3 ms·

How do modern sewers deal with this?

• DocTomoe 5y ago
  For the most part, they don't. Virtually all sever systems are populated by rats. Watch any manhole during a hot summer's day from afar, and you won't have to wait long to see a rat. Some factors like average flow speed and more slippery pipes, toilet cleaning chemicals, but also changes in how sewers are used (e.g. no longer for food waste disposal) have lowered rat population sizes - and Hanoi being a tropical city probably had some effects as well.
• Cthulhu_ 5y ago
  I am not an expert, but when I think of "old fashioned" sewers, I think of the vaults with a 'river' running, with footpaths on both sides - you know, the type from video games and movies. The sewers here are just pipes though, no room for people to walk through, no access points, no direct openings into a public waterway, and constant one-way flow. I'm not sure if they continuously run water through it, but I can imagine they would.
  • throwaway2048 5y ago
    you definitely don't want a sewer system that is only pipes, open channel flow is essential to ensure that sewage doesn't become pressurized, unless you want exciting effects like toilet fountains. Basically every sewer system has video game style free flowing open air vaulted areas, although usually at smaller scale.
• praptak 5y ago
  There was an article here on HN that a stable rat population is probably better than unsuccessful attempts at control. The reasoning was that rats live in groups which are territorial, so normally keep their distance, which limits the spread of diseases. Killing rats makes the groups flee their territories, which breaks this mechanism and thus helps pathogens spread.