Is HKD 30000 salary enough to survive in HK?

A large portion of the population lives with less than half of that, so yes.

It will depend on what kind of living standard you are looking for. For example, if you rent a flat with 2 bed rooms net area of 400 sq ft at the city area close to MTR station, you have to pay for HKD15,000/month.  It's quite common for HK people spend half of their monthly salary for paying rental.

I agree with you Emily, but for example, if you are willing to live without elevator and walk up to the 6 or 7th floor, you can find places around Sham Shui Po for under 10.000 HKD... but if you get one of this flat that has been split in 3 separate units, you can even find some for under 6000hkd )

Then you might spend around 700-1000 in transportation.
130 all included phone bill and unlimited internet data.
100 to 300 in Electricity if no Air conditioning, Water is Cheap, and for drinking I got a filter so I don't need buy big bottles of water.
3000 to 5000+ in food/groceries and cleaning ( this is what I do in an economical wayI cook at home 60 per cent of the month)

One of the cons about Hong Kong that normally when you rent a place everything is empty, you really need a lot of savings to start a life in Hong Kong.

I paid in one go, 3 months rent, plus half month of agent fee.
2000 to get second hand fridge, washing machine and gas cooker. (you can even get them for free if you are nor very picky)
Furnitures you can try to get second hand or free one from people near you, just get a GogoVan for transportation between 50 to 150 hkd  if not very far away.

Willing to answer more questions if needed