Water Chemistry

This is an introduction to water treatment systems and technology. It is not a design manual or an exhaustive treatise. It is intended for engineers who are not regularly involved in water treatment projects, but who are interested in learning some of the basics involved. Criteria to be followed in determining the necessity for and the extent of treatment are discussed here, as are procedures applicable to the planning of water treatment projects.

The 2006 version of the Pa. DEP Inorganic Contaminant Removal module has detailed advanced treatment information on this topic and can be obtained by e-mailing the Pa. DEP Safe Drinking Water Training Section at DEPWSTechtrain@pa.gov to request a copy. This advanced module has additional information on the removal of various inorganic contaminants as well as on oxidation, ion exchange, activated alumina and sequestration. The 2006 document also includes more detailed information on the inorganic contaminant treatments of GAC (granular activated carbon), coagulation/filtration, membranes, and lime softening. It includes the following information:

• Inorganic contaminant treatment selection considerations
• Advanced inorganic contaminant removal chemistry terminology
• Advanced inorganic contaminant removal chemistry explanations
• Conventional filtration and how it relates to inorganic removal
• Detailed information on treatments for iron and manganese removal
• Detailed information on treatments for hardness removal
• Detailed information on inorganic contaminant monitoring protocols
• Detailed tables on the following topics:
• Sources of 26 inorganic contaminants
• Common secondary standards with effects, inorganic contributors and indications
• Various treatment technology options to consider for 24 inorganic contaminants
• Potential forms of iron and manganese
• Iron and manganese sampling procedures
• Iron and manganese oxidant selection criteria
• Iron and manganese theoretical (initial) dosing criteria
• Potential treatments for less common inorganics
• Potential treatments for miscellaneous trace metals

Introduction: Desalination using seawater reverse osmosis (SWRO) technology is an important option available to water-scarce coastal regions. Worldwide sea water desalination is a very effective and economical way of producing potable water for drinking and industries. Reverse osmosis plants to convert sea water to potable drinking water and for other usages have been prevalent throughout the world for more than 4 decades. Design and operation of seawater reverse osmosis plants strongly depend on the raw seawater quality to be treated. The performance of desalination reverse osmosis (RO) systems relies upon the production of high quality pre treated water, and the selection of the best pre treatment technology depends on the raw seawater quality and its variations. Number of full-scale experiences has shown that pre treatment is the key for this application of reverse osmosis technology. It is why during these last years, an import effort has been done to identify and to characterise the diverse organic and mineral components present in the seawater in a view to optimise the seawater pre-treatment and to develop advanced analytical methods for feed water characterization, appropriate fouling indicators and prediction tools. This Chapter describes firstly a comprehensive approach to characterize raw seawater samples through analytical tools which allow the knowledge of the characterization of seawater from many aspects: (a) inorganic content, (b) natural organic matter, (c) enumeration of micro-organisms and phytoplankton. Secondly, this Chapter describes the effect of each of these parameters on the fouling of the reverse osmosis membrane. Finally, this chapter describes the different possible pre treatments available to reduce or remove the elements or substances up-stream reverse osmosis stage.

Access to safe drinking water is critical to survival, and its deprivation could affect the health, food security, and livelihoods of human beings. India achieved 93% coverage of access to improved water supply in rural areas in 2015 towards fulfilling its commitment under the Millennium Development Goal1. However, with reference to safely managed drinking water (improved water supply located on-premises, available when needed and free of contamination) as per Sustainable Development Goal, India still has major targets to achieve, and is geared up to accomplish the same by the end of 2024. With the shift from the Millennium Development Goals (MDGs) to the Sustainable Development Goals (SDGs) less than half of the total rural households in the country have access to safely managed drinking water (improved water supply located on-premises, available when needed and free of contamination).