Background: Ozone can be used as a single technology or in combination with other processes to improve the coagulation- flocculation or biodegradability in order to remove pollutants in natural water treatment.
Methods: In this study, the effects of pre-ozonation with coagulant substances on the quality parameters of drinking water were investigated using humic acid, kaolin, clay, and green algae in a pilot scale. This study was conducted under laboratory conditions (at both acidic and alkaline pH in different dosages of ozone and coagulant at ozone contact time with simulated water sample (5-20 minutes) in different scenarios).
Results: The highest removal efficiency of parameters in the state of pre-ozonation alone and preozonation with a coagulant was observed at contact time of 20 minutes, ozone dosage of 5 g/h, coagulant dosage of 25 mg/L, at alkaline pH along with a decrease in temperature. So that, the average removal rate of turbidity, total organic carbon (TOC), color, and chlorophyll a in contact time of 20 minutes was 76.9%, 52.8%, 66.6%, and 85%, respectively. However, compared to ozonation under similar conditions, the reduction in turbidity, TOC, color, and chlorophyll a was 36.13%, 24.4%, 32.13%, and 79.6%, respectively. Also, it was revealed that pre-ozonation with coagulant could effectively improve the removal of parameters.
Conclusion: However, since pre-ozonation can be effectively used to improve the coagulation efficacy in the drinking water treatment, the pre-ozonation combined with coagulation is proposed as an alternative to conventional coagulation to improve the process of drinking water treatment plant.

Background: One of the most important problems of dams is thermal layering which directly affects the water quality. This study was performed to propose a solution to increase the water quality of the Esteghlal Dam reservoir in Minab, Hormozgan.
Methods: The water quality of Esteghlal Dam was evaluated from 2016 to 2018. During this period, 18 samples were collected from three different points of the dam. The parameters of water temperature, electrical conductivity, total dissolved solids, total suspended solids, dissolved oxygen (DO), pH, nitrate, phosphate, turbidity, biochemical oxygen demand, chemical oxygen demand, total hardness, anions and cations, total phosphorus, physicochemical, and microbial parameters were measured according to the method recommended in the standard method book. The obtained data were used as the input for the model of reservoir water quality (CE-QUAL-W2) to simulate reservoir water quality and predict the thermocline cycle. Finally, by plotting hypolimnion oxygen content against time and finding the slope of regression line using the data, the hypolimnetic oxygen demand (HOD) was obtained.
Results: The findings showed that the anaerobic condition occurred in the hypolimnion layer during summer. Furthermore, it was revealed that the HOD of Esteghlal Dam is about 6 g of oxygen per square meter per day in the current situation.
Conclusion: Considering the dam’s conditions and its anaerobic problems, a hypolimnetic oxygenation system is proposed as a structural solution for this reservoir. Then, conductivity-temperature-depth (CTD) profiles and monitoring data were used for the oxygen supply model of plume. The reservoir was predicted after calculating the amount of oxygen required using the equations governing linear oxygen supply systems and the plume model.