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After toilet paper is flushed down a toilet and it goes to a water treatment plant, what happens next?

  1. Does it decompose, if so what gasses are released? Is the carbon sequestered in any significant way?
  2. Is it present in a solid form in the outflow of the treatment plant? (i.e. in to the sea?) Does that affect wildlife?
  3. What, if anything, is consumed as it is processed? (e.g. are chemicals consumed)

I see there is a questions about alternatives to toilet paper. I'd like to understand the impacts of using it. Of course there is the impact of its production, transportation, etc, but I think that is a separate question.

5

In a municipal scale sewage system toilet paper is barely detectable. It gets soggy very quickly and disintegrates. There are huge problems with wet wipes, tampons and menstrual pads, however, as those do not break down and need to be extracted and disposed of (this is an extremely gross process).

In a home septic system the same situation applies but in a more visible way. Toilet paper disintegrates then breaks down, with the cheaper paper apparently being better.

To answer your specific points:

  1. it will decompose somewhat into methane, carbon dioxide and water, but the cellulose content will mostly make it through the process unchanged.

  2. the material after treatment is very fine, even if it didn't disintegrate before treatment, so the wildlife affected will be mostly microscopic and they will either eat it or ignore it unless it's in sufficient volume to smother them.

  3. mostly what's consumed is energy. Different sewage treatment systems work in different ways, but the most common decomposition step is settling ponds with agitators to encourage aerobic decomposition (ie, less methane and more carbon dioxide produced). Chemical are mostly added when there are problems, and normally problems are chemical contamination when criminals dump toxic stuff into the sewers. Fixing that can mean rebalancing PH, other chemical neutralising agents, or simply excavating the affected ponds and restarting them with "clean" sewage (non-contaminated). That last is expensive, messy and slow, so most sewer systems will go to considerable lengths to prevent those problems.

  • Excellent detail Nui. I do know that our sewage solids are trucked to large open spaces preferably agricultural areas and PUMPED into the ground. The thinking that I have heard and had to bite my tongue was how our shit will enhance the crops. At 10-20 feet below ground someone needs to go back to school yet this is what they do. Some of these facilities make the BEST decomposed organic matter/mulch. Yet I'd never use it for my vegetable garden as its only draw back are heavy metals. And they pump it into our water table...?? Toilet paper is such a minuscule problem in comparison. – stormy Jul 22 '16 at 6:54

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