Challenge

While producing a highly varied and variable wastewater that includes condensate from cracking, spent caustic liquor, and wastewater from other processes, the refinery had to meet all MINAS (Minimal National Standards) for effluent discharge.

Solution

Siemens Water Technologies provided a treatment system consisting of PACT (powdered activated carbon combined with biological treatment) and Zimpro® wet air oxidation to enable the refinery to meet the MINAS requirements.

Results

The waste streams are combined in an equalization tank, and free and emulsified oil is removed by separation.  

• The PACT system, designed for 240 cubic meters per hour (about 1,050 gallons per minute) has demonstrated COD reductions of 95 percent.
• The wet air oxidation plant has successfully oxidized waste sludge solids/regenerated spent powdered activated carbon for reuse in the PACT system. The wet air oxidation system is auto-thermal (requiring no external heat source) at a seven percent solids concentration in the feed stream.
• The plant has been able to withstand shock loadings, and can treat toxics and remove color and odor.