When considering ammonia (Fig. 4A), the initial
concentration was 12.8 mg L-1 in treatment using nutrient
supplement as compared to 8.67 mg L-1 in treatments with
no nutrient supplement. Results also showed that ammonia
decreased very rapidly during the first two days of
experiment in treatments using nutrient supplements.
Ammonia that quickly decreased indicates the period of
time needed for algae to adapt to the new environment. In
this lag phase, algae used ammonium nitrate as a source of
nitrogen at first (Becker, 1994; Costa et al., 2001). In
addition, in an aerobic condition, ammonia was also
oxidized into nitrate. At the last stage of the experiment, it
was found that ammonia reached the lowest amount (0.71
mg L-1) in treatments using nutrient supplements thus
showing a 92% efficiency of reducing ammonia when
compared with initial wastewater (no nutrient supplement).
The treatments not applied with nutrient supplements had
lowest amount of ammonia at 0.83 mg L-1 at an efficiency
of 75% in reducing ammonium N.