Intelligent wastewater management for tanneries in India

India is not only the second biggest producer of footwear and leather garments in the world, it also accounts for around 13% of the world’s leather production of hides and skins. Over 50% of tanneries in India are located in India’s southernmost state of Tamil Nadu. The industry is highly water-intensive — even a small tannery with a capacity to process 3–4 tonnes of hides and skins a day uses up over 100,000 litres of water a day, which is the daily household requirement of at least 2500 people.

Due to the poor water resources compounded with the increasing population, pollution and the lack of efficient water management, the state of Tamil Nadu has been facing severe water stress for many years. To help resolve this, a non-profit company — Chennai Environmental Management Company of Tanners — was formed to carry out the Zero Liquid Discharge (ZLD) project announced by the state government, and six common effluent treatment plants (CETPs) were established in Tamil Nadu to help tanneries that were not able to install expensive water treatment facilities.

The existing CETPs are now facing problems that require upgrades or improvements. One of the six CETPS — Ranipet Tannery Effluent Treatment Company Ltd (Ranitec) — approached the Water Technology Research Division of the Industrial Technology Research Institute (ITRI) in Taiwan and Advantech, seeking solutions to improve their outdated facilities and reduce operating costs.

As a result, the ITRI helped the biggest CETP in Tamil Nadu to upgrade its system to reduce total operation cost and energy consumption, as well as increase water recovery rates.

Ranitec, as a benchmark plant, is the largest CETP in Tamil Nadu for the tannery and leather industry. Although pre-treatment facilities were constructed in both Ranitec and member tanneries’ sites, pre-treated wastewater still has high suspended solid (SS), biological oxygen demand (BOD) and chemical oxygen demand (COD) values, which resulted in several issues: ultrafiltration and reverse osmosis membrane fouling, low water recovery rates and high energy consumption, as well as a large amount of dry solid waste after the final mechanical vapour recompression (MVR) process. Membrane fouling requires intense cleaning or membrane replacement and increases the operating costs.

Ranitec has been operating for over two decades, and the accumulated amount of mixed solids, which cannot be recycled or reused, was getting out of control and far from the ZLD project’s goal.

To address the above issues, ITRI proposed a pilot project using its patented BioNET biological polishing system, combined with its membrane bioreactor (MBR) and electrodialysis (EDR) systems.

The BioNET reactor contains porous compressible carriers that offer large surface areas for the interception of suspended solids and the growth of microorganisms. After implementing ITRI’s water treatment solutions, the BioNET technology and MBR reduced ammonia use by up to 96%, and both BOD and COD were also greatly reduced from the wastewater — making the condensate reusable and improving water recovery rates, as well as extending the lifespan of ultrafiltration and reverse osmosis membranes. The EDR system also minimised the inlet volume of brine to the MVR, decreased energy consumption and increased the water recovery rate. After going through the membrane bioreactor, BioNET and EDR, the volume of the concentrated wastewater has decreased by about 100 tonnes per day and made it more efficient to treat in the final MVR process, which easily saved Ranitec operating costs of around US$1000 per day.

In order to remotely monitor ITRI’s wastewater treatment solutions and collect data from sensors, ITRI introduced Advantech’s hardware and water treatment industrial app. Chih Huang, AIoT Engineer at the Water Technology Research Division of ITRI, commented that ITRI and Advantech’s wastewater management solution has been used in several projects over the years. By leveraging ITRI’s water treatment expertise and Advantech’s experience in industrial applications, the wastewater solution was successfully replicated for Ranitec’s project.

The BioNET, MBR and EDR systems’ PLCs were connected with Advantech’s ECU series industrial edge computing gateway units. The data captured from the PLCs is sent to a WISE-PaaS platform, allowing ITRI to easily conduct monitoring of all data remotely at its office in Taiwan. Ranitec also has WISE-PaaS access for real-time monitoring of water quality and volume, equipment operating status and other related information for efficiency optimisation. After the pilot project, an AI engine was developed to further optimise ITRI and Advantech’s wastewater treatment solution.

Stepping into the IoT era, water and wastewater treatment will not only need automatic monitoring and control, but also the capabilities offered by cloud services. Advantech said its WISE-PaaS platform, with its functions and tools based on an open architecture, not only fulfils the existing system requirements but also takes future expansion into consideration.