Abstract
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.
Highlights
The input of nutrients especially nitrogen and phosphorus by human activities increased into biochemical cycles through agricultural practices, urbanization, industrialization and other activities
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
The C. curvisetus was grown fastest in NOÀ3 followed by urea whereas C. simplex was grown fastest in urea followed by NOÀ3
Summary
The input of nutrients especially nitrogen and phosphorus by human activities increased into biochemical cycles through agricultural practices, urbanization, industrialization and other activities. Nutrient enrichment or eutrophication of aquatic ecosystems can cause an increase in algae and aquatic plants, loss of component species and loss of ecosystem function. In connection with these problems, numerous studies have aimed on nitrogen and phosphorus removal from wastewater (Thakur and Kumar 1999). The phytoplankton has many advantages for application to nitrate and phosphate removal than macrophytes. It proliferates throughout the entire year with high growth rates when environmental conditions such as light, nutrients and water temperature are suitable (Alexander and Goldman 1994). Free-living and immobilized cells of microalgae have been extensively studied and used for the removal of the inorganic compounds from water (Garbisu et al 1992; Urrutia et al 1995; Gonzalez-Bashan et al 2000; Tam and Wong 2000)
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