Using Polymer to Treat Cyanide-Bearing Wastewater During Remediation at MGP Sites



Using Polymer to Treat Cyanide-Bearing Wastewater During Remediation at MGP Sites

Presenter:  Adam  Chen (Burns & McDonnell Engineering, Inc.)
Authors:  Adam Chen, Tom Marshall,  Donna Davis, and Joan Gonzalez (Burns & McDonnell Engineering, Inc.)


Unlike other contaminants associated to manufactured gas plant (MGP) sites such as VOCs, PAHs, PCBs and metals, cyanide compounds pose a unique challenge to handle in terms of its removal and destruction from aqueous waste.  For example, at MGP sites, a conventional treatment of cyanide-bearing aqueous wastes using GAC adsorption is problematic since cyanide mainly in forms of iron cyanide complexes cannot be effectively adsorbed by GAC media, therefore satisfying the discharge criteria regulated by the local POTW or State and/or USEPA is difficult to achieve.  As a consequence, the most of the cyanide-bearing aqueous waste from MGP sites during remediation is always ended up with costly off-site disposal.    To overcome these problems associated with treatment of cyanide-bearing wastewater and minimize the cost of transportation and off-site disposal, an effort is made to evaluate and test several potential cyanide removal, oxidation and/or destruction options to develop an innovative cyanide treatment process.  In this newly developed cyanide treatment process, a conventional filtration, air stripping and GAC adsorption treatment are used to remove VOCs, PAHs, PCBs, and metals first.  The water is then treated by the polymer to remove the cyanide from cyanide-bearing wastewater.    This paper presents a series of laboratory bench scale studies including a three-month column adsorption test conducted to evaluate cyanide treatment processes to adsorb and/or destroy cyanide and the field full-scale application.  The physical and chemical properties of the iron cyanide compounds are examined including how cyanide compound speciation in aqueous phase at MGP sites affects various physical, chemical and biological treatment processes.  The results from both laboratory tests and field full-scale application showed that the innovative cyanide treatment system can effectively remove and destroy various forms of cyanide compounds in wastewater and achieve a significant cost reduction in handling cyanide-bearing wastewater.


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