The invention provides a method of efficiently removing selenium from water. The method involves: adding an oxidant to the liquid, adjusting the liquid's pH to below 7.5, adding ferric salt in an amount such that less than a quarter of selenium in the liquid precipitates and adding a poly dithiocarbamate material to the liquid in an amount such that the amount of poly dithiocarbamate material (in ppm) is greater than the amount of ferric salt (in ppm). This method removes far more selenium than previous methods, and does it using a smaller amount of expensive chemicals. Moreover this method makes it far more likely to achieve cost effective compliance with the ever-increasing environmental standards for selenium in water.