The Louisville Resins operation manufactures a variety of resins for coatings manufacturers, including (modified) alkyds, aminos, emulsions, acrylics, and polyesters. Process wastewater discharge to Louisville’s Metropolitan Sewer District is regulated under the Organic Chemical, Polymer, Synthetic Fiber (OCPSF) category standards of the U.S. EPA. A traditional treatment system, installed in 1992, had suffered low throughput due to hydrocarbon loading and frequent fouling from heat polymerization.
Investment Payback < 2 Years
A demonstration of the MPPE technology proved consistent treatment at design rate without fouling. “The peace of mind alone was worth the investment in MPPE,” says plant manager, John Harris. “Energy and labor savings provide a payback bonus”.
Since start-up, the Resins MPPE unit has consistently delivered its promise. Wastewater treatment cost is reduced by 57%, and the wastewater treatment plant has capacity for a four-fold increase in throughput. Operating cost savings provide an investment payback of less than two years. Figures 2 and 3 provide a size and space comparison of the MPPE unit and the system which MPPE has replaced.
Performance Guaranteed During Operational Life
The specified performance is guaranteed and maintained by Akzo Nobel MPP Systems. Through a service contract, MPP Systems engineers monitor the process and, when the MPPE material gives indication of its exhaustion, replace the material at no additional cost to the client.
The MPPE Process
The Macro Porous Polymer-Extraction (MPPE) process of Akzo Nobel separates hydrocarbons from water by a unique and innovative liquid-liquid extraction process. A patented porous polymer developed by Akzo Nobel contains an extraction fluid within the pores. The polymer and the extraction fluid have a strong affinity for nonpolar compounds. Hydrocarbons, dissolved or dispersed in water, partition to the extraction fluid and remain in solution within the polymer pores. A strong attraction to the polymer coupled with an extremely low solubility in water serve to prevent transfer of the extraction fluid to the water.
The MPPE material operates in a packed column. As the water/hydrocarbon phase passes through an MPPE column, the hydrocarbon partitions to the extraction fluid. Very high mass transfer efficiency is achieved as the declining hydrocarbon concentration continuously contacts fresh extraction fluid in the polymer, the equivalent of many extractors in series. Influent concentrations of thousands of ppm are reduced to single-digit ppb in a single pass through a single MPPE column.
Over time, the extraction fluid reaches its hydrocarbon-loading capacity. At this point the MPPE is regenerated in situ by stripping the hydrocarbons from the extraction fluid. Low pressure steam is introduced into the top of the column. As the polymer heats, the hydrocarbon is vaporized from the extraction fluid and passes out of the column with the steam. Again, the strong affinity of the extraction fluid for the polymer, coupled this time with its very low vapor pressure, serve to keep the extraction fluid in the polymer pores. The steam and hydrocarbon are condensed together. Because the amount of steam required for stripping is very low relative to the amount of water in the extraction step, the concentration of hydrocarbon in the condensate is very high, which leads to phase separation. The free-phase hydrocarbon is available for beneficial reuse/recycle or disposal. The low-volume, high-concentration condensate is recycled to the MPPE columns in a closed loop. Figure 4 is a flow diagram of the MPPE process.
For Louisville Resins, the MPPE treatment system has relieved a production bottleneck, provided capacity for business growth, and increased assurance of discharge regulation compliance. “The Resins operation is poised for dramatic business growth. MPP Systems is pleased with the opportunity to clear one hurdle out of the way,” says Paul Brooks, MPP Systems.