Advanced treatment of swine wastewater by a green alga, Scenedesmus quadricauda = Scenedesmus quadricauda를 이용한 축산폐수의 고도처리

Abstract

A green to alga Scenedesmus quadricauda(Turpen) Brebisson was selected for the advance treatment of swine wastewater for its high efficiency of nitrogen and phosphorus removal and possibility of algal biomass use as feed. S. quadricauda grew well at 25℃ and optimum initial pH for growth was 8.0. Algal growth rate and the removal rate of nitrogen and phosphorus increased with light intensity in the range of 5~90μE/m super(2)/s. Algal growth increased with phosphorus concentration under N-fixed (60μM) conditions and also increased with nitrogen increase in the case of P-fixed (2μM) cultures. As a whole, algal growth increased in a big scale along with nitrogen increase in the case of P-fixed condition. Therefore, it seems that the growth of S. quadricauda was affected not only by N:P ratios but also by the absolute concentration of N and P in the medium. The secondary-treated swine wastewater containing 58.65mg/l of total nitrogen and 14.71mg/l of total nitrogen and 14.71mg/l of total phosphorus was diluted to 25%,50%, 75% and 100% with tap water. Nitrogen and phosphorus were concomitantly removed by the cultivation of S. quadricauda in all diluted swine wastewater among which the most effective removal was in 50% swine wastewater(swine wastewater:tap water=1:1). Under the optimized culture conditions, total nitrogen and phosphorus were effectively removed to 99.8% and 94.1%, respectively, after cultivation of 8 days at 25℃ under an irradiance of 100μE/m super(2)/s in 50% swine wastewater.