I assume you are referring to the killing of ethnic Bulgars by Ottoman forces during the April Uprising
It is a stretch to call this a genocide, at least under the traditional
definition of such. The massacres at Batak and other locations were certainly crimes against humanity (and attracted widespread condemnation by other European powers at the time). However, the killings were largely perpetrated by irregulars (the infamously undisciplined bashi-bazouk), many of whom would have been Pomaks or other Slavic Muslims. Not that the Ottomans are absolved of culpability, but what killings did occur were largely a result of local rivalries/disputes/jealousies (Bulgaria has a host of different tribes and ethnic groups, many of whom share mutual hatreds). There doesn't seem to me to be much evidence of a systematic attempt to wipe out the Bulgarians, "only" an excessively brutal suppression of a revolt.