Last winter, I traveled to see a good friend in Mexico. His Pacific coastal village of Trancones, Guerrero, has around 500 year-round residences that rely upon septic systems to treat wastewater. I was there to discuss how homeowners can improve their septic systems and plan for the future. One question came up several times during this trip: “Is it OK to flush my toilet paper?”

Honestly, having lived in the U.S. my entire life I had not really thought much about this issue. I have noticed on my travels to Europe that the use of bidets is common. And during the pandemic — when there was a shortage of toilet paper — more and more American began re-evaluating their hygiene regimen. 

A map made by Matt Kitson of mindofahitchhiker.com shows how much of the world (red colors) forbids toilet paper from being flushed. This clearly shows that a majority of the world either does not use toilet paper or does not flush toilet paper, which makes you wonder how flushing toilet paper impacts our septic systems and if we should consider other options. We all know that with small or damaged sewer lines, low-flow toilets, excessive toilet paper can cause blocked lines and plugged effluent baffles. But does it impact the need for pumping or what we are sending out to our advanced pretreatment or soil treatment areas?

All these questions lead to a small lab study at the University of Minnesota where we studied how toilet paper breaks down, and then measured how the tissue impacts typical wastewater parameters. In this study we tested three traditional papers (Scott Comfort, Scott Professional, Pacific Blue) and one bamboo product (Caboo). Traditional toilet paper is derived from tree pulp while bamboo is the largest member of the grass family.  

We added seven squares (average amount used per flush by an American) to 3 gallons of tap water and mixed it for 30 seconds and let the sample settle for 30 minutes and three days. As noted in the table, seven squares of each brand does not have the same mass therefore as the weight goes down the amount of toilet paper added goes down as well. The photos after 30 minutes look very different with the Caboo settled out, while the other three  brands still show large amounts of paper in suspension. After three days they all look very similar with all the toilet paper settled to the bottom.  [SFH1] 

It is likely in most wastewater treatment plants and septic systems that the toilet paper is settling out into the sludge layer. A 2019 article analyzing sewage sludge from wastewater treatment plants showed an average of 87% cellulose fibers. Toilet paper is contributing to the sludge production in our septic tanks.   

Our next question was: Does toilet paper add to the waste strength? To determine the impact, we took samples from the middle layer to avoid solids that had settled. Analysis of the total suspended solids and biochemical oxygen demand were performed. Nitrogen and phosphorus were measured too, but the data are not shown as all results were less than 2 mg/L. 

After we saw these results, we wondered how toilet paper would settle and break down in septic tank effluent, so we ran the study again mixing the toilet paper with effluent from a septic tank and analyzed samples after three days. The table compares the various toilet paper brands to regular septic tank effluent.

From the data with water after 30 minutes and three days, Caboo bamboo does have significantly higher levels of TSS, indicating more of the toilet paper was in suspension and not settling the same way as the other brands were. The Pacific Blue has higher BOD levels than the rest at 30 minutes, but this changed after three days, where the Caboo was the highest followed by Scott Comfort, Scott Pro and Pacific Blue. 

The results with septic tank effluent show the difference is not as significant, with Caboo being the only one significantly higher in TSS and BOD values. This data in general indicates toilet paper is not adding a considerable treatment load to downstream components, but producing more sludge in the system as it is settling out in septic tank. Homes or businesses that use a lot of toilet paper may need more frequent tank cleaning.

INSTALLING BIDETS

Bidets are a French invention that are common in western Europe and grew in popularity in the 1980s in Japan and South Korea when the toilet and bidet were combined into one unit, which also dries and sometimes even has a seat warmer. In the U.S. and Canada there has been an increase in bidet usage since the toilet paper shortage due to the recent pandemic.

There are other reasons why people may consider installing a bidet, including feeling cleaner, health and hygiene benefits and choosing the eco-friendliest option. The only concern with bidets is the potential increase in water usage in arid climates where water shortages are stressing water supplies. If you have a customer who installs a bidet, their need for septic tank pumping may decrease due to decreased sludge production.

The use or amount of toilet paper used in a home or business can cause plumbing and baffle problems. Toilet paper does contribute to sludge production, so facilities with high usage of toilet paper may need tanks cleaned more often than homes with bidets or very low toilet paper usage. In either case, the effluent parameters with and without toilet paper are very similar.

Based on this work, what should my friends in Mexico do?

There are two challenges in Mexico related to this topic — the first is that many septic tanks are smaller than those in the U.S. and the second is proper disposal of septage is often not done and when it is done correctly it is expensive. Therefore being conservative in the amount of toilet paper you use, not flushing the toilet paper, or using a bidet are all good options to reduce the frequency of tank pumping.