01274nam a2200241Ia 4500 IA_Because the COD test is important it can´t be omitted, it uses digester and catalyst solutions, which contain chromium (Cr), silver (Ag) and mercury (Hg), therefore, the residue obtained will contain these heavy metals in high levels, the concentration of these metals exceeds by far the maximum permissible limits established by mexican regulation, this liquid waste is considered hazardous according to NOM-052-SEMARNAT-2005. REDUCCION-PRECIPITACION DE METALES EN RESIDUOS DE 220117s xx 000 0 und d 186155 Disponible en PDF 1 ej. imp. ; 2 ej. CD Aguas residuales 2583 Chemical oxygen demand 161372 Demanda química de oxígeno 161373 Sewage 148728 Tratamiento de agua residual México Chapingo 161374 Wastewater treatment Mexico Chapingo 161375 Esparza Torres, Félix, asesor 163648 Espinosa Solares, Teodoro, asesor 163683 González Rangel, María del Carmen, dir. 161376 TESIS R34 2016 186155 186155