The objective of this work was to study the nutrient removal using the Woljfia arrhiza during the treatment of laying quails farm effluent. The relationship between W. arrhiza biomass and treatment time, the change in water qualities, and nitrogen-balance (N-balance) were evaluated. The results showed that a biomass of 12.0 g of W. arrhiza per liter of effluent and a treatment period of 30 days were found to provide the best conditions for W. arrhiza's growth and the quality of the treated effluent in terms of biological oxygen demand, suspended solids, total phosphorus, nitrate, total ammonia nitrogen and total Kjeldahl nitrogen. The pH and salinity were similar for each level of biomass. The W. arrhiza biomasses of 4.00-12.0 g/l of effluent were suitable for W. arrhiza survival over time. Since W. arrhiza can fix N in the atmosphere, it can grow very well in effluent containing a low level of N. (C) 2011 Elsevier Ltd. All rights reserved.