Beyond over 60% potable water used in the process of corn nixtamalization knows as nejayote is wasted in to the environmental water. Nejayote contains a high concentration of organic matter (20 to 30 g COD L^-1), a considerable amount of Ca²⁺ and PO₄^-2 as well as several nutrients. This work consists of assessing basically two issues. The first is the granular sludges methane production by diluting the nejayote with municipal wastewater of different organic loads. The second is the calcium effect over granular sludges by its precipitation through CO₂ bubbling. The most important results show first, more than twenty times methanogenic activity reduction without Ca²⁺ remotion. Second, COD removal efficiences turned beyond than 90%. Finally, calcium at low concentration increases granular sludges methanogenic activity. Based on these results, we suggest a treatment system wich could be addapted to the existing mills nixtamalization process in Mexico City.