Treating Wastewater From Tanneries With HyDAF

The global leather industry has expanded substantially over the past five decades, driven by demand for products ranging from footwear and clothing to saddlery and industrial goods. Central to leather manufacture is the tanning process, which converts raw hides into stable leather through a series of chemical and mechanical stages.

The wet blue tanning process is the most widely applied method. While effective in producing high-quality leather, it generates complex and variable wastewater streams that require multi-stage treatment. Typical contaminants include:

• High biological oxygen demand (BOD5) from proteins, fats, and other organics
• Total suspended solids (TSS) from hair, fleshings, and residual hide material
• Sulfides from the unhairing and liming stages, which are acutely toxic if untreated
• Organic nitrogen compounds contributing to nutrient loads
• Salts from hide preservation and pickling, leading to elevated conductivity
• Chromium (Cr III), introduced during tanning, which must be carefully managed due to the risk of conversion to Cr VI

If untreated, these pollutants can overload sewage treatment plants, disrupt biological processes, and cause severe environmental impacts. Chromium is of particular concern, as even small concentrations in sewage treatment plant biosolids can create significant challenges for disposal or beneficial reuse.

Hydroflux has designed and commissioned wastewater treatment plants for tanneries across Australia and New Zealand, often with Dissolved Air Flotation (HyDAF) at the core. However, our approach is never limited to a single technology. Instead, we design integrated systems tailored to the specific requirements of each site. Examples include:

• Upstream chemical oxidation of sulfides to eliminate odour and toxicity
• Isolation and treatment of chrome-rich streams in a dedicated DAF, reducing the volume of chrome-laden sludge before blending with the main flow
• Robust screening and equalisation to manage extreme hydraulic and pollutant load variations
• Application of HyDAF for bulk removal of solids, fats, oils, grease, and associated organics often in the final combined stream
• Selection of downstream biological or tertiary treatment processes to meet site-specific discharge limits and reuse objectives

The HyDAF remains a critical component in the treatment of tannery wastewater, providing high-efficiency clarification and consistently producing a stable effluent suitable for further treatment on site or at the local sewage treatment plant.

By addressing each contaminant stream independently and integrating the most appropriate technologies, Hydroflux delivers tailored, cost-effective, and sustainable treatment solutions. This ensures compliance and creates opportunities for resource recovery, such as chrome precipitation and reuse.

About The Hydroflux Group
The Hydroflux Group aims to deliver the highest level of engineering and scientific know-how to the emerging issues of sustainability, climate adaptation and environmental protection with a specific focus on water and wastewater.

As part of its vision and mission, Hydroflux has always taken its climate responsibility seriously. In 2022, Hydroflux became Australia’s first water treatment and technology company to achieve Climate Active carbon neutral certification for its organisation and products. It knows that partnering with customers and clients is the most significant impact it can have in its journey. The Group employs over 100 staff and operates throughout Australia, New Zealand and the Pacific Islands, with office locations in Sydney, Melbourne, Brisbane, Perth, Auckland, Suva and Portsmouth.

For more information, visit www.hydrofluxindustrial.au.