Assessment of a low-cost, point-of-use, ultraviolet water disinfection technology.

We describe a point-of-use (POU) ultraviolet (UV) disinfection technology, the UV Tube, which can be made with locally available resources around the world for under $50 US. Laboratory and field studies were conducted to characterize the UV Tube's performance when treating a flowrate of 5 L/min. Based on biological assays with MS2 coliphage, the UV Tube delivered an average fluence of 900+/-80 J/m(2) (95% CI) in water with an absorption coefficient of 0.01 cm(-1). The residence time distribution in the UV Tube was characterized as plug flow with dispersion (Peclet Number = 19.7) and a mean hydraulic residence time of 36 s. Undesirable compounds were leached or produced from UV Tubes constructed with unlined ABS, PVC, or a galvanized steel liner. Lining the PVC pipe with stainless steel, however, prevented production of regulated halogenated organics. A small field study in two rural communities in Baja California Sur demonstrated that the UV Tube reduced E. coli concentrations to less than 1/100 ml in 65 out of 70 samples. Based on these results, we conclude that the UV Tube is a promising technology for treating household drinking water at the point of use.

Discrete event simulation of emergency department activity: a platform for system-level operations research.

OBJECTIVES: This article explores the potential of discrete event simulation (DES) methods to advance system-level investigation of emergency department (ED) operations. To this end, the authors describe the development and operation of Emergency Department SIMulation (EDSIM), a new platform for computer simulation of ED activity at a Level 1 trauma center. The authors also demonstrate one potential application of EDSIM by using simulated ED activity to compare two patient triage methods. METHODS: The Extend DES modeling package was used to develop a model of ED activity for a five-day period in July 2003. Model input includes staffing levels, facility characteristics, and patient data drawn from electronic patient tracking databases, billing records, and a detailed review of 674 ED charts. The accuracy of model output was tested by comparing predicted and known patient service times. The EDSIM model was then used to compare the fast-track triage approach with an alternative acuity ratio triage (ART) approach whereby patients were assigned to staff on an acuity ratio basis. RESULTS: The EDSIM model predicts average patient service times within 10% of actual values. The accuracy of individual patient paths, however, was variable. In the authors' model, 28% of individual patient treatment times had an absolute error of less than one hour, and 59% less than three hours. A preliminary comparison of two triage methods showed that the ART approach reduced imaging bottlenecks and average treatment times for high-acuity patients, but resulted in an overall increase in average service time for low-acuity patients. CONCLUSIONS: The EDSIM model provides a flexible platform for studying ED operations as they relate to average treatment times for ED patients, but the model will require further refinement to predict individual patient times. A comparative study of triage methods suggests that ART provides a mix of benefits and drawbacks, but further investigation will be required to substantiate these preliminary findings.