Drinking Water Quality Criteria Research Articles

Hydrogeochemical characterization of groundwater in mountainous catchment and its suitability for drinking purposes in Irob, Tigray, Northern Ethiopia

Abstract The primary source of drinking water in Ethiopia's semi-arid mountainous regions is groundwater. The present study aims to assess the hydrogeochemical characteristics of low-grade basement rocks dominated by mountainous catchments. Moreover, it examines the suitability of the groundwater quality for drinking purposes in Irob, Tigray, northern Ethiopia. However, relatively little is known about the water chemistry and groundwater quality of the resources in the area. Fifteen samples of groundwater were collected and examined for ions according to standard procedures. The outcomes were assessed against the World Health Organization (WHO) drinking water quality criteria. To identify the source of dissolved ions and the process involved, graphic interpretations were applied. The results show that Ca–Mg–SO4–HCO3 and Ca–SO4–HCO3 were the dominant water types. Gibbs plots and ionic ratios reveal that silicate weathering, carbonate dissolution and ion exchange control water chemistry. Furthermore, the findings reveal that 60, 80, 46.67, 46.67, 60, 6.67, 60 and 53.33% of samples are above the safe limits of the WHO for hardness, alkalinity, total dissolved solids, electrical conductivity, calcium (Ca2+), potassium (K+), bicarbonate (HCO3-) and sulfate (SO42-), respectively. Consequently, the groundwater quality assessment demonstrates that the water sources in lower parts of the catchment are unsuitable for drinking.

Assessment of heavy metal pollution in Nigerian surface freshwaters and sediment: A meta-analysis using ecological and human health risk indices

Heavy metal pollution in surface freshwaters is prevalent globally and is an environmental issue of concern. Many studies have described sources, concentrations in selected waterbodies and toxic effects in biological systems. The purpose of the present study was to assess the status of heavy metal pollution in Nigerian surface freshwaters as well as the ecological and public health risks associated with current levels of pollution. A literature review of studies which assessed concentrations of heavy metals in named freshwater bodies around the country was done to gather relevant data. These waterbodies included rivers, lagoons, and creeks. The data gathered was subjected to a meta-analysis using referenced heavy metal pollution indices, sediment quality guidelines, ecological risk indices and non-carcinogenic and carcinogenic human health risk indices. The result obtained showed that concentrations of Cd, Cr, Mn, Ni and Pb in Nigerian surface freshwaters are higher than the maximum recommended levels in drinking water. The heavy metal pollution indices calculated using drinking water quality criteria by the World Health Organization and the US Environmental Protection Agency, were also significantly higher than the threshold value of 100 (13,672.74 and 1890.65 respectively). These results indicate that the surface waters are unsafe for drinking purposes. The enrichment factor, contamination factor and ecological risk factor indices for cadmium (684.62, 41.73 and 1251.90 respectively) were all higher than the maximum threshold for each index (40, 6, 320 respectively). These results indicate that cadmium contributes significantly to the ecological risk associated with pollution in Nigerian surface waters. In terms of public health risk, the current levels of heavy metal pollution in Nigerian surface waters pose both non-carcinogenic and carcinogenic risks to children and adults who are exposed through ingestion and dermal routes as shown by results from the present study. Nigeria is blessed with abundant surface freshwater resources and many coastal indigenous populations use the water resources for drinking and domestic purposes. Many of them are also commercial fish farmers earning their daily living from fisheries resources. Heavy metal pollution must be regulated to levels below which end users and aquatic life are protected from adverse impacts of pollution.

EVALUATION OF REFILLABLE DRINKING WATER QUALITY BASED ON MPN COLIFORM AND ESCHERICHIA COLI INSESETAN VILLAGE, SOUTH DENPASAR, BALI

Background: Refilled drinking water given by depots that currently have a permit for operation can be used to meet the community's drinking water demands. However, the quality of refilled drinking water has been tainted with pathogens that can cause health problems. Purpose: To assess the quality of replenished drinking water in Sesetan Village using Most Probable Number (MPN) Coliform and Escherichia coli as indicators. Method: A qualitative approach to descriptive observational research. The Ministry of Health standard 492/Menkes/PER/IV/2010 is used to assess drinking water quality. In this investigation, ten samples were used. Sampling was conducted in Sesetan Village, South Denpasar, Bali. Result: MPN Coliform was found in four samples: 96 MPN/100 mL (X1), 38 MPN/100 mL (X7), 15 MPN/100 mL (X8), and 5 MPN/100 mL (X10). Meanwhile, all of the samples tested negative for Escherichia coli. Conclusion: Based on drinking water quality criteria, 4 (40%) refilled drinking water depots (DAMIU) did not meet quality requirements (Ministry of Health Regulation number 492/Menkes/PER/2010).

Assessment of ground water from some agrarian communities of South Eastern Nigeria

ABSTRACT Drinking water samples were collected from natural sources (groundwater and surface water) in rural villages in southeastern Nigeria, and the results were compared to WHO and Nigerian drinking water quality criteria. To meet the study’s goal, 21 drinking water samples were collected from sparsely populated rural settlements in Ebonyi State (Ugwulangu, Okposi, and Uburu). pH, temperature, turbidity, conductivity, salinity, total dissolved solids, total hardness, alkalinity, chlorides, nitrates, sulphates, phosphates, and metals were all measured in the water samples. This study looked at eight metals: Ca, Mg, Fe, Zn, Pb, Cr, Mn, and Ni. Except for turbidity, conductivity, alkalinity, Pb, and Ni, all metrics were found to be within allowed ranges. The metal concentrations followed the order: Ca > Mg > Pb > Fe > Zn > Ni > Mn > Cr. Metal index, degree of contamination, and hazard index were all calculated using the metal concentrations. The metal index and degree of contamination results showed that the water sources were safe to drink. The hazard index assessed children’s and adults’ chronic risk levels. By ingesting metals in water samples, the Hazard Index assessed the risk that users of water are prone to. Children are more at risk than adults from drinking untreated water from Ugwulangu, Okposi, and Uburu, according to the findings of a hazard index study. To safeguard children’s health, it is strongly advised that they be provided with alternative drinking water.

Evaluating the source and Quality of River and Groundwater using hydrochemistry and stable isotopesin Tawi Watershed, Jammu District, Jammu and Kashmir, India

Hydrogeochemical and isotopic composition of river and groundwater in Kandi and Sirowal belts of Jammu District in the Union Territory of Jammu and Kashmir was carried out to understand the recharge source and chemical nature of these waters for drinking water quality criteria. Physical parameters (temperature, pH, Total dissolved solids, total hardness and electrical conductivity), major cations and anions (Ca2+, Mg2+, Na+, K+, HCO3-, Cl-, SO42-, NO3-) and stable isotopes (d18O and d2H) inTawi river and groundwater samples from hand pumps and tube wells were measured. The dominant cation is Ca2+ and the dominant anion HCO3- implyingCaHCO3type water in both river and groundwater. To assess the quality of water for drinking purposes, Groundwater Quality Index (GWQI) has been calculated. The GWQI indicates that Kandi and Sirowal belts are showing “Excellent” to “Good” category for drinking purposes. The stable isotopic composition of river water and groundwater is indicative of meteoric origin and enrichment before groundwater recharge. The stable isotopes in water suggest that the active canals in Sirowal belt,and rainfall and river water near the banks in Kandi belt contribute to ground water recharge.

Socioeconomic and recharge effect on spatial changes in the groundwater chemistry of Punjab, Pakistan: a multivariate statistical approach

This study presents deterioration in groundwater quality of highly populated region of Punjab Province, Pakistan, by linking chemical data with rain, river recharge, and socioeconomic factors. Various chemical parameters like total dissolved solid (TDS), arsenic (As), fluoride (F−), Iron (Fe), nitrate (NO3−), nitrite (NO2−), and pH were determined for 46,457 samples collected from 205,344 km2 area of the Punjab. The samples were collected, stored, and analyzed as per the Environment Protection Agency (EPA) methods at laboratory. Commercial kits were used for analysis of Fe, As, NO2−, NO3− and F−, while TDS and pH were measured by respective meters. Chemical parameters were correlated with human and animal population, fertilizers consumption, tube wells, industrial density, rain occurrence, and river recharge rate. Data were analyzed using XLSTAT, and GIS 10.3 was used to draw the maps. Spatial classification of the districts was performed by principal component analysis and hierarchal cluster analysis. TDS, As, F−, Fe, NO3−, NO2−, and pH were found to be 50–52,360 mg/L, 0–735 μg/L, 0–121 mg/L, 0–37.2 mg/L, 0–2215 mg/L, 0–3033 mg/L, and 0.09–10.9, respectively. The study revealed that 66.26% of the samples were fit for drinking purpose, while 33.74% were unfit. Further, it was found that 27% of the samples were non-saline, 26% were saline, and 47% were slightly saline based on the World Health Organization drinking water quality criteria. A nonlinear model was developed which explains 57% of variance in groundwater quality. Based on groundwater quality, the whole province was divided into three main regions: northwestern districts, central districts and southeastern districts. Central Punjab was highly polluted, followed by southeast region, while northwest Punjab has better quality water due to more rains and Indus River. Current study provides a model to predict future water quality of the region and suggests that new water canals in southeast Punjab can improve water quality. Moreover, it is recommended that agriculture and industrial effluents should be controlled to improve water quality, new smart cities should be built along Indus River, and population should be controlled in southeast and central Punjab.Graphical abstract

Drinking water quality from rural handpump-boreholes in Africa

Groundwater provides a vital source of drinking water for rural communities in many parts of Africa, particularly in the dry season when there are few safe alternative sources. This paper summarises results from a study (n = 428) assessing dry season water quality, both microbiological and inorganic chemistry, in handpump equipped boreholes (HPBs) across the Ethiopia Highlands (n = 142), Malawi (n = 162) and Uganda (n = 124) using a stratified, randomised sampling design. This study seeks to examine general water quality by randomly sampling rural groundwater supplies across larger areas with different geology and climate. The majority, 72%, of HPBs surveyed provide good quality dry season drinking water as defined by WHO drinking water quality criteria. Within this overall picture, the most notable constraints were from thermotolerant coliforms (TTCs), which exceeded the WHO drinking water guideline of zero colony forming units (cfu/100 ml) in 21% of sites (range 0–626 cfu/100 ml). TTC contamination was found to have a significant and positive correlation with annual average rainfall (ρ = 0.2, p = 0.00003). Across all three countries, WHO health based chemical drinking water quality values were exceeded at 9% of sites and were found for manganese (4%), fluoride (2.6%) and nitrate (2.5%); arsenic concentrations were below the guideline value of 10 μg l−1 (range < 0.5–7 μg l−1). The high percentage of Mn exceedances (14% ± 5.2% >400 μg l−1) found in drinking water sources in Uganda challenges the decision by WHO not to formalise a health-based guideline for Mn. While the overall level of microbiological contamination from HPBs is low, results from this study strongly suggest that at a national and regional level, microbiological contamination rather than chemical contamination will provide a greater barrier to achieving targets set for improved drinking water quality under the UN-SDG 6. Efforts should be made to ensure that boreholes are properly sited and constructed effectively to reduce pathogen contamination.

Cationic Starch and Polyaluminum Chloride as Coagulants for River Nile Water Treatment

Traditional water coagulants cause many problems in drinking water treatment processes and the quality of the produced water. In this current research, cationic starches (CSTs) were prepared with different degree of substitutions; DS (0.34, 0.85 and 0.97). The efficiency of the as prepared CST and the commercial polyaluminum chlorides (PAC) were evaluated in Nile water turbidity reduction. The application of coagulants in the treatment of Nile River water showed that the turbidity caused by algal biomass were decreased to 61.5% by using 0.5 ppm of CST; DS 0.85. For effective algal cells removal, pre-chlorination process is required. The maximum treatment was obtained through pre-chlorination/coagulation process using CST (DS = 0.97) with turbidity removal percentage; 73.1% and total algal removal reached 94.8%. All tested coagulants have a great effect on total bacteria counts in the presence of chlorine as a disinfectant without any significant changes in drinking water quality criteria.

Analysis of Water Well Quality Drilling Around Waste Disposal Site in Makassar City Indonesia

Clean water is one of human need which is very important in carrying out its life. Therefore, this article analyzes the quality of the well water dug around the landfill. The method used is a well water well sample taken from 4 wells around a landfill taken by a purposive sampling at a different distance. The parameters measured are physical, chemical, and biological properties. The results of the analysis were then compared with the standard of drinking water quality criteria allowed under The Regulation of Health Minister of Indonesia No. 416 year 1990 on the Terms and Supervision of Water Quality of the Minister of Health of the Republic of Indonesia. The result of the research shows that there are two wells whose water quality does not meet the physical requirement i.e Location of Points II and III, based on the construction of wells also does not meet the requirements of the wells in general. While at the well Locations Point I and IV the quality of water physically, chemically and biologically as well as well construction qualify. From the result of this research, the researcher give suggestion of the need to improve the physical condition of dug wells, it is necessary to do the extension to the well water user community for drinking water about the physical condition of the dug well, the need to monitor and supervise the quality of drinking water, and should involve the community to independently meet the needs absolute i.e clean water to drink.

A risk-based approach for assessing the recycling potential of an alkaline waste material as road sub-base filler material

In this work we present an integrated risk-based approach that can be used to evaluate the recycling potential of an alkaline waste material such as incineration bottom ash (BA) as unbound material for road sub-base construction. This approach, which is aimed at assessing potential risks to the groundwater resource (in terms of drinking water quality) and human health associated to the leaching of contaminants from the BA, couples the results of leaching tests for the estimation of source concentrations with the fate and transport models usually adopted in risk assessment procedures. The effects of weathering and of the type of leaching test employed to evaluate eluate concentrations were assessed by carrying out different simulations using the results of laboratory leaching tests. Specifically, pH-dependence and column percolation leaching tests were performed on freshly collected and 1-year naturally weathered BA samples produced from a grate-fired incineration plant treating Refuse Derived Fuel (RDF). To evaluate a broad span of possible scenario conditions, a Monte Carlo analysis was performed running 5000 simulations, randomly varying the input parameters within the ranges expected in the field. In nearly all the simulated conditions, the concentrations of contaminants in the groundwater for the specific type of BA tested in this work were well below EU and WHO drinking water quality criteria. Nevertheless, some caution should be paid in the case of the establishment of acidic conditions in the field since in this case the concentration of some elements (i.e. Al, Pb and Zn) is expected to exceed threshold values. In terms of risks to human health, for the considered utilization scenario the probability of exceeding the acceptable reference dose for water ingestion was usually less than 1% (except for Cr and Pb for which the probability was lower than 3.5% and 7%, respectively).

Multi-Elements in Source Water (Drinking and Surface Water) within Five Cities from the Semi-Arid and Arid Region, NW China: Occurrence, Spatial Distribution and Risk Assessment.

The purpose of this study was to identify the concentration of multi-elements (MEs) in source water (surface and drinking water) and assess their quality for sustainability. A total of 161 water samples including 88 tap drinking waters (DW) and 73 surface waters (SW) were collected from five cities in Xi’an, Yan’an, Xining, Lanzhou, and Urumqi in northwestern China. Eighteen parameters including pH, electrical conductivity (EC), total organic carbon (TOC) total nitrogen (TN), chemical compositions of anions (F−, Cl−, NO3−, HCO3−, SO42−), cations (NH4+, K+, Na+, Ca2+, Mg2+), and metals (lead (Pb), chromium (Cr), cadmium (Cd), copper (Cu)) were analyzed in the first time at the five cities . The results showed that pH values and concentrations of Cl−, SO42−, Na+, K+, Ca2+, Mg2+ and Cd, Cr, Cu in DW were within the permissible limits of the Chinese Drinking Water Quality Criteria, whereas the concentrations of other ions (F−, NO3−, NH4+ and Pb) exceeded their permissible values. In terms of the SW, the concentrations of F−, Cl−, NO3−, SO42− were over the third range threshold i.e., water suitable for fishing and swimming of the Surface Water Quality Standards in China. The spatial distributions of most MEs in source water are similar, and there was no clear variation for all ions and metals. The metals in DW may be caused by water pipes, faucets and their fittings. The noncarcinogenic risk of metals in DW for local children are in decreasing order Cr > Cd > Pb > Cu. The carcinogenic risk from Cr exposure was at the acceptable level according to threshold of USEPA. Although the comprehensive index of potential ecological assessment of Cr, Cd, Pb and Cu in SW ranked at low risk level and was in the order of Huang River in Xining > Peaceful Canal in Urumqi > Yan River in Yan’an > Yellow River in Lanzhou, their adverse effects to ecology and human health at a low concentration in local semi-arid and arid areas should not be ignored in the long run.

Study of Groundwater Salinity in Few Districts Adjoining River Ganga in Uttar Pradesh - A Case Study

Central Pollution Control Board has focused on impact assessment of sewerage system and groundwater studies on River Ganga particularly in Uttar Pradesh state. Variation of total dissolved solid values in groundwater in some of the locations reveal that the water has become ‘Saline’ and ‘Brackish’ which could be due to over-extraction, besides contamination from anthropogenic sources. The chloride concentration in groundwater in the study shows that 10 locations are beyond the desirable limit as specified by BIS. There is a direct relationship between total dissolved solid and sodium, indicating of contamination. Nitrate content in groundwater in only one location, i.e., Dinapur, exceeded more than 7 times from the Indian Drinking Water Quality Criteria. The higher value of fluoride in groundwater was observed at various locations of Uttar Pradesh and appeared an inverse relationship between calcium concentrations indicating the cause as anthropogenic sources. Similarly, sulphate in 16 locations and phosphate in various locations of Saharanpur and Unnao districts exceeded the maximum permissible limit of BIS specified. Total coliform and faecal coliform counts was found in 27 locations above the permissible limits of BIS specified.

Nutrients, emerging pollutants and pesticides in a tropical urban reservoir: Spatial distributions and risk assessment

Reservoirs located in urban areas suffer specific pressures related to human activities. Their monitoring, management, and protection requirements differ from reservoirs situated in non-urbanized areas. The objectives of this study were: (a) to determine the concentrations of select pesticides and emerging pollutants (EPs) present in an urban reservoir; (b) to describe their possible spatial distributions; and (c) to quantify the risks for aquatic life and safeguard drinking water supplies. For this purpose, the Guarapiranga reservoir was studied as an example of a multi-stressed urban reservoir in a tropical region. A total of 31 organic compounds (including pesticides, illicit drugs, pharmaceuticals, and endocrine disruptors) were analyzed twice over a period of one year, together with classical indicators of water quality. The physical and chemical data were treated using principal component analysis (PCA) to identify possible temporal or spatial patterns. Risk assessment was performed for biota and drinking water use, comparing maximum environmental concentrations (MECs) with the predicted no-effect concentrations (PNECs) or drinking water quality criteria (DWC), respectively. The results demonstrated the presence of pesticides and EPs, as well as pollution by high levels of nutrients and Chlorophyll a (Chl. a), during the study period. The nutrients and Trophic State Index (TSI) showed gradients in the reservoir and regional distributions, while the pesticides and EPs only clearly showed this pattern in the dry season. The concentrations and distributions of the pesticides and EPs therefore showed seasonality. These findings suggested that the two groups of pollutants (EPs+pesticides and nutrients) possessed different sources and behavior and were not always correlated in the reservoir studied. In the studied period, no risk was observed in raw water for drinking water use, but carbendazim, imidacloprid, and BPA showed risks for the biota in the reservoir.

A pragmatic approach to study the groundwater quality suitability for domestic and agricultural usage, Saq aquifer, northwest of Saudi Arabia.

The present study deals with detailed hydrochemical assessment of groundwater within the Saq aquifer. The Saq aquifer which extends through the NW part of Saudi Arabia is one of the major sources of groundwater supply. Groundwater samples were collected from about 295 groundwater wells and analyzed for various physico-chemical parameters such as electrical conductivity (EC), pH, temperature, total dissolved solids (TDS), Na(+), K(+), Ca(2+), Mg(2+), CO3 (-), HCO3 (-), Cl(-), SO4 (2-), and NO3 (-). Groundwater in the area is slightly alkaline and hard in nature. Electrical conductivity (EC) varies between 284 and 9,902 μS/cm with an average value of 1,599.4μS/cm. The groundwater is highly mineralized with approximately 30% of the samples having major ion concentrations above the WHO permissible limits. The NO3 (-) concentration varies between 0.4 and 318.2mg/l. The depth distribution of NO3 (-) concentration shows higher concentration at shallow depths with a gradual decrease at deeper depths. As far as drinking water quality criteria are concerned, study shows that about 33% of samples are unfit for use. A detailed assessment of groundwater quality in relation to agriculture use reveals that 21% samples are unsuitable for irrigation. Using Piper's classification, groundwater was classified into five different groups. Majority of the samples show Mix-Cl-SO4- and Na-Cl-types water. The abundances of Ca(2+) and Mg(2+) over alkalis infer mixed type of groundwater facies and reverse exchange reactions. The groundwater has acquired unique chemical characteristics through prolonged rock-water interactions, percolation of irrigation return water, and reactions at vadose zone.

HS-SPME-GC-MS analysis of antioxidant degradation products migrating to drinking water from PE materials and PEX pipes

Polyethylene (PE) and cross-linked polyethylene (PEX) pipes are frequently used in water supply systems. Such pipes contain added antioxidants with phenolic structures, e.g. Irgafos 168, Irganox 1010 and 1076, in order to improve durability. However, phenol, ketone and quinone antioxidant degradation products may leach and enter drinking water. The aim of this investigation was to develop a method for measuring these degradation products with a performance meeting the drinking water quality criteria of 20 µg L−1. Using headspace solid phase microextraction coupled to a gas chromatograph with a mass spectrometer, a method was established revealing limits of detection and quantification less than 0.4 and 1 µg L−1 respectively. The method was applied to migration experiments for two PEX pipes and one PE material, quantifying the release of two degradation products. Highest concentrations were observed for 2,6-di-tert-butyl-p-benzoquinone which in one of the two pipes was found in concentrations of 18–57 µg L−1 in each of eight consecutive release experiments.

Dynamics of toxic heavy metals in different compartments of a highly urbanized closed aquatic system

This paper deals with the dynamics of chromium, nickel, copper and lead among the different components namely water, surface sediments, submerged and free floating macrophytes and fish of the twin manmade lakes, Upper and Lower lakes, of Bhopal (M.P., India). Some basic parameters of water and sediment have also been studied. The basin of the lake system is densely populated and the water is used for various purposes including drinking. Ni and Pb along with nitrate in both lakes are significantly higher than the drinking water quality criteria of USEPA. The concentration of the metals in the sediments is noticeably higher than that present in the adjoining rock, particularly Ni and Pb. There is a significant uptake of metals by the macrophytes (Eichhornia crassipes and Hydrilla verticillata) and fish (Labeo rohita and Oreochromis niloticus) mainly in summer. The fish of Lower lake (O. niloticus) is unfit for human consumption. The data have been statistically treated. Principle component analysis and cluster analysis were performed to define the origin of metals and to assess the relationship among the sites. Overall the Lower lake is more polluted than the Upper lake. In aggregate, the lake system is under an environmental stress due to certain practices.

Pesticide Multiresidues in Waters of the Lower Fraser Valley, British Columbia, Canada. Part II. Groundwater

In Part I of this work we presented pesticide levels in the surface waters of the Lower Fraser Valley (LFV) region of British Columbia, Canada. In Part II pesticide levels in the groundwater of the LFV are presented. During the period 2003 to 2005 a study was conducted to determine the occurrence and spatial distribution of 78 pesticides in the groundwater of the LFV. Samples were collected and analyzed from one reference, nine agricultural, one urban, and three urban-agriculture mixed sites. Overall 24 different pesticides were detected in the sites monitored. The maximum single pesticide concentration observed was for simazine (90 ng L(-1)) at one of the agricultural sites. All concentrations of pesticides detected in groundwater samples were below Canadian surface water quality criteria and below available drinking water quality criteria set by World Health Organization (WHO), Health Canada, USEPA, and the European Union (EU). Pesticide levels in surface and groundwater were compared in the Abbotsford area. Generally, a pesticide with a high groundwater concentration tended to also have a high surface water concentration (Simazine 29 ng L(-1) in groundwater and 58 ng L(-1) in surface water, atrazine 5.5 ng L(-1) in groundwater and 14 ng L(-1) in surface water). For pesticides that were detected above 1 ng L(-1) concentration the only exception to this was desethylatrazine that showed greater concentration in groundwater (2.2 ng L(-1)) than surface water (1.5 ng L(-1)). Herbicides were the predominant pesticides detected in the agricultural sites and insecticides were predominant in the urban sites. Pesticide data presented in this study provide reference levels for future pesticide monitoring programs in the region.

Microbial counts and pesticide concentrations in drinking water after alum flocculation of channel feed water at the household level, in Vinh Long Province, Vietnam

Low technology water supply, treatment and sanitation techniques were reviewed in a Vietnamese village in the Mekong River Delta as part of an AusAID Project to reduce poverty and to improve the overall living standards and health in the Cuu Long (Mekong) delta for 500,000 rural poor. It was found that dosing of canal water in 200-1 ceramic jars with alum, PAC or PAC followed by hypochlorite provides a high level of treatment for drinking water at the household level in a rural village setting in the Mekong River delta. Seventy per cent (7 in total) of the 24 samples collected showed that Escherichia coli levels per 100 ml in the jars after treatment showed a 'no risk' profile (0 E. coli 100 ml(-1)) i.e. the water would be considered to be of very good quality for drinking according to World Health Organization Guidelines for Rural Drinking Water Supply. This included the eight samples that were dosed with hypochlorite. The remaining 30% of samples (seven in total) ranged from 14 to 47 E. coli 100 ml(-1) which is considered an intermediate risk (10-100 E. coli 100 ml(-1)) according to WHO guidelines. All control water samples (eight in total) were high or very high risk (>100 E. coli 100ml(-1).

Leaching of heavy metals (Cu, Ni and Zn) and organic matter after sewage sludge application to Mediterranean forest soils

In Mediterranean dry and semiarid areas, soil organic matter is often depleted due to ancient and intensive human activity. Under these conditions the use of sewage sludge as a land reclamation technique may be a means to revert desertification processes and to enhance soil function and nutrient cycling. However, applications of heavy metal-contaminated sewage sludges can significantly increase potentially toxic metal concentrations in soils and metal transfer to freshwater and plants. The aims of this study are 1) to investigate the leaching of Cu, Zn and Ni from three contrasted Mediterranean forest soils (a basic loam, a basic clay, and an acid loam) treated with sewage sludges and 2) to explore the relationships between metal mobility and soil properties and with the leaching of organic matter. The selected soils were incubated in columns (5 replicates × 3 soils × 3 treatments). Treatments were (a) soil application of low metal content sewage sludge (LMS), (b) soil application of metal-enriched sewage sludge (MES), and (c) control. The sewage sludge application represented a dose of 6 kg dry weight m − 2 . Soil columns were incubated at room temperature for 110 days and were irrigated weekly with deionised water to make a total of a 1130 mm. Leachates were collected and analysed for pH, EC, organic carbon Cu, Ni and Zn concentrations. The concentration of metals and organic matter in the leachates depended on the soil characteristics and on the type of sewage sludge added to the soil. Basic soils with a high amount of clay showed the highest metal retention capacity, while acid soils with low clay content showed the lowest. Of the three metals studied, Ni exhibited the greatest mobility. Zn mobility was also rather high, particularly in the acid soil. Despite the fact that basic soils showed greater OM content than the acid soil, organic carbon in leachates after sludge addition was of the same order of magnitude in all studied soils. OM mobility may enhance the leaching of metals while the OM bound to soil particles may enhance the retention of metals. The rate of leaching per unit of metal in the soil, for Cu in all soils and for Zn in the basic soils, did not increase even in soils amended with metal-enriched sewage sludge. However, the total amount of Cu, Zn, and Ni leached through the 30 cm columns of the metal-enriched sewage sludge increased in comparison to the control soils. In spite of this fact, metal concentrations were in most cases well below limit for drinking water quality criteria of Spanish legislation. Thus, after one single addition of metal-enriched sewage sludge, for the studied Mediterranean soils, the risk of heavy metal pollution of groundwater appears to be low.

Implementation of a continuous-flow stirred bioreactor system in the bioremediation of heavy metals from industrial waste water

The industrial applicability of immobilized non-viable yeast biomass (Saccharomyces cerivisiae) in continuous-flow stirred bioreactors was tested with respect to metal removal from electroplating effluent solutions containing Cu, Cd, Cr, Ni and Zn in excess of the stipulated water quality criteria. Two systems, a dual bioreactor and triple bioreactor system in series, were tested and compared regarding their efficiency of metal removal. The system containing two bioreactors linked in series provided a more efficient solution to the problem. The introduction of a third bioreactor into the system had a marginal effect on the amount of metal removed. Subsequent to treatment within the bioreactors the levels of Cu, Cr and Ni in the effluent complied with the stipulated drinking water quality criteria and, although in excess of these criteria only 18% of the initial Zn and 17% of the Cd remained in solution.