How did city planners solve the public health problems posed by polluted rivers and lakers?

City planners addressed public health issues from polluted rivers and lakes by implementing comprehensive wastewater management systems, including sewage treatment plants to reduce contaminants before they enter water bodies. They also established green spaces and buffers along water bodies to filter runoff and improve water quality. Additionally, urban zoning regulations were enforced to limit industrial activities near water sources, and public awareness campaigns promoted responsible waste disposal and environmental stewardship. These measures collectively aimed to enhance water quality and protect public health.