فهرست مطالب ramazan vagheei

Effective denitrification of water using photocatalytic reaction of active TiO2 particles doped with different oxides and metals has been the subject of numerous studies. For a particular research area, the potential of silica bond and its silicate based matrices with titanium dioxide and improving the photocatalytic performance using more economic methods is still challenging, and research in this field is attractive and ongoing. In this study, the effect of cement matrix and its complex bonds with industrial grade TiO2 particles was evaluated on the rate of water denitrification in a fixed bed circulating flow photoreactor. For this purpose, silica fume was substituted for cement in constant percent of 10 as a rich source of amorphous silica. Industrial grade TiO2 was added to the mix as5, 10 and 15 percent weight of cementitious materials (CM). Nano TiO2 was considered as a supplementary photocatalytic material with a constant 1% weight of CM in two mix designs. The results implied that the addition of 5% TiO2 increased the rate of nitrate concentration reduction by up to 10 times. Also, the specimen including 10% TiO2 increased denitrification rate by 107% compared to the previous content, which had much less impact. Also, the addition of nanoTiO2 increased denitrification rate up 113%.

Denitrification of drinking water has a research history of more than three decades in the field of water treatment and is still the subject of many research projects. The main purpose of this study is to obtain or modify methods for removing nitrate from drinking water in an economic way and force minimal adverse effects on the environment. The use of photocatalytic process for denitrification is not new, but there are still many ambiguities. In this study, the feasibility of using two different photocatalysts over the ultra-high performance concrete (UHPC) substrate was discussed. This new substrate is fabricated by immobilizing the photocatalyst inside a cement matrix which acts as an active layer over the UHPC surface. Optimum long-term lifecycle and higher efficiency of this active surface is achieved without a significant drop of the photocatalyst activity near the surface. In this study, the possibility of using photocatalytic composite layers over the elements made of UHPC for applications such as water supply channels was evaluated and the challenges of using such layers on UHPC surfaces were described. According to the studies, it was found that the use of fixed cement composite bed for photocatalytic treatment has advantages over other methods of photocatalytic water treatment.

Drought intensifies the water crisis and causes irreparable damage to communities. In recent years, machine learning methods have been considered by researchers for drought assessment. The goal of this study is drought assessment in Zabol and Zahedan cities during (1990-2020). In this regard, standardized precipitation index (SPI) at seasonal and annual time scales, partial autocorrelation analysis (PACF), and random forest algorithm (RF) were employed. After SPI calculation, the results of PACF analysis for SPI are used as inputs of the model. Training and testing data were verified with two different inputs. According to the results on a seasonal and annual scale of SPI, the normal drought category (N) has almost the highest frequency in both stations and according to the PACF analysis, the study areas have undergone climate change over 30 years. The results of the model were evaluated by several statistical parameters. The index of agreement (IOA) of Zabol station for training data by considering four time-lags (2, 4, 6, and 12 months) and three time-lags (2, 4, and 6 months) as input, were 0.9648 and 0.9256, respectively and for testing data was approximately 0.8556 and 0.8673, respectively. IOA at Zahedan station for training data with four time-lags (2, 4, 6, and 8 months) and three time-lags (2, 4, and 6 months) were 0.9495 and 0.9205, respectively, and for testing data were 0.7408 and 0.6303, respectively. Other statistical parameters also indicate the permissible accuracy of the RF model in SPI estimation.

Nitrate removal using biological heterotrophic denitrification is one of the most effective and economical processes to remove nitrate from drinking water. In recent studies, carbon sources such as acetic acid, methanol, ethanol, glucose, etc. have been used as a carbon source for heterotrophic bacteria. Inevitable residues of these carbon sources in effluent water and the cost of them are the key challenges for applying these carbon sources in drinking water, in the operational scales. To overcome these challenges, in this research, citric acid produced from sugar beet is used as a harmless, relatively economical and accessible carbon source. Also, to remove the remaining trace amounts of carbon source in denitrified water and disinfection of treated water, ozonation has been used as a dual-purpose process. Pilot studies of this process during the operation of about one year on natural water of one of the wells of North Khorasan province in Iran with the nitrate concentration of 104±10 ppm ppm as NO3- showed that in four column bioreactor packed with different media such as natural river gravel, polypropylene plastic (PP), polyethylene plastic (PE) and Pumice aggregates and by carbon to nitrogen ratio (C/N) of about stoichiometric amount and HRT of greater than 4 hours and without any other chemical addition, the nitrate removal rate of greater than 85% can be achieved. In the carbon concentrations, about 1.5 times the stoichiometric value and the HRT of about 5 to 7 hours, the removal efficiency can be as high as 95%. Ozonation of treated water in 30 to 60 minutes also showed that the ozone has the capability of the complete removal of carbon residuals in effluent of the process from 15-30 ppm as COD to about zero.