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In the present study, the ACF-TiO2 catalyst was synthesised and used as a catalyst for the destruction of toxic cyanide in both synthetic and real industrial wastewaters. The ACF-TiO2 catalyst was found to be micro-porous with the BET surface area of 163 m2/g. The effect of different operational parameters such as catalyst concentration, cyanide concentration, operation time, and ozone concentration were target parameters in the present study. The findings show that 500 mg/L of catalyst is the optimum value for the photocatalytical process to completely oxidise 25 mg/L of cyanide within 10 min. While it was found that 300 mg/L of catalyst in the presence of 200 mg/h ozone is enough to remove 25 mg/L cyanide within operation time of 24 min. Degradation of the cyanide in both investigated processes follow the pseudo-first-order kinetic and the reaction rate constant is almost 2 times higher in the photocatalytical process compared with catalytic ozonation process. Furthermore, the quenching tests using salicylic acid demonstrated the hydroxyl radical generation in the investigated process. Generation of highly oxidising hydroxyl radical makes the photocatalytical process a promising process for the transformation of noxious cyanide to much less toxic compounds (ammonia and nitrate). Accordingly, it can be concluded that ACF-TiO2 could be a catalyst for degradation and detoxification of cyanide. [ABSTRACT FROM AUTHOR]

Rotating dissolved air flotation (RDAF) has been utilized for several decades in paper‐recycling wastewater treatment; however, it has rarely been addressed in the literature, which makes research into this system challenging and complicated. However, in this work, a full‐scale industrial wastewater treatment system for a paper‐recycling mill in Mazandaran province, Iran, was evaluated. Experiments indicated that under the same wastewater and chemical conditions, there are differences in the removal efficiencies. This finding was investigated by conducting simulation in ANSYS CFX R18.0 and experimentation simultaneously. Thus, the main purpose of this research was to optimize the operation to achieve the highest removal efficiencies in a cost‐effective manner. For simulation, the flow was considered as a two‐phase homogeneous flow with a continuous solid–fluid phase, which discharges into the separation zone at different scenarios. Particles with diameters of 250, 500 and 1000 μm were introduced at four frame rotating speeds of 0.125, 0.25, 0.5 and 0.75 rpm. Measured qualitative parameters of the effluent included COD, BOD, TSS, TDS, conductivity and turbidity, whose removal efficiency ranges were (32.2%–54.8%), (32.7%–54.47%), (94.5%–97.1%), (0.47%–0.55%), (0.48%–0.59%) and (more than 55%), respectively. Moreover, the optimum rotating speeds of the frame for particles with diameters of 250, 500 and 1000 μm were obtained as 0.25, 0.5 and 0.125 rpm, respectively; these values were compared and found to agree with the experimental results. [ABSTRACT FROM AUTHOR]

In this research, the efficiency of the integrated fixed‐film activated sludge‐oxic settling anoxic (IFAS‐OSA) system in biological nutrient removal was studied. The oxic‐settling anoxic (OSA) process is known as a cost effective way to reduce the nutrients (nitrogen and Phosphorus). According to the results, the percentages of total nitrogen removal efficiency in the IFAS, IFAS‐OSA2h and IFAS‐OSA4h systems were 78.56 ± 2.46, 83.60 ± 0.92 and 85.03 ± 1.69, respectively, while the percentages of phosphorus removal efficiency in these systems were 32.69 ± 8.25, 36.35 ± 6.73 and 39.87 ± 3.61, respectively. The PCR‐RFLP method showed that C. albicans had the greatest prevalence (n = 36, 90%). Moreover, Vorticella convallaria was identified as the most abundant species of protozoa. The current research demonstrated that the efficiency of the modified IFAS‐OSA process was higher than that of IFAS in the removal of nutrients (TN and PO43–P) and can be a suitable method for upgrading the wastewater treatment plants worldwide. [ABSTRACT FROM AUTHOR]

A series of reactors including a sequencing batch reactor (SBR) and a sequencing batch biofilm reactor (SBBR) were used for nitrogen removal. The aim of this study was simultaneous removal of NH4+-N and NOx–-N from synthetic wastewater. In the novel proposed method, the effluent from SBR was sequentially introduced into SBBR, which contained 0.030 m3 biofilm carriers, so the system operated under a paired sequence of aerobic-anoxic conditions. The effects of different carbon sources and aeration conditions were investigated. A low dissolved oxygen (DO) level in the biofilm depth of the fixed-bed process (SBBR) simulated the anoxic phase conditions. Accordingly, a portion of NH4+-N that was not converted to NO3–-N by the SBR process was converted to NO3–-N in the outer layer of the biofilm in the SBBR process. Further, simultaneous nitrification and denitrification (SND) was achieved in the SBBR where NO2–-N was converted to N2 directly, before NO3–-N conversion (partial nitrification). The level of mixed liquid suspended solids (MLSS) was 2740 mg/l at the start of the experiments. The required carbon source (C: N ratio of 4) was provided by adding an internal carbon source (through step feeding) or ethanol. Firstly, as part of the system (SBR and SBBR), SBR operated at a DO level of 1 mg/l while SBBR operated at a DO concentration of 0.3 mg/l during Run-1. During Run-2, the system operated at the low DO concentration of 0.3 mg/l. When the source of carbon was ethanol, the nitrogen removal rate (RN) was higher than the operation with an internal carbon source. When the reactors were operated at the same DO concentration of 0.3 mg/l, 99.1 % of the ammonium was removed. The NO3–-N produced during the aerobic SBR operation of the novel method was removed in SBBR reactor by 8.3 %. The concentrations of NO3--N and NO2–-N in the SBBR effluent were reduced to 2.5 and 5.5 mg/l, respectively. Also, the total nitrogen (TN) removal efficiency was 97.5 % by adding ethanol at the DO level of 0.3 mg/l. When C:N adjustment was carried out SND efficiency at C:N ratio of 6.5 reached to 99 %. The increasing nitrogen loading rate (NLR) to 0.554 kg N/m3 d decreased SND efficiency to 80.7 %. [ABSTRACT FROM AUTHOR]

Biological nitrogen removal from industrial wastewater (pharmaceutical synthetic wastewater) was studied. Sequencing batch reactor (SBR) and sequencing batch biofilm reactor (SBBR) were utilized to treat ammonium-rich wastewater. No external carbon source was added to the reactors. At nitrogen loading rate (NLR) of 2.5 kg N/(m3·day), the efficiency of ammonium removal from synthetic wastewater in SBR was 86.9%. SBBR ammonium removal efficiency under fixed dissolved oxygen (DO) concentration of 0.3 mg O2/dm3 was 98.4%. Specific nitrification rate (SNR) and specific denitrification rate (SDNR) in SBR were 9.24 mg NH4-+N/(g MLVSS·h) and 18.56 mg NO-3-N/(g MLVSS·h), respectively. Nitrite accumulation rate (NAR) showed high correlation with DO decrement (R2 = 0.983), NAR and simultaneous nitrification and denitrification (SND) had high correlation, too (R2 = 0.976). SND efficiency in SBBR reached 94.1% while ammonium oxidizing bacteria (AOB) were dominant and NAR in SBBR process at the DO level of 0.3 mg O2/dm3 was 90.3%. [ABSTRACT FROM AUTHOR]