Integrated Treatment of Paint Wastewater Using Helix Pometia Shell Coagulant and Sludge Conversion to Biogas: Process Thermodynamics and Biogas Energy Content

Abstract

This work focused on treatment of paint wastewater and biofuel generation using post coagulation sludge (PCS). Helix potemia shell coagulant was used as a biocoagulant for paint wastewater coagulation. The PCS was converted to biogas via anaerobic digestion. The biogas production process thermodynamics and the energy content of the biogas were evaluated. The total solid (TS) content of the paint wastewater sample (3994mg/l) before the treatment reduced to 804mg/l (42% below the national discharge limit of 1905mg/l) after the coagulation treatment. The volatile solid content(%VS) and the C: N value of 76% and 25:1 indicate that PCS has propensity to yield gas. Cumulatively, 250ml of biogas was recovered within the 40days from 150g of PCS. The recovered biogas contained 63% methane. The negative gibbs free energy (ΔG) of -7.81E+04 shows that the digestion process was spontaneous. Positive enthalpy (ΔHo) and entropy (ΔSo) values of 259.1136KJ/Kg and 8.61E+03Kj/K depict the process was endothermic and entropy driven, respectively. The upper calorific value (UCV), lower calorific value (LCV), latent heat of vaporization (LHV), wobbies index (W) and adiabatic flame temperature (TTL) of 24385.54 kJ/m, 21964.34kJ/m3, 2421.202 kJ/m3, 30246.54 kJ/m3 and 813.1189K, respectively indicate that the biogas is within the standard that can be used in internal combustion engine or as cooking gas.