Suboptimal pH and high nitrogenous compounds content in metal industry wastewaters often make using traditional biological treatment methods problematic. It is too early to draw conclusions as to the best technology by comparing novel processes such as OLAND, CANON, SHARON, and ANAMMOX and so on, owing to the fact that most of these new processes are still to be fully tested at pilot and commercial scale. Therefore, it is worthwhile to review the novel nitrogenous compounds removal processes and to look at their potential for use in biological treatment of inorganic wastewaters with reference to the metal industry. The biochemical reactions and enzymes involved in each step of the nitrification and denitrification processes, microbiology of each process, different technologies such as OLAND, CANON, SHARON, ANAMMOX and their operational requirements in evaluating the application of the nitrification-denitrification process to metal industry wastewater are discussed in this review.