In this study, at first effective performance of electrocoagulation method using electrodes made of aluminum (Al) and coagulation-flocculation method using two types of coagulants lime and Polyaluminumchloride (PACl) in treatment of baker’s yeast wastewater were studied. In the electrocoagulation process effect of four factors including pH, current density, process time and magnetic stirrer mixing speed on removal efficiency of COD and turbidity were evaluated. The maximum removal efficiency of COD and turbidity in EC under optimum operating conditions, i.e., pH 5, current density of 120 A/m 2 , operating time of 20 minutes and mixing speed of 200 rpm were 77.64% and 97.49% respectively. Also in coagulation-flocculation method effect of three factors including concentration of coagulant, pH and fast mixing speed for lime and PACl investigated. The maximum removal efficiency of COD and turbidity using lime as coagulant under optimum operating conditions including concentration of 2000 milligrams per liter, pH 8 and fast mixing speed of 150 rpm, were 68.09% and 89.39% respectively and for PACl as coagulant in optimal conditions, i.e., concentration of 500 milligrams per liter, pH 8 and fast mixing speed of 200 rpm, were 71.05% and 90.62% respectively. In addition of removal efficiencies of pollutions, the operating cost of these two methods in their optimal conditions according to two units of dollars per every cubic meter of wastewater ($ / m3) and dollar per kilogram of COD removal from wastewater ($ / kg COD removed) evaluated and in electrocoagulation were 0.574 and 0.217 respectively, for coagulation by PACl 0.305 and 0.141 respectively and using lime as coagulant were 0.064 and 0.031 respectively. Then the treated wastewater with two electrocoagulation and coagulation-flocculation pretreatment processes used as feed of membrane systems ultrafiltration and nanofiltration. Two types of Hollow fiber membrane polypropylene (PP) and polyvinylidene fluoride (PVDF) in the same operating conditions (ambient temperature and pressure of 6 bar) used for ultrafiltration process and a spiral wound polyamide membrane at ambient temperature and pressure of 7 bar used in nanofiltration system. The maximum removal efficiencies of COD and turbidity using coagulation-flocculation as pretreatment in hybrid system of CC-PVDF-NF were 97.96% and 99.8%, respectively, and with treated wastewater of electrocoagulation pretreatment process in EC-PP-NF hybrid system were 98.99% and 99.9%, respectively. Also, for combination of two methods electrocoagulation and coagulation-flocculation, the removal efficiencies of COD and turbidity were 88.88% and 99.25% for EC-CC and 87.17% and 92.68% for CC-EC, respectively. Finally with combination of EC-CC system with ultrafiltration and nanofiltration systems, maximum COD removal efficiency of 99.67% for EC-CC-PVDF-NF hybrid system achieved. Keywords: Coagulation-flocculation, Electrocoagulation, Ultrafiltration, Nanofiltration, Baker’s yeast wastewater, hybrid methodes of wastewater treatment, COD removal efficiency, Turbidity removal efficiency