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CHAPTER 5

Wastewater Treatment Technologies

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astewater treatment technologies are used by PFPR facilities to remove or destroy pesticide active ingredients and other pollutants in facility wastewater. The treated effluent may be reused in PFPR operations or may be discharged to a receiving stream or treatment facility (such as a publicly owned treatment works (POTW)). This chapterdescribes five cost-effective technologies that remove or destroy pesticide active ingredients and priority pollutants, and references other technologies that also effectively treat PFPR wastewaters. A list of documents that contain more detailed information on these technologies is included at the end of this chapter. The technologies presented in this chapter have been identified through samplingvisits to PFPR and pesticide manufacturing facilities and through EPAsponsored treatability tests. The implementation of these, or equivalent, technologies has allowed PFPR facilities to reuse a greater percentage of wastewater in their operations without risking the quality of their final products. Additionally, by implementing these technologies, these facilities are able to discharge effluentsthat might otherwise require disposal.

Pretreatment Technologies
Emulsion Breaking
Many pesticide products are formulated by mixing pesticide active ingredients with inert materials (e.g., surfactants, emulsifiers, petroleum hydrocarbons) to achieve specific application characteristics. When these “inerts” mix with water, emulsions may form. These emulsions reduce the performance efficiencyof many treatment unit operations, such as chemical oxidation and activated carbon adsorption. In many situations, emulsion breaking is a necessary pretreatment step to facilitate the removal of pollutants from PFPR wastewaters. Although emulsion breaking is a pretreatment step, its importance in the treatment of PFPR wastewaters can make it a major part of the technolTypes of Emulsions ogy trainfor treating PFPR wastewaters. Facilities can break these emulsions through several methods. Temperature control and acid addition are common in the PFPR industry and are discussed in more detail below. Other methods of emulsion breaking, such as chemically assisted clarification, are not
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O/W Emulsion - a hydrophobic solvent, such as oil, dispersed in an aqueous medium W/O Emulsion - anaqueous medium dispersed in a hydrophobic solvent, such as oil.

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CHAPTER 5 Wastewater Treatment Technologies

Pollution Prevention Guidance Manual for the PFPR Industry

discussed in this manual. Additional information on these methods may be found in the Final PFPR Technical Development Document (EPA 821-R-96019). Temperature control and acid addition are simple, inexpensivemethods of breaking emulsions in a variety of PFPR wastewaters. Acid (e.g., sulfuric acid) added to emulsified wastewater dissolves the solid materials that hold the emulsions together. The demulsified oil floats because of its lower specific gravity and can be skimmed off the surface, leaving the wastewater ready for subsequent treatment. The demulsification also causes suspended solids with ahigher specific gravity to settle out of the wastewater. Heating the emulsion lowers the viscosities of the oil and water and increases their apparent specific gravity differential. The oil, with a significantly lower apparent specific gravity, rises to the surface of the wastewater. Heating the wastewater also increases the kinetic energy of the individual molecules in the wastewater, causing themolecules to collide with each other more frequently. The increased number of molecule collisions aids in breaking the film present between the oil and the water. Once freed from the water, the oil rises, where it can be skimmed from the surface of the wastewater. Emulsion breaking on PFPR wastewater has been effective in EPA-sponsored treatability tests when conducted at pH 2 and 60°C.

Other...