Drinking Water Treatment Technology— Comparative Analysis

Chapter 2

Drinking Water Treatment Technology— Comparative Analysis
Chittaranjan Ray and Ravi Jain

Abstract Water treatment technologies have evolved over the past few centuries to protect public health from pathogens and chemicals. As more than a billion people on this earth have no access to potable water that is free of pathogens, technologies that are cost effective and suitable fordeveloping countries must be considered. Sustainable operation of these treatment processes taking into consideration locally available materials and ease of maintenance need to be considered. In this chapter, we consider natural filtration for communities of various sizes. In natural filtration, slow-sand filtration and riverbank filtration are considered. Slow-sand filtration is suitable for smallto medium size communities, whereas riverbank filtration can be suitable for small to very large communities depending on site and river conditions. Membrane filtration is another technology that can have application to individual households to moderately large communities. Both pressurized and gravity-fed systems are considered. For the developing regions of the world, small membrane systemshave most applications. Solar distillation is a low-cost technology for sunny regions of the world. Particularly, it has the most application in tropical and semitropical desert regions. It can use low quality brackish water or groundwater for producing potable water. These systems can solely operate with solar energy. The scale of application is for individual households to very small communities.Solar pasteurization, like solar distillation depends on solar energy for purifying small quantities of water for individual or family use. It is most suitable for remote, sunny, high mountain regions such as the Andean mountains, central Africa or the Upper Himalayas where electricity is not available. Also, reliance on firewood is not feasible due to barren landscape in many of these regions.Also, case studies of natural (riverbank and lakebank) filtration, membrane filtration, solar distillation, and solar pasteurization are presented. Keywords Natural filtration • Solar distillation • UV radiation

C. Ray () Civil & Environmental Engineering, University of Hawaii at Manoa, 2540 Dole Street, Holmes Hall 383, Honolulu, HI 96822, USA e-mail: cray@hawaii.edu C. Ray, R. Jain (eds.),Drinking Water Treatment, Strategies for Sustainability, DOI 10.1007/978-94-007-1104-4_2, © Springer Science+Business Media B.V. 2011 9

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C. Ray and R. Jain

2.1 Introduction
The goal of all water treatment technologies is to remove turbidity as well as chemical and pathogenic contaminants from water sources in the most affordable and expedient manner possible. Many technologies, which havebeen developed, work best in demand-specific contexts: either the demand of mass-volume or of massflow. In all technologies discussed throughout this book, the sun’s energy or the soil’s filtration capacity or energy efficient membrane filtration are the primary mechanisms of purification. The main components which will be compared in this section include flow rate (m3/day), cost ofimplementation, maintainability (which includes cost of maintenance, availability of spare part and materials, and technical knowledge required for repairs), energy consumed (either MJ/h or kW/h), and reliability (as a function of total number of serial components and the sensitivity of each component to long exposure to adverse conditions). While discussing technology, it will be important to keep in mind theethic of engineering water systems, acknowledging the social re-shaping which occurs inherently within design implementation. As stated by Priscoli (1998) the answers to water management systems “depend, to a great degree, on what you want or think the ecology ought to be.” (Priscoli 1998) He outlines four main views of technological intervention: gigantism, technological triumphalism,...