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

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 performances 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)(2)SO4 and could effectively remove COD from monosodium glutamate wastewater even when the concentrations of NH4+-N and free NH3-N reached as high as 18977 and 879 mg 1(-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 8000 to 25000 mg 1(-1). The effluent was accompanied with suspended solids (SS) of over 4500 mg 1(-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 1(-1) by a combination process of activated sludge treatment and coagulation technologies.