Application of membrane and natural coagulants for stillage purification

Wastewater that remains after bioethanol production (stillage) is a major problem from the viewpoint of environmental protection. Besides the large volume, stillage contains high amounts of organic matter, suspended solids, dead yeast cells and their metabolites, so it should not be disposed in the recipient without previous treatment. In this work the possibility of usage of microfiltration for stillage purification was investigated. Also, the application of natural coagulants was investigated, in order to increase the efficiency of microfiltration for stillage treatment. Results obtained after microfiltration showed chemical oxygen demand (COD) reduction of 35% while the combined use of natural coagulants and microfiltration achieved 50% of COD reduction compared to the initial value. Many published works confirmed the activity of natural coagulants on model water but just few of them investigated the activity of natural coagulants in real samples of waters and wastewaters, which makes this paper significant.