Legal requirement for a sewage treatment plant (STP) in a factory

Hello,

We are an electronics assembly unit based in Gurgaon with employee strength of about 350. I wanted to understand the legal requirement for setting up a STP in our factory. Right now, our sewage is directly going to the municipal sewer line. We had taken pollution consent in 2016 when employee strength was 150 and sewage discharge was 8 KLD. Please advise if we need to set up the STP for our factory.