Addressing Bacterial Contamination in a Constructed Wetland

Ontario, California

Featured image for the project, Addressing Bacterial Contamination in a Constructed Wetland

Photo courtesy of Ontario, California


The community of Ontario, California is an incorporated city within the West Valley of the Southern California Inland Empire (Riverside – San Bernardino – Ontario Metropolitan area). The community faces issues with stormwater runoff and has a responsibility to provide clean water for users downstream in Orange County. To improve water quality in stormwater runoff, Ontario built a constructed wetland in the neighboring City of Chino, Mill Creek Wetlands in 2015. These wetlands are essential for local water quality management, but also provide recreational and educational opportunities for nearby residents.

This natural treatment wetlands project has been recognized by ASCE, APWA, and CASQA for its design and implementation.  However bacteria levels have been found to be consistently higher in outflow than inflow. The community must identify and address the source of this bacteria for regulatory purposes, as well as continued ecological and water treatment functions.

TEX has matched two scientists to work with the City of Ontario to identify the source of wetland bacterial contamination and provide recommendations for mitigation. The primary deliverables for this project will be the discovery of the source of 4 bacterial levels (Fecal Coliform, E. Coli, Streptococcus Bacteria, and Enterococcus Bacteria) and the development of an experimental mitigation plan.

Confidence in the source of bacterial contamination and the exploration of initial mitigation options will enable the community to pursue actions to ensure that the wetland works as intended, providing the community both water treatment functionality and a beautiful recreational area. This project will provide the community with opportunities to build on existing community education and foster interest and pride in the local constructed wetlands.


Cal Poly Pomona Students Process Ontario, CA Water Samples

Undergraduate students enrolled in undergraduate research at Cal Poly Pomona are getting some applied lab experience processing water samples collected from Ontario’s constructed wetlands. Under the supervision of Dr. Shelton Murinda, Professor in the Animal and Veterinary Sciences Department, students conduct fecal indicator bacterial counts using the IDEXX system.  Dr. Shelton Murinda adds “the students are isolating  E. coli and Enterococcus species on conventional agar media, and performing microscopy and other diagnostic tests.   Additionally the students are isolating DNA from the bacterial cultures and conducting Polymerase Chain Reaction (PCR) to confirm if the bacterial strains isolated from the water samples are target fecal indicator species, that is, E. coli or Enterococcus. They are also conducting PCR to confirm if the E. coli are Shiga-toxin producing E. coli (such as E. coli O157:H7) and if the Enterococcus are Enterococcus faecium or Enterococcus faecalis.” Shiga toxin producing E. coli will be confirmed using Recombinase Polymerase Amplification, a protocol developed by Drs. Murinda, Ibekwe and co-workers in 2014.

Shiga-toxin producing E. coli are known to cause outbreaks each year and are a particular concern to public officials, the City of Ontario included.  Enterococcus faecium and Enterococcus faecalis are also pathogenic when found outside the gastrointestinal tract of humans and animals.  Sample collection from the constructed wetlands is being facilitated by the City of Ontario team.

Photo Caption: Cal Poly Pomona students conduct PCR on DNA isolated from E. coli and Enterococcus to confirm the identity of the organisms obtained from Ontario, CA’s constructed wetlands.  Photo courtesy of Shelton Murinda.

All updates for this project

Project Team

Community Lead

Scott Murphy is the Planning Director for the City of Ontario.  Mr. Murphy has 30 years of both public and private planning experience in Southern California, working in various professional capacities. Mr. Murphy’s experience includes work on numerous specific plans, development codes, general plans, master plans, and major development projects. One of the key areas of focus presently is Ontario Ranch, a 13-square mile area annexed to the City of Ontario in 1999. Ontario Ranch anticipates the development of over 47,000 residential units, 5 million square feet of commercial space and 5.5 million square feet of industrial space. Mr. Murphy has a Bachelor’s degree in Urban and Regional Planning from Cal Poly Pomona.

Eric Woosley is employed by the City of Ontario and works in the Environmental Division of the Engineering Department. He has a Bachelor’s Degree in Civil Engineering from the California State Polytechnic University of Pomona, California, holds various certifications in stormwater, and has nearly a decade of experience with National Pollutant Discharge Elimination System (NPDES) compliance. He is the Project Manager of the Mill Creek Wetlands, and is responsible for managing the contractual agreements of multiple consultants and contractor team that performs the sampling and monitoring, reporting, and maintenance of the water treatment facility.


Scientific Liaisons

Dr. Abasiofiok (Mark) Ibekewe is a Microbiologist at the U.S. Department of Agriculture’s Agricultural Research Service in Riverside, California. Mark has 21 years of research experience with USDA-ARS, and has produced over 90 publications, including 67 peer-reviewed journal articles. He is an internationally recognized expert on the use of constructed wetlands for the removal of contaminant for water improvement, characterization of soil microbial community as a critical component of soil quality and health, and identification of factors and quantification of survival of E. coli O157 in different sample sources. Mark is interested in the use and manipulation of wetlands for improving regional water quality. Mark received his Ph.D. in Environmental Microbiology from the University of Maryland at College Park.


Dr. Shelton Murinda is a Professor in the Department of Animal and Veterinary Sciences at the California State Polytechnic University, Pomona (Cal Poly Pomona), CA. He is an Animal Scientist, Food Scientist (Microbiology, Safety, Chemistry & Processing) and Biotechnologist who has trained lived and/or worked on three continents (Africa, Europe and North America). He has extensive expertise in research, teaching extension and outreach, and has contributed to agricultural, food and research leadership for more than 20 years, and provides expertise on food safety and animal health issues nationwide. His current research topics focus on biosensor development for pathogen detection, prevalence of clostridia in horses, bovine mastitis, and an environmental sustainability project on development of safe nutritious animal feed from algae. Shelton received his Ph.D. in Food Science/ Microbiology from Pennsylvania State University.