Enthalpy recovery from wastewater: bioelectrochemical systems versus anaerobic digestion
One of the advantages of anaerobic digestion technology is that it facilitates the recovery of energy from wastewater.With this technology at hand,the energy content of wastewater is equal to its COD content: COD is converted into methane,and the maximum amount of energy that can be recovered from wastewater is the COD;64 gram COD equals 1 mole of methane.That (plus the energetic value of methane) has long been essentially all we needed to know to evaluate the potential energy content of wastewater.With the advent of bioelectrochemical technologies the answer to the question how much chemical energy is available in wastewater has become more complicated.COD (reducing equivalents) is converted into protons and electrons at the anode,the electrons flow to the cathode,generating recoverable energy and recombine at the cathode to re-produce reducing equivalent.Depending on the conditions applied these reducing equivalents can be coaxed to form various products or be combusted with oxygen.Here we present an acetate and glucose based evaluation of the enthalpy flow through the two archetypes of bioelectrochemical systems: microbial fuel cells (MFCs) and microbial electrolysis cells (MECs).In the literature MFCs and MECs are typically evaluated in terms of energy input (as substrate and electricity),and output of electricity and H2.Heat is missing from this evaluation.Our analysis shows that the anodic oxidation of glucose and acetate are both endothermic,indicating that in both cases heat is taken up from the surroundings.In theory this is a point in favour of microbial electrolysis cells over methane producing anaerobic digestion systems,but the substantial over-potentials generally encountered in the former will make it difficult to harness this additional energy.
Energy in wastewater anaerobic digestion thermodynamics enthalpy bioelectrochemical system methane
J.Dolfing E.S.Heidrich
School of Civil Engineering and Geosciences, Newcastle University, Newcastle NE1 7RU, England, UK
国际会议
The 15th IWA World Conference on Anaerobic Digestion( 第15届IWA世界厌氧大会)
北京
英文
699-702
2017-10-17（万方平台首次上网日期，不代表论文的发表时间）