Degradation of Organic Matter using Microbubble Diffuser

Aeration in biological wastewater treatment is where air is introduced to the aeration
tank for mixing purposes and to enhance biological growth. Air or oxygen is
supplied to the activated sludge by aerators. Fine bubble diffusion is a subsurface
form of aeration in which air is introduced in the form of fine bubbles built from
porous materials. However, in an attempt to increase the efficiency of biological
treatment of wastewater, the performance of fine and micro bubble diffusion aeration
systems was investigated in this study. The study evaluated the effectiveness of the
micro bubble diffuser compared to the millimeter bubble diffuser in the treatment of
municipal wastewater. Two batch reactors of size 140xl4Ox600 mm were
fabricated. Porous sintered glass with porosities of 10-16 micron was used to
produce the micro bubbles. Perforated aluminum disc of 3 mm thick with pore
diameters ranging from 0.1-0.4 mm was fabricated to produce millimeter size air
bubbles. Compressed air at a pressure of 63 kPa was forced through the diffusers
from the bottom of the reactor at a flow rate of 2.5 L/min. Seed biomass for the
wastewater treatment was obtained from a University Technology of Petronas
sewage treatment plant (STP). The raw wastewater for the batch study was also
taken from the STP. The wastewater sample was treated for a detention time of 48
hours and repeated for two runs. Sampling were conducted at 3 hours and 6 hours,
for the first and second run, respectively. The effectiveness of both diffusers was
evaluated based on removals of chemical oxygen demand (COD), and soluble
chemical oxygen demand (SCOD). From the study it was found that the micro
bubble diffuser has higher effectiveness in removing COD and SCOD with the
average reaction coefficient k, of 0.041 and 0.0595, respectively. However, the
average reaction coefficient k, for COD and SCOD using millimeter bubble diffuser
was found to be 0.0275 and 0.044, respectively. The average removal of COD was
found to be 86.8 % and 80.4 % for the micro bubble and millimeter bubble diffusers,
respectively. The average removal of SCOD was found to be 90.9% and 75.1% for
the micro bubble and millimeter bubble diffusers, respectively. It was also found
that the micro bubble diffuser and millimeter bubble diffuser could saturate distilled
water to 9.67 mg/L in 22 minutes and 94 minutes, respectively. As a conclusion,
micro bubble diffuser was found to be efficient in the degradation of organic matter.