Ratio of HF183 to PMMoV in Sewage and Its Change When Exposed to Different Temperatures and Sunlight Conditions

In surface waters with fecal pollution, the age of fecal pollution has a direct connection to human health risk. Current microbial source tracking methods distinguish human-associated fecal markers from animal-associated biomarkers. However, in waters containing human-associated fecal pollution, current source tracking methods do not effectively distinguish small amounts of fresh (new) fecal pollution from large amounts of aged (old) fecal pollution. We introduced a concept for a model that considers environmental factors such as sunlight and temperature to estimate human fecal pollution age based on the ratio of two human-associated fecal biomarkers with different levels of persistence in the environment: HF183 and pepper mild mottle virus (PMMoV). We assessed the HF183/PMMoV ratio using (RT-)qPCR in 98 wastewater samples from two university residence halls in southern California, finding that HF183 was 15 times higher than PMMoV on average. This ratio decreased under sunlight and at higher temperatures due to differing decay rates of the two biomarkers. We propose that monitoring the concentration of HF183 and PMMoV, as well as the HF183/PMMoV ratio, can help to distinguish between a small amount of fresh contamination and a large amount of aged contamination.