High organic load: low DO, light brown sludge, poor settling, foaming.
Low organic load: high DO, sludge settles quickly, compacts well, sludge is loose and brown. A layer of fat and scum appears on the surface.
Poor sludge settling:
– Floating on the surface: The denitrification process produces N2, malnutrition causes filamentous bacteria to appear, or excess nutrition causes dead sludge to float on the surface.
– Biomass grows scattered: due to high or low organic load, excess oxygen, poisoning.
– Coagulated biomass: Lack of oxygen, lack of nutrients, easily biodegradable organic matter.
Dissolved oxygen: Depends on organic load and biomass content. Suitable DO: 1-2 mgO2/l. Lack of oxygen will reduce treatment efficiency, appear rod-shaped bacteria and fungi, reduce sedimentation ability and inhibit nitrification process..
BOD after treatment is high due to: Overloading, lack of oxygen, pH changes, poisoning, poor mixing
N after treatment is still high due to: Unstable technology, presence of N compounds that are difficult to decompose, high sludge biomass in the tank, poisoning, bacterial death
High N-NH3 due to: inappropriate pH (<6.5 or > 8.5), low sludge age < 10 days, low DO < 2mgO2/l, high N load, presence of toxins, unstable operation , low temperature.
N-NO3; High N-NO2 due to: inappropriate pH (<6.5 or > 8.5), high N load, presence of toxins, unstable operation, low temperature, excess oxygen (anaerobic tank), lack of organic matter.