Water conservation behavior: Exploring the role of social, psychological, and behavioral determinants.

Water conservation is vital to safeguard future water availability when natural resources like water become extremely scarce. It is fundamental to understand the significant determinants of water conservation activities which can also facilitate the implementation of appropriate policies for water demand management. Thus, the goal of this study was to determine the important social, psychological, and behavioral factors of water conservation behavior. A questionnaire survey was used to collect the data from 625 international students and employees from different universities in Japan. The structural equation modeling demonstrated that the proposed model explained 46% of the variation in water conservation behavior. Awareness of water issues was highly related to attitude, responsibility, and culture. Except for culture, attitude and responsibility were significantly connected with emotion. Finally, emotion, habit, culture and involvement were significantly and positively associated with water conservation behavior. These factors are incorporated for the first time in this study into a single model to better understand individual water conservation behavior. The sequential regression model showed that all determinants including demographic factors raised the variation's proportion by 53% in water conservation. Female participants had a significantly higher positive attitude, emotion, and water conservation behavior than male participants. Older participants exhibited higher levels of awareness, habit, culture, and water conservation behavior when compared to younger people. Lastly, participants believed that the most dominant component in water conservation behavior was the awareness of water issues. These findings could assist policymakers in raising household awareness, accountability, and involvement towards water conservation efforts.

Multi-objective optimization of permeable reactive barrier design for Cr(VI) removal from groundwater.

The present study aims to develop a practical approach for the optimal permeable reactive barrier (PRB) design towards Cr(VI) removal from groundwater. Batch and column experiments were performed to investigate the characteristics of the four proposed reactive materials; nanoscale zero-valent iron (Fe0), bimetallic nanoscale zero-valent iron (Fe0/Cu), activated carbon (AC) and sand/zeolite mixture (S/Z). Kinetic analysis and dynamic modeling of the experimental data were implemented to determine the controlling conditions of the reactive performance of the PRB's materials. The sensitivity index of the design parameters was examined as an indicator of their effect on the reactive responses. Moreover, the Response Surface Methodology (RSM) was considered for optimizing the design variables of the PRB based on the practical factorial analysis. Results revealed that Fe0 and Fe0/Cu showed high performance in Cr(VI) removal, with a slight superiority to Fe0, with final removal efficiency values of 89.7 and 84.1%, respectively. Kinetic analysis depicted that pseudo second order was the best fitting model for Cr(VI) removal in the four materials' cases. ANOVA statistical analysis revealed that quadratic polynomial model was the best model, corresponding to the highest correlation efficiency and adequate precision, to describe the relationships in the four PRB's cases between the selected dependent variables; resident time (tR), reactive material mass per sectional area of contaminant plume (M/A) and reactive material cost (CostPRB) towards the independent parameters; barrier thickness (b) and permeability (Kr). Additionally, sensitivity analysis has been conducted which depicted the high sensitivity, in the four PRB's cases, of average pore water velocity within the barrier (vr) vr and Kr with the highest and the second-highest sensitivity index (SI) values towards tR, respectively. The RSM-optimization revealed that Fe0 is the most feasible reactive material, comparing to the other considered materials, with respect to the optimal conditions regarding the long residency (tR = 22 days) and low cost (b = 0.521 m), with around 95.2% desirability of its optimal solution. Overall, the current study represents a significant contribution and a vital step towards an accurate PRB's design based on previously determined optimal conditions.

Microbially formed Mn(IV) oxide as a novel adsorbent for removal of Radium.

Radioactivity of Ra isotopes in natural waters is of serious concern. Control of 226Ra concentrations in tailings ponds, which store waste from U ore extraction processes, is an important issue in mill tailings management. In this study, we tested microbially formed Mn(IV) oxide as an adsorbent for removal of Ra in water treatment. Biogenic Mn(IV) oxide (BMO) was prepared using a Mn(II)-oxidizing fungus, Coprinopsis urticicola strain Mn-2. First, adsorption experiments of Sr and Ba, as surrogates for Ra, onto BMO were conducted in aqueous NaCl solution at pH 7. Distribution coefficients for Ba and Sr were estimated to be ∼106.5 and ∼104.3 mL/g, respectively. EXAFS analysis indicated that both Sr and Ba adsorbed in inner-sphere complexes on BMO, suggesting that Ra would adsorb in a similar way. From these findings, we expected that BMO would work effectively in removal of Ra from water. Then, BMO was applied to remove Ra from mine water collected from a U mill tailings pond. Just 7.6 mg of BMO removed >98% of the 226Ra from 3 L of mine water, corresponding to a distribution coefficient of 107.4 mL/g for Ra at pH ∼7. The obtained value was convincingly high for practical application of BMO in water treatment. At the same time, the high distribution coefficient indicates that Mn(IV) oxide can be an important carrier and host phase of Ra in the environment.

Statistical optimization of nZVI chemical synthesis approach towards P and NO3- removal from aqueous solutions: Cost-effectiveness & parametric effects.

This study aims to conduct statistical optimization of nZVI synthesis parameters towards the removal efficiency of phosphorus (P) and nitrate (NO3-), considering for the first time the cost-effectiveness index. The detailed statistical analysis was implemented to evaluate the main effects and interactions of eight synthesis parameters, including reductant concentration (RC), reductant delivery rate (RDR), reductant liquid volume (RLV), pH, aging time (AGT), mixing speed (MS), temperature (T), and precursor concentration (PC). Results revealed that the experimental optimization of the synthesis factors improved the removal efficiency of NO3- and P by 27 and 9%, respectively, with respect to that before the optimization. ANOVA statistical results indicated the significance of RP (%) and [Formula: see text] (%) models with F-values of 4.480 × 108 and 23,755.08, respectively. Moreover, the p-values of all the eight main linear effects were less than 0.05 in both two models of RP (%) and [Formula: see text] (%). However, most of the interaction parameters were not statistically significant (higher than 0.05) in the case of [Formula: see text] (%), which is unlike RP (%) where all interaction parameters were statistically significant (less than 0.05). The normal probability plots of factors effects provided significant evidence of the significance of the investigated parameters RC had the highest positive statistically significant effect on RP (%) followed by RLV, RDR, MS and T. In case of [Formula: see text] (%), RLV had the highest positive significant effect, followed by AGT > RDR > pH > T > MS. The cost-effective optimal constraints in this study resulted in the best economically optimized values of the nZVI synthesis parameters in terms of higher reactivity and reduced synthesis cost.

Efficient treatment of ammonia-nitrogen contaminated waters by nano zero-valent iron/zeolite composite.

The aim of the present study is developing a magnetic nanoscale zero-valent iron/zeolite (nZVI/Z) composite towards the efficient removal of ammonia-nitrogen (NH4+-N) from aqueous solutions. Series of batch experiments were conducted to investigate the effect of different factors on the removal efficiency, including pH effect, aerobic/anaerobic, NH4+-N initial concentration, and temperature. The mixing mass ratio of nZVI/Z was optimized to reach the optimal ratio (0.25 g nZVI: 0.75 g zeolite), corresponding to the best removal efficiency of 85.7% after 120 min of reaction. Results revealed that nZVI/Z is efficient for NH4+-N removal from water at a wide pH range (3.0-10.0), with superiority to the neutral conditions. Moreover, aerobic ambient and normal temperature of 25 °C were the optimal conditions for the removal process of NH4+-N. Removal mechanisms involved electrostatic attraction, ion exchange, and adsorption. Generally, nZVI/Z has great potential towards the practical applications of NH4+-N removal from water.

Encapsulation of iron nanoparticles with magnesium hydroxide shell for remarkable removal of ciprofloxacin from contaminated water.

The rapid evolution of antimicrobial resistant genes (AMRs) in water resources is well correlated to the persistent occurrence of ciprofloxacin in water. For the first time, encapsulated nanoscale zerovalent iron (nZVI) with a shell of magnesium hydroxide (Mg/Fe0) was used to adsorb ciprofloxacin from water. Optimization of the removal conditions exhibited that 5% was the optimum mass ratio between magnesium hydroxide and nZVI [Mg(OH)2/nZVI)] as more than 96% of 100 mg L-1 of ciprofloxacin was removed. In addition, 0.5 g L-1 of Mg/Fe0 showed an extraordinary performance in removing ciprofloxacin over a wide range of pH (3-11) with removal efficiencies exceeded 90%. Kinetic analysis displayed that the kinetic data was well described by both Pseudo first-order and second-order models. Also, the equilibrium data was well fitted by Freundlich isotherm model. In addition, thermodynamic analysis evidenced that the removal of ciprofloxacin by Mg/Fe0 was exothermic, and spontaneous. The experiments also revealed that physisorption and chemisorption were the responsible mechanisms for ciprofloxacin removal. The proposed treatment system remediated 10 litters of 100 mg L-1 of ciprofloxacin solution with 100% overall removal efficiency. This treatment system could be a promising and practical solution to decrease ciprofloxacin concentration in different water bodies.

Magnetic zeolite synthesis for efficient removal of cesium in a lab-scale continuous treatment system.

Radioactive cesium was resealed to the environment as a result of many nuclear incidents. An effective treatment system is urgently needed to safely handle radioactive cesium-contaminated waters. Based on nanoscale zerovalent iron (nZVI) and zeolite, nine adsorbents were synthesized and applied to remove cesium from aqueous solutions. Magnetic zeolite composite (Ze/Fe0) was selected as the ideal adsorbent for treating cesium contaminated waters in a lab-scale continuous treatment system (LSCTS). The optimization process of the (Ze/Fe0) composite revealed that 1:1 is the optimum mass ratio between zeolite and nZVI. Furthermore, the optimization process proved that the initial pH and temperature have no significant effect on the adsorption of cesium by (Ze/Fe0) composite and the optimum dosage of (Ze/Fe0) composite is 5 g L-1. XRD and SEM results showed that the (Ze/Fe0) composite has an irregular shape with a poor crystalline structure. Kinetic and equilibrium data were best described by pseudo second order and Freundlich isotherm models. Seawater and groundwater experiments illustrated that the removal of cesium by (Ze/Fe0) composite was inhibited due to the existence of competing cations. Eight cycles of LSCTS were performed to examine the performance of (Ze/Fe0) composite in treating continuous streams of cesium contaminated waters. In all cycles except the cycle of treating contaminated seawater, LSCTS succeed to treat continuous flows of 1 mg L-1 cesium contaminated water with 100% overall removal efficiency. For treating contaminated seawater, pre-treatment unit is required to reduce the salinity of the contaminated seawater before staring the treatment process.