CV) and algal-BC were combined in this work to assess microalgal growth, carbon capture, TWW bioremediation, and biodiesel production. Results showed the highest optical density (3.70 ± 0.07 OD
680
), biomass productivity (42.31 ± 0.50 mg L
−1
d
−1
), and dry weight biomass production (255.11 ± 6.01 mg L
−1
) in an integrated system of CV-BC-TWW by capturing atmospheric CO
2
(77.57 ± 2.52 mg L
−1
d
−1
). More than 99% bioremediation (removal of MB-pollutant, COD, nitrates, and phosphates) of TWW was achieved in CV-BC-TWW system due to biosorption and biodegradation processes. The addition of algal-BC and CV microalgae to TWW not only enhanced the algal growth but also increased the bioremediation of TWW and biodiesel content. The highest fatty acid methylesters (biodiesel) were also produced, up to 76.79 ± 2.01 mg g
−1
from CV-BC-TWW cultivated-biomass. Biodiesel’s oxidative stability and low-temperature characteristics are enhanced by the presence of palmitoleic (C16:1) and linolenic (C18:3) acids. Hence, this study revealed that the integration of algal-biochar, as a biosorbent and source of nutrients, with living-microalgae offers an efficient, economical, and sustainable approach for microalgae growth, CO
2
fixation, TWW treatment, and biodiesel production.
Graphical Abstract
Geophysical method using vertical electrical sounding (VES) technique, in combination with borehole lithological data analysis was used to locate the subsurface layers containing good quality water ...in District Okara, Punjab Pakistan. Ten VES surveys (VES-1-10) were conducted by utilizing the Schlumberger electrode configuration. A calibrated model was developed for the study area by integrating the resistivity and lithological data. The model showed that the study area has three geoelectric layers below the water table with resistivities 50-100 Ω-m, 25-50 Ω-m and <25 Ω-m describing the good, marginal and poor quality water layers respectively. Integrated data analysis show that six sites (i.e., VES-1, VES-2, VES-3, VES-5, VES-7, & VES-10) have layers of good quality water at different depths. Out of these 6 sites, 3 sites (VES-3, VES-7 and VES-10) are suitable for installing the irrigation water wells in terms of water quality and potential while the remaining three sites (VES-1, VES-2 and VES-5) were not suitable due to shallow thickness of good quality aquifer. Three sites VES-3, VES-5 and VES-10 were selected for drilling in order to validate the modeled results, samples were collected from each 1.5–3.0 m depth for the laboratory analysis. The results showed that the resistivity data were in close agreement with the lithological data and VES-10 was most suitable for groundwater extraction. An Irrigation tube-well was installed at VES-10 and its quality was monitored for one year which showed successful supply of groundwater in terms of quality and potential.
Display omitted
•Geophysical method, GIS & IX1D software used to locate good quality groundwater.•3 to 4 geoelectric layers with different resistivity & aquafer thickness identified.•Integrated data analysis indicated 7 out of 10 site contain good quality water.•4 out of 7 sites had good potential to install irrigation water wells.•Lithological data validated VES results.
Traditional irrigation practices, low crop productivity, unlevelled fields, water losses taking place during conveyance and application phases, as well as low irrigation efficiencies are the main ...problems of the common farmers in Pakistan. These problems are more noticeable in the command area of Lower Chenab Canal (LCC), which is the main portion of the Indus Basin Project in Pakistan. To overcome these problems, different water management technologies such as precision land levelling (PLL), bed planting, drip irrigation systems, and watercourse improvement were introduced to farmers to increase water savings and crop yields in the area of five distributaries—Khurrianwala, Shahkot, Mungi, Khikhi, Killianwala and Dijkot—during the cropping seasons of 2008 to 2015. The use of drip irrigation resulted in savings of water and fertilizer and increased the crop yields by 30–40%. Three watercourses, one on each site of 1200 m in length, were lined, which resulted in improved conveyance efficiency of 15–20%. If wheat, rice and cotton in the command area of LCC are sown on precisely levelled fields and on beds, then about 2768.1 million m3 and 3699.3 million m3 of irrigation water can be saved. These results show the potential of water-efficient technologies for saving water as well as increasing crop yields.
Water-related soil erosion is a major environmental concern for catchments with barren topography in arid and semi-arid regions. With the growing interest in irrigation infrastructure development in ...arid regions, the current study investigates the runoff and sediment yield for the Gomal River catchment, Pakistan. Data from a precipitation gauge and gridded products (i.e., GPCC, CFSR, and TRMM) were used as input for the SWAT model to simulate runoff and sediment yield. TRMM shows a good agreement with the data of the precipitation gauge (≈1%) during the study period, i.e., 2004–2009. However, model simulations show that the GPCC data predicts runoff better than the other gridded precipitation datasets. Similarly, sediment yield predicted with the GPCC precipitation data was in good agreement with the computed one at the gauging site (only 3% overestimated) for the study period. Moreover, GPCC overestimated the sediment yield during some years despite the underestimation of flows from the catchment. The relationship of sediment yields predicted at the sub-basin level using the gauge and GPCC precipitation datasets revealed a good correlation (R2 = 0.65) and helped identify locations for precipitation gauging sites in the catchment area. The results at the sub-basin level showed that the sub-basin located downstream of the dam site contributes three (3) times more sediment yield (i.e., 4.1%) at the barrage than its corresponding area. The findings of the study show the potential usefulness of the GPCC precipitation data for the computation of sediment yield and its spatial distribution over data-scarce catchments. The computations of sediment yield at a spatial scale provide valuable information for deciding watershed management strategies at the sub-basin level.
Display omitted
•Sn-Pd-red mud catalyst showed a complete NO3− removal and high N2 selectivity.•High efficiency and N2 selectivity caused by an interaction between CaO and Fe2O3.•Sn-Pd-red mud ...catalyst revealed a remarkable performance over 11 recycling tests.•Stable and uniform distribution of Sn and Pd was preserved even after recycling.
The use of red mud as a support material was evaluated in this study to develop a novel bimetallic catalyst for highly reactive and selective nitrate removal from water and wastewater. The catalyst was optimized for the selection of promoter metal (i.e., Sn, Cu, In, and Zn) and then for noble metal (i.e., Pd, Pt, and Au). Sn-Pd-red mud and In-Pd-red mud catalysts achieved a complete nitrate removal. Sn-Pd-red mud showed 5.1 times higher removal kinetics (k = 11.57 × 10−2 min−1) than that of In-Pd-red mud (k = 2.27 × 10−2 min−1). The results from characterization study confirmed that the enhanced nitrate removal kinetics of Sn-Pd-red mud was mainly attributed to 1) its high affinity towards nitrate, 2) low alloying effect of Sn on Pd, 3) high reduction potential of Sn, and 4) high H2 activation by Pd, as compared to those of other red mud supported bimetallic catalysts. We also found that the interaction between CaO and Fe2O3 was the driving force for the enhanced nitrate reduction and high N2 selectivity in this study. A complete nitrate removal with high N2 selectivity (>88%) was preserved during the 11 times of recycling tests with consistent reduction kinetics (k = 10.87 ± 0.48 × 10−2 min−1), indicating that red mud could be an excellent support material for efficient and durable bimetallic catalyst for the enhanced selective nitrate reduction.
The presence of various oxyanions in the groundwater could be the main challenge for the successive application of Cu–Pd-hematite bimetallic catalyst to aqueous NO3− reduction due to the inhibition ...of its catalytic reactivity and alteration of product selectivity. The batch experiments showed that the reduction kinetics of NO3− was strongly suppressed by ClO4−, PO43−, BrO3− and SO32− at low concentrations (>5 mg/L) and HCO3−, CO32−, SO42− and Cl− at high concentrations (20–500 mg/L). The presence of anions significantly changing the end-product selectivities influenced high N2 selectivity. The selectivity toward N2 increased from 55% to 60%, 60%, and 70% as the concentrations of PO43−, SO32−, and SO42− increased, respectively. It decreased from 55% to 35% in the presence of HCO3− and CO32− in their concentration range of 0–500 mg/L. The production of NO2− was generally not detected, while the formation of NH4+ was observed as the second by-product. It was found that the presence of oxyanions in the NO3− reduction influenced the reactivity and selectivity of bimetallic catalysts by i) competing for active sites (PO43−, SO32−, and BrO3− cases) due to their similar structure, ii) blockage of the promoter and/or noble metal (HCO3−, CO32−, SO42−, Cl− and ClO4− cases), and iii) interaction with the support surface (PO43− case). The results can provide a new insight for the successful application of catalytic NO3− reduction technology with high N2 selectivity to the contaminated groundwater system.
Display omitted
•Evaluation of oxyanion influence on the catalytic NO3− reduction kinetics.•Cl−, PO43−, BrO3− and SO32− significantly inhibited the catalytic NO3− reduction.•Inhibition effect of PO43−, SO32−, and BrO3− by competing for active catalytic sites.•N2 production remained unchanged with the addition of Cl−, ClO4− and BrO3−•N2 selectivity increased with higher concentrations of SO32−, SO42− and PO43-.
Display omitted
•Removal of NO3− by metallic catalysts supported by diverse supports were reviewed.•Fe materials themselves cannot achieve high N2 selectivity at optimized conditions.•Passive ...supports showed better selective NO3− removal to N2 than active supports.•Metals, their contents, support materials, and pH influence selective NO3− removal.•Iron and zeolite can be used as proper support materials for the long-term use.
Contamination of surface and groundwater by nitrate ( NO3−) is one of the most serious environmental issues worldwide because of the increase in discharge of N-containing wastewater due to agricultural and industrial activities. Among various NO3− removal techniques, catalytic denitrification by metallic catalyst has been considered as one of innovative and promising techniques to convert NO3− to an ideal gas (N2) in natural and engineered environments. Extensive studies have developed diverse metallic catalysts for the enhanced catalytic removal of aqueous NO3−. Generally, the removal kinetics of NO3− and selectivity towards N2 are varied with experimental conditions such as type of the catalyst (mono- or bimetallic), support material, promoter, and noble metals and their contents, concentrations of catalyst and NO3−, suspension pH, and additional reductant (H2) flow. Therefore, selection of a proper combination of metals and support material and optimization of experimental factors are main challenges to achieve an efficient catalytic NO3− reduction, leading to the successful application of the technology to real water and wastewater treatment problems. This review presents an analysis of recent research works on NO3− reduction by the metallic catalysts, and discusses: (i) an assessment of various combinations of promoter and noble metals for mono- and bimetallic catalysts, based on their reactivity and selectivity to N2; (ii) investigation of the reaction mechanism; (iii) evaluation of effect of diverse environmental factors on the performance of the catalyst; and (iv) stability and durability of the catalyst. In addition, environmental implication and future prospect of the denitrification by metallic catalyst are provided.
In this study, we investigated catalytic nitrate removal using nanoscale zerovalent iron (NZVI) supported Cu–Pd bimetallic catalyst (Cu–Pd/NZVI) in a continuous reactor system. Control experiments ...showed that Cu, Pd, and a proper supply of H2 are essential for relatively sustainable nitrate (30 mg/L NO3 –-N) reduction in continuous mode. When we optimized operational parameters to enhance removal efficiency and N2 selectivity, we finally achieved complete nitrate removal with 48% N2 selectivity at 9 h. During a longevity test (200 h reaction), excellent removal was observed (>91% in 24 h) with 42–60% N2 selectivity. However, removal gradually decreased to 13% in 200 h with increasing nitrite production. X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy analysis revealed that both the support (NZVI) and the Cu(0) oxidized after continuous denitrification. This indicated that loss of NZVI reductive capacity and the oxidation of Cu(0) to Cu(I) and Cu(II) deactivated nitrate removal during the continuous nitrate reduction by Cu–Pd/NZVI.
PDF
