Abstract

S3-01

Biodegradation of Cyanogens in Cassava Starch/Sago Factory Effluents by Immobilised Microorganisms

Cassava starch/sago factory effluents, which have a high cyanide concentration, pose serious environmental problems to quality of life.  During the process of starch extraction, large quantities of cyanogens present in cassava roots are released from the disrupted cells and become the major source of high cyanide levels in 4000–6000 litres of wastewater discharged for every tonne of starch/sago produced.  The total cyanogens in the wastewater samples ranged between 10.37 and 27.4 mg/l while the levels of total cyanogens in the ground water sources near the factories ranged between 1.29 and 1.59 mg/l.  Micro-organisms capable of using cyanide as source of nitrogen viz. Bacillus sp., Saccharomyces sp and Aspergillus sp. that were isolated from the cassava starch factory effluents were immobilised in alginate beads by entrapment and on Keisulghur and brick powder by adsorption.  The ability of each organism to degrade cyanide was studied.  The percentage of cyanide reduction in the case of immobilised Bacillus cells was found to be the highest (80%) followed by Aspergillus cells (73%) and yeast cells (50%).  The results obtained showed the possibilities of exploring the use of immobilised microbial cells for the detoxification of cyanogens in the wastewater.  A low cost effluent treatment system was developed to protect the environment, produce methane gas and recycles the wastewater for aquaculture.