The visit made by Himanshu, Krishna & Priya to the effluent treatment plant (ETP) in Ranipet helped the team to understand the water treatment techniques being currently used in detail. There were many important things that the team discovered on their visit. These observations and inferences are hereby shared with all of you…

The following process was observed at the plant:

Storage Tank: There are two ways through which the effluent from the tanneries is received

  1. Through Gravity
  2. Pressured Pumping

A sieve removes all solid particles larger than 6mm in size.

Pre-settlers:

These are to remove only the core solids. The sludge received from here is the most dangerous, because there is no method developed to treat it and is highly Bio Hazardous Material.

Rotary Fine Screen:

This removes particles greater than 3mm in size and in the next phase it mixes the whole sludge to make it homogenous.

  1. The chemical processing is the next stage where alum, lime, polyelectrolyte are added.
  2. The biological processing is the next phase where oxygen is added to the sludge
  3. The next step involves the clarifier which allows the solid insoluble particles to settle down and release the remaining water to the canal

Notes:

  1. The water sent into the canals is used for specific irrigation purposes but is mostly hazardous as it may destroy the crop completely.
  2. The major air pollutant that the tanneries give out is the Hydrogen Sulphide gas which makes surrounding area smell like a rotten egg!!!
  3. Every tannery has 3 phases of treatment before releasing the sludge, here maximum chromium is re extracted and also heavy particles are removed. The remainder of the effluent is sent to the ETP.
  4. There are also chemical factories in Ranipet which pollute the underground water.
  5. Most of the tanneries send the waste through pipes to the ETP.
  6. The main problem of the existing ETP is removal of chloride from water.

Advancements:

  1. Reverse Osmosis process is being setup to enable zero water discharge in a period of 6 months and the project is half way through construction.
  2. This process will ensure that there is no effluent released to the barren ground.
  3. Hence there is no point of treatment of effluent water as there isn’t going to be any in a period of 6 months.

Problems:

  1. The underground water which has been polluted for many years now will continue to be contaminated for many years to come even if effluent discharge is stopped from the tanneries.
  2. The effluents from the surrounding chemical factories are still not being treated and this will continue polluting the underground water.
  3. The drinking water problem will remain unsolved if no action is taken.
  4. Rainwater cannot be an option as the area has very low rainfall.
  5. There are no rivers nearby to construct a pipeline for water.
  6. The humidity is very low hence evaporation is fast and air dehumidification cannot be an option for water source.

Possible Solutions:

  1. As the effluent discharge from tanneries is shortly going to be stopped, best source of water which can be treated is the Underground water.
  2. The effluents from the chemical factories cannot be treated as they contain complex chemicals and different chemicals at different times.
  3. Treated water can be sold easily as families are ready to accept cheaper and efficient water treatment techniques.
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Field Research

April 15, 2010

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