Sensitive Multi-Detection of Escherichia coli by Quartz Crystal Microbalance with a Novel Surface Controllable Sensing Method in Liquid Organic Fertilizer Produced by Sewage Sludge

The potential health hazards of pathogens, such as Escherichia coli (E. coli), have recently received extensive attention. However, the concentration change of E. coli in sewage sludge during the vermicomposting process is still relatively unexplored. In this study, sewage sludge, a byproduct of wastewater treatment, was used as bed materials with cow dung to produce valuable liquid organic fertilizer (vermicompost tea). A unique quartz crystal microbalance (QCM) detection system with a novel surface functionalization procedure, which allows selectively captured analytes to be removed from the surface in a controlled manner for possible extra genetic and serological detections, was also developed for low level detection of E. coli in vermicompost tea (VT) medium. The results indicate that sewage sludge became a valuable liquid organic fertilizer, which has total nitrogen and phosphorus content 22 % and 11 % higher than their initial levels, respectively. The QCM-based biosensing showed good detection sensitivity and stability at near 10(2) CFU mL(-1) level in VT samples. The developed QCM based method with a novel surface controllable biosensing mechanism provides a reliable and selective detection approach allowing other post analyses if needed for sensitive measurement of E. coli in vermicompost tea or different aqueous solutions. After the determination of pathogenic levels in vermicompost tea could be used as liquid organic fertilizer for a sustainable organic farming system.