Monthly Archives: May 2015

TTHMs not Associated with Neural Tube Defects in Mice

Melin VE; Johnstone DW; Etzkorn FA; Hrubec TC; Drinking water treatment is not associated with an observed increase in neural tube defects in mice. Environmental Monitoring And Assessment 2014 Jun; Vol. 186 (6), pp. 3717-24.

Disinfection by-products (DBPs) arise when natural organic matter in source water reacts with disinfectants used in the water treatment process. Studies have suggested an association between DBPs and birth defects. Neural tube defects (NTDs) in embryos of untreated control mice were first observed in-house in May 2006 and have continued to date. The source of the NTD-inducing agent was previously determined to be a component of drinking water. Tap water samples from a variety of sources were analyzed for trihalomethanes (THMs) to determine if they were causing the malformations. NTDs were observed in CD-1 mice provided with treated and untreated surface water. Occurrence of NTDs varied by water source and treatment regimens. THMs were detected in tap water derived from surface water but not detected in tap water derived from a groundwater source. THMs were absent in untreated river water and laboratory purified waters, yet the percentage of NTDs in untreated river water were similar to the treated water counterpart. These findings indicate that THMs were not the primary cause of NTDs in the mice since the occurrence of NTDs was unrelated to drinking water disinfection.

Paper is here (fee).

Microbial Contamination of Dental Unit Water Lines, Indoor Air

Duygu Göksay Kadaifciler, Aysin Cotuk. Microbial contamination of dental unit waterlines and effect on quality of indoor air. Environmental Monitoring and Assessment. June 2014, Volume 186, Issue 6, pp 3431-3444

The microbiological quality in dental unit waterlines (DUWLs) is considered to be important because patients and dental staff with suppressed immune systems are regularly exposed to water and aerosols generated from dental units (DUs). Opportunistic pathogens like Pseudomonas, Legionella,Candida, and Aspergillus can be present in DUWLs, while during consultations, bioaerosols can be dispersed in the air, thus resulting in effects on microbiological quality of indoor air. This present study represents microbiological air and water quality in dental offices (DOs) and also concerns the relationship between the quality of DO air and dental unit water. This study aimed to assess both the microbial quality of dental unit water and the indoor air in 20 DOs and to survey the effect on the quality of the indoor air with the existing microorganisms in dental unit water. Fourteen out of 20 (70 %) DUWLs were found to be contaminated with a high number of aerobic mesophilic heterotrophic bacteria. In terms of bacterial air contamination levels, in 90 % of DOs, a medium level (3) of contamination was determined, while in terms of microfungal air contamination, in all DOs, a low level (3) of contamination was determined. Potential infection or allergen agents, such as Pseudomonas, Micrococcus,Staphylococcus, Alternaria, Cladosporium, Penicillium, Aspergillus, and Paecilomyces were isolated from water and air samples. This study’s determination of contamination sources and evaluation of microbial load in DOs could contribute to the development of quality control methods in the future.

Click here for paper (fee).

Agricultural Buffers to Reduce Groundwater Nitrate

At first look studies like are promising. But this approach assumes that (1) the crops grown in the buffer area do not leach nitrate or other contaminants and (2) the “integrated model” represents reality. It does not. It may be useful at this point, but any use of an agricultural buffer to grow “cash” crops must pass the economic test of the free market.

Megan M. Mayzelle, Joshua H. Viers, Josué Medellín-Azuara, Thomas Harter. Economic Feasibility of Irrigated Agricultural Land Use Buffers to Reduce Groundwater Nitrate in Rural Drinking Water Sources. Water 2015, Vol. 7 Issue 1, p12-37.

Agricultural irrigation leachate is often the largest source for aquifer recharge in semi-arid groundwater basins, but contamination from fertilizers and other agro-chemicals may degrade the quality of groundwater. Affected communities are frequently economically disadvantaged, and water supply alternatives may be too costly. This study aimed to demonstrate that, when addressing these issues, environmental sustainability and market profitability are not incompatible. We investigated the viability of two low impact crops, alfalfa and vineyards, and new recharge basins as an alternative land use in recharge buffer zones around affected communities using an integrated hydrologic, socio-geographic, and economic analysis. In the southern Central Valley, California, study area, alfalfa and vineyards currently constitute 30% of all buffer zone cropland. Economic analyses of alternative land use scenarios indicate a wide range of revenue outcomes. Sector output gains and potential cost saving through land use conversion and resulting flood control result in gains of at least $2.3 billion, as compared to costs of $0.3 to $0.7 billion for treatment options over a 20 year period. Buffer zones would maintain the economic integrity of the region and concur with prevailing policy options. Thus, managed agricultural recharge buffer zones are a potentially attractive option for communities facing financial constraint and needing to diversify their portfolio of policy and infrastructure approaches to meet drinking water quality objectives.

Click here for paper (Open Access).

 

Minimizing Costs and Energy Consumption; Arsenic Removal by Reverse Osmosis

A. Abejón, A. Garea, A. Irabien. Arsenic removal from drinking water by reverse osmosis: Minimization of costs and energy consumption. Separation and Purification Technology Volume 144, 15 April 2015, Pages 46–53

Arsenic is one of the most serious inorganic contaminants in drinking water on a worldwide scale. To comply with the MCL (maximum contaminant level, 10 μg/l arsenic in drinking water) established by the World Health Organization, numerous techniques have been studied, such as ion exchange, coagulation and flocculation, precipitation, adsorption and membrane technologies. Among the available technologies applicable to water treatment, membrane filtration has been identified as a promising technology to remove arsenic from water.

The goal of this study is to demonstrate the technical and economic viability of removing arsenic (V) using an optimized reverse osmosis process, with minimization of the total cost as the objective of the optimization strategy. The optimization results showed that the total costs of a two-stage membrane cascade used for the removal of arsenic (V) from drinking water for a population of 20,000 inhabitants were 1041 $/d and 0.52 $/m3 of drinking water produced. Energy consumption was the most relevant cost, corresponding to 35% of the total cost. Sensitivity analysis was performed to determine the total costs of the installation for different scenarios in terms of drinking water production: (i) 0.44–0.56 $/m3 for electricity prices of 0.05–0.10 $/KW h; (ii) 0.88–0.45 $/m3 for populations ranging from 5000 to 50,000 inhabitants; and (iii) 0.52–0.61 $/m3 when the membrane lifetime was reduced from 3 to 1.5 years. The multiobjective optimization solutions, which consider the best compromises among the quality and cost objectives, indicated that the concentration of As (V) in the permeate water can be reduced to 0.5 μg/l at a feasible cost.

The paper is here (fee).

Alum Sludge Reuse in Agricultural Applications

Dassanayake KB, Jayasinghe GY, Surapaneni A, Hetherington C. A review on alum sludge reuse with special reference to agricultural applications and future challenges. Waste Management (New York, N.Y.) 2015 Feb 2

Alum salts are commonly used in the water industry to promote coagulation in the production of clean drinking water, which results in the generation and accumulation of ‘waste’ by-product ‘alum sludge’ in large volumes. Effective and efficient management of alum sludge in an economically and environmentally sustainable manner remains a significant social and environmental concern with ever increasing demand for potable water as a result of rapidly escalating world population and urban expansion. Various intensive practices have been employed to reuse the alum sludge in an attempt to figure out how to fill the gap between successful drinking water treatment process and environmentally friendly alum sludge management for over the years. This paper primarily aimed at comprehensive review of the existing literature on alum sludge characteristics, its environmental concerns and their potential utilization, especially in agricultural and horticultural sectors leading to update our recent state of knowledge and formulate a compendium of present and past developments. Different types of alum sludge utilizations in various fields were recognized and examined. The strengths, weaknesses, opportunities and potential risks of alum sludge reuse options with particular reference to agriculture were highlighted and knowledge gaps were identified. Research priorities and future challenges that will support in the development of effective alum sludge management practices in agriculture with multi-prong strategies were discussed.

Removal of Se(IV) and Se(VI) from Drinking Water by Coagulation

Chengzhi Hu, Qingxin Chen, Guixiav Chen, Huijuan Qu, Jiuhui Qu. Removal of Se(IV) and Se(VI) from drinking water by coagulation. Separation and Purification Technology. Mar2015, Vol. 142, p65-70.

Selenium (Se) is one of contaminants required to be regulated during drinking water treatment, however, little information has been collected to date regarding Se removal by coagulation. In this study, the performance of Se removal by coagulation has been evaluated with respect to the dependence on Se species, coagulant type, water pH and interfering ions. The results showed that a Fe-based coagulant was much more efficient than Al-based coagulants in Se removal. The removal of selenite (Se(IV)) by coagulation was much more pronounced than that of selenate (Se(VI)). With an FC dosage of more than 0.4 mM Fe/L, Se(IV) removal efficiency of more than 98% could be achieved when the initial Se(IV) concentration was 250 μg/L. For Al-based coagulants (AlCl 3 (AC) and polyaluminum chloride (PACl)) Se removal efficiency was positively correlated with the content of Al 13 species during the coagulation process. Adsorption onto hydroxide flocs was the most active coagulation mechanism for Se removal and precipitation also played specific roles at low dosage, especially for Se(IV) removal and with Fe coagulant. High coagulant dosage and weakly acidic pH could enhance the formation of hydroxide flocs having more active adsorption sites and high zeta potential, and thus favored Se removal. These findings are important to understand the efficiency and mechanisms of Se removal by coagulation.

Heavy Metals in Drinking Water and Cancer Incidence in Black Sea Area of Turkey

Colak EH, Yomralioglu T, Nisanci R, Yildirim V, Duran C. Geostatistical analysis of the relationship between heavy metals in drinking water and cancer incidence in residential areas in the Black Sea region of Turkey. J Environ Health. 2015 Jan-Feb;77(6):86-93.

In the study described in this article, the authors examined the relationship between heavy metals in the drinking water and cancer densities in residential areas. The Turkish cities of Trabzon, Rize, and Giresun in the eastern Black Sea region were chosen as the study areas. Cancer registry data, population information, heavy metal chemical analysis results for drinking water, and other spatial information for the region were collected in a database designed in GIS. Information on a total of 13,012 registered cancer cases from the years 2000-2007 was obtained from a cancer record center and depicted spatially on a map. The incidence values explaining cancer density in residential units were calculated. Chemical analyses were then conducted to determine the presence of 17 different heavy metals by collecting a total of 541 drinking water samples. It was determined that among the 17 analyzed heavy metals, beryllium, nickel, antimony, and molybdenum had a significant relationship with cancer incidence values in the residential units.