A coagulation–flocculation process was applied to wastewater of paint and construction chemicals producing factory in Turkey. Ferric chloride was used as coagulant and several natural based materials, namely limestone, pumice, sepiolite, bentonite and mussel shell were used as flocculant aids. The effects of dosage of flocculant aids on the pH, color and electrical conductivity of wastewater were studied. The experimental results showed that the treatment with all substances was very effective. The pHs of treated wastewater were obtained in the range of 5–7 without needing pH adjustment process. Fifteen Pt-Co color values were obtained on average, which is similar to pure water clarity. The amount of solute in the wastewater was evaluated by the electrical conductivity values. According to the results, under the optimum treatment conditions, chemical oxygen demands were determined. As a result of the work, the cost of chemicals for the wastewater treatment processes has been reduced by about 90%.