Enviromental Management

Enviromental Management

WATER TREATMENT
The main water supply is provided by boreholes, then stored in an underground tank. However, rainwater falling on the tannery roof is collected and mixed with the borehole supply, and provides about 30% of the water consumed. This sump also serves as a reservoir in the event of fire. To overcome the possibility of loss of electrical supply in this event, the pressure is provided by a standby water pump and generator.
All of the water required in process is first run into tanks fitted with calibrated level gauges, where hot and cold water are mixed to provide the right temperature. The water is then pumped directly into the processing vessel.

As each skin is shaved, it is checked for shaved substance.
Savings in water are made by recycling pickle liquors as far as possible, and this also reduces salinity in the final effluent. All of the used chrome liquors are separated via discharge gutters after chrome tanning and flow into a sump. This is then pumped into a settling tank to settle any solids that can be discharged from the tank base as sludge. The clear supernatant chrome solution is then recycled in subsequent tanning loads.

Wastewaters from soaking and liming and unhairing are discharged through common drainage. They first undergo a screening to remove gross solids on a self-cleaning screen, followed by removal of finer solids using wedge wide screens. This effluent is then settled using three settling pits, and the supernatant discharged into a collection sump serving the whole tannery. This effluent is continuously aerated to oxidise sulphides and to mix and blend the effluent. The effluent then flows to the effluent treatment plant, where it is dosed with aluminium salts and polyelectrolytes. It then flows through a series of sumps to allow settling of the solids, before screening to remove any residual fines.

 

 

 

The tannery applies chemical dosing and settling to the effluent before biological treatment. After this treatment the effluent has an extended settling period to remove residual suspended solids, and is then aerated before discharge into the river flowing alongside the tannery.
There is a novel system where the effluent passes through seven filter screens. The frame of each screen is made from bamboo, and the filter medium is coconut fibre sandwiched between split bamboo. The filtered effluent then feeds into the base of a second sump for up-flow through a second filter arrangement. This comprises alternating layers of coconut fibre and small river stones.

 

 

 

 A line of eight buffing wheels where each skin is buffed to clean the flesh before dyeing.
The clear effluent then flows into the activated sludge treatment plant for secondary treatment, with a retention time of three days. After secondary clarification, the supernatant is retained for a further three days in settling pits set in series as a form of tertiary treatment, then discharged through another series of sumps where the treated effluent is aerated before discharge to the river running alongside the tannery.

 

 

 

The interior of one of the suspension drying rooms. There is a second row of hanging rails set above those shown, and these are serviced from an elevated platform that runs on tracking so that it can be moved along the full length of the drying room.
There is considerable breakdown of solids in the activated sludge treatment plant, but surplus solids and solids from settling are mixed and blended in a collection sump. When there is sufficient volume, this mixed sludge is dewatered on a filter press.

 

 

 

The roning and embossing area, dealing mainly with shoe upper leather. The finishing department is spacious and fully equipped with presses, glazing machines and milling drums. Adjacent are two roller coating machines and five spraying machines all fitted with radiant drying cells.
The tannery has a small lab at the effluent treatment plant for performing COD analysis and holding records that show a reduction in COD of 90-95%. The effluent is also sampled and analysed by local authorities on a monthly basis.