Drinking　water　treatment　sludge,　characterized　as　accumulated　suspended　solids　and　organic　and　inorganic　matter,　is　produced　in　large　quantities　during　the　coagulation　process.　The　proper　disposal,　regeneration　or　reuse　of　sludge　is,　therefore,　a　significant　environmental　issue.　Reused　sludge　at　low　temperatures　is　an　alternative　method　to　enhance　traditional　coagulation　efficiency.　In　the　present　study,　the　recycling　mass　of　mixed　sludge　and　properties　of　raw　water　(such　as　pH　and　turbidity)　were　systematically　investigated　to　optimize　coagulation　efficiency.　We　determined　that　the　appropriate　dosage　of　mixed　sludge　was　60　mL/L,　effective　initial　turbidity　ranges　were　below　45.0　NTU,　and　optimal　pH　for　DOMs　and　turbidity　removal　was　6.5-7.0　and　8.0,　respectively.　Furthermore,　by　comparing　the　flocs　characteristics　with　and　without　recycling　sludge,　we　found　that　floc　structures　with　sludge　were　more　irregular　with　average　size　growth　to　64.7　mu　m　from　48.1　mu　m.　Recycling　sludge　was　a　feasible　and　successful　method　for　enhancing　pollutants　removal,　and　the　more　irregular　flocs　structure　after　recycling　might　be　caused　by　breakage　of　reused　flocs　and　incorporation　of　powdered　activated　carbon　into　larger　flocs　structure.　Applied　during　the　coagulation　process,　recycling　sludge　could　be　significant　for　the　treatment　of　low　temperature　and　micro-polluted　source　water.