Raw Groundwater Research Articles

Towards the development of a reactive filter from green resource for groundwater defluoridation

In order to develop a low cost reactive filter from a green biogenic resource, the shell of a Gastropod (GS) was calcined at different temperatures and the defluoridation efficiencies of the raw and calcined GS were evaluated in a batch process. The highest defluoridation efficiency was obtained with the GS calcined at 1000°C (i.e. TGS1000). The time–concentration profiles of the defluoridation process were described by the pseudo-second order kinetic equation and the Temkin equilibrium isotherm equation gave the best description of the defluoridation process in synthetic feed water and groundwater (GW) system. The determination of the effects of hydrochemistry on the defluoridation efficiency of the TGS1000 showed that variations in pH value, organic load and ionic strength had no visible influence on the magnitude and trend. Amongst the array of interfering ionic species studied, only carbonate exhibited negative impact on the defluoridation efficiency. Experimental evidences revealed that the underlying mechanisms of the defluoridation process were diverse (ionic bond formation, electrostatic attraction, ion exchange and occlusion into Ca(OH)2 framework) and not straitlaced. Groundwater (GW) defluoridation, using TGS1000, showed that the residual F− in the defluoridated water increased with initial F− concentration. The value of the monolayer Langmuir sorption capacity was lower in the GW system (qm=6.17mg/g) than in the synthetic feed water system (qm=19.84mg/g). The values of pH, electrical conductivity, Ca2+ concentrations, total hardness values were higher in the defluoridated water relative to the raw GW samples. The Mg2+ concentrations were below the detection limit and nitrate concentrations were appreciably attenuated in the treated water samples.

Toxicological and chemical assessment of arsenic-contaminated groundwater after electrochemical and advanced oxidation treatments

Owing to its proven toxicity and mutagenicity, arsenic is regarded a principal pollutant in water used for drinking. The objective of this study was the toxicological and chemical evaluation of groundwater samples obtained from arsenic enriched drinking water wells before and after electrochemical and ozone–UV–H2O2-based advanced oxidation processes (EAOP). For this purpose, acute toxicity test with Daphnia magna and chronic toxicity test with Lemna minor L. were employed as well as in vitro bioassays using human peripheral blood lymphocytes (HPBLs). Several oxidative stress parameters were estimated in L.minor. Physicochemical analysis showed that EAOP treatment was highly efficient in arsenic but also in ammonia and organic compound removal from contaminated groundwater. Untreated groundwater caused only slight toxicity to HPBLs and D. magna in acute experiments. However, 7-day exposure of L. minor to raw groundwater elicited genotoxicity, a significant growth inhibition and oxidative stress injury. The observed genotoxicity and toxicity of raw groundwater samples was almost completely eliminated by EAOP treatment. Generally, the results obtained with L. minor were in agreement with those obtained in the chemical analysis suggesting the sensitivity of the model organism in monitoring of arsenic-contaminated groundwater. In parallel to chemical analysis, the implementation of chronic toxicity bioassays in a battery is recommended in the assessment of the toxic and genotoxic potential of such complex mixtures.

Concentration and characterization of organic colloids in deep granitic groundwater using nanofiltration membranes for evaluating radionuclide transport

Abstract Understanding the properties of organic colloids is important for geological disposal of high-level radioactive waste in terms of radionuclide transport. To analyze organic colloids in deep groundwater, concentration techniques using adsorption resins and reverse osmosis (RO) membranes have been widely applied, because their concentrations in deep groundwater are very low and detection of the organic colloids in raw groundwater is difficult. However, these techniques have respective disadvantages such as chemical disturbance and membrane fouling caused by cations. To overcome their disadvantages, we propose a new concentration method using nanofiltration (NF) membranes to concentrate organic colloids rapidly without chemical disturbance and to selectively remove monovalent and divalent ions, which may cause inorganic and/or organic fouling. Concentration performance of the NF and RO membranes for aqueous solutions for humic acids was evaluated using a laboratory-scale membrane test unit. The time course of permeate flux and concentration of humic acids were measured. These membranes were applied to the concentration of actual groundwater obtained at a depth of 300 m at the Mizunami Underground Research Laboratory in Japan. The permeate flux and concentration of major ions and organic colloids were measured. The organic colloids concentrated by the NF membrane were successfully analyzed using pyrolysis gas chromatography coupled with mass spectrometry (Py-GC/MS) owing to their high concentrations and low concentrations of salts. The NF membrane was useful for the concentration of organic colloids and rare earth elements (REEs) in deep groundwater, and the findings of the organic colloid structures revealed by Py-GC/MS provided valuable information for evaluating the effect of organic colloids on radionuclide transport.

Estimation of Filtration Potential of an Effective Biosand Filter for Removal of Iron, Turbidity from Various Sources of Water

A study has been conducted for designing, constructing and evaluating of an effective biosand filter. Different types of charcoal mixture such as bamboo, coconut and wood and carbon mat as an important filter media was used for the modification of biosand filter. The filter had seven layers with gravel, sand, carbon mat and charcoal which were responsible for filtration process. The filtered water analysed in every 20 min interval. The raw ground water pH was 6.12 while it passes through bamboo, coconut and wood mixture filter, the filtered water showed higher pH value. The filter in which mixture of charcoal used as filter media showed better removal efficiency of turbidity compared to control filter without charcoal and mat. The value of turbidity in filtered water of charcoal mixture filter was below 2 NTU which is the permissible limit of drinking water according to World Health Organization but for control it was average 14 NTU. Initially the flow rate was higher and gradually decreases with time. The flow rate of the Biosand filtered water decreases significantly with increase in turbidity. The charcoal based filter showed better removal of iron (II) (95-98%) compared to control (73-76%). The charcoal based filter resulted tastier water by enriching of water with mineral like sodium and potassium.

POTENTIAL USE OF OZONATION WITH LIMESTONE ADSORPTION IN GROUND TREATMENT: A CASE STUDY AT KELANTAN WATER TREATMENT PLANT

Pollution of groundwater occurs due to rapid industrialization and agricultural activities. A desktop study was carried out to identify the actual groundwater problem occurs in Malaysia. The quality of groundwater was investigated to obtain the baseline groundwater data for an alternative integrated water treatment process that involved combination of ozonation and adsorption process. Preliminary data on groundwater pollution were collected from nine Mineral and Geoscience Department(JMG) groundwater monitoring wells, Air Kelantan Sdn Bhd (AKSB) water treatment plant and Natioal Hydraulics Research Institute of Malaysia (NAHRIM). The result shows that raw groundwater in Kelantan contains high concentration of Fe and thus an alternative treatment is necessary. However, based on the previous treated effluent data at one of the water treatment plants in Malaysia has indicated that the use of ozone alone may only remove Fe concentration up to 0.5- 0.8 mg/L. This exceeded the acceptable limit of 0.3 mg/L .1 Application of ozonation process for groundwater treatment has received more attention based on its capability to transform contaminants into non-harmful substance within a short period. Most previous literature found that limestone is very effective in removing more than 90% of heavy metal such as Cu, Zn, Cd, Ni, Cr, Fe and Mn in water. To improve the performance of ozonation process, an integrated treatment of ozonation and adsorption processes using limestone is proposed in the current study for groundwater treatment.

Foulant characterization and distribution in spiral wound reverse osmosis membranes from different pressure vessels

In this study, the origin and extent of membrane fouling on spiral wound module (SWM) elements from different pressure vessels and the distribution of membrane foulants inside the SWM elements were systematically investigated using the membrane autopsy methods. Three fouled SWM elements from different pressure vessels were examined for a quantitative and qualitative comparison of membrane foulants. Results obtained indicate that a major contributor to membrane fouling were fulvic acid components, consisting of small, hydrophilic compounds from the raw groundwater. A small amount of inorganic components such as Fe and Al, which can form a complex structure with fulvic acid, also partially contributed to the membrane fouling of lead elements in first pass RO vessels. In particular, through the elemental comparisons of two sheets (both sides) of fouled membranes obtained from identical positions of a membrane leaf, the distribution of membrane foulants inside the SWM elements was fully evaluated. Based on the data obtained, much more organic and inorganic foulants were accumulated on the back side of the membrane leaf than on the front side. Overall, these results would help improve understanding of fouling behavior inside membrane modules and pressure vessels.

Fluoride and Arsenic Removal by Nanofiltration Technology from Groundwater in Rural Areas of China: Performances with Membrane Optimization

Nanofiltration (NF) membrane configuration for fluoride and arsenic removal from groundwater has a key role in controlling operation performances and membrane fouling. Some bench-scale contrast experiments using commercial NF membranes were done to obtain the optimum arrangement performances. The NF membrane arrays included one-stage, two-stage, and three-stage systems. The NF membrane surface was negatively charged above its isoelectric point (approximately at pH 5.9–6.4). Accordingly, the raw groundwater was initially adjusted to a neutral or alkaline pH to enhance the effect of electrical charge repulsion and improve the ion removal efficiencies by NF. The encouraging results indicated that a membrane in a parallel-linear arrangement with staging 2:1 was the preferable arrangement to remove fluoride and arsenic from low-salinity groundwater in rural areas of China. With this optimal arrangement, the NF system obtained fluoride and arsenic removal efficiencies of 70˜73% and 92˜94% respectively, a preferable permeate flux of 73.37 L h−1 m2 and acceptable water flux recovery rate of 65% at 16°C. This optimal arrangement can further limit the potential membrane fouling by lowering the interstage Reynolds number. Moreover, the water product cost was lowest by the NF system with this optimal arrangement.

Sources and fate of perfluorinated compounds in the aqueous environment and in drinking water of a highly urbanized and industrialized area in Italy

Perfluorinated substances are listed among emerging contaminants because they are globally distributed, environmentally persistent, bioaccumulative and potentially harmful. In a three-year monitoring campaign (2010–2013) we investigated the occurrence, sources and fate of nine perfluoroalkylcarboxylic acids and three perfluoroalkylsulfonic acids, in the most industrialized region of Italy. Composite samples were collected in influents and effluents of wastewater treatment plants (WWTPs), in the main rivers flowing through the basin, and in raw groundwater and finished drinking water. Samples were analyzed by liquid chromatography tandem mass spectrometry. Perfluorinated substances were not removed in WWTPs and those receiving industrial wastes discharged up to 50 times the loads of WWTPs receiving municipal wastes. The mass balance of the emissions in the River Lambro basin showed continuously increasing contamination from north to south and differences in the composition of homologues in the west and east sides of the basin. Ground and drinking water were contaminated in industrial areas, but these substances were removed well in Milan. Contamination from industrial sources was prevalent over urban sources, contributing to 90% of the loads measured at the closure of the basin. The River Lambro was confirmed as one of the main sources of contamination in the Po River.

제주도 동부 해안대수층의 수리특성 산정과 지하수위 예측

Due to tidal force, it is very difficult to estimate the hydraulic parameters of high permeable aquifer near coastal area in Jeju Island. Therefore, to eliminate the impact of tidal force from groundwater level and estimate the hydraulic properties, tidal response technique has been mainly studied. In this study we have extracted 38 tidal constituents from groundwater level and harmonic constants including frequency, amplitude, and phase of each constituent using T_TIDE subroutine which is used to estimate oceanic tidal constituents, and then we have estimated hydraulic diffusivity associated with amplitude attenuation factor(that is the ratio of groundwater level amplitude to sea level amplitude for each tidal constituent) and phase lag(that is phase difference between groundwater level and sea level for each constituent). Also using harmonic constants for each constituent, we made the sinusoidal wave and then we constructed the synthesized wave which linearly combined sinusoidal wave. Finally, we could get residuals(net groundwater level) which was excluded most of tidal influences by eliminating synthesized wave from raw groundwater level. As a result of comparing statistics for synthesized level and net groundwater level, we found that the statistics for net groundwater level was more insignificant than those of synthesized wave. Moreover, in case of coastal aquifer which the impact of tidal force is even more than those of other environmental factors such as rainfall and groundwater yield, it is possible to predict groundwater level using synthesized wave and regression analysis of residuals.

TESTING OF A DEFLUORIDATING FILTER USING MgO-CaO-CaCI2 FOR USE IN RURAL RAJASTHAN

A Magnesium Oxide-based defluoridation technique using MgO-CaO-Calcium Chloride and pH adjustment by Sodium Bisulphate has been suitably modified for use with fluoride contaminated local groundwater having high alkalinity. Taking into consideration the high bicarbonate concentration in raw groundwater the proportion of the lime has been changed. It was found that sodium bisulphate was not suitable for pH adjustment due to the high concentration of sulphate in the pH adjusted water. Therefore dilute HCl was used instead. Six trials of the adapted defluoridation technique have been carried out in the laboratory successfully at a 50-litre scale.

The life and death of Dutch groundwater tax

We examine the Dutch national groundwater tax (GWT) – a ‘win–win, green’ tax that promised to reduce distortions by simultaneously reducing the income tax burden and improving environmental outcomes. We find no evidence of these impacts. Instead, we see that the GWT increased distortions by taxing a narrow base (a few drinking-water companies reliant on raw groundwater) and interfering with groundwater management programmes funded by an existing provincial groundwater fee. The Dutch government revoked the GWT for being fiscally inefficient and environmentally unhelpful on 31 December 2011, but this story provides some useful lessons.

Are existing drinking water sources safe from As contamination in Hanam province, Vietnam?

This study investigated arsenic (As) concentrations in existing drinking water sources in Hanam province, Vietnam. Sand-filtered groundwater, piped water, raw groundwater, and a type of drinking water mostly sourced from rainwater (hereafter referred to as the “stored rainwater”) are commonly used for drinking purposes in this area. It was found that all water sources contained different levels of toxic As. The highest levels were found in raw groundwater, followed by sandfiltered water, piped water, and stored rainwater. More than 50% of the stored rainwater samples contained As levels above the WHO recommendation value. As such, the daily As uptake in local residents from this kind of stored rainwater may be larger than previously considered because they consume stored rainwater as an alternative drinking water source. Relatively high levels of As in the stored rainwater samples also suggested that residents possibly mix rain and groundwater in rainwater containers in order to meet their daily water demand.

Field testing of a magnesium oxide-lime-calcium chloride hydrochloric acid based filter

AbstractField trials of a MgO-Lime-CaCl2-HCl filter has been carried out to test the operation of the filter during actual user conditions. Water quality parameters like pH, TDS, Ca, Mg hardness, total alkalinity, SO4-2, Cl- were found to be within permissible limits in the water obtained from the filter except nitrate, whose concentration was above permissible limits in the raw ground water itself. The dosage of HCl had to be adjusted and fixed in the field trials. In comparison to the laboratory trials conducted earlier it was found that during the field trials there was on an average 6% reduction in the fluoride removal efficiency of the filter. Operational user problems of filter were found and were addressed in the village.

Removal of natural organic matter and arsenic from water by electrocoagulation/flotation continuous flow reactor

The performance of the laboratory scale electrocoagulation/flotation (ECF) reactor in removing high concentrations of natural organic matter (NOM) and arsenic from groundwater was analyzed in this study. An ECF reactor with bipolar plate aluminum electrodes was operated in the horizontal continuous flow mode. Electrochemical and flow variables were optimized to examine ECF reactor contaminants removal efficiency. The optimum conditions for the process were identified as groundwater initial pH 5, flow rate=4.3l/h, inter electrode distance=2.8cm, current density=5.78mA/cm2, A/V ratio=0.248cm−1. The NOM removal according to UV254 absorbance and dissolved organic matter (DOC) reached highest values of 77% and 71% respectively, relative to the raw groundwater. Arsenic removal was 85% (6.2μgAs/l) relative to raw groundwater, satisfying the drinking water standards. The specific reactor electrical energy consumption was 17.5kWh/kg Al. The specific aluminum electrode consumption was 66g Al/m3. According to the obtained results, ECF in horizontal continuous flow mode is an energy efficient process to remove NOM and arsenic from groundwater.

The Life and Death of a Green Tax that Never Was: The Dutch Groundwater Tax

We examine the Dutch national groundwater tax (GWT) – a ‘win–win, green’ tax that promised to reduce distortions by simultaneously reducing the income tax burden and improving environmental outcomes. We find no evidence of these impacts. Instead, we see that the GWT increased distortions by taxing a narrow base (a few drinking-water companies reliant on raw groundwater) and interfering with groundwater management programmes funded by an existing provincial groundwater fee. The Dutch government revoked the GWT for being fiscally inefficient and environmentally unhelpful on 31 December 2011, but this story provides some useful lessons.

Development of an attached growth reactor for NH4–N removal at a drinking water supply system in Kathmandu Valley, Nepal

Higher concentrations of ammonium (NH4–N) and iron (Fe) than a standard for drinking are typical characteristics of groundwater in the study area. To remove NH4–N and Fe, the drinking water supply system in this study consists of a series of treatment units (i.e., aeration and sedimentation, filtration, and chlorination); however, NH4−N in treated water is higher than a standard for drinking (i.e., <1.5 mg NH4–N/L). The objective of this study, therefore, is to develop an attached growth system containing a fiber carrier for reducing NH4–N concentration within a safe level in the treated water. To avoid the need of air supply for nitrification, groundwater was continuously dripped through the reactor. It made the system simple operation and energy efficient. Effects of reactor design (reactor length and carrier area) were studied to achieve a high NH4−N removal efficiency. In accordance with raw groundwater characteristics in the area, effects of low inorganic carbon (IC) and phosphate (PO4–P) and high Fe on the removal efficiency were also investigated. The results showed a significant increase in NH4–N removal efficiency with reactor length and carrier area. A low IC and PO4–P had no effect on NH4–N removal, whereas a high Fe decreased the efficiency significantly. The first 550 days operation of a pilot−scale reactor installed in the drinking water supply system showed a gradual increase in the efficiency, reaching to 95−100%, and stability in the performance even with increased flow rate from 210 to 860 L/day. The high efficiency of the present work was indicated because only less than 1 mg of NH4−N/L was left over in the treated water.

Hydrochemical characterization of arsenic contaminated alluvial aquifers in Eastern Croatia using multivariate statistical techniques and arsenic risk assessment

Multivariate statistical analyses, cluster, factor and discriminant analyses, were used to estimate spatial variations in groundwater chemistry in Eastern Croatia and to identify the main geochemical processes responsible for high arsenic (As) concentrations in the groundwater analyzed. Cluster analysis revealed five different groups of sampling sites linked with groundwater evolution, hydrochemical characteristics and different As content in the groundwater. Two-model factor analysis explained around 50% of total variance of the data sets and enabled identification of the different geochemical processes responsible for higher As concentrations, i.e. decoupled Fe and As reduction and desorption. Using discriminant analysis, a three-parameter discriminant function was derived: electrical conductivity, nitrate and bromide, which yielded highly accurate classification of the samples according to the concentration of As as As-safe (<10μg/L) and As contaminated (>10μg/L). A health risk assessment model was applied to calculate cumulative exposure to As as well as toxic and carcinogenic risks resulting from drinking raw groundwater contaminated by As in Eastern Croatia. Although the results obtained indicate that adverse health effects could be observed among the residents of the villages in which raw groundwater with higher As concentrations has been used, there are no reported cases of arsenicosis.

A Residence Time Distribution Approach to Biodegradation in Fuel Impacted Karst Aquifers

It is widely perceived that karst groundwater often has insufficient residence time for significant biodegradation of contaminants to occur. It is perhaps due to these perceptions that less research has been conducted for quantitative modeling of biodegradation in karst as compared to consolidated aquifers. Modeling biodegradation in karst is in the domain of non-ideal chemical reaction kinetics. The residence time distribution function (RTD) for tracer molecules in a single karst conduit or a complex system of conduits is a probability density function which can be interpreted to define the probability that contaminant molecules present at the influent at time equals zero will arrive at the effluent after a particular amount of time. To demonstrate this methodology the biodegradation rate of a contaminant (toluene) in raw karst groundwater from a BTEX impacted site in central Kentucky was quantitatively measured in batch microcosm studies and the extent of biodegradation of toluene in the same groundwater was measured for a complex flow system.The values of the pseudo first order rate constant (k’) obtained ranged from 0.017 (hr)-1 to 0.0210 (hr)-1 compared to 0.0186 (hr)-1 for the microcosm experiments. The close agreement between the values of k’ obtained from the static microcosms and the ADE model indicate that the model adequately describes the RTD for modeling biodegradation in karst aquifers. The values of k’ obtained correspond to a half-life of less than two days for toluene and this has major

Arsenic (III) oxidation of water applying a combination of hydrogen peroxide and UVC radiation

Arsenic is toxic to both plants and animals and inorganic arsenicals are proven carcinogens in humans. The oxidation of As(III) to As(v) is desirable for enhancing the immobilization of arsenic and is required for most arsenic removal technologies. The main objective of this research is to apply an Advanced Oxidation Process that combines ultraviolet radiation and hydrogen peroxide (UVC/H(2)O(2)) for oxidizing aqueous solutions of As(III). For that purpose, a discontinuous photochemical reactor (laboratory scale) was built with two 40 W tubular germicidal lamps (λ = 253.7 nm) operating inside a recycling system. The study was made beginning with a concentration of 200 μg L(-1) of As(III), changing the H(2)O(2) concentration and the spectral fluence rate on the reactor windows. Based on references in the literature on the photolysis of hydrogen peroxide, arsenic oxidation and our experimental results, a complete reaction scheme, apt for reaction kinetics mathematical modelling, is proposed. In addition, the effectiveness of arsenic oxidation was evaluated using a raw groundwater sample. It is concluded that the photochemical treatment of As(III) using H(2)O(2) and UVC radiation is a simple and feasible technique for the oxidation of As(III) to As(v).

Effect of Irrigation Methods on Groundwater Recharge in Alluvial Fan Area

Estimation of water table and recharge is a key component in the control of groundwater level in arid and semiarid regions such as northwestern China. This study compared groundwater recharge in land subject to flood-irrigation and water-saving irrigation within the Manasi Basin, China, with the aim of analyzing the influence of irrigation method on the response characteristics of groundwater. A simulation of the two irrigation methods was conducted over four years, using a coupled MIKESHE/MIKE 11 model, from which the average water balance was calculated. Moran’s I was used to explain the spatial variability of recharge response associated with each irrigation method. ArcGIS 9.0 geostatistical and spatial analysis applications were used to interpolate/extrapolate and create grids for specific yield, bedrock elevation, and raw groundwater data. The results of the simulations are generally consistent with observed data, indicating that the method is capable of recognizing detailed characteristics of the groundwater response. The groundwater recharge intensity was found to become weaker in water-saving irrigation than in floodirrigation, but groundwater discharge is greater for water-saving irrigation than for flood-irrigation, making the reduction in depth more obvious. Furthermore, the reduction in depth of the groundwater level increases with site elevation. The results indicate that the proposed methodology are applicable to the management of groundwater resources in arid regions. The study quantified the processes affecting groundwater levels and provided an insight into their implications for the management and control of groundwater level.