So, just WHERE does all our poop go?

Dealing with sewage is not pretty. From the time of the first human civilizations to now, humans have had to confront the issue of what to do with our waste. Sewage infrastructure is a critical part of a functioning society. Public health, welfare and our very ability to live together depend upon it.

Clean water comes into our homes and then leaves through our toilets, sinks, washing machines and showers. Dirty. This wastewater goes to a septic tank in your yard or enters a sewer system – a labyrinth of pipes and pumping stations under our streets and cities. With a little luck, it makes its way to a sewage treatment plant where it is cleaned and disinfected before being released into a local waterway.

Someone has to keep this system running.
Or it leads to a big mess.

Sewer Systems
Sewer systems move sewage from homes and buildings to a wastewater treatment plant. Wastewater flows from sinks and toilets, showers and washing machines to underground sewer pipes that run beneath city streets. Manholes allow access for maintenance and repair.

Overflows
Sewer systems can overflow when they are overwhelmed with water, when pipes break or back up from clogging. Overflows are usually related to maintenance problems – sewer pipes in older cities can be 200 years old or older, made of clay or even wood. In many cities, sewer pipes are not replaced unless there is a massive problem, so no one really knows the state of those pipes. Maintenance and replacement of sewer pipes is expensive, but overflows are dangerous. Swimming in water contaminated with sewage can cause infections, gastroenteritis, dysentery, hepatitis and respiratory illness.

Some cities have combined sewer systems, which convey both sewage and stormwater (from streets and roofs) in the same pipes. During rainstorms, stormwater can overwhelm pipes or sewage treatment plants, resulting in a combined sewer overflow. The sewage that spills from combined systems maybe diluted by rainwater, but it is still very dangerous.

Treatment
Wastewater is ‘cleaned’ at a sewage treatment plant through a series of steps that are designed to meet the requirements of each plant’s Clean Water Act discharge permit. Solids and sludge are removed in each step and disposed.
1. Primary treatment uses screens and settling basins to remove solids and grit.
2. Secondary treatment uses microorganisms and/or chemicals to break down organic matter and nutrients and kill pathogens.
3. Tertiary treatment further breaks down the waste and removes contaminants from wastewater.

Wastewater treatment plants are usually located in low-lying areas because sewer systems rely on gravity to move the waste. Pump stations – sometimes disguised as small cottages – move sewage up and over hills. Treatment plants discharge their treated wastewater into public waterways.

Septic Systems
Septic systems are used in areas without sewer systems. A septic tank is an underground concrete or metal tank connected to a house’s plumbing. Heavy solids settle to the bottom of the tank and grease floats to the top. Naturally occurring bacteria inside the septic tank breakdown the waste. The septic tank must be pumped out every few years to remove the solids and scum that build up in the tank. Wastewater flows from the septic tank through pipes in gravel-filled trenches called leach fields. Dissolved waste and pathogens are trapped by soil particles or decomposed further by soil microorganisms. Treated wastewater eventually infiltrates to groundwater or evaporates from the soil.