Abstract:
Proper treatment of palm oil mill effluent (POME) is necessary to sustain the
progress of palm oil industry in Sri Lanka. A case study was conducted to improve existing
wastewater treatment system in a palm oil factory located in Galle district. The system
consists of a neutralization tank, anaerobic ponds followed by anaerobic biogas digesters.
Lime has been used to neutralize before sending to ponds for biological treatment.
However, this treatment did not bring optimum pH for microbial action in anaerobic
ponds. Therefore, performance of lime, caustic soda, iron lathe shavings and boiler ash
from the same factory were studied for pH adjustment. A lab scale leaching bed with boiler
ash was tested as it is freely available. Total carbon and total nitrogen in effluent were also
measured. It was found that the Ca(OH)2 availability in commercially available lime was
31% and less effective. The effective dosage of caustic soda to obtain neutral pH was 5
kg/m3 thus lead to high cost. Iron lathe shavings and boiler ash of palm oil mill were
effective and economically feasible in balancing pH. The boiler ash has shown significant
effect in pH neutralization with the rate of 60 g/l with 4 days hydraulic retention time.
Leaching bed with an ash layer shows an acceptable performance.
