Update on Status of Microbial Performance Based Training

By Bob A. Hegg and Larry D. DeMers – Process Applications, Inc.  

BACKGROUND:  The Microbial Performance Based Training approach is a key Targeted Performance Improvement tool used by the AWOP network to allow operators and managers at water utilities to achieve the full capability and performance potential of their existing facilities.   This protocol, originally piloted in 1999 has been demonstrated on a broad scale (an estimated 22 states and 200 water utilities) and has documented performance data available as well as documented state and operator skill improvement available to show overall impact.  From a microbial perspective operational skills for participating facilities have been enhanced to allow utilities to aggressively pursue optimized performance goals for filters of <0.10 NTU.  The protocol has impacted the way training is done for water utilities in many states.  In addition the protocol is being developed to apply to disinfection by-product and groundwater optimization efforts.  The purpose of this article is to provide an overview of the significant enhancements to the protocol that have occurred over the last ten plus years of PBT experience.  

CURRENT STATUS:  The current PBT approach has evolved and been enhanced with almost each training series that has been conducted, however, the basic protocol that was developed over 10 years ago has remained the same.  The protocol is applied at multiple treatment plants using a multi-faceted long-term training process.  Five strategic centralized training sessions are used to introduce key optimization concepts and skills to representatives from each of the participating plants and to facilitators.  The sessions are conducted over a 12 to15 month period.  The training emphasis of each session is:  Session 1 – Adopt Goals and Assess Data, Session 2 – Developing Priority Setting and Problem Solving Skills, Session 3 – Coagulation Control Tool Development, Session 4 – Assessing Current Plant Performance/Applying Skills and Tools, Session 5 – Reporting on Success.  

Between the training sessions, training facilitators work with the individual plants through limited site visits and phone contact to encourage implementation of the concepts and skills presented during the training sessions.  The impact of project activities on plant performance is measured by comparing turbidity data for the one-year periods before, during, and after the projects.    

ENHANCEMENTS:  Enhancements made to the training protocol have been based on an expanded experience base in implementing the protocol.  Some of the significant enhancements will be described in more detail in this article.  

  • Facilitator Training Session:  It was recognized after several initial PBT efforts that facilitator training was just as important during PBT as training for the actual utility personnel.  It was also recognized that facilitation skills vary widely.  Currently a formal one and ½ day facilitator training session has been developed and implemented.  This session focuses on providing an overview of PBT, teaching facilitation skills such as avoiding troubleshooting, teaching the facilitators how to obtain initial jar calibration settings for a utility, recognizing sampling challenges to supporting PBT data collection, and identifying on site activities.  Additionally this training is supplemented by phone consultation and routine facilitator/trainer conference calls throughout the PBT effort.  An associated major change has been that the jar test calibration spreadsheet is no longer taught or introduced in the training sessions.  Alternatively, facilitators are trained on using the spreadsheet, and they collect the necessary data and determine the initial settings.  The facilitators provide this information to their utility participants during or shortly after Session 3.  The utility staff is trained to “tweak” these settings using special studies to make the jar test tool specific to their plant.  As a component of the facilitator training session, a plant is visited and the initial jar calibration parameters are calculated using the jar test spreadsheet.  The facilitators that have been through this training have commented positively on the support this provides for their efforts.
  • Filter Backwash Performance Trending Spreadsheet:  This spreadsheet has been added to PBT and is used to collect data from participating PBT facilities on post filter backwash performance.  The spreadsheet was previously described in the August 2009 issue of AWOP News.  An example graph from the spreadsheet is shown in Figure 1

Figure 1: Example Spreadsheet Chart Showing Multiple Days of Backwash Recovery Data


  • Session 2 Homework:  Session 2 covers development of priority setting and problem solving skills.  The concept of special studies is introduced in this session, and the related homework assignment is to conduct two special studies.  In response to consistent feedback that the participants like visiting other facilities, assignments are now made to pair up the utilities and have them jointly conduct one of their special studies together.  For those ‘partner’ plants that have been able to complete the exchange of special study efforts the feedback has been positive.  The quality of the joint special studies has also improved.  It has been a challenge for some of the partner utilities to find the time to complete the joint efforts.
  • Session 2 and Session 3 Workshops:  The data collection for the workshops associated with Session 2 and Session 3 has been modified to be very prescriptive (e.g., data collection tables are provided in the workshops with the number and time for sampling specified).  This has allowed the data to be compiled during the workshops and graphically displayed at the end to enhance data interpretation during the training sessions, a critical skill needed for problem solving.
  • Session 3 Quality Control Special Study:  As a jar test calibration workshop activity during Session 3, some of the participants are requested to complete a quality control special study.  This study involves collecting equal amounts of raw water in two jars (2L each), adding equal amounts of coagulants at the same time and mixing simultaneously with equal amount of energy.  Once the mixing is complete, the water is drawn out at the same time from both jars at predetermined time intervals (i.e., 0, 1, 2,  4, 6, 8, and 10 min) and measured for turbidity.  Graphs (settling curves) are developed for each jar by plotting turbidity vs. time, and the results are then compared with each other.  If reproducible results cannot be achieved, then jar test techniques need to be developed further before the next steps of jar test calibration can be pursued. 

Variability in jar test results can occur for a variety of reasons such as:   

  • Inconsistency with filling up the jars to 2L mark with raw water
  • Inconsistency with dosing the exact amount of coagulant 
  • Inconsistency with opening the jar valves (taps) for sampling
  • Variability in the optical sensitivity of the round sample cells
  • Turbidity meter variability
  • Inconsistent mixing of samples before measuring turbidity

Despite these variations, proper technique should allow similar curves to be developed.  A spreadsheet-based tool has been developed to allow a comparison of settling curve results.  Two methods have been developed to determine how well settling curves match each other.  The first method assumes that the two settling curves are similar (i.e., they match) if the data fall within a range of +/- 15 percent of the average of the two curves.  Another method uses the development of an “Absolute Difference Ratio” to assess the similarity of the developed curves.  The data collected to date indi­cates that a ratio of less than 1.0 and preferably less than 0.7 indicates good quality control and settling curves that match each other.  This 15 percent difference and the ratio are automatically calcu­lated when the data is entered into the jar test calibration spreadsheet.  The objective is to work on jar testing technique until settling curves that are similar to each other can be developed (i.e., meet the +/- 15 percent criteria or meet the < 0.7 ratio).  Figure 2 shows results demon­strating good jar testing tech­nique.   


FIGURE 2. Example of Settling Curves That Demonstrate



  • PBT Follow-up Meetings:  A PBT follow-up session (i.e., 1 year later) was initiated with the Idaho PBT series in 2006 and a similar session was added to the DBP PBT pilot series in South Carolina.    The sessions were added to provide motivation for the PBT graduates to continue to focus on performance data collection and special studies after Session 5.  Minimal facilitation is provided during this post PBT period.  The agenda for these sessions includes a review of the performance data and short summaries of significant special studies that have been completed.  Feedback from attendees has been positive, and the effort encourages ongoing data collection and sustaining of the operator “network “.
  • State Enhancements:  Several of the AWOP states have made other enhancements to the PBT protocol to suit specific types of plants (KY – developed materials specifically for ActiFlo Plants;  AL – utilized a multi day Session for Session 3; IA inserted a session 2A to better emphasize special studies; and PA modified Session 3 to include running zeta potential on participants water. 


The results of PBT projects indicate that it remains a viable training tool for achieving performance improvements at multiple treatment plants, including small systems.  It also results in enhanced skill development and optimization implementation potential for utility personnel as well as for personnel fulfilling the facilitator role.  After 10 years of successful implementation the PBT protocol has proven to be a successful training approach, and enhancements have been an ongoing process to make this TPI tool even more effective.

About Anthony R. DeRosa
Proverbial box burner and unofficial tech guy for the drinking water community.

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