WesTech Engineering, Inc.

Liquid/solid separation equipment for steel and manufacturing - Metal - Steel

Coke Wastewater Treatment: Heating coal over 1100 Co in the absence of oxygen produces metallurgical coke. This process provides both heat and carbon (coke) required for iron production. During this process the volatile materials contained in the coal are driven off, leaving coke as the product. Gas produced by coking is withdrawn by means of blowers to recover energy-rich byproducts, including methane. Ammonia stills are the principal means of recovery. Recycled scrubber water is used as a coolant. Scrubber waste streams contain tars, organic matter, sulfides, cyanides, inorganic salts, suspended solids, phenols, and ammonia. Treatment of this wastewater involves removal of suspended solids and chemicals that are toxic to biological systems, followed by biological treatment.

Coking wastewater is fed into a rectangular decanter to remove large particles, including tar. Wastewater exiting the decanter is treated with polymer and coagulant before entering a primary clarifier. The primary clarifier facilitates suspended solids settling out from the wastewater stream. This unit is normally covered to prevent the escape of ammonia and volatile organics, which are regulated by EPA and may be explosive.

The primary clarifier effluent flows to biological treatment in an STM-Aerotor™. The STM-Aerotor™ removes the ammonia and organics from the wastewater with a fixed film and activated sludge process. Supplementing this wastewater with phosphate promotes proper microbial growth. WesTech recommends an STM-Aerotor™ instead of an activated sludge system for the following reasons:

  • It has lower operating costs.
  • It is easier to operate since no blowers are needed.
  • The combination of fixed film and activated sludge makes the system more robust and more resistant to toxic shock.

Wastewater exiting the STM-Aerotor™ flows to a COP™ Clarifier for organic matter removal. COP™ Clarifier underflow is split into return activated sludge (RAS) and waste activated sludge (WAS). RAS flows to the STM-Aerotor™, while WAS is sent to a thickener. COP™ Clarifier effluent may be recycled or safely discharged. This effluent may also be polished by a multimedia filter for better clarity.

The primary clarifier’s underflow and the waste activated sludge from the COP™ Clarifier are treated with polymer and then fed into a thickener to thicken the solids. The thickener effluent overflow is recycled back into the primary clarifier. The thickener’s underflow is again treated with polymer and sent to a filter press for dewatering. Filter pressate is recycled back into the primary clarifier while the solids are disposed of.