One of the water treatment methods is the Coagulation-flocculation process, it is very important process in water treatment industry , it is effected by many factors and there are many mechanisms to this process ,many types of coagulants and coagulants aid ( flocculants ) used in this process , it is used as widely in the water treatment plants even these plants used for purification the water or waste water for drinking and daily activities or used for treat the waste water for industry for example oil and gas industry, one of these plant it is the Basra oil company- water treatment plan which used to treat the water for use it in injection process to increase the oil reservoir pressure in the oil fields , this depends on the coagulation- flocculating for treat the water by using the dray aluminum sulfate( AL2(SO4)3 . 14 H2O) as coagulant and polyacrylamide high molecular weight as flocculant, many problems in this plant such as the optimal coagulant and flocculant doses and the optimal PH are missed ,( they are used coagulant dose 20 mg/l and flocculant dose 0.25 mg/l ) . no previous researchers focused on this issue and try to solve these problems, this study established to stand on this problems and solve it, further that to improve it through optimize the treated water characteristics, in this study used the design expert software , the method is Response surface methodology ( RSM) which used to establish the three level factorial design ( 3 level ) to used for creating the matrix. Within (32) runs extracted by the RSM ( 3 level factorial ) the input factors were the coagulant dose , flocculant dose and PH while the responses were the turbidity, TSS and filterability, the factors levels were ( 20,30,40 mg /l ) as coagulant dose , (0.15, .0225, 0.3 mg/l) as flocculant and (6,7 8) as PH range, jar test was done in the lab to measure the responses ( the treated water characteristics), the experimental results shown that the beast responses were turbidity with coagulant dose ( 30 mg/l ) and flocculant dose (0.3 mg/l) and PH (7) , the data had been analyzed by (ANOVA ) then illustrated graphically, these results had been optimized numerically by the RSM with 96% desirability as the optimization results were coagulant dose ( 27.7 mg/l) , flocculant dose (0.3 mg/l ) and PH (8) it is closely with the best results which obtained by the jar tests with , these data had been tested in the lab , the results were very closely, therefore this optimization conditions represented the optimal conditions. This study found when increase the coagulant dose over than (30 mg/l) the coagulation process be not effective , also found when increase the flocculant dose over than (0.3 mg/l) the filterability will increase which means the filtration time will increase and this is bad indicator , this study found the effect of PH insignificant on the filterability. The study recommended to do not increase the coagulant dose over than (30 mg/l) and flocculant dose over than (0.3 mg/l ) to keep the highly coagulation-flocculation performance in this plant.
