Dissolved air flotation (DAF) has been used with increasing frequency in recent decades for the treatment of industrial wastewater. Advances in the technology have expanded the range of applications for DAF; however, engineers and designers frequently use outdated and insufficient design data to design and specify DAF systems for industrial pretreatment. Discussions of advances in DAF design are discussed, including recycle pressurization, improved whitewater systems, enhanced chemical programs, and expansion of manufacturers' base of experience in industrial applications. The need for treatability testing is also emphasized. A case study illustrating these advances is presented, describing the application of DAF at a poultry rendering facility.
The molecular absorption spectrum in the midinfrared (mid-IR) region is typically measured by Fouriertransform infrared spectroscopy (FTIR). Such spectrometers require complex and delicately aligned interferometers, which increases their size and cost. Here, we present an alternative compact mid-IR spectrometer, which uses a variable mid-IR filter with a gradual change of cavity length between two silicon/air dielectric mirrors. When combined with a modern uncooled thermal imaging camera, hyperspectral filtering can provide a powerful solution for the miniaturization of mid-IR spectrometers. By using the hyperspectral filter, light from a broadband light source can be dispersed and assigned to individual pixels of a microbolometer array of the thermal imaging camera. This technology offers an inexpensive and compact mid-IR spectrometer design with no moving parts and rapid acquisition time.
Wastewater from a typical poultry processing plant in the southeastern U.S.A. was treated on site with a pilot-scale anaerobic packed-bed reactor. The reactor had a working volume of 3.2 m3, was filled with 15-cm diameter polyethylene random-pack media, and was operated at 35°C with a retention time of 21 hours and at a loading rate of 2.8 kgCOD/m3d−1. Under these conditions, treatment efficiencies were sufficient to meet typical surcharge-free municipal discharge requirements, with effluent soluble COD of 440 mg/L, soluble BOD5 of 190 mg/L, fats, oil and grease (FOG) of 10 mg/L, and total suspended solids of 140 mg/L. Results from pilot operation are compared to those of previous laboratory-scale studies, where similar results were obtained with less than half of the hydraulic retention time. Differences in treatment on pilot vs. laboratory scale were largely due to differences in wastewater variability and reactor operation. Recommendations for future studies to reduce the costs of treatment, including emphasis on types of low-cost packing, amounts of packing media, and heating requirements are presented.
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