Nanobubbles (NBs) have potential properties, are environmentally friendly, and are sustainable

to be used in a variety of applications: industries, agriculture, medical technology,

and engineering applications such as water/wastewater treatment. This paper focuses

on improving the characteristics of municipal secondary effluent (SE) utilizing oxygen

bubbles (OBs), conventional coarse air bubbles (ABs), oxygen nanobubbles (ONBs),

and air nanobubbles (ANBs). NBs were generated by injecting pressured gases through a

tubular ceramic membrane with nanopores. Several tests have been used to determine the

quality of tested SE before and after different injection times, including dissolved oxygen

concentration (DO), pH, chemical oxygen demand (COD), biochemical oxygen demand


BOD5), total dissolved solids (TDS), total suspended solids (TSS), sulfide, orthophosphate,

organic nitrogen, ammonia, oil and grease, and Escherichia coli (E. coli). The

results show the priority of ONBs in the enhancement of SE quality. For example, after

injecting ONBs, OBs, ANBs, and ABs in SE, the TSS was reduced by 57%, 42%, 28%

and 14%, the COD by 62%, 41%, 26% and 12%, the BOD5

by 73%, 56%, 43% and 21%,

and the organic nitrogen decreased by 19%, 11% and increased by 14% and 9%, respectively.

These findings are intended to grasp the gaps in our understanding of how NBs

affect the advanced treatment of SE.