Microbial Dosing Controls Odors in Florida Collection System
The city of Lakeland, FL, has been using a microbial dosing program to control odor from its collection system and treatment plant since 2001.
by Dan Williamson
The city of Lakeland, FL, has been using a microbial dosing program to control odor from its collection system and treatment plant since 2001. The city recently signed a three-year contract extension with In-Pipe Technology Co. (IPTC) to continue the service that has also metabolized what would have been more than a 32% increase in organic plant loading over six years.
Odor control within a wastewater treatment system is critical to the quality of life in a community - citizens expect and demand odor-free neighborhoods. Odor is primarily associated with the production of hydrogen sulfide gas by sulfate-reducing bacteria under anaerobic conditions. Over the years Lakeland had unsuccessfully tried a variety of methods to solve odor problems.
Dosing panels are installed at strategic locations in the collection system. Each panel contains a replaceable liter bottle of the bacterial consortium and can provide time-controlled treatment for up to 90 days.
In 2000 the city called In-Pipe. At that time there had been only targeted, periodic sampling of atmospheric hydrogen sulfide, and there was limited data to document H2S levels at any specific location. In fact, at that time a reliable instrument that could provide good data was not readily used in the industry. However, due to the complaints they received, city officials knew that the odor problem was system-wide and especially acute in neighborhoods around one particular cascading gravity line and one 3 mgd pumping station; one that was being replaced due to corrosion.
In-Pipe Technology began treating Lakeland in February 2001. The company’s wastewater treatment service involves the introduction of a customized formulation of naturally occurring facultative, planktonic bacteria into the outermost reaches of a municipality’s collection system. With continuous dosing, the bacteria become the dominant organism. Within a period of time, the bacteria convert the biofilm on the walls of the system piping into a controlled, beneficial biological population, creating a pretreatment reactor that, among other effects, reduces the production of hydrogen sulfide in the collection system and in the treatment plant. The company owns three patents on this process, one for odor control and one for biosolids reduction. The other is a Canadian combination patent.
IPTC’s microbiological treatment for any system is driven by such factors as organic and solid loads, time of year, distribution, hydraulic flow in sections, and weather, among others. Simple dosing panels are installed at strategic locations in the collection system and precisely administer dosing. Each panel contains a replaceable liter bottle of the bacterial consortium and can provide time-controlled treatment for up to 90 days.
After just a few months of treatment, Lakeland officials saw an end to community complaints about odor from the district’s 100-square-mile service area.
“Whatever the city’s been doing to combat the odors in this neighborhood is the best thing since I’ve lived here. Even when you pop that manhole cover to get your odor tracking device out of there, I don’t smell the odors,” said a Lakeland resident in the cascading gravity neighborhood shortly after the treatments began.
While limited analytical data exists to document the treatment’s effectiveness in reducing odor, zero complaints is a significant data set as far as Lakeland officials are concerned.
Data from the wastewater treatment operation at Sarasota, FL, is available to make the point, however. Sarasota implemented IPTC treatment in 2006 after consulting with Lakeland staff.
Prior to treatment, strong odors were perceived in the collection system at several lift station locations. Graph 1 shows the Odalog values for four recent monitoring periods. Atmospheric sulfides declined 87%. The decline in base hydrogen sulfide values with each passing monitoring period is evidence towards a dominant shift of bacteria in the system.
Field inspections by IPTC’s service team in January 2007 revealed no detectable odors in the treated areas. Most importantly the collection system managers reported no citizen complaints.
Solution sulfide grab samples obtained at Lift Station 30 established a baseline of 1.8 mg/l during pre-IPTC testing on August 22. Within 30 days of treatment, the number decreased 72% to 0.5 mg/l and has consistently remained at about this value.
In-Pipe Technology has impacted Lakeland’s wastewater treatment in other important ways. Lakeland is growing rapidly with population increase between 2000 and 2006 estimated at 19% from growth in the total number of residential water meters. In addition, the amount of industrial BOD entering the sewer system in 2006 is 26% greater that in 2000, as reported by industrial pretreatment monitoring.
In total, BOD sewer influent organic load has increased more than 32% since 2000. Yet BOD influent loading at the treatment plant in 2006 remains unchanged from 2000. In addition, influent TSS, measured in lbs/day, is down by 22% in 2006 compared to 2000.
While elimination of odor complaints was critical, Lakeland staff also knows that the associated reduction in sulfides - both in solution and atmospheric - will also help reduce corrosion in the collection system.
About the Author:
Dan Williamson, President and Co-Founder of In-Pipe Technology. With over 20 years experience in the wastewater and liquid purification industries, Williamson has an educational background in cell biology, molecular genetics, and biochemistry. Founded in 1999, In-Pipe Technology is currently serving over 35 municipalities in North America and Asia. For more information, visit the company’s website at www.in-pipe.com.