Using ammonium-tolerant yeast isolates: Candida halophila and Rhodotorula glutinis to treat high strength...

Two ammonium-tolerant yeast strains were isolated from sludge samples contaminated with monosodium glutamate manufacturing wastewater and were identified as Candida haplophila and Rhodotorula glutinis. The tolerance of the two yeast isolates to ammonia and their chemical oxygen demand (COD) removal perfomances were evaluated under batch and bench-scale conditions. The mixture of the two isolates was found to grow well in an artificial medium containing 25% (NH4)2SO4 and could effectively remove COD from monosodium glutamate wastewater even when the concentrations of NH4+-N and free NH3-N reached as high as 18,977 and 879 mg l(-1) respectively. A fixed-bed yeast reactor, which was initially inoculated with the yeast mixture, permitted a constant COD removal rate of over 80% during a period of near 2-month continuous running even when the influent COD was increased from 8,000 to 25,000 mg l(-1). The effluent was accompanied with suspended solids (SS) of over 4,500 mg l(-1), which was mainly composed of yeast cells and could be considered as a source of animal forage additive. The residual COD of effluents from the yeast reactor could be further reduced to under 500 mg l(-1) by a combination process of activated sludge treatment and coagulation technologies.