Nowadays, one of the utmost dilemmas is environmental pollution, particularly aquatic pollution due to rapid industrialization and urbanization. Water, despite being the most plentiful natural resource of the world, only about 1% of the water is accessible for the use of human beings (Anjum et al., 2019; Madhura et al., 2019). The industrial effluents (IE) from different industries such as steel, textile, electro-plating etc., enters aquatic environments through domestic and industrial sewage, shipping, runoff, leaching, and harbor activities, thus affecting aquatic ecosystems (Sononeet al., 2020). The IE contains inorganic contaminants that include different types of HM such as mercury (Hg), cadmium (Cd), cobalt (Co) copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), chromium (Cr) and Arsenic (As) (Naskar et al., 2018). HMs are non-degradable and can become dangerous due to their toxicity, and tendency to accumulate in living bodies in higher levels (Fatima et al., 2020). The effluents of such industries are widely used for irrigation purposes which causes severe effects on plant growth and quality. Particularly, by the process of biosorption and bioaccumulation, levels of HMs ions may increase across the food chain and ecosystem (Mehmood et al., 2019), become a health hazard and exert chronic and acute effects on animals, plants and humans (Umer et al., 2018). Thus, it is needed to effectively treat the IE before its final release in the environment (Ayaz et al., 2020) to avoid unevenness in supply of nutrients, which may cause excessive vegetation growth, reduced quality, uneven fruit maturity (Libutti et al., 2018).
The traditional physical methods (aeration, skimming, sedimentation, and screening) and chemical methods (electrochemical process, precipitation, flocculation, and coagulation) are in use to treat polluted waters; but, to meet the standards of water quality these methods are often considered as less efficient (Saikia et al., 2019). Moreover, these techniques have some disadvantages such as the process cost, high energy, time for operation, incomplete pollutants removal, release of toxic materials from sludge, need of stable lagoons installation and oxygen diffusional resistances (Mahmoud et al., 2020). Bioremediation is an environmentally friendly process that utilizes the innate ability of organisms like fungi, bacteria and algae to detoxify inorganic and organic contaminants from IE (Bharagavaet al., 2018). In the bioremediation technique, pollutants are transformed into some inorganic substances such as methane, water and carbon dioxide, and thus results in detoxification (Saxena et al., 2020). Bioremediation mainly relies on the inherent metabolic ability of microorganisms to degrade and alter the contaminants, which is greatly affected by bioavailability of contaminants. It can be carried out either ex situ (remediation elsewhere) or in situ (remediation at the site). Algae are most enviable because they are photosynthetic, capable of carbon fixation, thereby justifying the hazardous effects of greenhouse gas and quickly produce biomass using nutrient-rich wastewater (WW). In phycoremediation, the HMs either bind with the cell surface or with the intracellular ligands of the living algae. These HMs bounded ligands accumulate further by active biological transport (Aracenaet al., 2019). Carboxylate, amines and hydroxyls are the different functional groups which form complexes with HMs that affect the removal mechanism of these HMs from contaminated water (Piotrowska-Niczyporuk et al., 2015). Some organo-metallic complexes are also separated in the vacuoles that are formed due to action of HMs and peptides of algae to reduce the amount of these metals in the cytoplasm and overcome their toxic effect (Srivastava, 2016). Therefore, Cladophora glomerata and Vaucheria debaryana can be utilized for the removal of various HMs.
Agriculture constitutes a vital sector of the economy of developing countries like Pakistan. Majority of the population, directly or indirectly, is dependent on this sector. Water quality in Pakistan is affected badly due to numerous practices, like discharge of IE and agricultural run-off comprising fertilizers and pesticides. The economic hub of the Khyber Pakhtunkhwa is Hayatabad Industrial Estate (HIE) but lacks any adequate treatment facility for WW. Untreated IE and Municipal run together and released into Bara River. For agricultural practices, the main source of irrigation is the Bara River in Peshawar. Thus, it is needed to remediate the IE to elude the contamination food chain. In underdeveloped countries, the idea of algal utilization for the treatment of polluted IE is not in use generally. For IE treatment, algae may prove a better choice than traditional physical methods (aeration, skimming, sedimentation, and screening) and chemical methods (electrochemical process, precipitation, flocculation, and coagulation). Therefore, it is assumed that algae may contribute in purifying and reclaiming the IE released from HIE, Pakistan. The present research study aims to evaluate the pollution load of industrial effluents (IE) of Hayatabad Industrial Estate (HIE), assess the removal efficiency of the selected algae for the selected HMs (Cd and Pb) and to identify the most efficient algae for the of HM removal (Cd and Pb) present in IE. For the proposed study, pot experiment was performed for individual algal species.