The　effects　of　ultrasound　frequencies　(25　kHz　and　40　kHz),　energy　density　(0.025-7.000　W/mL)　and　sonication　time　(0-30　min)　on　the　flocs　characteristics　of　a　drinking　water　treatment　sludge　(DWTS)　were　investigated　using　both　bath　and　probe　sonoreactors.　The　results　indicate　that　the　flocs　size　decreases　as　result　of　disintegration　of　DWTS　flocs　structure　which　occurs　mainly　during　the　first　5　min　ultra-sonication.　The　extent　of　the　disintegration,　accompanying　with　the　reduction　in　flocs　size　is　greater　at　higher　frequency　than　the　lower　one.　The　specific　surface　area　of　pre-sonciated　flcos　gradually　increases　as　sonication　is　prolonged,　and　it　increases　greater　at　higher　frequency.　The　flocs　size　is　greatly　reduced　at　higher　energy　density,　the　highest　reduction　rate　reaches　above　50%.　The　specific　surface　area　of　pre-sonciated　flcos　reduces　in　case　of　the　higher　energy　density　and　longer　sonication　time　together.　The　smallest　flocs　size　and　highest　specific　surface　area　of　pre-sonciated　flcos　can　be　obtained　at　40　kHz　with　25　mW/mL　of　energy　density.　The　lower　solid　content　is　benefit　to　the　lower　extent　of　attenuation　when　transmitted　in　such　medium　and　the　higher　DWTS　disruption.　Ultrasound　has　little　influence　on　pH　and　Zeta　potential　of　the　pre-sonicated　flocs.　©　2016,　Central　South　University　of　Technology.　All　right　reserved.