Section 30(6)(a) in The Merchant Shipping (Prevention of Pollution by Oil from Ships) Rules, 2010
(a)Segregated ballast and clean ballast may be discharged below the waterline-(i)in ports or at offshore terminals;(ii)at sea by gravity; or(iii)at sea by pumps if the ballast water exchange is performed under the provisions of regulation D-l.l of the International Convention for the-Control and Management of Ship's Ballast Water and Sediments: