According to WHO, in 2017, 71% of the global population (5.3 billion people) used a safely managed drinking-water service. We can say that about 30% is facing the problem of unsafe drinking water.

Dear, Monitoring of surface and ground water quality is required regularly to detect the pollution sources and treat or prevent these sources. Also, WHO guidelines for using water in different purposes should be followed.

Water Mission, a Christian Engineering Company, in Charleston SC is working to address some of these water treatment and management problems for areas willing to cooperate. They have some excellent displays and Powerpoint slides that explain some of the issues they have faced and addressed. https://watermission.org/

You might find some of their information helpful.

Water-borne diseases are known! They are due to the contamination of drinking water by pathogenic microorganisms such as cross-connection! It's very common in developing countries.

Water pollution is a major global problem. It has been suggested that it is the leading worldwide cause of deaths and diseases, and that it accounts for the deaths of more than 14,000 people daily. An estimated 700 million Indians have no access to a proper toilet, and 1,000 Indian children die of diarrheal sickness every day. Some 90% of China's cities suffer from some degree of water pollution, and nearly 500 million people lack access to safe drinking water. In addition to the acute problems of water pollution in developing countries, industrialized countries continue to struggle with pollution problems as well.