**7. Challenges and future perspective**

Despite of the importance of algae mediated wastewater treatment and further production of several bioproducts form harvested algae biomass such as (fuel,

## *Algal Biorefinery: A Synergetic Sustainable Solution to Wastewater Treatment and Biofuel… DOI: http://dx.doi.org/10.5772/intechopen.104762*

feed, food, ferilizer), some challenges are also associated with algae technology. Various microbial contaminants can also be act as inhibitors to algae growth. The pH and organic impurities such as i.e. lignin and tannins present in wastewater can affects the algal growth negatively and the concentration of heavy metals above the permissible levels can unfit the products for subsequent utilization of the pharmaceutical products. The microbe (bacteria, protozoa) present in wastewater may affect the growth of algae, there pre-treatment methods such as autoclaving, filtration is not feasible at large scale production. Therefore, advanced technologies are required for the removal of pathogens particularly for the commercial scale production. The major problem associated with conventional wastewater treatment process is generation of sludge. The algae mediated wastewater treatment process overcomes the problem of sludge generation as sludge contains only algae biomass [61]. Different types of wastewater has different composition in terms of pollution load like TDS, heavy metals contents, dissolved oxygen, so the selection of microalgae and its strain should be according to the source of the wastewater, resistibility to the pollution load, easily accessible and achieve the goal of preferred outcome. The harvesting methods of microalgae from wastewater are tedious, costly and laborious too, particularly for the unicellular microalgae. But with scientific development, biotechnological approach and emergence of advanced technology, the problem of microalgae harvesting would be elucidated. Genetic modifications of microalgae hold a great potential for biofuel production from commercialization point of view. However, there are certain challenges that need to be overcome for its large scale production. Hence, more and more studies are required to unfold the enzymatic pathway of lipid/ biofuel production to understand the mechanism involved in the process. To date, several metabolic engineering processes have been developed for enhanced production of algal biofuel, high carbohydrate and lipid content in algal biomass and improving the photosynthetic efficiency of algal species through the cellular expression or down regulation of various genes encoding a specific enzyme [62–64]. The complex nature of fatty acid biosynthetic pathway and lack of molecular transformation techniques for most of the oleaginous microalgae is cumbersome for genetic engineering process. Moreover, enhanced lipid production through genetic manipulation are not fully evolved and recent advancement in the genetic engineering methodology and techniques still promising to reach the desired goal. For the commercial purpose, mass multiplication of microalgae is required. The growth of microalgae is governed by the temperature, seasonal variations and climatic conditions. The laboratory facility with controlled condition of temperature, humidity and invariable seasonal variation is required for the mass multiplication. By viewing the importance of microalgae in the wastewater treatment, production of various valuable products and its combination with the other emerging technologies would definitely overcome the current challenges and cost in near future.
