The objectives of this paper are the characterization of the pretreatment of wastewater by microfiltration (MF) membranes for river maintenance and water recycling. This is done by investigation of the proper coagulation conditions, such as the types and doses of coagulants, mixing conditions (velocity gradients and mixing periods), pH, etc., using jar tests. The effluent water from a pore control fiber (PCF) filter located after the secondary clarifier at Kang-byeon Sewage Treatment Plant (K-STP) was used in these experiments. Two established coagulants, aluminum sulfate (Alum) and poly aluminum chloride (PAC), which are commonly used in sewage treatment plants to treat drinking water, were used in this research. The results indicate that the optimal coagulation velocity gradients (G) and agitation period (T) for both Alum and PAC were 200-250 s-1 and 5 min respectively, but the coagulation efficiencies for both Alum and PAC were lower at low values of G and T. For a 60 min filtration period on the MF, the flux efficiencies (J/J0 (%)) at the K-STP effluent that were coagulated by PAC and Alum were 92.9 % and 79.9 %, respectively, under the same coagulation conditions. It is concluded that an enhanced membrane process is possible by effective filtration of effluent at the K-STP using the coagulation-membrane separation process.

Abstract
 1. Introduction
 2. Materials and methods
  2.1. Sewage treatment plant effluent
  2.2. Coagulation tests
  2.3. Coagulation-membrane separation process
  2.4. Determination of coagulation-membrane separationprocess
 3. Results and discussion
  3.1. Optimum velocity gradient
  3.2. Optimum response time by coagulation agent
  3.3. Coagulation characteristics by type of coagulationagent
  3.4. Flux characteristics of membrane separationby coagulation agent
 4. Conclusions
 References

• Jin-hee Jung(Department of Environmental Engineering, Dong-A University)
• Young-ik Choi(Department of Environmental Engineering, Dong-A University)
• Young-rip Han(Department of Environmental Engineering, Dong-A University) Corresponding author