Clean Abundant Fresh Water

Published Date: 02 Nov 2017

Chapter 1

INTRODUCTION

BACKGROUND

Ensuring the availability of clean, abundant fresh water for human use is among the most important issues facing both developed and developing countries. "More than one billion people in the world lack access to clean water, and things are getting worse. Over the next two decades, the average supply of water per person will drop by a third, possibly condemning millions of people to an avoidable premature death" 1(Kolesnichenko et al., 2006).

Pakistan has a marked decline in its per capita water availability from 5600 to 1,000 m3 2(Kahlown et al., 2001). Pakistan Council of Research in Water Resources (PCRWR) launched a National Water Quality Monitoring Programme (2001 - 2006) in the country and the findings of this mega water quality monitoring program for 24 major cities of Pakistan has recognized the existence of four major water quality problems such as bacteriological contamination (68%), arsenic (24%), nitrate (13%) and fluoride (5%) in the surface or groundwater sources 3(Tahir and Rasheed 2008). The presence of biological contamination in drinkning wate resulting into waterborne diseases like Typhoid, hepatitis A and hepatitis E, polio and cholera. Chronic high-level exposure to fluoride can lead to skeletal fluorosis. Arsenic presence in water results in arsenic poisning which leads to cancer. High nitrate concentration in drinking water is an environmental health concern results in methaemoglobinaemia, commonly called "blue-baby syndrome," and carcenogenic amines.

NITRATE IN DRINKING WATER

Nitrate refers to a large family of nitrogen-containing organic and inorganic compounds. Chemistry of nitrate as nitrogen is a wide subject due to its number of natural and man-made sources for the release into the environment. Nitrate from drinking water accounts for 15 - 75% of person’s exposure to nitrate from environmental sources 4 (Vladeva et al., 2000). The presence of elevated concentrations of nitrate in drinking water has become a serious concern worldwide over the past few decades. Nitrate is a water soluble ion that does not readily bind to the soil causing it to be highly susceptible to run-off migration 5 (Nuhoglu etal., 2002). Point and non-point sources of nitrate contamination can include agricultural and urban runoff, disposal of untreated sanitary and industrial wastes in unsafe manner, leakage in septic systems, landfill leachate, animal manure, NOx air stripping waste from air pollution control devices. Nitrate, due to its high water solubility, is possibly the most widespread groundwater contaminant in the world, imposing a serious threat to drinking water supplies and causing ecological disturbances 6 (Liu etal., 2005). Increasing nitrate concentrations in drinking water causes two adverse health effects the induction "blue-baby syndrome" (methemoglobinemia), especially in infants, and the potential formation of carcinogenic nitrosamines 7 (Majumdar etal., 2000).

Studies have also suggested that nitrate in drinking water may be linked with increased risk for bladder and ovarian cancer, non-Hodgkin’s lymphoma, genotoxic effects at chromosomal level and insulin dependent diabetes 8 (Ward et al., 1996).

1.3 TECHNOLOGIES FOR NITRATE REMOVAL

A wide range of physico-chemical processes such as ion exchange, reverse osmosis, electrodialysis, chemical denitrification and biological denitrification are currently being developed for removal of nitrate from drinking water 9(Kapoor and Viraraghavan, 1997).

Ion exchange has been one of the most widely used methods for removing nitrate ions from water. The method of ion exchange on selective anion-exchange resins is much easier to implement in water treatment systems. Nitrate removal from water raises troublesome technological problems. Among the available methods technically feasible are biological denitrification and ion exchange. 10 Clifford and Liu (1993) conducted a study to estimate nitrate removal from drinking water by ion exchange. The raw water contained NO3-N, reduced the nitrate level to below acceptable level but the problems associated with ion exchange include disposal of the spent regenerant brine containing nitrate and excess NaCl.

Reverse osmosis (RO) and electrodialysis (ED) can effectively separate nitrate from well water. However, both systems cannot separate nitrate selectively, for example the processes will reduce the concentration of all dissolved solids. RO refers to a process whereby ionic species present in water are removed by forcing the water to be transported across a semipermeable membrane, effectively leaving the nitrates behind. This process is accomplished by subjecting the water supply in the RO cell to pressures exceeding its corresponding osmotic pressure 11 (Rautenbach et al. 1986).

1.5 THE PRESENT STUDY

Among the avalible technoglies ionic exchange process is considerd as the most efficent technolgoy. Diffrent nanoparticles also have been applied for the removal of nitrate from water. A well known nanoparticle NZVI (Nano scale zero valent iron) with combinatoin of other metallic nanoparticle can be used for the removal of nitrate from water. Bimetallic nanoaprticles will be applied on nitrate conating water to determine the effect on the nitrate reduction.it will be invistigateed that whether ionic exchange process or nanoparticles are the most suitible materils for the removal of anion like nitrate.