{"id":116020,"date":"2022-10-19T13:58:24","date_gmt":"2022-10-19T17:58:24","guid":{"rendered":"https:\/\/savethewater.org\/?p=116020"},"modified":"2022-11-08T17:55:07","modified_gmt":"2022-11-08T22:55:07","slug":"solar-disinfection-sodis-time-to-revive-an-underexploited-technique","status":"publish","type":"post","link":"https:\/\/savethewater.org\/solar-disinfection-sodis-time-to-revive-an-underexploited-technique\/","title":{"rendered":"(SODIS) Solar Disinfection: Time to Revive an Underexploited Technique"},"content":{"rendered":"

By Sakshi Kabra Malpani, <\/span>Publishing Associate: Researcher and Writer <\/span>at Save the Water\u2122 | October 19, 2022.<\/span><\/p>\n

SODIS is a World Health Organization (WHO)-approved, cheap, old-school process commonly used for domestic water treatment. It does not change the taste of water. <\/span>The USA is one of the top countries in the world publishing research in this growing area of interest.<\/span><\/a><\/p>\n

More About SODIS<\/span><\/h2>\n

SODIS is basically an environment-dependent, repeatable process. We can start it at our home by using ordinary plastic bottles or containers. It is mainly used in areas where sunlight is abundant. <\/span>Ultraviolet (UV) rays<\/span><\/a> of sunlight can effectively kill viruses and microorganisms like <\/span>E. coli<\/span><\/i><\/a> present in contaminated water which are even resistant to chlorination. These rays inactivate and damage cells of microorganisms, thus, preventing them from multiplying further. Additionally, <\/span>such microorganisms cause various water-borne diseases<\/span><\/a> like typhoid, dysentery, fever, intestinal infection, and many more. Water is treated and stored in the same container, hence it is an overall cheap, less time-consuming, space-occupying technique with fewer chances of recontamination.<\/span><\/p>\n

How Does it Work?<\/span><\/h2>\n

SODIS works by using UV-A and <\/span>infrared (IR) radiations<\/span><\/a> of sunlight altogether. Initially, UV-A radiations damage living cells of microorganisms. After that, when temperature of water rises to 70-75 \u00b0C, IR rays help in thermal disinfection, or <\/span>pasteurization of water. <\/span><\/a>Therefore, the overall efficiency of the process increases. Since microorganisms are extremely sensitive to heat, they do not survive in these specific conditions.<\/span><\/p>\n

This method appeared to be better at killing microorganisms in water, when compared with other traditional water treatment techniques like <\/span>chlorination<\/span><\/a>, <\/span>filtration<\/span><\/a>, <\/span>ozonation<\/span><\/a>, <\/span>electroflocculation<\/span><\/a>, <\/span>advanced oxidation<\/span><\/a>, and others. Besides, it does not produce harmful by-products and certainly <\/span>is way cheaper<\/span><\/a>.<\/span><\/p>\n\n\n\n\n\n\n\n
Name of water treatment techniques<\/span><\/td>\nAmount spent in $ (Per person per year)<\/span><\/td>\n<\/tr>\n
SODIS<\/span><\/td>\n0.63<\/span><\/td>\n<\/tr>\n
Chlorination<\/span><\/td>\n0.66<\/span><\/td>\n<\/tr>\n
Filtration<\/span><\/td>\n3.03<\/span><\/td>\n<\/tr>\n
Electroflocculation<\/span><\/td>\n4.95<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

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Time Taken by SODIS<\/span><\/h2>\n

Sunny days- 6 hours.<\/span><\/p>\n

Cloudy days- 48 hours.<\/span><\/p>\n

Not favorable during rainy days.<\/span><\/p>\n

If the turbidity of contaminated water is high, then the period of SODIS treatment extends.<\/span><\/p>\n

Some Real-world Examples<\/span><\/h2>\n
    \n
  1. \u00a0 \u00a0 \u00a0 <\/b>Lexington, KY, USA:<\/b><\/a> Environmental Research Training Laboratory (ERTL) at the University of Kentucky conducted some experiments to study the feasibility of SODIS in removing <\/span>E. coli <\/span><\/i>from turbid water at temperature less than 50 \u00b0C. When the turbidity of water was increased from 30 to 200 <\/span>Nephelometric Turbidity Unit (NTU), <\/span><\/a>the efficiency of SODIS in killing microorganisms decreased accordingly.<\/span><\/li>\n
  2. \u00a0 \u00a0 \u00a0 <\/b>Ecuador<\/b><\/a> and <\/b>Bolivia<\/b>:<\/span><\/a> Jonathan Spear & Valerie Grosscup, The Colorado College, USA, helped about 35 communities and more than 3,500 people on the northern coast of Ecuador with their seven-week SODIS project. Engineers Without Borders (EWB)-USA has run the SODIS project to improve water quality in rural communities of Bolivia. Missouri University of Science and Technology conducted SODIS experiments, under sunny and cloudy weather conditions. Later, it was concluded that on sunny days, <\/span>E. coli <\/span><\/i>were completely removed from water while on cloudy days, only 50% were removed efficiently.<\/span><\/li>\n<\/ol>\n

    \u00a0Advantages of SODIS<\/span><\/h2>\n