Influences of partially hydrolyzed polyacrylamide (HPAM) residue on the flocculation behavior of oily wastewater produced from polymer flooding

Polymer flooding technology has been used successfully in some oil field, but the produced water is more difficult to treat than that from water flooding. The influences of temperature and concentration of partially hydrolyzed polyacrylamide (HPAM) residue on the treatment of simulated oily wastewater from polymer flooding were studied in this paper. Polyaluminum chloride (PAC) and cationic polyacrylamide (CPAM) were used as flocculant, respectively. The results indicated that the light transmission of wastewater got to the maximum in a range of flocculants concentration and then decreased with the increasing flocculants concentration. Flocculation performance improved with the increasing temperature while PAC was used. However, the performance decreased while CPAM was used. The flocculation performance decreased markedly with the concentration of HPAM residue increasing as to these two kinds of agents. When HPAM residue in wastewater increased from 100 mg/l to 600 mg/l, the light transmission decreased from 96.4% to 70% after treating with PAC of 600 mg/l at 37 °C. It decreased from 87.3% to 50% with CPAM of 150 mg/l. The flocculation effect of PAC was excellent. However, the floc was abundant, small, loose and unstable. While CPAM was used, the floc was less and more stable, but the performance was poor and the cost was expensive.