**3. Challenges in bioremediation application**

Notwithstanding the benefits (such as environmental friendliness, selectivity, adaptability, self-reproducibility, and the ability to recycle bioproducts) of the bioremediation technique, some setbacks have hindered the successful application of this technology. The delay of the operations and the complexity in managing the procedures are the two most significant disadvantages of this technique of treatment. Since the elimination of significant concentrations of heavy metals is a priority, and that the world has become more aware of the environmental concerns caused by other approaches, microbial procedures offer the most rational and long-term answer for treatment. As previously stated, while a variety of microbial contaminant bioremediation techniques to address contamination have been developed, their extensive use and application on a commercial scale are still restricted by some factors. A further point to mention is that the long-term viability of microbial decontamination is still a subject of significant importance, given the paucity of investigations into its long-term performance. Due to the extremely high accumulation of inorganic contaminants (heavy metals) in heavily inhabited places of the world, updating existing microbial bioremediation technologies to an industrial level by making the procedures quicker, more reusable, and easier to regulate will be a big issue in the future. Furthermore, another limitation of bioremediation is that not all substances

are biodegradable while some hydrocarbon components are recalcitrant to microbial breakdown, which restricts the scope of the remediation technique. Even when a material is biodegradable, its downstream operation and breakdown can result in the production of harmful by-products in some situations.
