New Frontiers For Odor Research

From BioCycle
Journal of Composting &Organics Recycling
September 2001, Page 46

ADVANCING THE SCIENCE
NEW FRONTIERS FOR ODOR RESEARCH
Identifying the causes of odor at wastewater treatment plants is rapidly advancing the knowledge of how to minimize odors in biosolids, and is providing valuable tools and insights for project operators handling all types of organic residuals.
Nora Goldstein

WHEN Richard Giani started in the Biosolids Section for the Division of Wastewater Management in the Pennsylvania Department of Environmental Protection (PADEP), he quickly learned that the majority of complaints regarding land application of biosolids centered around odors. “I asked if there weren’t odor complaints, how much the complaints would be knocked down,” Giani recalls. “The response was, ‘at least 90 percent.’”

Unlike biosolids quality and control parameters such as pollutant limits and pathogen and vector attraction reduction, management of odors does not lend itself to a regulatory framework. The science and technology for accurately collecting and analyzing odor emissions are not fully mature. Even if regulatory limits were set, adequate methods for controlling and measuring odors from biosolids have yet to be demonstrated. In addition, there is still a fair amount of subjectivity in determining levels of nuisance and what is objectionable.

Still, because of the universality of odor generation from biosolids, state and federal agencies have been under pressure to develop odor “standards” for the land application of biosolids. Significant progress has been made controlling odors from biosolids composting operations, and steps have been taken to minimize odors at land application sites themselves, e.g. provide storage if fields are inaccessible, develop adequate buffers, being sensitive to wind direction, incorporating applied biosolids, etc. While these measures help, there has been growing consensus over the past few years that the key to controlling odors at land application sites is to control the odors in the biosolids themselves. And that can only be done effectively at the wastewater treatment plant – the point of generation.

Because many states face these odor dilemmas, some agencies are supporting research that focuses on creating tools to provide biosolids treatment facilities with standardized methods to index and catalogue odors associated with present treatment processes. In conjunction with these tools, there are several projects investigating techniques aimed at minimizing odors during the treatment process, subsequently reducing odor emissions in the field.

IDENTIFYING THE ISSUES

In November, 1999, the U.S. Environmental Protection Agency sponsored a two-day workshop, “Operations and Design To Control Ultimate Recycling and Disposal Odors of Biosolids,” in Potomac, Maryland. The invitation-only workshop was designed to identify research and information needs on how the design and operation of waste-water treatment plants and solids processing impacts the potential for biosolids to produce or not to produce odors at the point of recycling or disposal. The sessions focused on the following issues: Links between wastewater treatment plant (WWTP) management to off-site management; The psychology and politics of odors in the field and in transport; Odor precursors, monitoring and standards; WWTP operations and design practices; Transport and field practice including storage; and Land application contracts.

Participants in each session were asked to define the issues and goals, describe the current knowledge, report on good practices and research needs, and contribute to a bibliography on this subject matter. Workshop organizers emphasized the link between the outcome of the workshop and the National Biosolids Partnership’s Environmental Management System (EMS) initiative for biosolids. Part of the EMS implementation process is to identify critical control points within the treatment plant and biosolids management program. States a publication of the workshop: “An important thesis of the workshop is that one important critical control point for odor management is within the wastewater treatment plant. This critical control point for odor at the treatment plant involves issues associated with design and operation and requires close linkages among operations at the treatment plant and the subsequent processing and ultimate recycling or disposal practices.”

Giani attended the workshop, anticipating he would be tapping into some important research findings and field experiences. “What I had expected to find wasn’t there,” he says. “And I wasn’t alone in that discovery. But what did happen at that workshop was that the lack of concrete information set the research tone for what should be happening. We were able to learn what research was being conducted and what needed to be focused on from an operations standpoint. We walked away with questions such as how do we create a standard to measure odors.”

DEVELOPING, TESTING AN ODOR INDEX

Giani wanted to get the research ball rolling, and connected with Dr. Bradley Striebig of The Applied Research Laboratory at The Pennsylvania State University (Penn State). Striebig already had carried out some research on analytical tools to measure and quantify odors related to the landfilling of biosolids. The PADEP applied to the U.S. EPA Region 3 office for a grant to work with Penn State. The goal of this research is to create a standardized method for odor measurement. Facilities and research scientists can use the method to develop treatment processes and management tools for odor control (including an odor index for a treatment plant).

Funding was received from the EPA Region 3 office; additional funding in 2001 is expected from both Regions 2 and 3. Striebig and Giani are the principal investigators for the project, which runs through December 2002. Phase I, which is near completion, involved developing a standard analysis procedure for collecting and analyzing samples (yielding data to develop an odor index). Phase II, underway now, involves collecting odor samples and applying an odor index at the facility level. The odor index also is being tested for comparison with olfactometry methods that involve a human odor panel that characterizes the intensity of the odor. Ned Ostojic from Odor Science & Engineering, Inc., with the support of Synagro, Inc., will be studying these comparisons.

A key goal of the PADEP/Penn State research is to create a tool to compare processes within a WWTP — from the sewer pipes and influent end through to solids processing — and between WWTPs with similar technologies. “The odor index is related to a specific sample,” explains Striebig. “It involves coming up with one number at one point in time that is fairly representative of an odor so that the sample can be catalogued and compared to other samples as the data comes in from the facilities taking measurements. The process we utilize is to collect an air sample in a container and draw the air into a chemical analysis system that concentrates and separates the chemicals for identification. The purpose of our tool is to help define the chemistry and chemical complexity of the odor, then the WWTP can identify the odors that are most problematic and specifically address processes to minimize their problem. At this point, I view the odor index as a visualization tool. It’s not accurate enough to say this number will cause a complaint and this number will not. However, if we can tie those numbers to olfactometry information, then the process can be standardized.” (See sidebar.)

Chris Peot, biosolids manager for the District of Columbia Washington Area Sanitary Authority (DCWASA), has tested the odor index and provided data to the PADEP and Penn State. “Putting the psychological/olfactometry together with the analytical will let us know if we will be improving odors,” says Peot.

The general methodology developed in Phase I will be included in a report that Striebig expects to submit to the PADEP by the end of 2001. In the meantime, Giani and Striebig and several graduate students are taking measurements at different WWTPs within EPA Regions 2 and 3 and feeding that into a data base. They only are sampling at facilities managing biosolids through beneficial use practices as the overall goal is to address complaints that come in from the field. “We are looking at what we can do to this product before it leaves the WWTP to go out into the field,” says Giani. “How can we make it the best it can be before it leaves the gates, because if it’s odorous at the WWTP, it most likely will be odorous at the land application site.”

ODOR SAMPLING

Because of limited funding resources, sampling is being narrowed to specific plants. Facilities are identified through the EPA regional offices and the state biosolids coordinators. Facilities are then chosen based on specific types of biosolids treatments and intensities of odors emitted (or not emitted) from their final product. “We ask them to give us plants with and without odor problems,” he adds. “Then we will pick out three or four on that list and work with the states to decide where to go. Facilities that are not selected, or that are not in EPA Regions 2 and 3, are encouraged to participate in the project if they are interested. These particular plants may need to find ways to raise their own funds or solicit their particular state or EPA region to help provide funding.”

Air, liquid and/or solids samples are taken from the wastewater solids treatment train, usually starting with the thickeners and through every subsequent process (including composting if done at the same site). Interviews also are done with the operators to obtain an understanding of the entire WWTP operations and water quality data (i.e., percent solids, BOD, pH, total suspended solids, etc.). Samples are brought to the Applied Research Lab at Penn State within 24 hours for analysis. “We analyze the samples for a wide variety of odors including sulfur-based compounds, nitrogen-based compounds and organic acids,” says Striebig. “Because we are trying to do all of these, the limits for detection are not as good as if we were focusing on only one constituent. We do a general analysis and try to determine concentrations and then compare those to referenced odor thresholds in the literature. That gives us the odor index value over a range of samples — a value associated with a sample so it can be tracked from the holding tank for wastewater solids to the digester and any further handling.”

The goal is to get as many WWTPs as possible feeding into the data base, especially plants that are using the same treatment technologies but are having different experiences in terms of odors. “If one has an odorous product and the other does not, we can get an odor index for both, break down the compounds and compare the concentrations,” says Giani. “The next step is to backtrack using various parameters, e.g., water quality, chemicals added and in what concentration, storage time at various points in the process, and try to pinpoint the differences and hopefully the cause of the odors. Basically, we will have a stack of data for each plant, and the idea is to enter it into a data base and analyze the difference because we know, odor index wise, that there is a difference. The goal is to identify the difference and relay that information to the plant, where in turn, the operator can focus troubleshooting efforts. There are facilities that know they are having problems with odors, but don’t know how to start to address the situation. Conducting on-site sampling and developing an odor index gets them started down the road to a solution.”

As the sampling is done, the researchers will start to identify what are the most important measurements to take and what interferences there may be. The key is to get to a point where the methodology is acceptable for a wide variety of applications and odors.

Striebig emphasizes that the PADEP/ Penn State project does not involve development of new analytical techniques, but instead is based on the idea of communication and agreeing upon a method to evaluate the data. “The analytical technology isn’t cutting edge but communication and coordination is allowing us to provide a useful tool. If we were doing this in a vacuum, for example, just giving the method to the DEP and only Pennsylvania WWTPs used it, we couldn’t compare how well it worked. The communication and sharing aspects are inherent in the obligations of our contract.” Facilities have to make a commitment to share the data gathered in return for receiving information from other WWTPs.

Eventually, there will be enough data available to identify patterns that lead to odor production or which minimize odors. “If we do enough systems, we expect to see patterns repeating, especially if a facility makes a change and that gets measured in the odor index,” says Giani. “We will have the information captured and it can be shared.”

While it isn’t a requirement, Striebig recommends that a WWTP do a preliminary assessment and sampling of odor sources to develop a baseline for odors associated with their products. That assessment should be done with fairly sophisticated analytical equipment and analyzed in a laboratory. “Once that is done, operators will know what specific compounds are most likely to cause a problem,” he says. “Then they can focus on testing for that particular chemical, which is more cost-effective.”

ODOR RESEARCH GROUP

Through contacts made at the EPA odor workshop in 1999 as well as through other avenues, Giani and Striebig became familiar with other research initiatives that directly relate to their project. At the invitation of Dr. Sudhir Murthy of CH2M Hill, who is working with DCWASA, researchers from all of these projects met at the Blue Plains Pollution Control Facility (Blue Plains) in Washington, D.C. to share information. Many of these individuals participated in the EPA odor workshop and also recognized the need for research or were already undertaking the research. The other projects are described below:

New Analytical Methods for Fast Odor Measurements: Dr. Laura McConnell and Dr. Hyunook Kim of the U.S. Department of Agriculture (USDA), in support of biosolids research being performed at Blue Plains, are working to develop fast, sensitive methods to accurately measure key odor chemicals such as dimethyldisulfide and trimethylamine from sludge, wastewater, biosolids and composts. These methods are being utilized at Blue Plains to study odors and odor intensities caused by different unit processes. This group also is involved in studying odors released from compost production and heat dried biosolids material.

Process Control: Several projects are underway that are investigating digestion, dewatering and conveyance techniques and their effects on odor emissions from biosolids. Dr. Matt Higgins (Bucknell University), Dr. John Novak (Virginia Tech) and Dr. Sudhir Murthy (CH2M Hill) are the lead project scientists. Their work focuses on optimizing digested solids with respect to dewatering and odors. The research is supported by DCWASA at Blue Plains and the Philadelphia Water Department at its Biosolids Recycling Center, where some preliminary research has occurred. Murthy and Chris Peot from DCWASA also have been evaluating the mechanisms responsible for generating odorous compounds in both digested and lime stabilized biosolids. (See sidebar for summary of research and findings to date at Blue Plains.) Others are working on the contribution of polymers to biosolids odors. Steve Dentel and Peter Griffin from the University of Delaware along with Mohammad Abu-Orf from U.S. Filter, are studying the mechanisms of polymer chemistry that generate odors, specifically polymer breakdown in lime-stabilized biosolids and resulting amine generation.

Realizing the similarity of the overall goal and the relationships that each project has to one another, the project managers mentioned above (and including Giani and Striebig), decided to form an odors research group. This group, facilitated by Giani and John Walker of USEPA, meets quarterly to share data and experiences relating to their specific projects. Between meetings, investigators also are collaborating on projects in the field, in some cases testing research concepts that were presented at their meetings. This type of support allows resources to be shared and provides an enormous amount of expertise that is available for data collection, analysis and eventual implementation. Each project adds an important piece to the odor generation and management puzzle, and maximizes the research dollars being invested.

The overall goals of the group are to: Gain a better understanding of the compounds responsible for odors in biosolids; Understand the conditions at the plant that promote production of these compounds; Evaluate the mechanisms responsible for generating these compounds; and Determine the critical control points in the treatment process and the process parameters that can be monitored to help predict and prevent nuisance odors. It was decided that in order to compare sampling data collected from the various research experiments, that everyone should be using the same types of methodology. Methodologies like those being developed by Penn State are being utilized by the research group.

One of the concerns about involving EPA and state regulatory personnel in the group was the perception that the goal was to work toward regulatory limits for odor emissions. “The science really isn’t there to regulate odors,” notes Peot. “But in the process of getting various states involved with sampling at WWTPs, biosolids coordinators and regulators are seeing what is going on at plants and learning along with everyone else. They are seeing that the outcome of this process shouldn’t be a regulation.”

The group also has managed to sidestep the competitiveness and intellectual property issues often associated with research. “What we have are universities, companies and government agencies involved and what it all came down to is there is a lot of work to be done,” adds Giani. “To get a complete study done, the reality is that we should be working together, which has helped in getting around the standard competitiveness of research.” Adds Peot: “Naturally, people like to protect interests and intellectual property, but everyone has been very open.”

The odor research group will consider other research proposals from WWTPs or a group of WWTPs if the financing is available to support the work. “The more facilities that come on board, the more situations we can look at and learn from,” says Giani. “In turn, facilities can take advantage of various expertise and benefit from the focus of the whole group.”

Most projects’ results will be published individually over the next two years. At the end of 2002, the group hopes to provide a compilation of all the research conducted into a manual that can be used as a management tool for facility managers, design engineers and government agencies to control and optimize odors emitted from biosolids products.

For more information, contact Richard Giani, Pennsylvania Department of Environmental Protection, Division of Wastewater Management; rgiani@state.pa.us.

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