Chemical Waste Treatment
Wastes that are not easily treatable at a building or factory are sent to a Waste Processing Plant specially built for this type of work. These are called scheduled wastes. All the concentrated waste obtained from the internal treatment plant are also sent there. This includes sludge, solid or concentrated wastes containing heavy metals, oils, and other harmful compounds. The various scheduled wastes are grouped as follows:
- Group A - Mineral Oil Waste
- Group B - Organic Chemical Waste containing Halogens or Sulfur > 1%
- Group C - Waste Solvents containing Halogens or Sulfur < 1%
- Group H - Organic Chemical Waste containing Halogens or Sulfur < 1%
- Group K - Waste containing Mercury
- Group T - Pesticide Waste
- Group X
- Inorganic Waste
- Group Z - Miscellaneous Waste
Chemical Waste Treatment
The function of the Chemical Waste Treatment Plant is to ensure that all the effluent being discharged to the environment can comply with the minimum requirements of the Environment Quality Regulations.
Several parameters are monitored - temperature, pH, BOD at 20°C, COD, suspended solids, various different concentrations of heavy metals, phenol, free chlorine, sulfide, oil and grease.
A most basic chemical treatment plant will have facilities to neutralize acid or alkali, and to remove heavy metals. The control of pH is quite straightforward. Acidic waste is neutralized with the dosing of Sodium Hydroxide, while alkaline waste can be neutralized with Sulfuric Acid.
Converting its soluble salt to insoluble salt usually does the removal of heavy metal. This is done by the addition of flocculent. Once the insoluble salts are formed, they are encouraged to clump together to form larger flocs. Coagulants are added to the water to achieve this. The large flocs become heavier, and are able to sink down to the bottom.
Coagulation tanks are designed to allow the larger flocs to settle down at the bottom. From here, the solids, called sludge, are pumped to another tank for further thickening.
The thickened sludge is pumped to the dewatering equipment for drying. The dried sludge are collected in bags or containers and sent out as scheduled wastes.
The clear and neutralized water, after neutralization and removal of heavy metals can normally be discharged out to the environment through the drains. Monitoring of the effluent water is required to ensure compliance to the Environment Quality Regulations.
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