Asessment can be done based on oxygen content and its variations at a preliminary stage and later can be assessed for the remaining parameters for a minimum of 3 season.

I think the assessment of the point of pollution of the river needs to be done. Then, periodical and interval assessment of water quality parameters will be carried out to determine the self-purification process in relation to the baseline-quality at the point of pollution.

Thank you do much for your valuable information and interest in this topic, i asked what are the possible ways to determine the self purification process

@Dr. Kani-To my knowledge, i think ways of determining the self-purification is by assessing the water quality parameters of the river. And this assessment can only be valid when a certain pollution regime is established and assess the rate of recovery using the quality parameters.

Thank you so much dear Clement for the worthfull information

Maybe checking bioindicators

Initially by checking the pH of river water we can judge the quality of water and then the other parameter.

There is a formula for calculating or evaluating the recovery capacity of water quality or sediment quality downstream from a point discharge of waste.

The paper below highlights the mechanisms that contribute to this ability in freshwater ecosystems.

https://www.researchgate.net/publication/225189101_Spatial_and_Temporal_Variations_in_Water_and_Sediment_Quality_of_Ona_River_Ibadan_Southwest_Nigeria

Article Spatial and Temporal Variations in Water and Sediment Qualit...

Biomonitoring of the stretch of river from the point prior to the pollution source to the point where the species under observation are found can be an indicator to assess the purification process stretch. However, the purification process by measurement of DO for organic load is an acceptable method.

For specific pollutants, concentration measurement can be adopted.

The advantage of the recovery capacity formula is that it gives a representation of river recovery in terms of percentage reduction of pollutant down a concentration gradient along the river length.

Interesting answers from all of you most respected persons; it's great, i did some of these things but yet not tried some of it too. Thank you so much for your valuable recommendations, i expect all your suggestions in future too

By the deviation of the parameters from the optimal conditions (differences in pH, DO, Inorganic/organic carbon, COD/BOD, TKN, alkalinity...etc). The difference between the optimal values and the current values of whatever parameters overtime is a measure of the performance of the river.

Thank you so much Dear Mohamad Yassine

Assessment of species diversity for a re-appearance of lost species (i.e. a biotic index) due to pollution incidence is another trusted method. Biotic Index is a scale for showing the quality of an environment by indicating the types of organisms present in it. It is often used to assess the quality of water in rivers and its progressive recovery or deterioration.

Nice to hear from you dear Azubuike Chukwuka and thanks for the same too

Rivers are generally resilient which means that they can easily bounce back after they have been polluted if given enough time. You can check factors such as the pH, amount of elements or compounds present, the population of the species present and other bioindicators