(60ci) Enhancement of Flocculation and Dewaterability of MBR Activated Sludge Using a Hybrid System

This study investigates the influence of hybrid coagulation-flocculation system on the flocculation and dewaterability efficiency of a real highly stable membrane bioreactor (MBR) sludge. Two organic coagulants, polyDADMAC (FL 4440) and polyamine (FL 2949) coupled with different structured polyacrylamides (PAMs) are used. Residual turbidity, zeta potential (ζ), flocs size and capillary suction time (CST) are used to assess the impact of the hybrid system on the degree of flocculation and dewaterability of MBR sludge. Addition of FL 4440 and FL 2949 prior to PAM has greatly reduced the turbidity and ζ of the sludge suspension by decreasing the required doses of PAMs 67% to 80% depending on the type of the PAMs used. Polyamine coagulant was more efficient in coagulation and hybrid coagulation-flocculation for MBR activated sludge. The impact of FL 2949 and FL 4440 was more significant on the linear structured PAMs with 71 and 80% reduction in the required PAM’s dose for 40% CD (FO 4490 SSH) and 60% CD (FO 4690 SSH), respectively followed by slightly and highly branched structured PAMs. Similar observations were observed for flocs size and dewaterability (CST) measurements of the flocculated MBR sludge. The results showed a maximum reduction of 58% in the flocs size for sludge conditioned with PAMs in the presence of FL 2949 and FL 4440. Nevertheless, comparable results were obtained for the dewaterability of the flocs produced by PAMs individually and hybrid system. Overall, this study successfully determines the effect of hybrid coagulation-flocculation on the flocculation performance of the MBR sludge.