Decolorization, COD and turbidity removal of the raw vinasse effluent by a one-step electro-oxidation process on a Pb/PbO2 anode.

In this research, and for the first time, the application of anode Pb/PbO2 (prepared from combined thermal oxidation and electrochemical oxidation method) and steel cathode in a flow sample electrochemical treatment process of vinasse and in the wastewater of alcohol factories, has been investigated. The combination of electrodes of Pb/PbO2 as an anode, steel, and/or graphite as a cathode was used in the proposed electrochemical treatment setup. The efficiency of the proposed electrochemical treatment was determined by the removal percentage of chemical oxygen demand (COD), turbidity and color of vinasse samples. The response surface method (RSM) by Minitab 18 was used to determine the effect of the studied factors as well as to detect the relationship between variables. The results showed that under optimum conditions (Pb/PbO2 electrode as the anode and steel electrode as the cathode, a voltage of 30 V, pH 6.5, and reaction time of 45 min), the percentage reduction values of COD, turbidity and color were 97.7, 77.3 and 92.7%, respectively.

Analysis of nitrogenous and algal oxygen demand in effluent from a system of aerated lagoons followed by polishing pond.

In this descriptive-analytical study, nitrogenous and algal oxygen demand were assessed for effluent from a system of facultative partially mixed lagoons followed by the polishing pond using 120 grab samples over 1 year. Filtered and non-filtered samples of polishing pond effluent were tested in the presence and absence of a nitrification inhibitor. Effective factors, including 5-day biochemical and chemical oxygen demand (BOD and COD), total suspended solids (TSS), dissolved oxygen, chlorophyll A, and temperature, were measured using standard methods for water and wastewater tests. The results were analyzed using repeated measures analysis of variance with SPSS version 16. Findings show that the annual mean of the total 5-day BOD in the effluent from the polishing pond consisted of 44.92% as the algal carbonaceous biochemical oxygen demand (CBOD), 43.61% as the nitrogenous biochemical oxygen demand (NBOD), and 11.47% as the soluble CBOD. According to this study, the annual mean ratios of algal COD and 5-day algal CBOD to TSS were 0.8 and 0.37, respectively. As the results demonstrate, undertaking quality evaluation of the final effluent from the lagoons without considering nitrogenous and algal oxygen demand would undermine effluent quality assessment and interpretation of the performance of the wastewater treatment plant.

The investigation of catalytic ozonation and integrated catalytic ozonation/biological processes for the removal of phenol from saline wastewaters.

The effectiveness of the catalytic ozonation process (COP) with a GAC catalyst was assessed based on the degradation and COD removal of phenol from the saline wastewater, as compared with the single ozonation process (SOP). The COP attained a much higher level of phenol degradation compared to the SOP. The influence of several variables was investigated, including pH of solution, NaCl concentration, and dosage of GAC, for their effects on COP phenol degradation in a synthetic saline wastewater. The maximum degradation of phenol was achieved at pH 8 and 20 g/L GAC. NaCl had no adverse effect on phenol removal at ranges between 0.5 and 50 g/L. The activated carbon acted mostly as a catalyst for ozone decomposition, and the subsequent generation of hydroxyl radicals. Furthermore, the GAC preserved its catalytic properties after 5 times reuse. The capability of a biological process to treat COP effluent was also investigated. Results showed that a 10 min reaction time in COP under optimum conditions reduces the concentrations of phenol and COD to an acceptable level for efficient post-treating in a suspended growth bioreactor at a short aeration time of 4h. Thus, the integration of COP with a biological process is proven to be a technically and economically effective method for treating saline wastewaters containing recalcitrant compounds.