One of component of primary health care is specific protection from disease infection. And there water-based diseases which infecting agents spread by contact with or ingestion of water ; schistosomiasis, guinea worm, filariasis, onchocerciasis, thread-worm to mention but a few. Baptism by immersing one in river can subject converts to these diseases if care not taken.
Aware of this. Jesus in his form of baptism washed his disciples’ feet.
John 13 : 3-5 ; “Jesus knew that the Father had put all things under his power, and that he come from God and was returning to God ; so he got up from the meal, took off his outer clothing, and wrapped a towel around his waist. After that, he poured water into a basin and began to wash his disciples’ feet, drying them with the towel that was wrapped around him.” End of quote.
This calls for disinfection of water before immersing converts for baptismal in river or do it Catholic church way.