The sludge in the anaerobic tank is light yellow – why doesn’t it turn black?
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During the commissioning of a wastewater treatment project at our company, we noticed that the sludge in the anaerobic tank was light yellow in color, similar to that in the aerobic tank. No aeration, normal nutrients, possibly even in excess. Aren’t anaerobic sludge black? I would like to ask the more experienced colleagues for some guidance.
1. Since it is in the initial debugging phase, it is not clear whether yellow sludge was added. 2. Is there sludge return from the aerobic tank, or sludge from the secondary sedimentation tank returning to the hydrolysis-acidification tank? 3. If the wastewater is yellow in color (due to rust or similar), the sludge will also be colored. 4. Is the dissolved oxygen level in the hydrolysis tank too high? 5. The sludge in the hydrolysis tank is usually yellow; could the load be too low?
By raising the temperature of the anaerobic tank to above 15°C, reducing or temporarily stopping water inflow, and enhancing recirculation, the sludge will gradually turn black.