Thermodynamic studies of anaerobic digestion of post coagulation sludge from petroleum produced water and cow dung

• Main Authors: I.G. Ezemagu, M.I. Ejimofor, M.C. Menkiti
• Format: Article
• Language: English
• Published: Elsevier 2020-06-01
• Series: Current Research in Green and Sustainable Chemistry
• Subjects: Post coagulation sludge; Cow dung; Anaerobic digestion; Thermodynamics; Thermo physical properties
• Online Access: http://www.sciencedirect.com/science/article/pii/S2666086520300400

Post coagulation sludge (PCS), a by-product generated after coagulation of petroleum produced water using tympanotonos fuscatus coagulant (TFC), was used as a potential substrate in association with nutrient rich biowaste material (cow dung) for biogas production. This novel concept was experimentally evaluated and analyzed using thermo-physical properties like specific internal energy, specific heat capacity at constants volume and pressure and specific enthalpy. Also, the thermodynamic parameters such as Gibbs free energy, entropy and enthalpy of biogas were estimated. The substrates C:N values were found to be 23:1 and 25:1 for PCS and PCS ​+ ​CD, respectively. Cumulatively, 446 ​ml was recovered from PCS, while 631 ​ml was recovered from PCS ​+ ​CD digestion system. The recovered biogas contained 83.53% and 89.5% of CH4 for PCS and PCS ​+ ​CD digestion systems respectively. The thermo physical properties of the biogas content increased with increase in temperature. Compared to other gaseous components of the biogas recovered, methane has the highest Cv and Cp of 3.6209 kJkgK and 4.8278 kJkgK for PCS digestion system and 3.0867 kJkgK and 7.4480 kJkgK for PCS ​+ ​CD system. The biogas process was found to be thermodynamically feasible, spontaneous and endothermic in nature with ΔG°av. (kJmol) of −50.019, ΔH°(kJmol) of 280 and ΔS°(Jolmol.K) of 10.9 for PCS ​+ ​CD digestion system under mesophilic condition.