It is commonly known that the Mayim Aharonim has a "Ruach Ra’ah"-foul spirit. The Shulhan Aruch (Siman 181) implies that this is only if the water reaches the earth-not carpet or flooring. That is why Maran states that one should not wash Mayim Aharonim over ground upon which people walk, since they may come to harm. The Levush (R. Mordechai b. Avraham Yoffe, 1530-1612, Europe), as cited by the Be’ur Halacha, maintains that the "Ruach Ra’ah" takes effect even if the water is poured into a vessel. According to him, one should immediately dispose of the water in the vessel so that nobody is exposed to it.
Hacham Ovadia is lenient and rules in accordance with Maran. Therefore, there is no problem to pour the Mayim Acharonim onto plates or into the sink, as long as they are washed off afterwards. This is opposed to the opinion that many sicknesses are due to people who eat from plates upon which Mayim Acharonim was spilled, even if they were later washed off. Someone who wants to be strict and only wash into disposable bowls or a special receptacle is praiseworthy, but there is no problem according to the letter of the law.
One may pour Mayim Aharonim onto the floor under the table; likewise there is no problem pouring the water on dinner plates or in the sink, if he washes it afterward.