Final answer:
To prevent a trickling filter with an excessively thick zoogleal mass from turning anaerobic, it is necessary to increase the O2 concentration, lower nutrient levels, and mechanically remove excess algae rather than flood the system, which can worsen the condition.
Step-by-step explanation:
If the zoogleal mass in a trickling filter becomes excessively thick, the approach should be to prevent the system from becoming anaerobic, which is a state without oxygen. Flooding the filter could worsen the situation by further reducing oxygen access to the lower layers. Instead, it is crucial to prevent the formation of a dense 'pond' on the surface which restricts oxygen penetration.
The ideal solution involves increasing the O2 concentration in the water, lowering the nutrient levels to discourage excessive algal growth, and possibly mechanically removing some of the algal biomass. These measures can enhance the penetration of light and mixing of the water column, thereby preventing anaerobic conditions and the formation of dead zones. This is particularly important in water bodies experiencing eutrophication, where nutrient levels are high and can lead to significant algal blooms.
Environmental conditions, such as dissolved organic carbon (DOC) levels, can also influence algal growth. Larger particles of DOC can block sunlight and prevent algal blooms, while smaller particles allow for greater sunlight penetration, potentially leading to eutrophication.