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

Abstract

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% (NH,)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 18977 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 8000 to 25000 mg l⁻¹. The effluent was accompanied with suspended solids (SS) of over 4500 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