This specificity suggests the possibility of tailoring algal

This specificity suggests the possibility of tailoring algal phycoremediation processes to suit specific contaminant conditions, as well as the possibilities for enhancing both uptake limits and uptake specificity through genetic engineering of algal species. The down side of active approaches involving chemical, biological and microbiological processes is the issue of clogging due to metals precipitation which hinders the biological and microbiological activities, as confirmed by Kalin et al. (2006). Table 1 presents some performance data collected from studies that have used some algae species regarding AMD bioremediation.
Discussion According to Das et al. (2009), more research should focus on the use of Lepocinclis sp. and Klebsormidium sp. for AMD treatment as they show promising features regarding their growth and distribution. It was also recommended that algae and fungi can be used as consortium in AMD either when used as groups or individuals. They have an advantage of working in symbiosis and synergy. Also, high concentration of heavy metals, acidity, low availability of organic carbon and phosphates are detrimental to the growth of algae and fungi. This can be challenging for an efficient treatment process because AMD contains high levels of heavy metals with a very low Phos-tag Acrylamide which is an indication of high acidity. Compared to studies mentioned before, specially the one completed by Ben and Baghour (2013), in which there was a successful removal of heavy metals using algae based treatment despite the high levels of heavy metals or acidity present in AMD. The study completed by Das et al. (2009) focused on specific species such as Spirulina sp., Lepocinclis sp. and Klebsormidium sp. thereby limiting the scope of their study. Therefore, for a conclusive study it is important to assess various algae species, their removal mechanisms and their growth, pH, temperature, residence time and flow rate of the AMD. A large variety of algal species exist naturally; however, they can be classified as ‘extremophiles’, both requiring and thriving in unusual or extreme environmental conditions. Therefore, there is a need to examine in detail their adaptability to be used in phycoremediation processes more especially for AMD.
Shortcomings of phycoremediating using aquatic plants Phycoremediation is a better emerging environmentally friendly and cost-effective method for the treatment of wastewater and polluted environments (Sharma et al., 2014; Sood et al., 2012; Emmanuel et al., 2014;Newete and Byrne, 2016) when compared to conventional methods. Its ability to grow fast and to produces a biomass is an advantage while its poor tolerance to high metal concentrations and its seasonality is a disadvantage to this treatment technology (Rai, 2008; Mannino et al., 2008). Due to the high concentration of heavy metals and their toxicity, phycoremediation is used as either a secondary or tertiary treatments method for industrial or mine wastewater treatment (Sharma et al., 2014). So for effective phycoremediation treatment, there should be regular harvest and safe disposal of the biomass (Rai, 2008) to avoid the release of the absorbed or adsorbed metals back into their source when the plant dies and decompose. The safe disposal of phycoremediation aquatic plants is an emergent area of research that needs to be addressed (Newete and Byrne, 2016). The use of hyper accumulating aquatic plants such as algae for treatment technology of arsenic has an environmental and promising economic prospects but the accumulation and removal of the metalloid is not enough for the successful implementation of this technology if it is not effectively managed and disposed (Rahman and Hasegawa, 2011)
Unsolved issues and novel approach
Challenges and future prospective
Conclusions and recommendations
Acknowledgments
Introduction Potassium nitrate (KNO3) is used as a food preservative, fertilizer and heat transfer agent in chemical industries. KNO3 is also essential in the production of explosives, glass and steel (Abidaud, 1991; Freilich, 2005; Jaroszek et al., 2016). The only known ore of KNO3 is caliche mined in Chile (Freilich, 2005; Velasco, 1992). Potassium chloride (KCl), also known as potash, is another mined compound of potassium. To meet the high demand of KNO3, the mineral deposits are supplemented with the manufactured compound. The following chemical processes have been developed for its production: