Chemical oxygen demand and tannin/lignin removal from paper mill wastewater by electrocoagulation combined with peroxide and hypochlorite treatments.

The present investigation sought to assess the practicality of utilizing a combined pre-treatment approach comprising electrocoagulation, peroxide, and hypochlorite treatments for the removal of chemical oxygen demand (COD) and tannin/lignin from paper mill wastewater. The study aimed to optimize the operating parameters with a view to maximizing the removal efficiencies while minimizing energy consumption. A pair of iron electrodes were used as anode and cathode in the study, and the main operating parameters were determined as initial pH, applied current, treatment time and oxidant dosage/COD ratio. Response surface methodology (RSM) was used to evaluate the effect of these parameters on COD and tannin/lignin removals. The primary findings of the investigation indicated that the integration of electrocoagulation with peroxide and hypochlorite treatments exhibited efficacy in removing COD, tannin/lignin, colour, phenol, and turbidity from paper mill wastewater. The optimized conditions resulted in COD removal efficiencies of 48.13 ± 2.2% and 29.53 ± 1.4% for EC with H2O2 and Ca(OCl)2, respectively. Tannin/lignin removal efficiencies were 92.59 ± 3.6% and 94.09 ± 1.8% for EC-H2O2 and EC-Ca(OCl)2, respectively. The specific energy consumption (SEC) values showed that EC-Ca(OCl)2 required 7 times more energy than EC-H2O2 for removing 1 kg COD. The principal deduction drawn from the study was that EC-H2O2 pre-treatment demonstrated superior COD removal efficiency and lower energy consumption, while EC-Ca(OCl)2 pre-treatment exhibited greater efficiency in removing toxic and recalcitrant pollutants. In future studies, it would be useful to conduct research to increase COD removal efficiency in addition to tannin/lignin removal in EC-Ca(OCl)2 process.

Performance evaluation of ceramic membrane bioreactor: effect of operational parameters on micropollutant removal and membrane fouling.

This paper presents the removal of nine potential endocrine disruptors including pesticides, pharmaceuticals and industrial chemicals using a submerged membrane bioreactor (MBR) system. Two lab-scale submerged MBRs having ceramic membranes were operated at three different sludge retention times (SRT: 15, 45, 90 days) and two hydraulic retention times (HRT: 12, 6 h) and the effects of SRT and HRT on both micropollutant removal and membrane fouling were investigated. While the effect of SRT and HRT change was observed on the removal of atrazine, fluoxetine, penconazole, no significant change was detected for the other micropollutants studied. It was determined that physicochemical properties such as distribution coefficient (LogD) and hydrophobicity of micropollutants are also effective on the removal efficiency of micropollutants. High removal efficiencies ([Formula: see text] 97.5%) were observed for hydrophobic pollutants (logD > 3.2) except for penconazole (72.1%) and for hydrophilic pollutants (logD < 3.2) except for atrazine (42.5%). Membrane fouling was significantly affected by different operational parameters applied, with the slowest fouling occurring at 45 days of SRT and 12 h of HRT. However, micropollutant addition did not have a significant effect on membrane fouling. It has been shown that the simultaneous and effective treatment performance for micropollutants makes the membrane bioreactor system a promising wastewater treatment process.

Preliminary study testing the effects of tea and coffee on sludge characteristics and N-butyryl-l-homoserine lactone in an MBR system.

Membrane bioreactors (MBRs) are rapidly developing systems widely used for the treatment of municipal and industrial wastewater prior to their discharge into the environment. Membrane fouling is the most important challenge in MBRs, because it negatively affects membrane performance, resulting in low permeate flux, higher transmembrane pressure and frequent membrane cleaning/replacement. In this study, the effect of tea and coffee on sludge characteristics, membrane fouling and the bacterial signalling molecule N-butyryl-l-homoserine lactone (C4-HSL) in a membrane bioreactor system were investigated. For this purpose, four different continuously operated membrane bioreactors, treating synthetic domestic wastewater and dairy wastewater were operated in parallel under the same conditions. The results indicated that the soluble microbial products (SMP) and the extracellular polymeric substances (EPS) in the reactors showed similar trends for both synthetic domestic and dairy wastewater, where protein levels were higher than carbohydrate levels. Other parameters such as floc size, zeta potential, hydrophobicity, sludge volume index and capillary suction time were also analysed prior to and after the addition of coffee and tea. Analysis of the wastewater samples by GC-MS revealed that coffee and tea significantly enhance the extraction efficiency of C4-HSL. The results obtained in this study can serve as a good basis for further research.

Performance evaluation of conventional membrane bioreactor and moving bed membrane bioreactor for synthetic textile wastewater treatment.

In this study, conventional membrane bioreactor (MBR) and moving bed-membrane bioreactor (MB-MBR) processes were compared in synthetic textile wastewater treatment. For this purpose, the bioreactors were operated as a conventional MBR, an MB-MBR with a biocarrier filling ratio of 20 % and an MB-MBR with a biocarrier filling ratio of 10 %, respectively. In the conventional MBR operation, 93.1 % chemical oxygen demand (COD) and 87.1 % color (Reactive Red 390) removal efficiencies were obtained. In both MB-MBR operations, almost equal COD and color removal efficiencies were found as 98.5 % and 89.5 %, respectively. Moreover, offline physical and chemical membrane cleaning processes were applied every other day and every 15 days throughout the conventional MBR operation, respectively, while no physical or chemical membrane cleaning was required during both MB-MBR operations. Furthermore, lower polysaccharide concentrations of extracellular polymeric substances (EPS) and floc sizes of sludge and higher zeta potential of sludge were determined in MB-MBR. Considering the obtained results, it may be stated that the MB-MBR process is an attractive treatment technology for reducing membrane fouling propensity for treatment of textile wastewater.

Binary Dispersive Liquid-Liquid Microextraction Strategy for Accurate and Precise Determination of Micropollutants in Lake, Well and Wastewater Matrices.

In this study, a binary mixture in dispersive liquid-liquid microextraction was used for the preconcentration and determination of selected pesticides, pharmaceutical and hormone by GC-MS. A Box-Behnken experimental design was used to optimize the amounts of binary mixture, dispersive solvent and salt. The optimum parameters obtained were dichloromethane/1,2-dichloroethane binary mixture (200 µL), ethanol (2.0 mL) and potassium nitrate (1.0 g). Analytical performance of each analyte was determined under the optimum conditions and the lowest and highest detection limits calculated were 0.43 and 5.9 ng/mL. Low relative standard deviations were obtained even in the lowest concentrations in linear calibration plots, signifying high precision for the sample preparation procedure and instrumental measurement. Accuracy of the developed method and applicability to real samples was tested on well, lake, hospital and municipal wastewater. The percent recoveries acquired at different spiked concentrations were satisfactory (89%-108%), validating the accuracy of the method for the quantification of the analytes in the selected matrices.