1.2. The Need for Drinking Water Treatment Plants

Substances that are removed during drinking water treatment process include suspended solids, bacteria, algae, viruses, fungi, minerals such as iron, manganese and sulfur, and other chemical pollutants such as fertilizers. Measures are taken to ensure that not only the water quality during the treatment process, but during its conveyance and distribution after the treatment as well. It is therefore common practice to have residual disinfectants in the treated water in order to kill any bacteriological contamination during distribution.

Table 1.1. Some common water contaminants found in the water treatment plant and treatment option:

The treatment of water to make it potable is a multi-tiered process that often includes chemical, physical and biological methods.

The chemical processes include oxidation, coagulation and disinfection. The physical processes consist of flocculation, sedimentation, filtration, adsorption and disinfection with the use of ultraviolet light. The biological activated carbon (BAC) and sand filtration comprise of the biological processes.

The types of treatment depend on the source and size of the water system. For example, if the water source is from the surface, it is more exposed to direct wet weather runoff and to the atmosphere, therefore, these sources (such as lakes, rivers, reservoirs, etc.) are more easily contaminated and will require additional treatment in order to make the water more potable. Whereas ground water sources are more likely to require minimal treatment as it is not as exposed to the elements and goes through the natural sedimentation process of purifying the water through the soil.

A combination of the following processes is just some of the processes used for municipal drinking water treatment worldwide:

There is no single solution/process regarding the purifying of water, especially when water is derived from different sources. In addition, treatability studies must be carried out during different seasons in order to arrive at the most suitable processes.

Technologies for potable water treatment are well developed, and generalized designs are available that are used by many water utilities (public or private). In addition, a number of private companies provide patented technological solutions. Automation of water and waste-water treatment is common in the developed world. Capital costs, operating costs available quality monitoring technologies, locally available skills typically dictate the level of automation adopted.

High quality, safe and sufficient drinking water is essential for our daily life, for drinking and food preparation. We also use it for many other purposes, such as washing, cleaning, hygiene or watering our plants. 

The European Union has a long history of drinking water policy. This policy ensures that water intended for human consumption can be consumed safely on a life-long basis, and this represents a high level of health protection. The main pillars of the policy are to:

• Ensure that drinking water quality is controlled through standards based on the latest scientific evidence;
• Secure an efficient and effective monitoring, assessment and enforcement of drinking water quality;
• Provide the consumers with adequate, timely and appropriately information;
• Contribute to the broader EU water and health policy.