Electronic noses detect odours at wastewater treatment plant
The first permanent US installation of a unique technology that can actually “smell” an odor problem before it occurs has been on line in Tucson, Arizona, since 2009.
The Roger Road Wastewater Reclamation Facility (RRWRF) –TucsonAZ-is an older 41-MGD secondary wastewater treatment facility. Last upgraded and expanded in 1985, the Roger Road WRF was well known for having odor emission problems. Pima County Regional Wastewater reclamation Department completed in 2007 over 7-million dollars worth of odor control improvements at the facility. The facility is located along the banks of the Santa CruzRiverwash, at the base of theTucson Mountainsand adjacent to the I-10 Freeway.
This plant has odor emission sources:
As mentionned by Mr. Dennis Froehlich MS PE, System Wide Odor Control, Engineering Manager,Pima County, during his last presentation at the WEF 2012 Odors & Air Pollutants conference (The Relative Benefits of Dynamic vs Steady-State Continuous Odor Emissions Dispersion Monitoring for Multiple Sources) ''All of these sources have in common one characteristic: significant intermittent (read: dynamic) emissions driven by diurnal fluctuations in the plant processes and local meteorological conditions. So first they have to be identified and then quantified before they can be constructively addressed with a control plan. This meant continuous emissions monitoring.''
In January 2009, the OdoWatch Odor Continuous Monitoring System was installed for source emissions and controls monitoring to provide operators a consistent means of odor event awareness, process issue identification, and receptor impact estimation.
This system continuous emission monitoring system, the Odowatch System, employs a network of electronic noses monitoring odor and a local 10-meter tower with a meteorological station transmitting continuous emissions and met data via radio to a signal transceiver and router sending the data to a central modeling server. This server uses the data to update a locally calibrated Aermod dispersion model and serve the data in realtime to a windowing webpage presenting all of the data, plume map, alerts, and configuration data in four windows. This system also provides user configurable sampling locations where odor data at a given location are estimated from them model and saved.
OdoWatch®, operational at the Roger Road Wastewater Reclamation Facility, where six e-noses (electronic noses) calibrated to smell odors like the human nose are installed at the facility. The unit performs real-time air dispersion modelling to generate a colour-coded plume indicating the level of odour on a map of the site.
The odor monitoring system is capable monitoring facility’s compliance performance in terms of odor concentrations for nuisance threshold at fenceline, assumed as 7 D/T.
The odor is quantified by the system, and if the level begins to approach the threshold that can be perceived as a nuisance by a human nose, an alert notifies operators that actions must be taken to mitigate the situation. OdoWatch® can also be used to determine which source at a facility is causing the alert.
Mr. Froehlich reported that ''...this system is clearly state of the art... As a result of the monitoring, between 2009 and 2011, the low-pressure digester gas system was rebuilt, a flare shroud was designed and installed to shield the laminar flame from winds, and a chemical feed system was improved for chemical sulfide control in the primary clarifiers.''