Applied Water Science (v.4, #4)

Biosorption of zinc ion: a deep comprehension by Vishal Mishra (311-332).
Massive industrialization and urbanization of civilization during the last few decades have made a thrust in heavy metal pollution in various water bodies. In past, various kinds of conventional metal ion remediation technologies, such as cementation, osmosis, reverse osmosis, ultrafiltration, etc., have been practised. However, most of these technologies are quite expensive, and lead to the generation of secondary chemical sludge. However, biosorption of heavy metal ions is significantly inexpensive and an eco-friendly technology. Among the series of heavy metals, zinc has gained the significant interest due to its toxicity and easy availability in water bodies. Biosorption of zinc in liquid phase by living, nonliving, conventional and non-conventional biosorbents has been practised extensively in the past. This literature review focuses on the recent trends practised in the field of biosorption of zinc from liquid phase. The present work provides deep insight into various aspects of biosorption of zinc by different mechanisms of biosorption, bioaccumulation, isotherm, kinetic and mechanistic modeling. An exhaustive comparison among different sorts of biomasses has also been given in the present work to enlist all the milestones of biosorption.
Keywords: Biosorption; Bioaccumulation; Zinc; Biomass

Effect of microwave heating on the regeneration of modified activated carbons saturated with phenol by B. S. Ondon; B. Sun; Z. Y. Yan; X. M. Zhu; H. liu (333-339).
The purpose of this work was to investigate the effect of microwave irradiation on the regeneration of modified activated carbons (GAC/MW, GAC/Ni, and GAC/Cu). The untreated activated carbon (GAC pure) was used for blank experiment. Microwave heating was used for preparation and regeneration of the modified activated carbons. The effect of loading Ni2+ and Cu2+ ions on the activated carbon adsorption capacity was investigated. The results showed that the activated carbon loaded with Ni2+ has no significant effect on phenol adsorption, while the adsorption capacity of activated carbon loaded with Cu2+ significantly decreased. Microwave irradiation showed a positive effect on activated carbon adsorption capacity. Under optimal conditions, the results showed that there was no effect when changing temperature and pH. The effect of ions Ni2+ and Cu2+ loaded into activated carbon were also investigated. During the regeneration process, the activated carbon loaded with Ni2+ showed a strong microwave energy adsorption than the activated carbon loaded with Cu2+. The effect increasing Ni2+ quantity decreases the activated carbon regeneration efficiency. During the regeneration of activated carbons, the highest temperature was observed in the cases of GAC/Ni. During regeneration, the temperature increases when the quantity Ni2+ loaded increases. The regeneration efficiency of activated carbons reaches 98 % even after 10 times of regeneration cycles. After several regenerations, MW/GAC and GAC/Ni regeneration efficiency was high, while regeneration efficiency of GAC/Cu decreased considerably. GAC regeneration efficiency also decreased several cycles. During regeneration process, phenol was simply desorbed from activated carbons under microwave irradiation.
Keywords: Phenol; Microwave energy; Modified activated carbons; Microwave regeneration; Microwave irradiation

The present study was carried out to evaluate the groundwater quality and its suitability for drinking purposes in the urban coastal aquifers of part of south Chennai, Tamil Nadu, India. Twenty-three groundwater samples were collected during March 2012. The minimum and maximum values of pH (6.3–8 on scale), electrical conductivity (620–12,150 μS/cm), total dissolved solids (399.28–7,824.6 mg/l), carbonate (0–30 mg/l), bicarbonate (0.9–58.9 mg/l), chloride (70.9–4,067.89 mg/l), sulphate (17.4–105 mg/l), nitrate (0.4–6.0 mg/l), calcium (30–200 mg/l), magnesium (1.2–164 mg/l), sodium (69–1,490 mg/l) and potassium (8–340 mg/l) were recorded in the coastal aquifers of Chennai city. The groundwater samples show that the majority of the sampling points clustered on the NaCl and mixed CaMgCl facies of the piper trilinear diagram. In the Gibbs diagram, the majority of the sampling points fall under rock water and evaporation dominance field. Fuzzy membership classification suggests that the majority of the samples fall under good water type followed by excellent water and poor water categories. Groundwater quality index showing the majority of the samples falls under excellent to poor category of water. A positive correlation was observed with Cl, SO42−, Ca2+, Na+, K+, EC and TDS. The extracted results of the correlation matrix and geochemical analysis suggest that the dominant ions of groundwater (Na+, Ca2+, K+, Cl and SO42−) were derived from seawater intrusion and gypsum dissolution process. Nitrate concentration is most significantly derived from anthropogenic sources.
Keywords: Groundwater quality assessment; Geochemistry; Coastal aquifers; Chennai City

An assessment of the physico-chemical parameters of Oran sebkha basin by Boualla Nabila; Benziane Ahmed; Moussa Kacem (351-356).
Growing populations and increasing industrialization cause increase in living standard, which result in decrease in the quality of water and may put stresses on natural waters by impairing both the quality of the water and the hydrological budget. This research aims at determining the origin of the chemical elements of groundwater from the Oran sebkha basin. It applies the inverse geochemical modeling to derive the sources of variation in the hydrochemistry by Belkhiri et al. (doi: 10.1016/j.geoderma.2010.08.016 , 2010). Fifty-five water samples were selected from different point in Oran sebkha basin for sampling purpose in July 2011. Physico-chemical parameters such as pH and electric conductivity were measured in situ. Moreover, chloride, sulfate, alkalinity, calcium, magnesium, sodium and potassium were measured in the laboratory. Inverse geochemical models of the statistical groups were developed using PHREEQC to elucidate the chemical reactions controlling water chemistry. The inverse geochemical modeling demonstrated that relatively few phases are required to derive water chemistry in the area. In a broad sense, the reactions responsible for the hydrochemical evolution in the area fall into three categories: (1) dissolution of evaporite minerals; (2) precipitation of carbonate minerals; and (3) weathering reactions of silicate minerals by Belkhiri et al. (doi: 10.1016/j.geoderma.2010.08.016 , 2010). The high values of the physico-chemical parameters of water obtained in the present study sites indicate a variation in the physico-chemical parameters demonstrated that relatively few phases are required to derive water chemistry in the area. Range of values was found as pH (5.1–7.6), conductivity (720–15,820 μS cm−1), chloride (994–7,810 mg l−1), sulfate (6.1–112.4 mg l−1), alkalinity (421–19,962 mg l−1), calcium (80–680 mg l−1), magnesium (212.4–4,525 mg l−1), sodium (124.2–4,687.4 mg l−1) and potassium (0.9–42.5 mg l−1).
Keywords: Physico-chemical parameters; Water; Sebkha

Purification of drinking water by low cost method in Ethiopia by Yasabie Abatneh; Omprakash Sahu; Seid Yimer (357-362).
Nowadays, water treatment is a big issue in rural areas especially in African country. Due to lack of facilities available in those areas and the treatment are expensive. In this regard’s an attempt has been made to find alternative natural way to treat the rural drinking water. The experiment trials were undertaken on the most promising plant extracts, namely: Moringa oleifera, Jatropha curcas andGuar gum. The extracts were used to treat contaminated water obtained from a number of wells. The results showed that the addition of M. oleifera can considerably improve the quality of drinking water. A 100 % improvement both in turbidity and reduction in Escherichia coli was noted for a number of the samples, together with significant improvements in colour.
Keywords: Coagulants; Moringa oleifera ; Plant extracts; Shallow wells

Relationship between SCS-CN and Sediment Yield by Sarita Gajbhiye; S. K. Mishra; Ashish Pandey (363-370).
Accurate estimation of runoff and sediment yield amount is not only an important task in physiographic but also important for proper watershed management. This paper proposes a seasonal relationship between Soil Conservation Services, runoff curve number (CN) and sediment yield (SY). Short-term sediment yield value of duration range from 1 to 30 day was correlated with the runoff CN derived for the respective duration from observed rainfall–runoff data. It is derived empirically from short-term (10 years) daily rainfall–runoff data of the Shakkar watershed of Narmada Basin falling in Madhya Pradesh (India). The resulting coefficient of determination (R2) values range (0.76–0.79) strongly support the versatility of the derived relationship and invokes determination of SY from the available National Engineering Handbook (NEH-4) CN values.
Keywords: Sediment yield (SY); Curve number; Soil conservation service; Prediction model; Catchment

Seeds of bottlebrush, a novel plant material, were found to exhibit excellent adsorption capacity over a wide range of Cd(II) concentration. It was characterized by Fourier transform infrared spectroscopy and Scanning Electron Microscopy to support the adsorption of Cd(II) ions. Effect of various parameters like pH, contact time, initial concentration and different electrolytes was investigated using batch process to optimize conditions for maximum adsorption. The adsorbent data were analyzed using Langmuir, Freundlich, Temkin and Dubinin–Redushkeuich isotherm equations at 30°, 40° and 50 °C. Thermodynamic parameters such as standard enthalpy change (ΔH°), free energy change (ΔG°) and entropy change (ΔS°) were also evaluated and the results indicated that adsorption of Cd(II) are spontaneous and endothermic. Various kinetics models including the Pseudo-first-order kinetics, Pseudo-second-order kinetics and Intraparticle diffusion models have been applied to the experimental data to predict the adsorption kinetics. Kinetic study was carried out by varying initial concentration of Cd(II) at constant temperature and it was found that pseudo-second-order rate equation was better obeyed than pseudo-first-order equation supporting that chemisorption process was involved.
Keywords: Adsorption; Bottlebrush; Cd(II); Isotherms; Kinetics

Quality of water resources in the Bandalamottu area of Guntur District of Andhra Pradesh in South India is facing a serious challenge due to Pb mining. Therefore, 40 groundwater samples were collected from this area to assess their hydrogeochemistry and suitability for irrigation purposes. The groundwater samples were analyzed for distribution of chemical elements Ca2+, Mg2+, Na+, K+, HCO3, CO32−, F, Cl, and SO42−. It also includes pH, electrical conductivity, total hardness, non-carbonate hardness and total alkalinity. The parameters, such as sodium absorption ratio (SAR), adjusted SAR, sodium percentage, potential salinity, residual sodium carbonate, non-carbonate hardness, Kelly’s ratio, magnesium ratio, permeability index, indices of base exchange (IBE) and Gibbs ratio were also calculated. The major hydrochemical facieses were Ca–HCO3, Ca–Na–HCO3 and Ca–Mg–Cl types. The result of saturation index calculated by Visual MINTEQ software combined with Gibbs diagram and IBE findings indicate that, dolomite and calcite dissolution and reverse ion exchange can be a major process controlling the water chemistry in the study area. The results also showed that the salinity (85 %, C3 class) and alkalinity due to high concentration of HCO3 and CO3 and low Ca:Mg molar ratio (97.5 %, <1), are the major problems with water for irrigation usage. As a result, the quality of the groundwater is not suitable for sustainable crop production and soil health without appropriate remediation.
Keywords: Groundwater quality; Hydrogeochemistry; Irrigation; Salinity hazard; Alkalinity hazard; Bandalamottu area; South India

This paper presents the results of investigations on groundwater nitrate contamination in the Dharapuram area of Tamil Nadu in south India as a primary step to initiate denitrification. Groundwater samples were collected from 26 selected locations during the pre-monsoon season in July 2010 and analysed for nitrate and other water quality parameters. Two important water types were identified, viz. Ca–Na–HCO3 and mixed Ca–Mg–Cl. It is found that the majority of samples possess high nitrate concentration; 57 % of samples exceeded the permissible limit of Indian (45 mg/L) and WHO (50 mg/L) drinking water standard. Spatial distribution map of NO3 suggested that major contamination was observed in the SW and NW parts of the study area. This result was in agreement with the corresponding land-use pattern in this study area. Denitrification process at greater depths was evident from the negative correlation between NO3 and well depth. The sources and controlling factors of high nitrate were investigated using cross plots of NO3 with other selected hydrochemical parameters. Positive correlation for NO3 was observed with EC, K, Cl and SO4. This analysis was capable of differentiating the various sources of nitrate in groundwater. The major sources of nitrate contamination are identified as areas of high fertilizer application, sewages and animal waste dumping yards. Regulation of these pollutant sources with appropriate and cost-effective denitrification process can restore the water quality in this area.
Keywords: Groundwater; Nitrate contamination; Dharapuram; South India

Inefficacy of osmotic backwash induced by sodium chloride salt solution in controlling SWRO membrane fouling by A. Mohammed Farooque; Subhi Al-Jeshi; Mohamed O. Saeed; Ali Alreweli (407-424).
A study was conducted to evaluate the efficacy of osmotic backwash induced by high salt (NaCl) concentration solution on feed side of seawater reverse osmosis (SWRO) membranes, online and offline, in controlling membrane fouling and therefore minimizing/eliminating the need for chemical cleaning. SWRO membranes were deliberately fouled by feeding seawater from an open intake located on the Arabian Gulf Coast without dosing chemicals. The fouled membranes were subjected to offline cleaning with the salt solution of up to 25 % concentration. Despite the partial removal of foulants from the membrane surface, SWRO membrane performance could not be restored, indicating the ineffectiveness of osmotic backwash in aiding offline salt cleaning. Similarly, online osmotic backwash was found to be not only ineffective in removing foulants from membrane surfaces but actually increased the fouling rate, as indicated by faster fouling rates compared to other cases. Although the driving force required for the osmotic backwash existed, the generated back flow proved to be insufficient to detach foulants from membrane surfaces. During the study period, the average SWRO membrane flux was maintained between 19 and 23 LMH, whereas the average generated back flow flux by high salt concentration solution was only 11 LMH, which was not adequate to remove foulants from membrane surfaces. Moreover, it seems that the membrane configuration as well as inherent microstructure of SWRO membrane places certain constraints on the osmotic backwash process and renders osmotic backwash ineffective in tackling SWRO membrane fouling. Hence, chemical cleaning is essential to restore SWRO membrane performance whenever fouling occurs, and the use of highly concentrated salt solution does not have any significant benefit. Membrane autopsy revealed only an insignificant accumulation of biofouling layer despite the absence of disinfection. However, it was shown that culturable biofilm bacteria species isolated from membranes tolerated exposure to high salt concentrations at pH range of 7–8. In addition, the overall findings of the study indicate that SWRO membranes can be operated in Gulf seawater at a recovery of 30 % without using any chemicals, such as coagulant, disinfectant and antiscalant, for an acceptable period of time without performing membrane cleaning. This is highly likely, if media filters are used in the pretreatment and SWRO membranes are operated at normal flux and recovery ratio.
Keywords: SWRO membrane; Fouling; Cleaning; Osmotic backwash; Salt cleaning

Water quality management using statistical analysis and time-series prediction model by Kulwinder Singh Parmar; Rashmi Bhardwaj (425-434).
This paper deals with water quality management using statistical analysis and time-series prediction model. The monthly variation of water quality standards has been used to compare statistical mean, median, mode, standard deviation, kurtosis, skewness, coefficient of variation at Yamuna River. Model validated using R-squared, root mean square error, mean absolute percentage error, maximum absolute percentage error, mean absolute error, maximum absolute error, normalized Bayesian information criterion, Ljung–Box analysis, predicted value and confidence limits. Using auto regressive integrated moving average model, future water quality parameters values have been estimated. It is observed that predictive model is useful at 95 % confidence limits and curve is platykurtic for potential of hydrogen (pH), free ammonia, total Kjeldahl nitrogen, dissolved oxygen, water temperature (WT); leptokurtic for chemical oxygen demand, biochemical oxygen demand. Also, it is observed that predicted series is close to the original series which provides a perfect fit. All parameters except pH and WT cross the prescribed limits of the World Health Organization /United States Environmental Protection Agency, and thus water is not fit for drinking, agriculture and industrial use.
Keywords: Statistical analysis; ARIMA; Time-series analysis; Prediction model