Growth and nutrient removal properties of the diatoms, Chaetoceros curvisetus and C. simplex under different nitrogen sources

To investigate the suitability of the marine diatoms, Chaetoceros curvisetus and C. simplex for the removal of macronutrients from different wastewater, the growth and nitrate-phosphate removal properties were studied with nitrate, ammonium and urea nitrogen sources. Three separate experiments were conducted using modified F/2 medium with 12.35 mg L 1 total nitrogen and 1.12 mg L 1 total phosphorous (simulating the typical concentration of nitrogen and phosphorus in secondary effluent) as growth medium. The maximum cell densities of C. curvisetus and C. simplex were 7.16 ± 0.34 × 104 cells mL 1 in $ {\text{NO}}_{3}^{ - } $ and 3.88 ± 0.32 × 105 cells mL 1 in urea, respectively. The maximum chlorophyll a per cell was 1.7 and 4.7 pg for C. simplex and C. curvisetus, cultured with urea and nitrate, respectively. The high protein contents of 4.7 pg cell 1 in C. simplex with urea and 19.7 pg cell 1 in C. curvisetus nitrate nitrogen sources were found. The higher cell density and protein content of both species from urea and nitrate nitrogen sources (p < 0.05) have shown that these were utilized by microalgae and were converted to protein. The C. simplex and C. curvisetus showed maximum removal efficiencies of nitrate by 97.86 and 91.62 % and phosphate by 98.5 and 100 %, respectively when urea used as nitrogen source than ammonia. The results indicated the C. simplex was more efficient than C. curvisetus and suitable for the removal of macronutrients when cultured with urea and nitrate nitrogen sources.