Learning Objectives
• Estimate the quantity and quality of wastewater generated in a community
• Analyze water quality data and determine treatment needs for different water uses
• Identify contaminants in untreated water or wastewater and the extent of removal required based on prevalent standards
• Describe the objective of each treatment unit to be used in water or wastewater treatment
The first step in the design of water and wastewater treatment plants is identification of appropriate treatment processes for meeting the required standards or treatment objectives. This requires identification of contaminants in water or wastewater based on regulatory standards that are applicable and an understanding of the extent to which treatment objectives can be achieved by a given treatment process. In many cases, treatment objectives cannot be fulfilled by one treatment process and a combination of two or more processes becomes necessary. All sections in this chapter address the issue of treatment objectives and the choice of treatment processes that can be used to achieve these objectives. Conventional drinking water treatment processes for surface and groundwater are addressed first, followed by non-conventional water treatment. Specific treatment methods (combinations of unit processes) for removal of specific pollutants like arsenic, fluoride, and nitrate are discussed in this section. The last section deals with conventional and higher levels of municipal wastewater treatment.
CONVENTIONAL DRINKING WATER TREATMENT SCHEMES
The main objective of any water supply scheme is to provide safe and adequate amount of potable water to all residents in the service area. This requires ‘sourcing’ of water so that it is of good quality to begin with. Protection of raw water quality for maintaining its quality in the future and ensuring that it remains a sustainable source is the next important aspect of a water supply scheme. The source water then has to be treated to the level of the prevailing drinking water standards. Water treatment has two major outputs: finished water which is provided to the consumer through the distribution system and wastewater including sludge which requires further management. Wastewater generated at the drinking water treatment plant, includes backwash water, wastewater generated from housekeeping in the treatment plant, and supernatant from the sludge drying beds.
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