Removal efficiency of organic load from a detergent wastewater by a bench scale physical-chemical treatment is reported. The results of the wastewater characterisation showed that the concentrations of the organic matter were very high, expressed as COD, ranging from 2400-26,400 mg/l, while the biodegradable portion was very low, since the BOD/COD ratio was low. These values indicate that organic compounds are not easily subjected to biological treatment. In addition, methylene blue active substances appeared in high concentrations as well as sulphates and ammonia.
The experiments for the treatment of the wastewater were performed using various chemicals such as lime, alum and polyelectrolyte. The use of lime gave a 26% average COD removal, while by using alum a slightly lower removal was achieved, 23%. The use of lime (pH=9-10) in combination with alum led to a 41% COD reduction. Similar removal was achieved by using alum (pH=5-6) in combination with lime, 43%. Finally, the addition of polyelectrolyte in the systems of lime and alum did not improve total removal of organic matter giving reductions of 46% and 48%, respectively.