An integrated approach for tannery effluent treatment with ozonation and phycoremediation: A feasibility study

Advanced Oxidation Processes and Biotechnological Alternatives for the Treatment of Tannery Wastewater

“…Tannery wastewater is the product of a transformation process from organic matter to non-degradable matter, which requires the addition of compounds and additives that allow such transformation, generating in turn waste highly polluting not only for human health, but also for the environment [ 34 ]. These wastewaters have as main characteristics a dark brown color, a characteristic odor due to the presence of volatile organic compounds, organic and inorganic carbon, phosphorus (P), nitrogen compounds (N) [ 9 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ], fats and other highly polluting compounds at certain concentrations, such as chemical oxygen demand (COD), biological oxygen demand (BOD), total dissolved solids (TDS), chlorides, sulfates and heavy metals such as Zinc (Zn) and chromium (Cr), among other things [ 37 , 43 , 44 , 45 , 46 ]. Goswami and Mazumder [ 47 ] reported a typical characterization of tannery wastewater, where COD concentrations were observed between 500 and 11,500 mg*L −1 , total Kjeldahl nitrogen (TKN)—200–550 mg*L −1 , observing that the highest fraction is available as ammonia nitrogen (NH 3 –N), total chromium concentrations (Cr(VI) and Cr(III)) in a range of 5–140 mg*L −1 , slow biodegradability due to the content of biodegradable compounds is less than 50% and very high total dissolved solids (TDS) compared to total suspended solids (TSS).…”

“…The contents of other compounds present in the wastewater are also influential in the efficiency of chromium removal since they compete for the interaction with the functional groups of the microalgae, showing that in synthetic wastewater with significant concentrations of chromium (20 mg/L), there is greater efficiency than in tannery wastewater, the interaction of pH, chromium concentration, strain used and temperature also playing an important role [ 43 , 184 ]. Chlorella strains have been extensively studied [ 182 , 184 ], exhibiting optimal growth in tannery wastewater diluted to 50%, guaranteeing the phycoremediation of heavy metals of up to 73.1%, 90.4%, 92.1 and 81.2% for Cr, Cu, Pb and Zn, respectively, contributing to the accumulation of a high yield of lipids (by 18.5%) and unsaturated fatty acids (by 50.05%) [ 185 ].…”

“…Likewise, studies with C. vulgaris also showed significant removals of DQO, NO 3 –N, PO 4 –P, SO 4 –S and Cr of 94.74%, 100%, 91.73%, 99% and 100%, respectively, between the 6th and the 21th days of culture [ 42 ]. In strains of C. vulgaris and Pseudochlorella pringsheimii , significant reductions in the concentration of contaminants were observed, greater than 65% for NH 3 –N, 100% for PO 4 –P, greater than 63% for COD and greater than 80% for total chromium, in dilutions of up to 30% of the residual water (6.25 mg/L of chromium); in addition, lipid accumulation of up to 25.4% was observed for Pseudochlorella and 9.3% for Chlorella vulgaris in a 20% dilution [ 43 ]. Da Fontoura et al [ 186 ] reported positive results in strains of Scenedesmus using a central compound design, demonstrating that the concentration of wastewater and the intensity of light influence the amount of biomass produced and the removal of nitrogen and phosphorus.…”

“…Currently, the implementation of composite systems between advanced oxidation and phytoremediation processes are being evaluated ( Figure 4 ). Studies have shown an optimal correlation between ozonation and phytoremediation with the microalgae Nannochloropsis oculata , where a removal of 84% was achieved for COD, 60% for color, 100% for odor, 90% for inorganic carbon, 84% for NH 4 + –N, 100% for PO 4 –P, 97% for chromium and 10% for TDS; however, it is necessary to maximize the efficiency of ozone utilization to minimize operating costs and continue research regarding operating conditions [ 43 ]. Microalgae have demonstrated their ability to absorb various heavy metals, exhibiting greater effectiveness under certain conditions, as in the case of Dunaliella salina , which exhibited a greater capacity for chromium (VI) biosorption with an efficiency of 66.4% at an optimal pH (8.6) and an inoculum size of 10% within the first 120 h, demonstrating a viable solution for the bioremediation of wastewater with a high content of heavy metals [ 177 ].…”

Influence of period light on cultivation of microalgae consortium for the treatment of tannery wastewaters from leather finishing stage

“…The high chemical load, turbidity and salinity in the raw tannery wastewater restricts the growth of microalgae (Saranya and Shanthakumar, 2019). Therefore, some applications of microalgae in tannery wastewater were carried out with pre-treated wastewater (Saranya and Shanthakumar, 2020), diluted (Fontoura et al, 2017) or added culture medium (Sundaramoorthy et al, 2016).…”