Strong denitrification efficiency can be justified
by several factors including aerobic and anoxic zones (2.1 mg
DO/L on the surface and 0.5 mg DO/L on the bottom) always being
present, a large area for a biofilm to attach, optimal pH and temperature
ranges, and availability of food (BOD) for heterotrophic
microorganisms (denitrificants). Also, nitrate (NO3) was detected
sometimes, usually during the summer, reaching 32 mg/L. However,
because nitrate can be used by both duckweeds and denitrificant
bacteria, the nitrate concentration ranged widely (Table 3).