Natural organic substances (NOM) found in drinking water are a major contributor to disin-fection by-product formation and are potentially toxic to humans. Conventional water treat-ment techniques may not always effectively treat NOMs. Therefore, an advanced treatment method such as adsorption can be inexpensive, simple and efficient. The selected adsorbent's and the NOMs properties both affect the removal effectiveness of the adsorption method. Activated carbon (AC), which is widely used in real-scale water treatment plants, has been modified and used in recent years in order to oxidize the porous carbon surface, raise its acidic qualities, eliminate mineral components, and enhance the surface's hydrophilic qualities. In this research, AC was modified with nitric acid (M-PAC) and NOM removal was investigated. In addition, it is discussed how the modification with nitric acid changes the adsorbent struc-ture and chemistry. A morphology with smooth and irregular voids was observed as a result of nitric acid modification of the original AC by scanning electron microscopy (SEM) analysis. The particle size increased from 387.65 nm to 502.07 nm for the M-PAC adsorbent. The fouri-er transform infrared spec trophotometer (FTIR) spectrum indicates that structures connected to aromatic rings get formed in the M-PAC adsorbent as a result of the modification. The high-est NOM removal for the original powdered activated carbon (PAC), 47%, was observed at 36 hours of contact time. On the other hand, M-PAC adsorbent achieved 40% NOM removal at contact times of 72 hours and above. It was concluded that the pseudo-second order kinetic model better represented NOM adsorption for both adsorbents.