I am assuming you are looking for science/engineering approaches in a generic way. Use of watershed systems of the rivers to model point and nonpoint sources of pollution into the river and hydrologic processes is a main approach. Given the system is complex and involve multiple processes, simulation modeling is needed to assess the loading and the dynamics of the system. With this information, options for pollution reduction at the sources, during transfer and reduction in water bodies is modeled. Engineering and management practices along with change in polluter behaviors (social) are main ways to reduced pollution.

Ingeneral river water polluted due to anthropogenic activities. For this Awareness in people is must.

Please have a look at these useful RG links.

https://www.researchgate.net/publication/271560976_Urban_River_Pollution_Control_and_Remediation

Article Water Pollution: Source and Treatment

https://www.researchgate.net/post/How_can_the_river_pollution_conditions_in_Indian_be_minimize

https://www.researchgate.net/post/how_can_reduce_the_river_pollution

https://www.researchgate.net/post/Which_is_the_best_methodology_to_clean_a_river

Good luck!

Ok,

science/engineering approaches can be found in the attached pdf

Sincerely

Dear sir, which pollution you means Bilogical, chemical or physical pollutions

thanks sir,

for providing Water Pollution: Source and Treatment link for understanding the current problems.

This winter has already brought significant snowfall to much of the U.S. Historically, more snow has meant more road salt. It’s an effective way to clear roads — but also brings cascading environmental impacts as it washes into rivers and streams...

The use of road salt during winter is nothing new for people across the Midwest, particularly in its upper stretches where the presence of snow and ice can linger from December into April. But there’s growing awareness of the harm it can cause to freshwater resources — wreaking havoc on aquatic life, disrupting ecosystems, making its way into groundwater, and corroding pipes...

https://undark.org/2023/01/17/decades-of-road-salting-is-polluting-the-mississippi-river/

Pollution in river is difficult to cantrol . Only self realisation and awareness may be effective.

A new “smart rust” could one day help pull pollutants out of waterways, leaving cleaner water behind.

Researchers adorned tiny particles of iron oxide, better known as rust, with “sticky” molecules that grab on to estrogen and similar hormones in water samples. A magnet can then remove both the particles and the trapped pollutants from the water...

The new technology could potentially limit excess estrogen’s harmful effects on animals, especially those that live in waterways.

With the nanoparticles, we are able … to clean very different kinds of environmental pollutants,” says Müller, of Friedrich-Alexander-Universität Erlangen-Nürnberg in Germany...

https://www.sciencenews.org/article/magnet-rust-nanoparticles-estrogen-out-water

Rivers are considered the lifeblood of the Earth. Together with pollution, drying of rivers are the major threats to rivers.

💧Happy World Rivers Day, everyone!💧