The STP in our apartment (4 years old) in Bangalore is built in the basement. The problem is that no  adequate aeration has  not been provided by the builder. This has resulted in a bad odour for a whole block whenever the door is opened. We have been trying to get someone knowledgable to retrofit some good aeration and exhaust systems to fix the issue but to no avail.

I would like help in two areas :

1. How best can such a situation be remedied?

2. Do you know of any knowledgable and reliable people/companies that can take a look and suggest/implement a solution to this problem?

Thanks in advance!