Evaluation of three granular activated carbon filters for the treatment of collections foul air entering a water resource recovery facility.

The treatment of raw foul air that could escape to the atmosphere from the head space of the incoming wastewater sewer lines into a Southern California Water Resource Recovery Facility was evaluated by using a 1/20th scale pilot unit consisting of three different granular activated carbon filter technologies, operating side by side, under similar operating conditions, each having an average 3.8-s contact time. The three activated carbon filters contained each 0.07 m3 of coconut, coal, and coconut mixed with permanganate media. The foul air entering the granular activated carbon filters contained 82% to 83% relative humidity. No moisture removal mechanism was used prior to treatment. The removal of six different odor characters from eight chemical odorants present in the foul air were assessed. These were rotten egg (hydrogen sulfide), rotten vegetables (methyl mercaptan), canned corn (dimethyl sulfide), rotten garlic (dimethyl disulfide), earthy/musty (2-methyl isoborneol and 2-isopropyl 3-methoxy pyrazine), and fecal (skatole and indole). This is the first time a study evaluates the removal of specific odors by simultaneously employing sensory analyses using the odor profile method, which defines the different odor characters and intensities, together with chemical analyses of the odorants causing these odors. The results show that the three granular activated carbon filters, before hydrogen sulfide breakthrough, provided significant improvement in odor intensity and odorant removal. Breakthrough was reached after 57 days for the coconut mixed with permanganate, 107 days for the coconut, and 129 days for the coal granular activated carbon filter. Breakthrough (the critical saturation point of the activated carbon media) was considered reached when the hydrogen sulfide percentage removal diminished to 90% and continued downward. The coconut mixed with permanganate granular activated carbon filter provided the best treatment among the media tested, achieving very good reduction of odorants, as measured by chemical analyses, and reasonable removal of odor intensities, as measured by the odor profile method. The coconut mixed with permanganate granular activated carbon is recommended for short-term odor control systems at sewer networks or emergency plant maintenance situations given its shorter time to breakthrough compared with the other granular activated carbons. The coal and coconut granular activated carbon filters are generally used as the last stage of an odor treatment system. Because of the observed poor to average performance in removing odorants other than hydrogen sulfide, the treatment stage(s) prior to the use of these granulated activated carbons should provide a good methyl mercaptan removal of at least 90% in order to avoid the formation of dimethyl disulfide, which, in the presence of moisture in the carbon filter, emit the characteristic rotten garlic odor. The differences observed between the performances based on odorant removal by chemical analysis compared with those based on sensorial analyses by the odor profile method indicate that both analyses are required to understand more fully the odor dynamics. PRACTITIONER POINTS: Three virgin granulated activated carbon media were evaluated in a field pilot unit using raw collections foul air. Coal, coconut, and coconut mixed with permanganate were tested until breakthrough. Samples were analyzed both chemically (odorants) and sensorially (odors). Coconut mixed with permanganate proved to be the media that better reduced odorants and odors.

Evaluation of bioscrubber and biofilter technologies treating wastewater foul air by a new approach of using odor character, odor intensity, and chemical analyses.

The treatment of raw foul air that could escape to the atmosphere from the head space of the incoming wastewater into a Southern California Water Resource Recovery Facility was evaluated by using a 1/20th scale pilot unit consisting of five different biological media technologies, operating side by side, under different operating conditions. The removal of six different odor characters from eight chemical odorants present in the foul air were assessed. These were rotten egg (Hydrogen Sulfide), rotten vegetables (Methyl Mercaptan), canned corn (Dimethyl Sulfide), rotten garlic (Dimethyl Disulfide), earthy/musty (2-Methyl Isoborneol and 2-Isopropyl 3-Methyl Pyrazine) and fecal (Skatole and Indole). This is the first time a study evaluates specific odors by simultaneously employing sensory analyses using the Odor Profile Method, which defines the different odor characters and intensities, together with chemical analyses of the compounds causing these odors, known as odorants. The paper discusses the efficiencies in removing odor characters as well as odorants by two different bioscrubbers (reticulated polyurethane cube foam and polypropylene mesh with layered polyester foam) and three different biofilters (engineered media, seashells, and lava rock). The results show that the two bioscrubbers, even with greater empty bed gas retention times, did not provide significant improvement in odor intensity and odorant removal. However, the biofilters showed that larger empty bed gas retention times provided significant improvements in diminishing the odor intensities and better odorant removal. The biofilter with lava rock media at 45 s empty bed gas retention time provided the best treatment among the technologies tested, achieving the following odorant reductions: 99.8% for hydrogen sulfide, 98.4% for methyl mercaptan, 57.0% for dimethyl sulfide, and 52.7 for dimethyl disulfide. This biofilter also achieved the following odor intensity reductions: 47% for rotten vegetable odors, 50% for earthy/musty odors, and 100% for fecal odors. The odor panel detected odors by the Odor Profile Method that were below the detection limit of the corresponding chemical analytical method for specific chemical compounds causing these odors. Differences were observed between the performances of bioscrubbers and biofilters, based on odorant removal compared to those based on sensorial analyses, indicating that both analyses are required to understand more fully the odor dynamics. Furthermore, a total odor removal of 99.2% was observed by the dilution to threshold olfactometer method even though nearly half of the rotten vegetable and earthy/musty odors remained based upon the Odor Profile Method. This shows the olfactometer method did not correctly define the degree of odor nuisance in the foul air in this study. Bioscrubbers have in general a better economic return when used at low EBGRTs and as preliminary (first stage) treatment systems. Biofilters are more effective when used at high EBGRTs and can be used as stand-alone or polishing systems.

SARS-CoV-2 viral load assessment in respiratory samples.

Real-time reverse transcriptase polymerase chain reaction (rRTPCR) has been the main method for diagnosis of SARS-CoV-2 infection in the early stages of the COVID-19 pandemic. De-identified results from upper and lower respiratory samples submitted to a reference laboratory demonstrated a positivity rate of 14.9 % (4428 of 29,713 samples tested). Distribution of results by birth year cohort and specimen type suggested general consistency in mean, median and peak values but higher positivity rates in individuals born from 1964 to 1974. Female patients had a significantly lower positivity rate (P < 0.0001), although similar load mean and median values, compared to males. Overall, 15.3 % (676 of 4428 positive results) of positive results had viral loads greater than 8 log10 copies/mL, with occasional samples exceeding 10 log10 copies/mL. These results support quantitative assessment of SARS-CoV-2 viral load in patient testing and efforts to control viral transmission.

Abu Dhabi's strategic tunnel enhancement programme: odour extraction system approaches.

The Emirate of Abu Dhabi has experienced tremendous growth since the mid-1970s resulting in significant overloading of its existing sewerage system. Master planning determined that the best long-term wastewater collection and conveyance solution was construction of a deep tunnel sewer system. Implementation of this massive project faced numerous challenges, including the goal of no odours and limited odour control facilities. To accomplish this, the consultant team examined a unique approach of a single odour control system installed at the proposed downstream tunnel pumping station. Rigorous analysis utilising computer-based models confirmed the viability of this approach. However, other approaches including multiple satellite (localised or regional) odour extraction systems were considered. To better understand entrained air forces at vortex drops, and to confirm the preferred odour extraction approach, physical modelling of drop structures and overall tunnel system was implemented. Results and findings concluded that a regional odour extraction system approach was preferred over a single (centralised) extraction approach. This paper focuses on the process of selecting the preferred odour extraction approach and preliminary capacity sizing of regional systems.

Ribosomal RNA sequence analysis of Brucella infection misidentified as Ochrobactrum anthropi infection.

A Brucella isolate was identified from purulent material collected during a hip surgery. Two previous blood cultures from the same patient yielded Ochrobactrum anthropi. After rRNA sequencing, all the isolates were identified as Brucella species and subsequently serotyped as Brucella suis. Misidentification of Brucella species remains a problem with bacterial identification systems.