Sanitary-chemical and sanitary-toxicological methods were used to study two repurification schemes for biologically purified waste waters from a petrochemical industrial complex. These repurification schemes were, (1) filtration through quartz sand, adsorption to activated charcoal, chlorination; (2) coagulation, filtration through quartz sand, adsorption to activated charcoal, chlorination. Both repurification schemes considerably improved the composition and properties of the waste waters in terms of organoleptic and sanitary-chemical indices. Scheme 1 also considerably lowered the toxic properties of the waste waters and Scheme 2 abolished them completely. Provided that the corresponding sanitary norms are observed, the use of repurification Scheme 1 would be economically reasonable where repurified waste water is recirculated in the industrial plant. Repurification Scheme 2 is recommended where purified waste water is disposed into low-capacity reservoirs.