Volume 19 - 2017

The aim of this study is to investigate the performance of solar photo-Fenton process (H2O2/Fe2+/Solar) to treat petroleum wastewater from Sohar oil Refinery, Oman. The effect of operating conditions such as pH, reaction time, Fenton ratio, and Fenton reagent concentrations are investigated. The obtained optimum conditions include H2O2 dosage (1 g L-1), Fe+2 dosage (0.08 g L-1), pH (3) and reaction time (180 min). TOC and COD removal rates are 64 % and 78 %, respectively. However, the photolytic process was less efficient in the petroleum wastewater treatment, achieving an 11.5% and 9% of COD and TOC removals, respectively. The solar photo-Fenton process has well efficient for petroleum wastewater treatment in the acidic conditions and more economic by free energy.

This study describes the removal of Cr (VI) ions from aqueous solutions using silver oxide/sawdust nanocomposite (Ag2O/SD NC) that was prepared using the chemical precipitation method. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques were used for characterization of Ag2O/SD NC. The effect of various parameters such as feed solution pH (2, 6, and 10), influent concentration of Chromium (VI) (25-100 mg/L), flow rate (1-5 mL/min) and bed depth (4-12 cm) on breakthrough curves (BTC) were investigated. Three well-known column adsorption kinetics models including Thomas, Adams-Bohart and Bed Depth Service Time (BDST) models were applied to fitting the column experimental data. Based on Thomas model, the equilibrium adsorption reached 13.41 mg/g when a Cr (VI) polluted solution with influent concentration of 25 mg/L Cr (VI) passed through the column with a flow rate of 2 mL/min. Desorption studies reveal that recovery of uploaded Cr (VI) from the Ag2O/SD NC adsorbent or exhausted column regeneration can readily be achieved using a dilute solution of NaOH (0.01 M) as eluent. This study indicated that the Ag2O/SD NC can be used as an effective, efficient and environmentally friendly adsorbent for the removal of Cr (VI) ions from water resources.

The objective of this study is to summarize studies and investigations about advanced oxidation processes (AOPs) used for the treatment of petroleum wastewater, which mainly contained oil, organic matter and other compounds. The big difference was shown in the specification of wastewater among the investigated studies and a wide variety of pollutants at varying concentrations. The most compounds in petroleum wastewater were the mixture of hydrocarbons and inorganic compounds. Advanced oxidation processes (AOPs) have a capability of rapid degradation of recalcitrant pollutants in the aquatic environment. However, the literature regarding petroleum wastewater treatment is very little and advanced oxidation processes (AOPs) are still not being used on an industrial scale in oil refineries. Most studies were focused on the degradation of some pollutants found in the petroleum wastewater such as sulphides, ammonia, phenols and organic materials. This review focused on works that investigated advanced oxidation processes (AOPs) by monitoring general petroleum wastewater parameters such as TOC, COD, BOD, oil, and phenols. It presented an overview of photocatalytic degradation of pollutants in petroleum wastewater and highlighted the basics of these processes including the optimum parameters.

Salinity is a key environmental factor for the successful application of anammox technology in wastewater treatment, because it impacts the activity and the community structure of anammox bacteria. In this study, the changes in activity and population shifts of an anammox system response to the elevated salt stress (0, 5, 10, 20, 30 and 40 g NaCl/L) were studied.

The results show that the anammox reactor performed effectively even at 30 g NaCl/L salinity after an appropriate acclimatization. The nitrogen removal rate maintained at 0.28 g N L-1d-1 with the nitrogen removal efficiency of 76%, though the high environmental salinity might inhibit the anammox growth in the long-term operation. 16S rRNA high-throughput sequencing results revealed that Ca. Brocadia, Ca. Jettenia and Ca. Kuenenia were the dominant anammox bacteria at all salinities. Ca. Brocadia and Ca. Jettenia were quite sensitive to salinity, and 5 g NaCl/L dosing could cause a sharp decline in their abundance. Nevertheless, these three anammox genus finally survived in the system with a steady specific anammox activity of 0.13 g N g VSS-1d-1. Specially, a novel cluster, Brocadiaceae_unclassified, which possibly belongs to anammox bacteria, became the dominant genus at the salinity over 20 g NaCl/L and likely contributed partially to the nitrogen removals. Our findings elucidated the inherent link between community dynamics and anammox system performance and stability under salty environment, and proved that anammox technologies can be an effective technology for treatment of saline ammonia-rich wastewater.