From the Guidelines
When the toilet is flushed, feces travels through pipes to a sewage treatment system, where it undergoes multiple treatment stages to remove solids and break down organic matter, ultimately being released into the environment or filtered through soil in septic systems. The process of treating feces after flushing a toilet involves several stages, including primary treatment, secondary treatment, and tertiary treatment, as described in the context of municipal sewage systems 1. In homes connected to municipal sewers, the waste flows through larger sewer lines that lead to a wastewater treatment plant, where the sewage is treated to remove pathogens and other harmful substances. For homes with septic systems, flushed waste enters a septic tank where solids settle to the bottom forming sludge, while liquids flow into a drain field where they filter through soil, with the bacterial decomposition process playing a crucial role in breaking down organic waste into simpler compounds 1. Key factors influencing the treatment of feces include the type of sewage system in place, with municipal systems requiring community infrastructure upkeep and septic systems needing periodic pumping to remove accumulated solids, typically every 3-5 years depending on household size and usage. It is also important to consider the potential for pathogens, such as coronaviruses, to be present in feces and sewage, highlighting the need for effective treatment and management of wastewater to prevent the spread of disease 1. Overall, the treatment of feces after flushing a toilet is a complex process that involves multiple stages and requires regular maintenance to ensure the protection of public health and the environment. Some of the key points to consider when evaluating the treatment of feces include:
- The type of sewage system in place, whether municipal or septic
- The effectiveness of treatment stages in removing solids and breaking down organic matter
- The potential for pathogens to be present in feces and sewage
- The need for regular maintenance and upkeep of sewage systems to prevent the spread of disease
- The importance of bacterial decomposition in breaking down organic waste into simpler compounds.
From the Research
Fecal Aerosols and Toilet Flushing
- When a toilet is flushed, it generates and spreads fecal aerosols, potentially leading to infection transmission risk 2.
- These aerosols can spread to the breathing zone, deposit on floors and partitions in toilet cubicles, and even spread beyond to the restroom lobby 2.
- The concentration of aerosols decays rapidly, with an 86.8 ± 2.2 % reduction in the second minute after a previous flush compared to that in the first minute 2.
Movement of Feces in Sewer Systems
- Gross solids, such as fecal stools, are introduced into the sewer network via the toilet 3.
- The transport behavior of gross solids in small pipes is not fully established, but it is dependent on factors other than just toilet flush volume 3.
- There are three different mechanisms of movement of solids in intermittent flow, and the concept of "limiting solid transport distance" is introduced 3.
Sewer System Dynamics
- In-sewer deposits in combined sewer systems are closely related to the behavior of first foul flush and combined sewer overflows 4.
- The washoff behaviors of each pollutant, including bacterial indicators and enteric viruses, are different from each other and can be categorized into several groups 4.
- River water intrusion can serve as a main source of extraneous water in sanitary sewer systems, which can affect the assessment of extraneous water 5.