system
Given the following post, respond as if you're commenting on Reddit:
human
How do cities without bodies of water/rivers nearby deal with sewage? Examples: Johannesburg, South Africa or Lodz, Poland.
gpt
Smaller cities in the desert can run sewage through an activated sludge plant. The raw sewage runs through huge, open air chambers similar to oversized swimming pools.  Multiple chambers run in series combine to form an entire plant. As the sewage runs through each chamber, air is blown through diffusers in the bottom of each chamber. This introduces oxygen into the raw sewage, known as sludge. The oxygen promotes bacterial growth. Each chamber's oxygen level increases as the sludge flows through it. These bacteria eat the raw sewage, and with enough treatment, you are essentially left with trillions of dead microbes. After digestion, the solids (dead microbes) are separated from the water in very still settling tanks. The clear water remaining is sterilized using chemicals or lights with specific wavelengths. It is then pumped into rapid infiltration beds, big holes in the ground. The water seeps into the ground, which essentially filters out any remaining biological contamination. If the waste is properly treated, there are almost none anyway. This water works it's way downward into the water table. The remaining solids are either landfilled or composted.