An integrated approach to identify the influential priority of the factors governing anaerobic H2 production by mixed cultures.

An integrated approach incorporating response surface methodology, grey relational entropy, and fuzzy analytic hierarchy process is established to prioritize the influence of main factors governing the anaerobic H(2) production process and their influential priority. Response surface methodology is employed to design experiments, and the grey relational entropy is used to evaluate the influential grade of the three input factors, i.e., pH, temperature and initial substrate concentration (S(ini)), on the H(2) yield, maximum H(2) production rate and volatile fatty acid yield. In addition, through a combination of grey relational entropy, fuzzy analytic hierarchy process, which is used to determine the weight, and accelerating genetic algorithm, which is employed to minimize the nonlinear function in fuzzy analytic hierarchy process, the overall H(2) production process performance could be comprehensively evaluated. The results show that pH is the most important factor influencing the yields of H(2) and volatile fatty acids, while S(ini) has the most significant effect on the maximum H(2) production rate. Compared to pH and S(ini), temperature has a less important effect on the overall H(2) production reactor performance. This approach provides an appropriate way to identify the influential priority of input factors and to evaluate the overall performance for the anaerobic H(2) production process, and it can also be used for other complex biological and non-biological wastewater treatment systems.