The discharge of poorly treated effluents into the surface water such as streams, rivers and lakes had far – reaching impacts on human activities and aquatic life forms. Therefore, it needs to be cleaned to acceptable levels. For polluted water and wastewater treatments, biological methods are often preferred; in which the usage of highly efficient bioflocculants produced by flocculants producing bacteria (FPB) were selected because low cost, harmlessness to human and environment. In order to reduce water pollution in fish ponds and treat wastewater piggery of post-biogas in pig farms in the Mekong Delta, Vietnam, Protein FPB isolates and Polysaccharide FPB isolates were isolated from soil and water samples; identified by 16S rRNA gene sequencing; and then investigated its characteristics and flocculation activities. The good isolates were selected to optimize parameters of flocculation and its applications in treatments of the polluted water of tra-fish ponds and the wastewater piggery of post-biogas in pig farms. Targets of the quality of output wastewater were compared to standards of the Regulation QCVN40 (A standard (mg/L): TSS < 50; COD < 75; BOD5 < 30; TN < 20; Nitrite (NO2 - ) < 0.01; Nitrate (NO3 - ) < 50; TP < 4 and PO4 3- < 6). From the polluted water in tra-fish ponds: From 155 samples of 10 sites in the Mekong Delta, 389 FPB isolates were isolated including 154 Protein FPB isolates and 235 Polysaccharide FPB isolates. Among the FPB isolates, a total of the 20 isolates (10 of Protein FPB isolates and 10 of Polysaccharide FPB isolates) having the highest flocculating efficiency were selected to identify, the results showed 16 strains belonged to genus Bacillus, 2 strains belonged to genus Staphylococcus, 1 strain was genus Arthrobacter and 1 strain was Agrobacterium, respectively. Among the 20 isolates, the polysaccharide FPB Agrobacterium tumefaciens strain STT37PS (optimal growth medium: adding 1% sucrose and 5% glutamic) was selected to treat wastewater of three-month old bronze featherback (ThacLac) fish and ababas (RoDong) fish ponds. The quality of treated wastewater reached the standards of Regulation QCVN40 in a short time (3 days for bio-floc stage, 2 days for Lemna stage). From the wastewater piggery of post-biogas in pig farms: One hundred-nineteen (119) isolates including Protein FPB isolates (53.85 %) and 102 Polysaccharide FPB (46.15 %) isolates were isolated from 147 samples collected from 13 cities and provinces in the Mekong Delta. A total of the 34 isolates (18 of Protein FPB isolates and 16 of Polysaccharide FPB isolates) having the highest flocculating efficiency were chosen to identify. Among of them, all of the 18 Protein FPB isolates belonged to genus Bacillus; the 16 Polysaccharide FPB isolates belonged to genus Bacillus (majority) (10/16), genus Klebsiella (3/16), Ochrobactrum anthropi (2/16) and genus Sphingobacterium (1/16), respestively. Out of the 34 isolates, 2 strains had the highest flocculating activities were Bacillus megaterium LA51P (Protein FPB) and Bacillus aryhadtai KG12S (Polysaccharide FPB). Combination of Bacillus megaterium LA51P and Bacillus aryabhattai KG12S applied in the wastewater treatment (at volume: 1 m3 and 50 m3 ) showed that the criteria of the treated wastewater were lower than the standard A of the Regulation QCVN40.