Ioannis A. Katsoyiannis

As(III) removal from groundwaters using fixed-bed upflow bioreactors

The application of biological oxidation of iron and manganese, as a potential treatment method for the removal of arsenic from contaminated groundwaters, was examined in this paper. This method was based on the growth of certain species of indigenous bacteria, which are capable of oxidizing the soluble iron and manganese ions; the oxidized forms can be subsequently removed from the aqueous stream by over 97%, through their transformation to insoluble oxides and separation by a suitable filter medium. Arsenic was removed by around 80%, under certain conditions, which were found to be sufficient for Fe(II) removal (dissolved oxygen 2.7 mg/l, redox 280-290 mV, pH 7.2, U 8.25 m/h). The specific treatment technique presents several advantages towards conventional physicochemical treatment methods, such as enhanced coagulation or direct adsorption since: (a) it does not require the addition of other chemicals for oxidizing and removing As(III), (b) it does not require close monitoring of a breakthrough point, as in conventional column adsorption processes and (c) it could find application for the removal of, at least, three groundwater contaminants (Fe, Mn, As).

REMOVAL OF ARSENATES FROM CONTAMINATED WATER BY COAGULATION–DIRECT FILTRATION

The present study has been directed towards the removal of arsenic, applying a modification of conventional coagulation/flocculation process. The modifications refer to the introduction of “pipe flocculation” process in the first stage of the technique, whereas the second step has been performed by direct filtration with sand filters, instead of separation by sedimentation. Alum or ferric chloride was the coagulant agent used, enhanced in certain cases by the presence of cationic or anionic polyelectrolytes (organic polymers). The efficiency of coagulant/polymer addition was investigated, using different ratios and for different initial As(V) concentrations. The effect of linear velocity during sand filtration was also examined. In general, both the coagulants were found to be efficient regarding arsenic removal and in both cases the use of coagulant aids increased the overall efficiency of the method—reaching in some cases arsenic removals up to 99%.

Removal of uranium from contaminated drinking water: a mini review of available treatment methods

Abstract In the present article, the major treatment methods applied for uranium removal from groundwater, with specific applications in drinking water treatment, are reviewed. These include pump-and-treat technologies, such as membrane filtration methods, anion exchange, and the use of adsorbents, such as iron oxides, or titanium dioxide, as well as the application of coagulation processes with the addition of Fe/Al salts, or by lime softening. In all cases, uranium removal is mainly dependent on its speciation, which is greatly affected by the (usually coexisting) carbonate ions in the contaminated water. Under circumneutral pH values, uranium forms anionic complexes with carbonate of the type , or . In situ treatment technologies comprise mainly the use of permeable reactive barriers. These contain reactive materials, such as zero valent iron or hydroxyapatite, and uranium is usually removed by reduction to the respective insoluble products of U(IV); reducing bacteria, when present, can play a suppleme...

Mapping human health risks from exposure to trace metal contamination of drinking water sources in Pakistan

The consumption of contaminated drinking water is one of the major causes of mortality and many severe diseases in developing countries. The principal drinking water sources in Pakistan, i.e. ground and surface water, are subject to geogenic and anthropogenic trace metal contamination. However, water quality monitoring activities have been limited to a few administrative areas and a nationwide human health risk assessment from trace metal exposure is lacking. Using geographically weighted regression (GWR) and eight relevant spatial predictors, we calculated nationwide human health risk maps by predicting the concentration of 10 trace metals in the drinking water sources of Pakistan and comparing them to guideline values. GWR incorporated local variations of trace metal concentrations into prediction models and hence mitigated effects of large distances between sampled districts due to data scarcity. Predicted concentrations mostly exhibited high accuracy and low uncertainty, and were in good agreement with observed concentrations. Concentrations for Central Pakistan were predicted with higher accuracy than for the North and South. A maximum 150-200 fold exceedance of guideline values was observed for predicted cadmium concentrations in ground water and arsenic concentrations in surface water. In more than 53% (4 and 100% for the lower and upper boundaries of 95% confidence interval (CI)) of the total area of Pakistan, the drinking water was predicted to be at risk of contamination from arsenic, chromium, iron, nickel and lead. The area with elevated risks is inhabited by more than 74 million (8 and 172 million for the lower and upper boundaries of 95% CI) people. Although these predictions require further validation by field monitoring, the results can inform disease mitigation and water resources management regarding potential hot spots.

Comparative evaluation of conventional and alternative methods for the removal of arsenic from contaminated groundwaters.

The present paper intends to summarize the recent findings regarding the development of alternative treatment methods applicable to small municipal drinking water systems. Small systems are frequently affected by the new permissible arsenic concentration rules, as imposed by several international organizations-World Health Organization, European Commission, United States Environmental Protection Agency. The innovate treatment methods reviewed are (a) adsorptive filtration, using iron oxide coated sand or polymeric materials; (b) zero-valent iron; (c) solar disinfection, solar oxidation and removal of arsenic (SORAS); (d) iron-based adsorbents, such as granular ferric hydroxide (GFH); (e) biological oxidation and removal of arsenic, accomplished simultaneously with the biological iron oxidation. In addition, other more conventional methods for arsenic removal are also discussed, such as iron or alum coagulation, lime softening, ion exchange, activated alumina and membrane separation processes. The aforementioned methods have been comparatively evaluated and the relevant conclusions have been drawn with respect to the applicability of arsenic treatment methods, depending on certain parameters, such as locally varying water quality characteristics, sustainability, and economic feasibility.

Enhanced As(III) oxidation and removal by combined use of zero valent iron and hydrogen peroxide in aerated waters at neutral pH values

The oxidation and removal of As(III) by commercially available micro-scale zero-valent iron (mZVI) was studied in aerated synthetic groundwater with initially 6.7 μM As(III) at neutral pH values. Batch experiments were performed to investigate the influence of ZVI and H2O2 concentrations on As(III) oxidation and removal. Oxidation and removal kinetics was significantly increased by increasing ZVI concentration or by adding H2O2 in micromolar concentrations slightly higher than that of initial As(III). Observed half-lifes for arsenic removal without added H2O2 were 81-17 min at ZVI concentrations of 0.15-2.5 g/L, respectively. X-ray absorption spectroscopy (XAS) confirmed that almost all As(III) was converted to As(V) after 2 h of reaction in the pH range 5-9. Addition of 9.6 μM H2O2 to 0.15 g/L ZVI suspensions diminished half-lifes for arsenic removal from 81 to 32 min and for As(III) oxidation from 77 to 8 min, i.e., by approximately a factor of 10. The increased rate of As(III) oxidation is attributable to enhanced formation of oxidants by the Fenton reaction with higher initial concentrations of H2O2. In practice, results of this study suggest that addition of small amounts (<1 mg/L) of H2O2 in various forms (e.g. stable and widely available Na-percarbonate) to water prior to treatment could significantly enhance As(III) oxidation and removal with ZVI.

Arsenic occurrence in Europe: emphasis in Greece and description of the applied full-scale treatment plants

The presence of arsenic in groundwater comprises a worldwide problem and is recognized as a human health threat. The present work summarizes the arsenic contamination in Europe, where many countries are affected by elevated arsenic concentrations (i.e. Greece, Hungary, Romania, Croatia, Serbia, Turkey, and Spain). In particular, in Greece, several groundwater resources contain arsenic at increased concentrations, which render these water sources as non-potable. Arsenic-affected regions in Greece are classified mainly in three categories, namely, the geothermal-affected waters, the alluvial deposits of rivers and aquifers, and those influenced by mineralization and are typically close to mining activities. In Greece, arsenic concentrations in geothermal waters vary from 30 to 4,500 μg/L, in the regions close to alluvial deposits from 15 to 100 μg/L and in areas affected by mining activities from 20 to 60 μg/L. Arsenic-removal plants have been installed in several towns in Greece. The applied removal technologies are mainly based on chemical precipitation with FeClSO4 or adsorption onto iron oxide materials, such as Bayoxide, granular ferric hydroxide or AquAsZero. In the cases where As(III) is present, biological oxidation or ozonation is applied to convert As(III) to the less mobile forms of As(V). Specific arsenic removal capacity at an equilibrium concentration equal to the regulation limit of 10 μg/L was between 1.7 and 4.2 mg As/g of adsorbent for adsorption processes and between 18 and 59 mg As/g Fe for chemical precipitation.

Arsenic levels from different land-use settings in Pakistan: Bio-accumulation and estimation of potential human health risk via dust exposure

The present study aims at assessing arsenic (As) levels in outdoor dust and human exposure risks at different land use setting (i.e., rural, industrial, urban) from Punjab, Pakistan. The results showed higher As concentrations (mg/kg) in all the sample types ( i.e., dust, hair and nail) collected from industrial sites (9.78, 2.36, 2.5) followed by urban (7.59, 0.38, 0.88) and rural sites (6.95, 0.52, 1.12), respectively. In the current study, we also carried out human risk assessment via contaminated dust exposure, which suggested that dust ingestion is the major route of As contamination for the associated population, followed by the inhalation and dermal contact, at all studied land use settings. Hazard Index (HI) calculated for non-carcinogenic health risks for adults showed higher values at industrial (0.65) and urban (0.53) sites, which reflected that dust exposure is the major contributing source of human arsenic burden and may pose several adverse health effects. Carcinogenic risk values showed that at industrial areas the risk of carcinogenesis to the associated population is mainly due to As contaminated dust exposure. Hair (60%) and nail samples (70%) collected from industrial land use were found above the WHO threshold limit of 1mg/kg, suggested high risks for human health in the studied area. The results of the present study would be useful for assessing the human health risks due to arsenic contamination via dust exposure in different parts of country.

Human lead (Pb) exposure via dust from different land use settings of Pakistan: A case study from two urban mountainous cities.

The current study aims to determine the dust-borne lead (Pb) levels into outdoor dust, which were collected from the areas nearby the cities/districts of Islamabad and Swat in Pakistan. In general dust samples from all land use settings (industrial, urban and rural) showed significantly higher (p<0.05) Pb-levels (median, ppm) from Islamabad (110, 52, 24) than those of Swat district (75, 37, 21), respectively. Index of Geo-accumulation (Igeo values) indicated that industrial and urban areas of both sites were highly polluted due to severe anthropogenic influence, whereas the rural areas were in most parts unpolluted and where moderately polluted, this was mainly due to geological factors and short and/or long distance atmospheric deposition from surrounding polluted areas. According to the calculated chemical daily intake (mg/kg-day) values, dust ingestion is one of the major routes of human exposure for lead. Hazard Index (HI) values, calculated for both adult and children populations, were above unity in industrial and urban areas, indicating serious health risks especially to the children populations.

Novel Water Treatment Processes Based on Hybrid Membrane-Ozonation Systems: A Novel Ceramic Membrane Contactor for Bubbleless Ozonation of Emerging Micropollutants

The aim of this study is the presentation of novel water treatment systems based on ozonation combined with ceramic membranes for the treatment of refractory organic compounds found in natural water sources such as groundwater. This includes, firstly, a short review of possible membrane based hybrid processes for water treatment from various sources. Several practical and theoretical aspects for the application of hybrid membrane-ozonation systems are discussed, along with theoretical background regarding the transformation of target organic pollutants by ozone. Next, a novel ceramic membrane contactor, bringing into contact the gas phase (ozone) and water phase without the creation of bubbles (bubbleless ozonation), is presented. Experimental data showing the membrane contactor efficiency for oxidation of atrazine, endosulfan, and methyl tert-butyl ether (MTBE) are shown and discussed. Almost complete endosulfan degradation was achieved with the use of the ceramic contactor, whereas atrazine degradation higher than 50% could not be achieved even after 60 min of reaction time. Single ozonation of water containing MTBE could not result in a significant MTBE degradation. MTBE mineralization by O3/H2O2 combination increased at higher pH values and O3/H2O2 molar ratio of 0.2 reaching a maximum of around 65%.