Garbage is best removed at ...

Garbage is best removed at the point of generation, i.e. homes, businesses, etc.  Even with the best engineering and optimum conditions to prevent and blockages in the sewer pipes, any garbage grinding device that discharges into a sewer would only move the garbage from the generator to the sewage treatment facility - which is designed to biologically treat WASTEWATER, not garbage.  Most treatment plants are designed with preliminary treatment such as screening and grit removal, which serves to protect the downstream treatment processes and equipment.  The preliminary treatment equipment is designed to remove a "normal" amount of inorganic and non-treatable material, and the device you are proposing would potentially overload the equipment and cause MAJOR problems for the plant operators and staff.  Consider this:  Would you rather pick up garbage off the floor or ground at your office, or would you rather clean up a garbage mess after it has been mixed with domestic and/or industrial sewage?  I would recommend that you visit SEVERAL treatment plants to tour the facilities to gain a better perspective than what I am able to convey with words.  Maybe even try to pitch your idea to the operators or maintenance staff.