In case of Foreign Railways discharge treatment is different. Have seen the treatment in case of China - Tibet rail line shown in Nat Geo. They said that all Coaches have a discharge box underneath and this is where the discharges are stored. Once the train halts at a major station (usually every 6-8 hrs or so) where halt is 10 mins, a special teams awaits. The discharge is pumped out from the carriage to the trucks waiting (by use of pipes). The trucks ten take it to the treatment plant / sewage plant etc. The entire pumping process takes 10 mins max as they ensure everything is ready when the train arrives.
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They...
more... have also given the reason stating that if it is discharged enroute they will have to incur additional costs as lyf of the rail track and sleepers decreases.
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I have for a longtym felt that such discharge system should be used in Indian Railways also.