In this paper we investigate the impact of bake plate temperature variability throughout the entire bake trajectory on resulting critical dimension. For a poorly-controlled bake plate, it is found that the correlation between the temperature profile and CD distribution is high throughout the entire bake cycle, including the steady state sector. However, for a well-controlled, multiple-zone bake plate, the correlation is only significant during the transient heating sector, since in those cases the steady state plate behavior has already been optimized for CDU performance. An estimate of the potential improvement yet to be gained by improvement of transient heating uniformity is calculated.
In 1995, PBS&J was retained by the Narragansett Bay Commission to study and design improvements to the dewatering and incineration facilities at the Field's Point Wastewater Treatment Facility. In the process of designing the various facilities, several unique evaluations were undertaken, including the following:• Dewatering evaluation: The project began with a conventional comparison of dewatering technologies, between belt filter presses and centrifuges. Once the initial selection of centrifuges was made, the process proceeded to an in depth evaluation of centrifuge technology and manufacturers. The evaluation included the following steps:Two centrifuge pilot tests An evaluation of technical information from the manufacturers User contact of various centrifuge installations Recommendation of procurement strategy to the NBC Development of a request for proposals Evaluation of proposal submittals Selection of centrifuge manufacturer• Air pollution control evaluations: The existing incinerator meets all existing air pollution regulations. However, the NBC decided to take a proactive approach and evaluate potential future regulations. In addition, there were potential improvements which could improve the operation of the existing incinerator. The evaluations included the following:An evaluation of potential future regulations Comparison of technologies Cost comparison for both current and future needs Evaluation of alternatives, keeping in mind potential future requirements Selection of appropriate air pollution control equipment.The selected dewatering and air pollution control technologies were implemented into a two phase design of new facilities. The new dewatering facilities (Phase I) will include liquid sludge storage, high speed centrifuges, high solids pumps, combined dry and liquid polymer system, backup lime stabilization and truck loading systems, and packed tower odor control. Steps were taken in the design to improve operation and reduce costs.The new incineration facilities (Phase II) will include a wet electrostatic precipitator for particulate removal, flue gas recirculation for nitrogen oxide removal and improved performance, as well as overfire air systems for improved incinerator performance.Each phase will have state-of-the-art control systems to function with the plants existing distributed control system. Ultimately, the new facilities will allow for improved maintenance and performance of an aging dewatering and incineration system.
The Narragansett Bay Commission (NBC) has recently completed converting their aeration tanks to ten parallel integrated fixed film activated sludge (IFAS) reactors at the 291 MLD (77 MGD) Field's Point Wastewater Treatment Facility (FPWWTF) to meet a future total nitrogen permit limit of 5 mg-N/L. Performance testing conducted during April and May of 2013 demonstrated that the IFAS process was able to meet a total inorganic nitrogen (TIN) limit of 3 mg-N/L and a 1 mg-N/L ammonia-nitrogen limit as stipulated by the process performance guarantee. Start-up and testing of the IFAS process revealed that a bulk-phase dissolved oxygen concentration in the IFAS cell of 4.5 mg/L or greater was required to maintain an ammonia-nitrogen concentration less than 1 mg-N/L in the secondary effluent at the FPWWTF. Performance testing confirmed that process conversion to a four-stage Bardenpho process with an aerobic IFAS zone was capable of meeting treatment objectives: 5 mg-TN/L, 10 mg-BOD 5 /L, and 30 mg-TSS/L on a monthly average basis.
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