How do urban ecosystems deal with human wastes?

Question

In a natural ecosystem, the wastes from the organisms that live there are usually broken down and recycled in that ecosystem. How do urban ecosystems deal with human wastes? What other wastes are created in urban ecosystems? What is done with them?

Answer 1

In large cities, the sewage goes to central processing facilities where it is processed through a variety of methods including settling (to separate solids from liquids), chlorination (to kill of nasty pathogens), microbial activity (to break down as much of the solid as possible).

The water part of the waste is treated using chemicals and then it is usually released into rivers or put back into city water supply.  The solids can be dealt with a number of ways.  They can be made into sludge that is used as industrial fertilizer, they can be incinerated, they can be put into a landfill.  More often now before their final destination they are being used to produce methane gas as an energy supply.

NYC has a great schematic diagram of their waste treatment process at: http://www.nyc.gov/html/dep/images/featu...

Other wastes:

All our trash including food wastes, paper wastes, glass, metal, chemicals.  Most go to the landfill.  Some is incinerated.  Some is recycled.