Does a screenings washer add back BOD? Is a screenings press better?

[JoePr]

We are looking at retroactively adding a screenings washer to an existing mechanical screen, in a prison. The prison wants to be able to discard the screenings in the local landfill, instead of having to truck them several hours each way for disposal. But they also are subject to a possible surcharge by the municipality if their BOD levels exceed certain levels.

Their BOD levels are OK now, but I am concerned that the screenings washer will return enough of the organics back into the sewage to possibly incur the surcharge. How much of the organics would probably be washed back, and how much would be trapped in the compressed screenings?

Would an unwashed ram press be a better choice? The rep tells me the odor might be worse if it is unwashed, but the screen has been at the prison nearly 10 years, and I doubt the odor would be any worse than it aldeary is. I also was told the ram press is less prone to clogging in a prison setting - does anyone have experience with that?

Thank you very much.

 

[SteveWag]

The ram is more reliable and will smell worse. I don't understand what you mean when you say:

"The prison wants to be able to discard the screenings in the local landfill, instead of having to truck them several hours each way for disposal."

Where are they going now?

Some landfills object to un-washed screenings.

Steve Wagner

 

[JoePr]

SteveWag, the local town does not accept the screenings that come off the mechanical screen, which are unwashed and unpressed. These need to be trucked to a different facility, incurring more expense. The local town will accept screenings which have been either pressed or washed or both. We are looking for the appropriate piece of equipment to make that possible.

Thanks for your help.

 

[gerhardl]

What about looking at it this way:

You have a possibel win situation( less trucking and disposal expenses - which can be expressed as aneconomical figure ), certain requirements (existing today), but also a future situation (possibly altered outlet limit/rules together with lifetime, operation and maintenance cost for the existing system).

Maybe your problem is purely a minor mechanical and process one, easily solved at low cost with small adjustment to existing equipment.

On the other hand: what about the payback time for getting a complete set of new equipment, doing all you want and adjusted to incorporate possibly future demands.