Integrated algal cultivation for environmentally friendly bioremediation in order to remove eutrophicate nutrients from liquid fertilizer

Abstract

Livestock wastewater is considered a very difficult problem in terms of environmental protection and food resource production. Although the environmental burden has been weakened by the development of manure treatment technology in recent years, it is necessary to develop new technology that can use eutrophicate nutrients for various purposes. The production of liquid fertilizer in Jeju Island exceeds the amount supplied by the supplier (about 100 tons per day), which puts a very heavy burden on environmental policies. The purpose of this study is to develop a technology that can remove eutrophic substances from liquid fertilizer produced in Jeju Island using micro- and macroalga, and to verify the eco-friendliness by estimating the amount of organic-inorganic pollutants that can be removed from the system. In addition, we would like to present data that can be used as animal feed for the biomass produced in the system. Laboratory and pilot-scale experiments for this purpose were conducted to verify successive bioremediation and algae biomass production. The integrated hybrid cultivation system strategy proposed in this study is to consecutively perform the primary cultivation of Spirulina sp. and the secondary cultivation of Ulva sp. through a culture medium that combines liquid fertilizer in an appropriate ratio. The experimental results showed that the maximum Spirulina dry biomass was reached at 0.76 ± 0.02 g/L despite the high turbidity of modified media. The maximum removal efficiency of ammonia, total nitrogen, total phosphorus, BOD, COD, copper and zinc were recorded 100%, 34%, 35%, 50%, 39%, 38% and 81% respectively under 30% v/v liquid fertilizer concentration of whole medium. As a result of analyzing Spirulina powder, it was confirmed that it can be used as a raw material suitable for Korean animal feed standards. This cultivation system is to be an innovative cultural process that can prevent environmental pollution by optimizing the concentration of organic matters, nitrogen, phosphorus and heavy metals with high contamination loads of the liquid fertilizer based on the standard for effluent discharge. The present study demonstrates the potential of an ideal eco-friendly virtuous circulation structure to prevent water pollution through bioremediation of the liquid fertilizer and use the algae biomass as animal feed supplement.