Importance of Water Purification to Public Health and Safety

Water purification forms a critical link in promoting public health and safety. It involves variety of steps which depend upon the type of impurities in the raw water source. The major operations done are sedimentation, flocculation, filtration and disinfection. Raw water becomes potable after this treatment in the figure below.

Impurities in raw water include suspended, dissolved, colloidal solids, bacteria, toxic substances, color, odor and mineral or organic matter. These can be categorized as chemical, physical and microbiological.

Read Also: Microbiological Examination of Water

The table below indicates the drinking water standards adopted from that obtained in India. Different unit processes and operations are performed to remove different impurities as presented in the tables below.

Importance of Water Purification to Public Health and Safety
Fig.: Sequence of Processes in Water Purification. Source: Anuradha S. Nrurkar, 2006

Table: The Bureau of Indian Standards Defined Levels of Substances in Water and their Permissible Levels

S/NSubstance/TestUnitDesirablelimitMaximumpermissiblelimit*
1.Physical turbidityNTU510
2.Chemical pHNumber6.5 – 8.5No relaxation
3.HardnessAs (CaCO ) 3 mg/l300600
4.Chlorideas Cl mg/l2501000
5.Ironas Fe mg/l0.31.0
6.Nitrateas N mg/;45No relaxation
7.Fluorideas F mg/l1.01.5
8.Residual chlorinemg/l0.2 – 0.5No relaxation
9.Arsenicas As mg/l0.05No relaxation
10.ColiformsMPN/100 ml10**No relaxation
11.E. coliMPN/100 ml0No relaxation
Source: Anuradha S. Nrurkar, 2006

Table: Unit Processes and Operations and Specific Impurities Removed

S.No.UnitProcesses/operationsEffect
1.Aeration, chemical oxidation, ion exchange, sedimentationColour and precipitate removal
2.Chemical precipitation, (dosing, mixing, flocculation, settling) ion exchangeSoftening (Ca, Mg removal)
3.Chemical coagulation, (dosing, mixing, flocculation, settling) filtrationTurbidity removal
4.Aeration, chemical oxidation, adsorptionTaste and odour removal
5.Irradiation, ozonation, chlorinationDisinfection
Source: Anuradha S. Nrurkar, 2006

Most details of the above processes have been discussed in the course- Hydrology and Sanitation (EHS 304); hence you will gain much by referring to that for details. It should be known that without applied microbiology, the knowledge and practice of water purification would not have been easy.

Most processes that take place in water treatment or purification still obtain in waste-water or sewage treatment. Against the above background, most of the above processes form different units in this course as you will see. The degree of treatment depends on the intended use or place or fate of final disposal site.

Read Also: Impacts of Waste-water on the Environment, Treatment objectives and Disposal Regulations

Potable water meant for drinking has to meet standards which will not allow the spread of water related and water borne diseases. To this end, any well-meaning country should meet with the standard approved by the World Health Organization (WHO). Applied water microbiology helps in achieving this.

This is done through proper checking of water sources, storage, distribution, and supply systems to avoid its contamination/pollution. There is no denying the fact that EHO‘s are involved in doing this all important work.

The Nigerian Standard for Drinking Water Quality for instance covers all drinking water except mineral water and packaged water. The standard applies to: drinking water supplied by state water agencies, drinking water supplied by community managed drinking water systems, drinking water supplied by water vendors and water tankers, drinking water used in public or privately owned establishments, drinking water used in food processing by manufacturers, drinking water from privately owned drinking water system and used solely for the family residence.

Also, mineral water and packaged water shall comply with Nigerian Industrial Standards for Natural Mineral Water (NIS 345:2003) and Potable Water (NIS 306:2004) and used for regulation and certification by the National Agency for Food and Drug Administration and Control and SON respectively. (It is important to mention here that the standards for mineral water and packaged water have different allowable limits for various parameters presented here).

Do you have any questions, suggestions, or other contributions? Kindly use the comment box provided below for all your contributions. You are also encouraged to please kindly share this article with others you feel can benefit from this information if found useful enough as we may not be able to reach everyone at the same time. Thank you so much for sharing!

Benadine Nonye

An Agric. Consultant & a Writer (With over 12 years of professional experience in the agricultural industry) - National Diploma in Agricultural Technology - Bachelor's Degree in Agricultural Science - Master's Degree in Science Education... Visit My Websites On: Agric4profits.com - It's All About Agriculture, The Way Forward! Agric4profit.com - The Most Reliable Global Agricultural Forum! Agric4profit.com.ng - The Most Reliable Nigeria's Agricultural Job Board! TheAgriPedia.com - For Everything Premium Agriculture! WealthinWastes.com - For Proper Waste Management and Recycling Practices. Join Me On: Twitter: @benadinenonye - Instagram: benadinenonye - LinkedIn: benadinenonye - YouTube: Agric4ProfitsTV - Pinterest: BenadineNonye4u - Facebook: BenadineNonye

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