The two most important things that civil engineering provides people in an urban environment with are cheap and clean water supply, and cheap and clean sewage systems. There are arguments about which of them is more important than the other, but sewage can’t be temporarily replaced like water can be with bottled water, so at least during a short term crisis the risks of a sewage system that isn’t working is higher.
Sewage pipelines typically run under roads throughout the UK, and it is very important that no leaks occur. Any leak can spread germs and diseases which can present significant harm in people, which can then spread even further. Therefore in order to prevent widespread contamination it is very important that sewage pipes are well maintained.
As for developing and improving sewage systems, coming up with new ways to implement sewage management focusses largely upon coming up with methods which reduces damage caused by leaking and coming up with technologies which require less maintenance.