2020-2021 Executive Summary
Microbial water quality is a focused area of aquatic microbiology dedicated to minimizing the risk of human exposure to waterborne pathogens. Whether swimming and surfing at the beach, or consuming shellfish harvested from coastal waters, the public depends on rigorous, fully vetted science to rapidly detect aquatic microbial contamination and to inform remediation strategies. Advances in molecular microbiology are enabling the water-quality management community to develop incrementally stronger, more effective solutions for protecting public health. SCCWRP is working to improve methods for evaluating microbial water quality and assessing risks to public health from waterborne pathogen exposure. SCCWRP’s goal is not only to improve the speed at which microbial contamination can be detected, but also to develop molecular methods for tracing contamination back to its source and pinpoint its origin point. SCCWRP also is focused on helping water-quality managers better understand how field measures of microbial contamination correspond to specific levels of health risk.
SCCWRP’s microbial water quality research is focused around three major areas: (1) Rapid methods for microbial contamination detection, which involves validating the accuracy and applicability of DNA-based methods for measuring microbial contamination; the molecular methods can produce results in about two hours, enabling public health officials to issue same-day warnings to beachgoers when microbial contamination reaches potentially unsafe levels; (2) Microbial source tracking, which involves using molecular methods to identify whether humans vs. various individual animal species are responsible for observed contamination – and to identify where in a watershed the contamination is coming from and potentially which specific type of stormwater or wastewater infrastructure is responsible; and (3) Microbial risk assessment, which involves quantifying health risk for Southern California’s beachgoing population through epidemiological studies, as well as through health risk modeling approaches such as Quantitative Microbial Risk Assessment (QMRA) that estimate illness risk based on site-specific considerations.
This year, SCCWRP will continue to focus on human fecal source tracking, examining risk-based water quality objectives for recreational shellfish waters, and examining the prevalence of antibiotic-resistant bacteria and the genes that confer resistance in wastewater treatment plants and discharges. SCCWRP’s focus for 2020-21 will be on:
- Identifying human sources of fecal contamination during wet weather: SCCWRP is working to identify the specific sources of human fecal contamination that are widespread in Southern California waterways discharging to the coastal ocean during wet weather. SCCWRP will identify the relative contributions of public sewers, private laterals, septic systems, illicit connections and illegal discharges, and individuals experiencing homelessness. This work, which includes quantifying both relative contributions and the factors that control these contributions, builds on previous SCCWRP research that has shown that the risk of gastrointestinal illness from body contact recreation during wet weather is greater than the risk illness during dry weather, and that genetic markers of human fecal contamination (i.e., HF183) and human pathogens are commonly found in wet-weather discharges. With managers no longer asking “Are human fecal sources found in wet weather?” but rather “What are the human source(s) found in wet weather?” the goal of this research is to help managers most efficiently and effectively remediate human fecal sources to protect the public health of beachgoers following storm events.
- Evaluating the SHEL water-quality standard: SCCWRP and its partners are continuing to investigate whether a water-quality standard designed to protect the health of people who consume shellfish from Newport Bay in Orange County has been appropriately set. The study’s goal is to examine whether California’s existing standard for permissible fecal coliform bacterial levels in the water correlates to potentially unsafe levels of pathogens in the tissue of bivalve shellfish harvested from Newport Bay. If the water-column bacterial measurements of indicators positively correlate with pathogen levels found in the shellfish, researchers would conclude that California’s existing standard for recreational shellfish harvesting is working as designed. However, if there is no relationship between water-quality indicators and pathogens found in the shellfish, the study could provide a scientific basis for developing a site-specific standard for Newport Bay, or trigger follow-up studies examining the appropriateness of using a fecal coliform-based standard to protect California shellfish.
- Evaluating antibiotic-resistant bacteria and genes in wastewater: SCCWRP is continuing to quantify the prevalence of antibiotic-resistant bacteria in wastewater treatment plants and their discharges. The study was prompted by media reports that potentially pathogenic antibiotic-resistant bacteria and antibiotic resistance genes may persist and even multiply during the wastewater treatment process before being discharged into the environment with treated effluent. The goal of the study is to gain information about the type and prevalence of antibiotic-resistant bacteria and antibiotic resistance genes in southern California wastewater treatment plants and their discharges.