A study of turbidity interference in a new, automated Escherichia coli and total coliform detection method and application of the method on the Yangtze River in China

Abstract

According to Sustainable Development Goals, water quality assessment is vital to sustainable water management. Bacteria monitoring is an important part of water quality management. Traditional methods for bacteria detection in water have limitations such as being time-consuming, expensive and inconvenient. In this study, a new, rapid bacteria detection system called the TECTATM B16 (TECTA) was used. The TECTA system was designed for clean water, therefore, there has been less experience measuring some highly polluted water samples, where high turbidity may interfere with the detection. In this study, experiments have been done both in the laboratory and the field to determine the interference from turbidity. The results from the laboratory showed that the turbidity from organic particles interfered with the bacteria detection by causing delayed E. coli or total coliform time-to-detection and lower signal. The turbidity from inorganic particles didn’t interfere with total coliform detection but interfered with E. coli detection by creating false signal. If the turbidity of a water sample is lower than 150 NTU, the interference from the turbidity could be ignored. The field research was implemented on a ship on the Yangtze River in China in May 2019. Overall, the turbidity of the Yangtze River was lower than 40 NTU with the exceptions of the upstream part of the Yangtze River, so interference in the results was not expected. The results showed E. coli levels mostly in the 200-2000 CFU/100 mL range, with a few much higher levels at the docks in some cities. The distribution of bacteria levels were consistent with official Government of China data, providing confidence that the TECTA instrument was successfully applied on the ship. The results also indicated that bacteria contamination in the Yangtze River was strongly linked to the location of cities.