Consumption of Salt from Tanning industry


Consumption of Salt from Tanning industry

It’s no secret that the tanning industry produces a large amount of solid waste, liquid waste and even gaseous waste. However, with the right clean technology practices in place, such as using resources efficiently (e.g. chemicals and water) and recycling and purifying process floats, tanners can reduce waste disposal costs and meet environmental waste discharge requirements. The tanning process often involves the use of salt to preserve and tan hides and skins. Salt is one of the most difficult solids to remove from wastewater, so it’s no surprise that it’s a major concern in the leather industry. In this article, we’ll look at ways to reduce the salt levels in tannery waste, especially how they can be reduced through modifications to manufacturing processes and the chemicals used

  • TDS is a measurement of the total dissolved solids in a water sample. It’s important to note that this method doesn’t measure only the salts, but all soluble solids, so it might not be the best solution for some industrial waste water.
  • A conductivity meter is used to measure the electrical conductivity of the water. In fresh water, the electrical conductivity increases linearly with the salt content, making it easy to measure just the total salt content

What is the total salt content measurement method? Different countries use different methods for measuring total salt content. For example, in India, the total dissolved salts (TDS) is usually the preferred measurement. In South Africa, the conductivity is measured for the wastewater. It is important to note that the TDS value for wastewater before treatment is a combination of total dissolved salts (TSD) and the total dissolved oxygen (COD). However, after treatment, the majority of the COD will be removed leaving only the salt content.

To reduce the salt offer what are the methods:

There are a number of ways to reduce the overall salt load in your wastewater, but the one that has the most impact is to not process salted hides or skins. In many countries, salted hides are not allowed to be processed, so your tannery must use them. Other ways to significantly reduce the salt load in your effluent are application processes, such as low salt pickling, and the use of salt free chemical products

  • Reduce conservation salt Conservation salt makes up about 60% to 70% of the overall salt freight in your tannery wastewater. The simple step of removing the conservation salt from your hides and skins can significantly reduce the salt going into your wastewater
  • Eliminate salt for conservation If your slaughterhouse is relatively close to your tannery and your logistics for delivery are well organized, you can process your fresh hides directly. If your hides come from further away, they can be transported chilled directly to your tannery.

Reducing Salt in the Pickling Process

  • Reduce Salt in the Low-Salt Pickling Process Sellatan P Liq can be used in the low salt pickling process to replace some mineral acids and significantly reduce the amount of common salt used. The collagen forms an electrostatic bond between the polysulfonic acid and the collagen, similar to a syntan, and the exhaustion is excellent. In practice, the hides are not swelled and the growth marks on the neck are very flat. A stabilization takes place and the shrinkage temperature increases by around 10°C, making it easier to handle for the next mechanical processes, such as samming, splitting, and shaving. The chromium salt, or other tanning agent, can also diffuse more easily into the skin. By using Sellatan PA Liq, you can replace all mineral acids and still reduce the common salt by 40% when pickling.
  • Most tanneries have considered recycling, but it is often only partially or not implemented at all. Recycling works best when the throughput is relatively constant and requires additional holding tanks, pumps, and control equipment. To avoid chemicals build-up in recycled floats, it is important to analyse the floats on a regular basis. The benefits of recycling are significantly reduced amounts of water and the use of basic chemicals such as salt and acids, which are only used to 'top-up' as needed instead of adding a full amount for every fresh float. In well-controlled systems, savings are more than 50% for salt and 20% for acids.
  • Salt-free liquid chemicals Both the beamhouse and the wet-end processes often use a large amount of powder leather chemicals, which can significantly increase the sulfate load in wastewater. Powder products can be standardised at specific concentrations using inert salts such as sodium sulphate, and in many cases the use of equivalent salts-free liquid products such as Sellatan, Sellasol, and other synthetics and auxiliaries.


The total salt load in wastewater can be significantly reduced. This is especially true for tanneries that have a beamhouse. Of course, fresh or chilled hides are the best option from an environmental point of view, but the tannery must be close to the slaughterhouse. When salted hides need to be processed, the first step is to mechanically remove the curing salt. During the processing process, the best way to reduce salt in wastewater is through the use of low salt pickling systems with modified polysulfonic acid products. This method does not require additional infrastructure as in the case of recycling processes.

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