Cowden, Scott

Scott Cowden is a professional engineer with over 35 years of experience in the area of odor control applications for municipal wastewater treatment systems. His expertise includes both vapor phase and liquid phase technologies. He also has extensive experience in the area of odor control master-planning including site sampling, emissions modeling, and dispersion modeling. Mr. Cowden has designed vapor phase odor control systems from 500 cfm capacity to greater than 1,000,000 cfm capacity.

Titles from this speaker

Description: An Odor Attribution Study to Determine the Relative Contribution from Three Closely...

An Odor Attribution Study to Determine the Relative Contribution from Three Closely Located Facilities

Abstract

An Odor Attribution Study was undertaken for an Air Quality Management Agency that included gathering extensive data from specific sources and ambient locations to better understand odor impacts within the local communities. The study was 'one-of-a-kind' in that it combined multiple innovative techniques for identifying fingerprint odorants attributed to specific odor generating facilities. Odor has historically been an issue in this area for decades. Over the years, various odor mitigation approaches have been undertaken with varying degrees of success. While the number of odor complaints from residents has decreased in recent years from a peak of 3,500 in 2015, the high number of complaints (1,500) reported in 2018 indicates a persistent and ongoing odor issue. The odors in the area originate primarily from three closely located facilities including: -Facility A: An Anaerobic Organic Material Digestion Facility -Facility B: A Solid Waste Resource Recovery Park (a recycling facility, a composting facility, and a landfill) -Facility C: A Water Resource Recovery Facility (WRRF) Other natural sources were also considered (e.g.; bay, estuary). The goals of the project were to determine the contribution and variability of odor causing compounds from these facilities and develop a strategy for measuring how often and at what concentration these potential odor causing compounds may be passing into the local community. The study approach went beyond using the traditional, common practice of using odor threshold or odor intensity as the measure of odor nuisance. Instead, Weber-Fechner (persistency) curves were used as part of the Odor Profile Method (OPM) developed by Dr. Mel Suffet of the University of California-Los Angeles. The usefulness of the OPM lies in the fact that the human nose is, for the most important odorants, many degrees more sensitive than the standard chemical compound identification analytical methodologies. Examples of the OPM results are shown in Figure 1 and illustrate the odor intensity reduction with dilution (persistency curves) as well as the character of the dominate type of odors at each dilution (e.g.; musty, rancid, sweet). This illustrates how odor intensity and odor character changes as it travels from the different odor sources into the community, demonstrating the 'peeling the onion' phenomenon. The OPM approach was combined with comprehensive chemical compound identification analyses, lab olfactometric analyses, field olfactometry sampling, as well as a proton-transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) to provide targeted measurements of specific VOCs to identify chemical fingerprints associated with the different sources. Comprehensive chemical compound analyses resulted in the following key findings in terms of fingerprint odorant types attributed to each facility: -Facility A - Anaerobic Organic Material Digestion Facility: Sweet, Rancid, Musty -Facility B - Solid Waste Resource Recovery Park: Rancid, Sweet, Sulfur -Facility C - WRRF: Sulfur, Decaying Vegetables The field surveys using field olfactometers were undertaken on a regular basis over a period of 18 months. Figure 2 shows a BLOB map of the likely odor impacts in the community and the contributions to the odor intensity from each facility based on the odor character descriptions during the in-field odor olfactometric assessments. The PTR-TOF-MS provided real-time (1/sec) 'chemical fingerprints' of over 550 tracked compounds and showed that the plumes from each facility were unique for the key odor sources at the facilities and that the contribution of each facility could be quantified. Plumes and/or odors in the communities were also collected. The plume data (concentration and ratio between individual species) were then fed into Sartorius Multivariate Analysis (MVA) software to determine correlations between facility plumes and community plumes. The data correlations were determined using Principle Component Analysis (PCA) which identified where plumes within the communities originated, including the facility releasing them. It also confirmed the results that were obtained using the in-field olfactometric analyses, the OPM analyses, and the lab chemical analyses as well as the lab olfactometric analyses that the odor signature is unique for each facility. The findings provided a solid basis for developing a method to employ ongoing monitoring along each facility's fence line, or at other locations in the community. The preferred monitoring system would include multiple sensors, weather station, data processing and visualization platform, and auto bag sampler (at community locations). The autosampler would fill a bag sample for remote analysis by proton-transfer reaction (PTR). This successful study provided an improved understanding of the relative contribution of odor causing compounds from the three adjacent facilities by assigning specific fingerprint odorants to each and provided insight as to how the unique odorants impact the local community. These findings are considered essential to better: 1.Inform future actions to reduce odors (best practices, enforcement, rules) 2.Establish methods to measure progress on facilities' future odor reduction actions 3.Educate the community in terms of what's causing the odors, how complex they are, and teach them how to characterize odorants to better inform ongoing improvement efforts.

This paper was presented at the WEF Odors and Air Pollutants Conference, May 16-19, 2023.

SpeakerCowden, Scott

Presentation time

14:00:00

14:30:00

Session time

13:30:00

16:45:00

SessionYou Can't Manage What You Can't Measure

Session number3

Session locationCharlotte Convention Center, Charlotte, North Carolina, USA

TopicOdor Measurement, Monitoring, and Performance

Author(s)

S. Cowden

Author(s)S. Cowden 1; B. Kraakman 1; J. Bovee 2; P. Zemek 3; M. Suffet

Author affiliation(s)Jacobs1; Bay Area Air Quality Management District2; Montrose Environmental Group3; UCLA4

SourceProceedings of the Water Environment Federation

Document typeConference Paper

PublisherWater Environment Federation

Print publication date May 2023

DOI10.2175/193864718825158757

Volume / Issue

Content sourceOdors and Air Pollutants

Word count15

Cost of Being a Good Neighbor

Abstract

An iteration of this abstract was accepted at the previous WEF Odors and Air Pollutants conference and was eventually presented as a video presentation. However, due to very limited audience exposure as well as the desire to include additional good neighbor 'hot button' items into the paper (permit requirement and food waste impacts), I feel that the conference audience could benefit from 're-presenting' this paper in an expanded and updated form. As population densities increase and expanding residential areas encroach closer to water resource recovery facility (WRRF) property boundaries, less tolerant communities are steadily placing more pressure on facilities to implement 'good neighbor' policies. The term 'good neighbor' can apply to multiple criteria including odors, noise, or even safety. In the context of this paper the term pertains exclusively to odor and toxic emissions control. A benchmarking study was conducted in 2016 by the Air Quality and Odor Control Committee of the Water Environment Federation (WEF). In that study, top drivers urging odor control/management decisions were identified including external customers, regulatory, and internal goals. The study found that almost 50 percent of the agencies who participated in the study implemented odor control strategies that went beyond strictly regulatory requirements. The study also quantified costs associated with odor control for conveyance system and WRRF components which included both vapor phase and liquid phase treatment. Since costs are a function of population and system scale, all costs were normalized by dividing by population served and system scale (defined as millions of gallons per day [MGD] x miles of pipeline). Both Operation and Maintenance (O&M) costs and capital costs (5-year capital improvement costs) were included. This paper focuses on five top odor performing utilities in the United States and what they spend to maintain good neighbor status. These top performers were chosen based on the following criteria: Reputation: Recognized as good neighbors by the community. Top performers don't stop at regulatory requirements for preventing nuisances. They maintain a program of continuous improvement. Diversity: All four agencies utilize unique approaches to odor control; from greater emphasis on conveyance system mitigation to greater emphasis on WRRF vapor phase systems to somewhere in the middle. This swath of approaches provides excellent comparison and allows for broader representation. Sensitivity: All four agencies are located in relatively sensitive urban locations and therefore must comply with strict regulatory as well as local requirements Costs related to odor control management for each agency were quantified and broken down into the following categories: Infrastructure capital costs (CAPEX) (based on today's dollars) for both conveyance and WRRF Direct O&M costs (OPEX) pertaining to maintenance, chemical dosing, and utility costs including electrical and water for both conveyance and WRRF Indirect OPEX Some differences between this study and the previous study include the following: OPEX in this study include indirect costs such as chemical sludge processing and hauling, chemical dosing to accommodate settling problems associated with volatile fatty acids (VFAs), additional scum pumping, and various maintenance process related maintenance activities CAPEX in this study were calculated based on existing odor control infrastructure converted to today's dollars versus 5-year capital improvement costs Cost metrics for this study were developed based on per capita (i.e.; population) and MGD versus per capita and system scale (i.e.; MGD mile) Data from the WEF study relied on numerous survey responses. This study is based on a limited number of performers and therefore takes on a more case study approach for supplementing the benchmarking study. Understanding the relative costs, cost metrics, and individual cost proportions can assist utilities in understanding where they stand and areas where there may be room for improvement or optimization. This paper discusses how the approaches of the best agency programs differ from more typical agencies as well as lessons learned from these top performers. Results of this study will prompt other agencies to ask the following key questions. How much do you spend to prevent and remedy the offsite environmental impact of your operations? Is it enough? Is the money being spent in the places where it can have the most benefit? Do you think you can do better? No two WRRFs are alike and what works for one facility might not work for another. There are differences in flow, population served, population density, climate/temperature, age and condition of infrastructure, characterization of the influent, community sensitivity, offsite odor goals, and other factors. However, there are best practices, approaches, and decisions that are common among the best performing utilities in how they minimize their off-site odor impact. This study examines holistic approaches used by top performing agencies for balancing CAPEX and OPEX for conveyance systems with those of downstream WRRFs to reduce overall odor impact. Consequences of offsite odor goal selection have a direct impact on CAPEX and OPEX related to implementation of an odor management program. More stringent odor standards result in higher present-worth costs because more stringent standards typically require larger, more expensive odor control systems that consume greater amounts of labor and energy and other consumables (e.g., chemicals, media, etc.). A representative graph of offsite odor complaints versus present-worth costs is provided in Exhibit A that shows that reducing complaints to near zero becomes exponentially more costly. Similarly, other Agency-unique and regional/localized issues can also have a direct impact on CAPEX and OPEX including permitting requirements, extent and configuration of collection system, plant processes, and high odor emitting sources including food waste receiving. Knowing where to spend odor control dollars must begin with understanding the sources of odor at a WRRF or in the conveyance network. In part, this comes from process knowledge, but measurement, monitoring, and even modeling play a critical role in informing these decisions. What may be considered 'hidden' costs are presented in this study. For example, septic plant influent can exhibit high levels of volatile fatty acids (VFAs) which can lead to problematic filamentous sludge bulking at primaries. This can in turn require additional polymer usage at downstream biosolids processes impacting costs. Certain liquid phase chemical treatment technologies can prevent septicity while others simply treat the septic sewage by removing dissolved sulfides. Understanding these hidden costs can help in implementing the best options as part of one's odor control program. A breakdown of per capita annual costs for all five agencies are provided in Exhibit B. Agency names remain anonymous while locations and specific characteristics are provided. Agencies are described as follows: PNW: Pacific Northwest agency NV: Nevada agency NoCal: Northern California agency SoCal: Southern California agency EAS: South-Eastern agency

The following conference paper was presented at Odors and Air Pollutants 2021: A Virtual Event, April 20-22, 2021.

SpeakerCowden, Scott

Presentation time

15:00:00

15:20:00

Session time

15:00:00

16:30:00

SessionPlanning the Odors Away

Session number3

Session locationLive

TopicCapital Planning, Cost of odor impact, Odor/Air Emissions