dariush zeynalzadeh

Background and Many conventional disinfection methods of effluents raise some health, efficiency and economic concerns. In order to increase the efficiency of disinfection of real effluent, in this study, the catalytic ozonation process was performed and economically compared with chlorination.
Magnetic activated carbon was used as acatalyst in a semi-continuous reactor for disinfection of effluent of municipal wastewater treatment plant in Bandargaz, Iran in 2015. The efficiency of disinfection was determined by thermo-tolerant coliform as indication, and the effect of parameters such as catalyst concentration (0, 0.5, 1, 2, and 5 g/L), initial number of coliforms, contact time (1, 2, 5, 10, 20 and 40 min) and catalyst reuse on disinfection process was evaluated. Finally economic comparison was done with the chlorination.
The results showed that the efficiency of disinfection was increased by increase in the concentration of carbon nano-composite and contact time; at 1 g/L concentration of Catalyst about 1.99 log reduction was observed after 2 min exposure time in which the effluent standards were obtained; while 1.91 log reduction of micro-organisms was measured for single ozonation. The first-order kinetics constant of single ozonation (0.42 min-1) showed an approximately 9-fold increase when the catalyst (2 g/L) was added to the solution. After 7 times reuse of nano-composite, the diminution of efficiency was negligible (1.5%); and more than 57% fall of the cost was observed in a 5-year operational period compared with chlorination.
The catalytic ozonation with the new catalyst of effluent could effectively disinfect the effluent in a short-contact-time, and due to economic considerations it can be used as an effective and economical method in wastewater treatment plants.

Background and Antibiotics have worldwide uses and they can enter water sources through different ways. Due to their different inappropriate effects, they have created a major concern in environmental control practices. Metronidazole (MTN) is an example of these antibiotics. This study was performed to investigate the efficiency of ozonation process (SOP) in MTN removal from aqueous solutions. The solution pH (3-12), reaction time and initial MTN concentration (1-40 mg/L) were investigated for their effects on efficiency of the removal process. The MTN concentration was analyzed by HPLC. Biodegradability improvement and mineralization rate were studied by BOD5/COD and TOC tests, respectively. The optimum pH for SOP was 10. The best compatibility for drug degradation kinetic was found with pseudo-second order (liner type II) model. The BOD5/COD increased from 0.09 in SOP influent to 0.33 in SOP effluent and the MTN mineralization rate was about 68%. Higher ozone decomposition in alkaline pH increased the radical production and improved removal efficiency. Moreover, higher mineralization rate reduced the environmental risks of effluent discharges.

Dyes are widely used in different industries and consequently are disposed through different industrial effluents into the environment. Chronic and/or acute effects of the chemicals on microorganisms have been documented. Dyes may absorb and reflect the entering sun lights into the water and thereby decrease the algal photosynthesis. The later in turn can affect the food chain seriously. The aim of this study was، therefore، to use MgO nanoparticles as catalyst in heterogenic catalytic ozonation process (COP) for reactive red 120 dye removal (decolorization) from synthetic wastewater. MgO nanoparticles were produced by sol-gel method. The influences of several operational parameters including solution pH، reaction time، MgO dosage and initial dye concentration on removal (decolorization) efficiency were evaluated. The optimum pH and MgO dosage for COP were determined as 10 and 3 g/L، respectively. Decolorization of 500 mg/L of dye was almost complete after 12 min under achieved optimum conditions. MgO nanocrystals markedly affected the COP and enhanced the dye removal efficiency by approximately 49% compared with the sole ozonation process. Higher O3 decomposition in presence a small amounts of catalyst and alkaline pH increases the radical production which in turn improves the decolorization efficiency. Increasing the initial concentration of dye deteriorated the removal efficiency; however، this can be compensated by increasing the ozonation rate.