The builders of Thiruvananthapuram has proposed to include Sewage Treatment Plant (STPs) as a mandatory requirement for every apartment project. The project generally gets delayed as the city corporation demands that builders submit 'consent to operate' certificate from the Pollution Control Board (PCB) before issuing the occupancy certificate. The Centre has already notified that the environment clearance for buildings above 1.5 lakh sq ft be embedded in the building rules. States have been asked to take steps to implement this.