Avoiding digester upset.

The acetate uptake bioassay (AUB) is a predictive measure for determining the stability of anaerobic digesters, but its use is rare due to the limited availability of gas chromatography equipment at wastewater treatment facilities. A water displacement system was compared and evaluated as an alternative to gas chromatography analysis for conducting the AUB. Results indicated that methane generation rates measured by the two methods were statistically the same. Precision of the method varied by less than 5%. Accuracy was quantified by measuring near stoichiometric volumes of carbon dioxide gas production from abiotic tests using sodium carbonate and hydrochloric acid. The method detection limit (MDL) was 0.6 mL. The effective use of a water displacement system as a surrogate for gas chromatography analysis could make the adoption of the AUB for predicting digester stability a practical option for treatment facilities.

Prospective Case-control Study of Contact Tracing Speed for Emergency Department-based Contact Tracers.

INTRODUCTION: In Snohomish County, WA, the time from obtaining a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test and initiating contact tracing is 4-6 days. We tested whether emergency department (ED)-based contact tracing reduces time to initiation and completion of contact tracing investigations. METHODS: All eligible coronavirus disease 2019 (COVID-19)-positive patients were offered enrollment in this prospective case-control study. Contact tracers were present in the ED from 7 AM to 2 AM for 60 consecutive days. Tracers conducted interviews using the Washington State Department of Health's extended COVID-19 reporting form, which is also used by the Snohomish Health District (SHD). RESULTS: Eighty-one eligible SARS-CoV-2 positive patients were identified and 71 (88%) consented for the study. The mean time between positive COVID-19 test result and initiation of contact tracing investigation was 111 minutes with a median of 32 minutes (range: 1-1,203 minutes). The mean time from positive test result and completion of ED-based contact tracing investigation was 244 minutes with a median of 132 minutes (range: 23-1,233 minutes). In 100% of the enrolled cases, contact tracing was completed within 24 hours of a positive COVID-19 test result. For comparison, during this same period, SHD was able to complete contact tracing in 64% of positive cases within 24 hours of notification of a positive test result (P < 0.001). In the ED, each case identified a mean of 2.8 contacts as compared to 1.4 contacts identified by SHD-interviewed cases. There was no statistically significant difference between the percentage of contacts reached through ED contact tracing (82%) when compared to the usual practice (78%) (P = 0.16). CONCLUSION: When contact tracing investigations occur at the point of diagnoses, the time to initiation and completion are reduced, there is higher enrollment, and more contacts are identified.