• A tannery is the place where the skins are processed.
  • Tanning hide into leather involves a process which permanently alters the protein structure of skin.
  • The alteration makes it more durable and less susceptible to decomposition and also possibly coloring it.
  • Tanning is a widespread, global industry that works with both light and heavy types of leather.
  • Light leather is generally used for shoes and other soft products such as purses, and heavy leather is used for straps, belts and in various machineries.


Pollution from Tanneries

  • The two main types of tanning are:
  1. Chrome tanning
  2. Vegetable tanning
  • Chromium compounds are applied to protect hides from decay and to make them more durable against moisture and aging.
  • Other materials that may also be used in the pre-treatment and tanning processes include sulfuric acid, sodium chlorate, limestone, and limestone soda ash.
  • Due to the repeated processes of soaking raw hides and wringing them out, the tanning process creates large amounts of wastewater that is contaminated with many different chemicals.
  • Chromium from leather tanning can make its way into air, soil, food, and water, and the most common forms of exposure are through inhalation of dust or fumes and ingestion of or contact with contaminated water.


Pollution hazards of tanaries

  • Continuous discharge of untreated effluents from tannery areas has an adverse effect on water quality, soil and human health.
  • If tannery effluents are discharged on land it may affect ground water quality due to presence of high concentration of chromium and chlorides. It renders the land unsuitable for cultivation due to high salt content.
  • The suspended solids, in the form of lime, hair, flesh etc. settle to the bottom and both lowered dissolved oxygen and suspended solids can harm aquatic life.
  • Tannery effluents are very toxic in nature and have an obnoxious smell. It has alarming levels of Arsenic, Cadmium, Mercury, Nickel and Chromium VI.
  • According to the World Health Organisation, these heavy metals have a lethal impact on public health when they enter the food/ water chain.
  • Diseases caused by heavy metals include Minamata by Mercury, Itai-Itai by Cadmium, Nickel-Itch by Nickel, Black-foot disease by Arsenic and respiratory distress by Chromium VI.
  • Cadmium is a potent kidney toxicant and Mercury is a potent neurological toxicant. Chromium VI is a known human carcinogen.


The Common Effluent Treatment Plant (CETP)

  • Effluent treatment plants need land for construction, capital cost, power and specialized manpower for their operation and maintenance.
  • Because of these constraints, small scale tanneries cannot afford to have their own effluent treatment facilities and therefore, combined effluent from all tanneries is to be brought to a centralized place for treatment. This facility is called a Common Effluent Treatment Plant (CETP).
  • For operation and maintenance of CETP, small scale tanners formed a co-operative society. The expenses for operation and maintenance of CETP are being shared by participating tanneries.
  • Thus Common Effluent Treatment Plant (CETP) is a way by which the small tanneries can treat pollution at cheaper way.


What is no- development zone?

  • ‘No-development zones’ are areas where no construction including commercial or residential buildings can come up.

What is In-Stream Mining?

  • In- Stream Mining involves the mechanical removal of gravel and sand directly from the active channel of rivers and streams. In-stream mining commonly results in opening of the channel bed, which can spread upstream and downstream as well.
Section : Environment & Ecology