Zero discharge fermentation plant design

In recent years, there has been an increasing thrust towards zero-discharge operation of waste-water treatment plants. This has been driven by increasingly stringent discharge standards, as well as fi nancial benefi ts stemming from the recycling of water around such facilities. The molasses-based fermentation industry is associated with high consumption of water and a high generation of high-strength effl uent, due to the widespread use of molasses feeds. Traditional biological treatment for this effl uent is incapable of meeting stringent discharge and reuse stan-dards; therefore it must be supplemented with tertiary treatment options. The main options for water recovery are reverse osmosis (RO) membrane fi ltration and evaporation. The main prob-lems for these treatment options is the high energy consumption associated with their use and the requirement for pre-treatment leading up to the RO stages. This paper will compare potential treatment options for high water recovery from the high-strength effl uent generated by distill-eries and yeast production plants on an economic basis, incorporating both operating costs and capital costs. Treatment options are considered for several different effl uent sources. This includes a comparison of the use of both reverse osmosis and evaporation technology for water recovery on end-of-line effl uent streams. The potential for a salt recycle from the end-of-line streams t