Several pretreatments
have been appointed for enhancing the production of H2 in a two-stage digester, such as a low
pH control [9], temperature shock of the inoculums for removing hydrogen consuming non-spore forming
bacteria [6], and chemical addition by means of specific methanogenic inhibitors [3]. Special attention has
been given to pre-treatments with Microwave (MW), due to its uniformity on heating and the precise
control of the process temperature that is applied to the sludge. Significant concentration of soluble COD
(sCOD), phosphate and ammonia are released; reduction of capillary suction and improvement of the
sludge dewaterability and high water content in the sewage sludge can absorb MW energy efficiently [10,
11].