VPE 511: Environment and Environmental Hygiene (2+1)

IMPACT OF HAZARDS AND PREVENTION

• In many countries tannery effluents are discharged into sewers or inland surface water or brought onto the land with irrigation water.
• The high concentrations of salt and hydrogen sulphide affect the quality of water and may cause bad taste and odour. Though the suspended matter (lime, hair, fleshigns, etc.) makes the surface water turbid, it eventually settles at the bottom.
• Both processes create unfavourable conditions for aquatic life. Mineral tannery waste water that is discharged on land, affects the productivity of soil adversely and may cause land to become infertile. As a result of infiltration, the quality of ground water is also affected adversely.
• Discharge of untreated tannery effluents into the sewer system causes deposition of calcium carbonate and choking fo the sewer. It is possible to treat the waste water effectively before it is discharged into surface water. As a result of this purification, the chromium and BOD levels of the purified water are relatively low. However, the sludge in the wastewater systems has to be brought to special dumping grounds because of its chromium content.
• The tanning industry discharges different types of waste, primarily in the form of liquid effluents containing organic matter, chromium sulphide, ammonium, pentachlorophenol (PCP) and other salts which not only affect the quality of the environment, but also are toxic for flora and fauna.
• Some times the concentration of chromium in tannery effluent reaches upto 6500 ppm, however, pentachlorophenol used as biocide concentration reaches upto 25 ppm, thus, major pollutant of the effluent.