For Equivalency Recommendation by the U.S. EPA’s Pathogen Equivalency Committee (PEC)
The following outline is provided as guidance for preparing a full application for an equivalency recommendation as part of the Pathogen Reduction Equivalency Package (Section K). Download Equivalency Application Package (Word)(7 pp, 162 K) , which is a fill-in form of the Package. Inadequate information will delay the review process. The submitted application should be made as complete as possible by including all of the applicable information requested. (For more information on how to apply)
Table of Contents
- Provide a general overview of the disinfection process.
- Include the full name and any acronyms or trade names used for the process.
- Very briefly describe the basic disinfection method that is the basis for the process’ effectiveness (e.g., change in pH, change in temperature for a period of time, chemical addition, etc.).
- Clearly identify the purpose of the application, especially in regards to the following:
- Type of equivalency recommendation sought.
– Process to Significantly Reduce Pathogens (PSRP)
– Process to Further Reduce Pathogens (PFRP)
- Level of equivalency recommendation sought – Is the disinfection process to be used at a particular site (site-specific equivalency) or is it intended for national usage (national equivalency)?
- Type of equivalency recommendation sought.
- Briefly describe the plant or plants at which the process was tested, delineating exactly where the process was located in the treatment train. Use of diagrams is encouraged. The relative scale of the process should be indicated.
2.0 Process Description
- Summarize all pertinent background material regarding the basic disinfection method and the process itself. This section should include theoretical rationale for why the process will reduce pathogens.
- Break the process down into key steps, providing definitions for any uncommonly used terms. Graphically display these steps, if possible, in a quantified flow diagram that shows all inputs and outputs along with their relative mass or volume. Indicate whether the treatment process under consideration constitutes the entire sludge treatment process or only a portion of it. If only a portion, specify which steps are to be included in the review for PSRP or PFRP equivalency consideration.
- Describe the materials/additives that are used in the process. Provide specifications for these materials as appropriate (MSDS, etc.).
- Specify the treatment type (batch or continuous process) and the capacity or size of the treatment units.
- Provide sufficient information for a mass balance calculation, such as actual or relative volumetric flows and solids concentration in and out for all streams and additive rates for bulking agents or other additives.
- Provide a description of the process parameters for each step of the process, giving typical ranges and mean values where appropriate. The specific process parameters discussed will depend on the treatment process. However, the following examples of process parameters are likely to affect pathogen reduction or process reliability and therefore should be included in the process description:
- Residence/detention time
- Organic loading rate (e.g., kg volatile solids/m3/day)
- Operating temperature(s) (including maximum, minimum, and mean temperatures)
- Operating pressure(s) if greater than ambient
- Types of chemical additives and their loading rates
- Mixing procedures
- Aerobic vs. anaerobic conditions
- Duration/frequency of aeration (if appropriate)
- Dissolved oxygen level maintained (if appropriate)
- Depth of sludge
- Duration and type of storage (e.g., aerated vs. non-aerated)
- Describe how each of the relevant process parameters is monitored and the process’ uniformity and reliability. Provide actual monitoring data when appropriate.
- State whether the sludge must be previously treated in a certain way, such as by anaerobic, aerobic digestion, or pH adjustment before entering the proposed treatment process.
- Describe the climate at the location of the sludge sampling/testing. Important climatic factors may include:
- Ambient temperature (average and range) over the course of sampling
- Ambient seasonal temperatures (averages and ranges)
- Precipitation (both seasonal averages and the average over the coarse of sampling)
- Humidity (both seasonal averages and the average over the coarse of sampling)
- Solar radiation
- Wind speed, direction, and fetch, if applicable
- Discuss the possible affects these parameters may have on the efficiency or reliability of the process. Provide supporting data if necessary.
4.0 Experimental Approach
Put some thought into the experimental approach and sampling procedures. In addition to the results from sampling, the PEC will evaluate the approach’s overall design including representativeness of the samples and the adequacy of the sampling techniques.
- Describe the following key points of the experimental approach (use diagrams and tables where applicable):
- The general approach and the test conditions for each experimental phase
- All details of the experimental design and/or sampling strategy
- If spiking is necessary, provide a detailed description of the spiking method. The spiking description should include:
- Source of spiking stock (It is recommended that Ascaris eggs for this purpose be obtained from fecal discharges of humans or pigs since these eggs will have developed maximum hardiness.)
- Any techniques used in preparation and storage of the spike
- Method of adding the spike to the process feed (include when and where with respect to the treatment process, the amounts added and the target concentrations, method of ensuring uniform incorporation, etc.)
- Location of sample collection—The sampling points should correspond to the beginning and end of the treatment process, as defined previously in Section 2.0.
- The frequency of sampling/monitoring events, as well as the number of samples for each sample type and/or location, including quality control (QC) and reserve samples
- All measurements or parameters of interest (i.e., analytical [e.g., chemical, microbiological, assays], physical [e.g., temperature], and process [e.g., flow rate]) for each sample
- Evidence demonstrating that the design/strategy was appropriate to support process equivalency, i.e., a description of the statistical method or scientific rationale used to select sample sites, number of sampling events, number of replicates per sample, and sample timing. The experimental design should include sampling under all possible operating conditions, especially under those least favorable, such as wintertime.
5.0 Sampling Procedures
- Describe the following key points of the sampling procedures (use tables where applicable):
- General sampling monitoring procedures
- Sampling methods used (grab vs. composite) - If composite, how were the individual samples taken, and how many samples were compiled?
- Sampling equipment used, if any, and the measures taken to ensure cross-contamination between samples is avoided
- Sample sizes and sub-sampling procedures, if any
- Sample containers used (type, cleaning, and pretreatment, if any)
- Sample handling, preservation, packaging, and transportation or shipping procedures
- Sample holding time requirements
- Discuss the representativeness of the sampling procedure:
- Include any steps taken to ensure the samples were representative of the sewage sludge as it entered and left the disinfection process. For example, was it considered necessary to allow for processing time?
- If samples were taken from a pile, include a schematic of the pile and indicate where the sub-samples were taken.
- Discuss how the dates and times of sample collection related to important process parameters that could affect the results of their analysis (e.g., turning over, beginning of drying)
- Report the amount of time that elapsed between sampling and analysis and how this relates to the sample holding time requirements. Holding time requirements can be found in the analytical procedures for each microbiological contaminant.
6.0 Analytical Methods
- Identify the analytical methods used. Identify standard or EPA-approved methods by number. Describe any non-standard methods in detail. Methods preferred by the PEC are published in Environmental regulations and technology: control of pathogens and vector attraction in sewer sludge, Report #EPA 625/R-92/013 (U.S. EPA, 2003). See EPA-625-R-92-013 Appendices section for a link to these methods.
- Any deviation from referenced methods must be reported/indicated and discussed.
- Detection limits for each analytical method must be reported.
7.0 Quality Assurance/Quality Control
- Discuss the QA objectives for each analyte/organism and/or the project as a whole associated with accuracy (matrix spikes), precision (agreement of replicate analyses), detection limits, and completeness for critical measurements, as well as any split sampling events or project-specific QA criteria. The discussion should include a comparison of the collected data to predetermined quantitative acceptance criteria for each specified QA objective. If at any time the QA objectives were not met, the discussion should also include a description of the corrective actions performed. Tabularized summaries are encouraged.
- Discuss the QC measures taken for each analyte/organism and/or the project as a whole (e.g., negative and positive controls, field blanks, laboratory blanks, etc.). The discussion should include a comparison of the collected data to predetermined quantitative acceptance criteria for each QC measure. If at any time the quantitative acceptance criteria were not met, the discussion should also include a description of the corrective actions performed. Tabularized summaries are encouraged.
- Identify the qualifications of the in-house or contract laboratory staff used. Their experience in analyzing sludge samples for the organisms/analytes included in the study should be presented.
8.0 Analytical Results
- Provide a discussion of the results. Support your discussion and conclusions with summaries of the analytical results in tabular form or graphically where appropriate. All tables and graphs should be appropriately labeled with headings (tables) or captions (figures). Do not present a table or graph without a detailed description and adequate interpretation of the data within the report text. Examples of results that should be presented in this section are detailed in the bullets.
- Monitored Characteristics – Describe the results of any monitored process parameters. Information should include, but not be limited by, the following:
- Means or averages in process parameters
- Ranges and stability/variability in the data collected
- Comparison of observed data to expected data
- Any trends observed (e.g., diurnal temperature swings)
- Any upsets and what was done to correct the situation
- Physical Characteristics – Describe in detail the sewage sludge that was used in testing the treatment process, before and after treatment. The following criteria as well as any other sludge characteristics that may affect the efficiency of the treatment process being evaluated should be addressed:
- Sludge type(s) (unstabilized vs. stabilized, primary vs. secondary, domestic vs. industrial, activated sludge treatment process, etc.)
- Sludge age
- Sludge quantity as compared to sample size
- Chemical characteristics of the untreated sludge (as they affect pathogen survival/destruction)
- Possibility of the formation of harmful byproducts
- Temperature of sludge before and after treatment (both at time of sampling and analysis)
- Moisture/total solids content of sludge before and after treatment
- Total suspended solids of sludge before and after treatment
- Volatile solids content of sludge before and after treatment
- Microbiological Characteristics – Describe in detail the results of all microbiological analyses. Each of the following points should be presented:
- The distribution of both influent and effluent sludge samples and the variability experienced (minimum, maximum, variance)
- Any exceedances in the target effluent concentrations (number and percentage of samples)
- Log reductions (mean, minimum, maximum, variance)
- All results must be presented in the appropriate units (fecal coliform, # per gram of total solids (dry weight); Salmonella sp., enteric viruses, and viable helminth ova, # per 4 grams of total solids (dry weight))
9.0 Rationale for Equivalency Recommendation
- Restate the type and scope of equivalency being sought.
- Summarize all supporting information from the literature on why the process qualifies for equivalency.
- Summarize the microbiological data presented in section 9.0 that supports consistent achievement of the target log reductions and effluent concentrations.
- Review particular aspects of the process that contribute to pathogen reduction and summarize the monitoring data presented in section 9.0 that support expectations of consistent operation of the process.
- Discuss why the process’ effectiveness is expected to be independent of the location of operation if national equivalency is being sought.
Raw data and any other supporting documentation