54 States have signed the IMO Convention, representing 53.30% of the world’s global tonnage, and it will enter into force on 8 September 2017.
Due to the fact that the United States isn’t one of the states that signed the convention, there has been some confusion in the industry regarding the regulations. The United States has its own regulations required by the US Coast Guard (USCG).

You can find FAQ about ballast water management and Coast Guard type-approval, here.

As for the IMO, more than sixty ballast water management systems have already received basic or type approval by the IMO. You can verify the list here.

IMO is making a decision about the implementation deadline for ballast water management systems in July this year, and for this reason some shipowners are hesitating the ordering of the systems as they wait for a decision. However, industry experts say that considering the timeline for assessing and preparing for treatment system integration, there is no reason to delay installing of ballast water management systems. For tens of thousands existing vessels worldwide that need retrofit solutions, the time is now to start preparations.

It has been estimated that the cost of installing approved ballast water management system will be anywhere from 1 to 5 USD million per vessel, depending on the type of vessel.
Installation of a ballast water treatment systems on existing vessels requires comprehensive retrofitting schedule and includes technical aspects to be considered. This means that it is essential for shipowners to stay on top of the rapid developments in terms of regulations and in terms of new technology.