Masu, SmarandaSmarandaMasuGrecu, EugeniaEugeniaGrecu2017-11-142017-11-1420161224-7154http://hdl.handle.net/123456789/1084Studia Universitatis Babes-Bolyai Chemia, vol. 61, no. 4, pp. 189-202, 2016Coagulation is one of the most important stages of the oil wastewaters pre-treatment. Oil wastewaters coagulation that we have studied and which had a content of 95.9-270.6mg Total Petroleum Hydrocarbon (TPH)•L-1 required optimal doses of polyaluminum chloride (PAC) coagulant between 12.0-16.4mgAl•L-1. In the PAC coagulation, the use of various coagulants aids with absorbent properties, such as: indigenous volcanic tuff, charcoal, anaerobic biologic sludge led to: 1. The PAC dose reduction with 30-50%; 2. Turbidity, Total Organic Carbon (TOC), TPH and absorbance at wavelength 254 nm, A254, of treated samples in the presence of aids and reduced PAC doses were similar vs. samples treated with non-reduced PAC doses in aids absence. The use of indigenous volcanic tuff as coagulation aid led to coagulation sludge which are able to sediment with faster than the sludge obtained with PAC coagulation but without aid. More the volume of the coagulation sludge obtained is reduced with 50% vs. one obtained in other variants. By adding coagulation aids there was a reduction of coagulation reagent costs up to 50%. The correlation between A254 and TPH parameters can be useful in establishing on-line relationships that could ease the operators’ activity in wastewater treatment plants.en-USTotal Petroleum HydrocarbonsWastewater coagulationPolyaluminum chlorideCoagulant aidsCostsArticle