Utilizing treated wastewater (TWW) for irrigation results in biological and chemical deposits. TWW components such as bacteria and suspend minerals interact under different environmental conditions, forming aggregates varying in size and stability that may adversely affect water flow in drippers. Our aim in this study was to characterize aggregates’ size and stability in suspensions of bacteria and clay particles, under different conditions prevailing in TWW. Flocculation value tests, thermal analysis, microscopy and particle size distribution were used to measure bacterial–clays interaction in suspension. Our results showed suspension stability increase with an increase in bacterial population. Dissolved organic carbon (DOC) produced by bacteria or added as fulvic acid was found to be the most important parameter involved in determining aggregate size and stability under similar environmental condition. The presence of these components most commonly resulted in higher stability of the suspension, mainly smaller particles in suspension. A novel measurement aimed to determine size and stability parameters for suspended particles has been established and was found to be useful in predicting suspended compound interactions. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.