Combining visualization and statistical analysis to improve operator confidence and efficiency for failure detection and localization

Web applications suffer from software and configuration faults that lower their availability. Recovering from failure is dominated by the time interval between when these faults appear and when they are detected by site operators. We introduce a set of tools that augment the ability of operators to perceive the presence of failure: an automatic anomaly detector scours HTTP access logs to find changes in user behavior that are indicative of site failures, and a visualizer helps operators rapidly detect and diagnose problems. Visualization addresses a key question of autonomic computing of how to win operators' confidence so that new tools will be embraced. Evaluation performed using HTTP logs from Ebates.com demonstrates that these tools can enhance the detection of failure as well as shorten detection time. Our approach is application-generic and can be applied to any Web application without the need for instrumentatio

Effects of livestock wastewater variety and disinfectants on the performance of constructed wetlands in organic matters and nitrogen removal

Background, aim and scope: Treatment performance of constructed wetlands (CWs) is largely dependent on the characteristics of the wastewater. Although livestock wastewater is readily biodegradable in general, its variety in biodegradability can still be significant in practice. In addition, it is a common practice to periodically use disinfectants in livestock activities for health concerns. Obviously, the residual of the disinfectants in livestock wastewater may have serious inhibitory effect on the microbial activities during wastewater treatment. Thus, the main objective of this study was to examine the variety of livestock wastewater in biodegradability and its effect on the performance of a pilot scale tidal flow CWs (TFCWs) in organic matter and nitrogen removal. Furthermore, investigation of the potential inhibition of the chosen disinfectants on organic matter biodegradation and nitrification was another aim of this study. Materials and methods: The TFCWs system consisted of four-stage downflow reed beds with a hydraulic loading rate of 0.29 m3/m2·per day. Long-term stored livestock wastewater and fresh livestock wastewater were used, respectively, as feed to the system in different periods. Meanwhile, batch aeration tests were carried out to investigate the difference in biodegradation of the two types of wastewaters. Inhibitions of two types of disinfectants, namely UNIPRED and HYPROCLOR ED, on microbial activities were investigated in laboratory batch tests, with dosage of from 0.05% to 0.5%. Results: With fresh livestock wastewater, removal efficiencies of up to 93% and 94% could be achieved with average of 73% and 64% for chemical oxygen demand (COD) and TN, respectively. The performance deteriorated when the system was fed with long-term stored wastewater. In the batch tests, the long-time stored wastewater was characterized as non-biodegradable or at least very slowly biodegradable, while the fresh wastewater was readily biodegradable. UNIPRED showed very strong inhibition on both heterotrophic organisms and nitrifiers. Tested inhibition started from content of 0.05%, which is 1/10 of the recommended usage rate. Inhibitory effect of HYPROCLOR ED on COD degradation started from 0.1% and complete inhibition occurred from content of 0.3%, while significant inhibition on nitrification started from 0.1%. Conclusions: Livestock wastewater could vary significantly in biodegradability and it may turn to be non-biodegradable after a long-term storage. The variety of the livestock wastewater has a decisive influence on the performance of the CWs system, especially in TN elimination. In addition, the application of disinfectants UNIPRED and HYPROCLOR ED may cause serious inhibition on microbial activities and subsequent system failure.Department of Agriculture, Fisheries and Food, Ireland: Research Stimulus Fund (project no. RSF 07-528