BIOLOGICAL TREATABILITY OF PHOTODISTILLATES FOR DISCHARGE INTO SEPTIC-TANK SYSTEMS

For locations not serviced by municipal sewers, vacuum distillation an d discharge of the resulting evaporator distillate to septic tank syst ems has been proposed as a disposal method for photofinishing waste wa ters. The main objective of this study was to evaluate the effect of p hotodistillates generated by vacuum distillation on the biological pro cesses taking place in septic tanks treating sanitary waste waters. Ph otodistillates were prepared by vacuum distillation of mixtures of spe nt photographic solutions. Three batch tests were performed to assess the effect of the photodistillates on the biological processes commonl y encountered in septic tanks. In these tests, raw sewage samples were amended with photodistillates at three volumetric levels. Significant photodistillate-related oxygen demand was destroyed under both aerobi c/anoxic and anaerobic conditions, and no adverse effects on the biolo gical processes tested were observed. These results are very promising for the use of septic tank systems for the disposal of photodistillat es. Blending photographic effluents of different strengths and pH valu es before distillation is recommended to achieve neutralization and a decrease of acetate levels.