||The treatment of nitrate and phosphate ions in fresh water such as streams,
reservoirs, and wetlands through biological treatment has been getting more
crucial and popular
in recent years. This paper reports the reduction of nitrate and phosphate ions
in modified low
salinity fresh water via the cultivation of a microalgae strain, e.g., Tetraspora
sp. and Spirogyra sp.
The low salinity fresh water (9054 to 9992 ppm) was modified with the
addition of organic fertiliser
(VermiCompost Tea) and used as the cultivation medium to grow microalgae.
The microalgae strains
were grown under controlled conditions in an indoor laboratory for 14 days.
The initial concentrations
of nitrate and phosphate ions in the modified fresh water sample were 1.17
mg/L and 0.10 mg/L,
respectively. The reduction of nitrate and phosphate ions associated with the
effect of cultivation
of Tetraspora sp. and Spirogyra sp. in ambient air (0.03% of CO2) and 15% of
CO2 was investigated.
In ambient air, the cultivation of Tetraspora sp. and Spirogyra sp. greatly
reduced the nitrate ions
concentration from 5.96 0.28 to 0.37 0.05 mg/L and from 2.35 0.19 to
0.59 0.08 mg/L,
respectively. A 100% reduction of phosphate ions was observed in the
cultivation of Tetraspora sp. and
Spirogyra sp. from 0.52 0.10 mg/L in 13 days of and from 0.63 0.15 mg/L
in 6 days, respectively.
Meanwhile, with the aeration of 15% of CO2, after the 14 days cultivation of
Tetraspora sp. and
Spirogyra sp. reduced the nitrate ions concentration from 5.27 0.06 to 1.80
0.20 mg/L and from
4.73 0.12 to 2.80 0.10 mg/L, respectively. The excessive CO2 in water
consequently lowered the
pH of water medium from 7.18 to 6.60 due to the formation of carbonic acid
(H2CO3). It was feasible
to couple the removal of nitrogen and phosphorus in Sungai Sura
(442”28.2 N 10326”12.1 E)
while cultivating microalgae through biological treatment to produce biomass
for biofuel production