单项选择题 It is that reduce the BOD by converting the organic content of the sewage to a chemically and organically inert sludge（）

单项选择题 The basic process of biological sewage treatment consists of the liquor either by bubbling air through it or by agitating the surface（）

单项选择题 When the garbage is mixed with some discharges having different disposal or discharge requirements, shall apply（）