The answer to homelessness is more affordable housing, the lack of which is both a local and national crisis. We have low wages and high rents. 

Until that housing can be built, we need more transitional and emergency shelter, like Opportunity Village and the legal "rest stop" camps run by Community Supported Shelters and Nightingale Health Sanctuary. Besides keeping their own camps clean, rest stop residents have volunteered to clean up other sites. Residents of unsanctioned camps, such as OURS, have also cleaned up their camps, with the help of housed volunteers who take trash to the dump. 

As for the unorganized camps, the city could help keep them clean by providing portapotties and dumpsters. When you have to walk everywhere, carrying all of your belongings, it's difficult to dispose of trash.

We all generate trash, housed and unhoused. 

Learning about the issue helps.
https://www.facebook.com/homeless.action.coalition/