The effluents released by the paper and pulp industry have a harmful impact on both soil and aquatic environments. These discharges occur at regular intervals, containing varying chemical compositions, including sulphate, phosphates, cadmium, zinc, and other pollutants. Therefore, the variation in effluents collected at regular intervals also influences the geotechnical properties of soils, necessitating a thorough investigation. This paper aims at multi-objective optimization of geotechnical properties of red soil (RS) and black cotton soil (BCS) mixed with paper and pulp industry effluents (10%, 20%, and 40%) collected during the first three weeks of a month and cured for specific durations (0, 14, and 28 days). Advanced analyses including Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDAX), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) were conducted to assess the microstructural and chemical changes in the soils. These tests confirmed significant deterioration in the properties of both RS and BCS upon addition of paper industry effluents. Response surface methodology indicated a higher desirability value of 0.8119 for BCS compared to 0.6935 for RS, demonstrating that the effluent parameters have a more pronounced effect on BCS.