This book will provides the readers with basic as well as advanced knowledge of bacterial precipitation and its uses for toxic arsenic removal from water. Iron and Manganese are used for producing bacterial precipitation and harvested for removal of arsenic. Batch tests as well as upflow reactor are used for adsorptive removal of arsenic from water. Lastly, tea-bag test, suspension test and ABIL test are also conducted in context practical uses. Bio-iron showed a significant amount of arsenic removal with compare of available technology. Costs are also calculated and compared. It is found that this method is cost effective for third world countries like Bangladesh.