Title: Establishing the fundamentals for a self-sustainable and cost-efficient tannery effluent treatment system: Towards the production of industrial application enzymes based on bioremediation process
Abstract:
The tannery industry produces approximately 24 billion square feet of leather annually, with an estimated worth of $ 45 to $ 50 billion. It has a significant impact on the economies of developing countries, providing income and employment. This industry is tightly linked to agriculture, as bovine hides account for almost 65% of the raw materials. Moreover, this industry has high water consumption and, therefore, produces abundant effluent containing many contaminants. Among these contaminants are heavy metals, such as Chromium. Lead, Nickel, Cadmium, and Copper. Thus, tannery effluents pose a greater danger to the population and the environment.
In Peru, the tannery industry is a significant economic activity, providing over 64,000 direct jobs, which represent almost 1% of Peru's GDP. As of 2023, there are 6,339 registered factories, of which 95% are classified as micro-factories (<10 workers); big factories (>250 workers) represent less than 0.3% of all factories. The great majority of factories (over 91%) are located in the cities of Lima, Trujillo, and Arequipa.
In Arequipa city, the tannery industry is comprised of small and medium-sized factories concentrated in the Rio Seco Industrial Park (PIRS) in the Cerro Colorado district, approximately 20 minutes by car from the downtown area. Leather production is based on methods using chromium salts and vegetal extracts; the former method is the most widely used due to its cost-effectiveness.
The oxidation lagoon is the main tannery effluent treatment process used in Arequipa; however, it is overflooded by the effluent volume, forming streams that contaminate the surrounding area. These streams flow to the Añashuayco ravine, which empties into the Chili River, used for irrigation that produces food for local and regional consumption.
Studies on the effectiveness of bioremediation systems based on microbial and plant agents have been published. Both systems showed promising results, removing between 80% and 98% of the chromium, and reducing and improving physicochemical parameters. However, these methods face important challenges due to industry characteristics, scale, variation in effluent production, personnel training, cost, and environmental considerations, and are viewed as only cost-driven processes, making their implementation difficult.
Our work focuses on establishing the fundamentals for an “ex-situ” tannery effluent bioremediation system based on a land farming model using Medicago sativa, which shows effective chromium removal. We are testing the ultrasound pulse as a pretreatment and sterilization method. The bioremediation system, which combines both methods, can be adapted to variations in effluent volume, offering promising low operation costs and resistance to environmental changes due to the characteristics of the bioremediation agent. Furthermore, we are investigating the coupling of the bioremediation system to Lacasse enzyme production by native fungal and bacterial species using plant biomass, thereby converting this process into a production system. The Lacasse enzymes have a major industrial application in the textile sector, which is an important economic industry. Thus, our goal is to propose and implement a biotechnological production system that gives aggregated value to tannery effluents.
