Evaluation of Pre-treatment on the First Stage of an Anaerobic Digester for Enhancing Bio-hydrogen Production and its Associated Energy Balance

One of the biggest challenges to overcome in WWTPs in developing countries is the reduction of energy consumption, and optimization of the different processes and services at the facility. This challenge could be reached by implementing a pre-treatment of sludge and a two-stage anaerobic digestion for increases the yield of hydrogen (H2) and methane (CH4) as source of green energy (GE). A pre-treatment should selectively inhibit methanogenic bacteria and increase the production of acetic acid and acetate, thus achieve the highest possible H2 yield. Furthermore, several techniques have been appointed as potential pre-treatments due to their simplicity, contribution to hydrolysis of organic material presented in the biomass. Moreover, H2 has the highest energy content per unit weight of any known fuel (120.21 MJ/kg). This is particularly interesting, as there are additional socio-economic benefits for using bio-H2 as a source of energy. Therefore the production and in-situ used of GE in WWTP is turning into the eye of many companies in developed countries, where Biosolid are normally disposed or used as soil amendment. This study focused in two main topics: 1) Four pre-treatments: temperature shock, pH control, chemical addition and a combination of the above mentioned and 2) Real Case Study (Switzerland), where a selected pre- treatment was implemented for enhancing H2 and CH4 production. Therefore, the aims of this research were: a) To study the influence of different pre-treatments on the 1st stage of a two-stage AD; b)To select the most suitable pre- treatment for enhancing the bio-H2 production for scaling-up; c) Perform and energy balance for justifying the energy neutrality of the process in a real case WWTP.