In addition to what you have ...
Published by Permod Gupta, Chief Technical Advisor at UNIDO
In addition to what you have covered for self-purification, it seems there is no other remedy but to pre-treat the waste inlet sources and avoid flooding irrigation in Ganges catchment area to minimise fertilizers and pesticide inflow to water. Self-purification is limited to organic pollutants for metals.pesticides and other inhibitive or prohibitive substances treatment prior to discharge is only way to clean Ganga