A review on the present situation of wastewater treatment in textile industry with membrane bioreactor and moving bed biofilm reactor

Membrane bioreactor (MBR) is one of the advanced treatment technologies used in industrial wastewater treatment due to its various advantages over conventional biological processes. Recently, the application of MBR in treatment of textile wastewater has increased significantly with an effective removal of contaminants. Moving bed bioreactor (MBBR) has been efficiently used for the treatment of different municipal and industrial wastewater during the last decades and it is a relatively novel and effective technology applied in textile wastewater treatment. This review paper presents the situation of MBR and MBBR technology for textile wastewater purification under different conditions and collates results of previous studies during the past years about MBR and MBBR treatment technologies used in textile processes. Both of these two technologies have shown their efficiency, but they still have problems in textile wastewater treatment. To this end, MBR-MBBR hybrid system could be an attractive solution for textile wastewater purification because of the high efficiency and low consumption of energy and spacePostprint (author's final draft

Treatment of domestic wastewater in an up-flow anaerobic sludge blanket reactor followed by moving bed biofilm reactor

The performance of a laboratory-scale sewage treatment system composed of an up-flow anaerobic sludge blanket (UASB) reactor and a moving bed biofilm reactor (MBBR) at a temperature of (22-35 A degrees C) was evaluated. The entire treatment system was operated at different hydraulic retention times (HRT's) of 13.3, 10 and 5.0 h. An overall reduction of 80-86% for CODtotal; 51-73% for CODcolloidal and 20-55% for CODsoluble was found at a total HRT of 5-10 h, respectively. By prolonging the HRT to 13.3 h, the removal efficiencies of CODtotal, CODcolloidal and CODsoluble increased up to 92, 89 and 80%, respectively. However, the removal efficiency of CODsuspended in the combined system remained unaffected when increasing the total HRT from 5 to 10 h and from 10 to 13.3 h. This indicates that, the removal of CODsuspended was independent on the imposed HRT. Ammonia-nitrogen removal in MBBR treating UASB reactor effluent was significantly influenced by organic loading rate (OLR). 62% of ammonia was eliminated at OLR of 4.6 g COD m(-2) day(-1). The removal efficiency was decreased by a value of 34 and 43% at a higher OLR's of 7.4 and 17.8 g COD m(-2) day(-1), respectively. The mean overall residual counts of faecal coliform in the final effluent were 8.9 x 10(4) MPN per 100 ml at a HRT of 13.3 h, 4.9 x 10(5) MPN per 100 ml at a HRT of 10 h and 9.4 x 10(5) MPN per 100 ml at a HRT of 5.0 h, corresponding to overall log(10) reduction of 2.3, 1.4 and 0.7, respectively. The discharged sludge from UASB-MBBR exerts an excellent settling property. Moreover, the mean value of the net sludge yield was only 6% in UASB reactor and 7% in the MBBR of the total influent COD at a total HRT of 13.3 h. Accordingly, the use of the combined UASB-MBBR system for sewage treatment is recommended at a total HRT of 13.3 h

The evolution of glutathione metabolism in phototrophic microorganisms

The low molecular weight thiol composition of a variety of phototropic microorganisms is examined in order to ascertain how evolution of glutathione (GSH) production is related to the evolution of oxygenic photosynthesis. Cells were extracted in the presence of monobromobimane (mBBr) to convert thiols (RSH) to fluorescent derivatives (RSmB) which were analyzed by high performance liquid chromatography (HPLC). Significant levels of GSH were not found in green sulfur bacteria. Substantial levels were present in purple bacteria, cyanobacteria, and eukaryotic algae. Other thiols measured included cysteine, gamma-glutamylcysteine, thiosulfate, coenzyme A, and sulfide. Many of the organisms also exhibited a marked ability to reduce mBBr to syn-(methyl,methyl)bimane, an ability which was quenched by treatment with 2-pyridyl disulfide or 5,5 prime-bisdithio - (2-nitrobenzoic acid) prior to reaction with mBBr. These observations indicate the presence of a reducing system capable of electron transfer to mBBr and reduction of reactive disulfides. The distribution of GSH in phototropic eubacteria indicates that GSH synthesis evolved at or around the time that oxygenic photosynthesis evolved

Effect of dissolved oxygen and chemical oxygen demand to nitrogen ratios on the partial nitrification/denitrification process in moving bed biofilm reactors

Partial nitrification was reported to be technically feasible and economically favorable, especially for wastewater with high ammonium concentration or low C/N ratio. In this study, the effect of dissolved oxygen (DO) and influent ratio of chemical oxygen demand to nitrogen (COD/N) ratio on biological nitrogen removal from synthetic wastewater was investigated. Experiments were conducted in moving bed biofilm reactors (MBBRs) on partial nitrification process in pilot-plant configuration for 300 days. DO levels were changed from 0.04 to 0.12 and 0.42 to 3.4 mg/l in the anoxic (R1) and aerobic (R2) reactors, respectively. The optimum DO for partial nitrification was between 1-1.5 mg/l in the aerobic reactor (R2). Influent COD/N ratios between 20 and 2 g COD/g-N were tested by changing the nitrogen loading rate (NLR) supplied to the pilot plant. During operational conditions when the DO concentration in aerobic reactor was above 1 mg/l, near complete organic carbon removal occurred in the total MBBRs system. The effluent total nitrogen concentration in the operational conditions (1.7-2.1 mg O2/l and NH+ 4-N=35.7 mg N/l) was obtained in the range of 0.85-2 mg/l. The highest nitrite accumulation (50%- 52%) took place at the DO concentration of 1-1.5 mg/l and increased with decreasing COD/N ratio in aerobic reactor (R2). This study showed that the average nitrification rate at various COD/N ratios is about 0.96 gN/m2 per day while the maximum nitrification rate is about 2 gN/m2 per day at COD/N ratios lower than 6. The experimental COD/N ratio for denitrification was close to complete sum of NO2 - and NO3 - (NOx) removal efficiency (about 99%) at COD/N ratio equal 14 in the operational conditions in the anoxic reactor (R1)

Arabidopsis thaliana dehydroascorbate reductase 2 : conformational flexibility during catalysis

Dehydroascorbate reductase (DHAR) catalyzes the glutathione (GSH)-dependent reduction of dehydroascorbate and plays a direct role in regenerating ascorbic acid, an essential plant antioxidant vital for defense against oxidative stress. DHAR enzymes bear close structural homology to the glutathione transferase (GST) superfamily of enzymes and contain the same active site motif, but most GSTs do not exhibit DHAR activity. The presence of a cysteine at the active site is essential for the catalytic functioning of DHAR, as mutation of this cysteine abolishes the activity. Here we present the crystal structure of DHAR2 from Arabidopsis thaliana with GSH bound to the catalytic cysteine. This structure reveals localized conformational differences around the active site which distinguishes the GSH-bound DHAR2 structure from that of DHAR1. We also unraveled the enzymatic step in which DHAR releases oxidized glutathione (GSSG). To consolidate our structural and kinetic findings, we investigated potential conformational flexibility in DHAR2 by normal mode analysis and found that subdomain mobility could be linked to GSH binding or GSSG release

New functional biocarriers for enhancing the performance of a hybrid moving bed biofilm reactor-membrane bioreactor system

© 2016 Elsevier Ltd. In this study, new sponge modified plastic carriers for moving bed biofilm reactor (MBBR) was developed. The performance and membrane fouling behavior of a hybrid MBBR-membrane bioreactor (MBBR-MBR) system were also evaluated. Comparing to the MBBR with plastic carriers (MBBR), the MBBR with sponge modified biocarriers (S-MBBR) showed better effluent quality and enhanced nutrient removal at HRTs of 12 h and 6 h. Regarding fouling issue of the hybrid systems, soluble microbial products (SMP) of the MBR unit greatly influenced membrane fouling. The sponge modified biocarriers could lower the levels of SMP in mixed liquor and extracellular polymeric substances in activated sludge, thereby mitigating cake layer and pore blocking resistances of the membrane. The reduced SMP and biopolymer clusters in membrane cake layer were also observed. The results demonstrated that the sponge modified biocarriers were capable of improving overall MBBR performance and substantially alleviated membrane fouling of the subsequent MBR unit

Investigating the removal of some pharmaceutical compounds in hospital wastewater treatment plants operating in Saudi Arabia

The concentrations of 12 pharmaceutical compounds (atenolol, erythromycin, cyclophosphamide, paracetamol, bezafibrate, carbamazepine, ciprofloxacin, caffeine, clarithromycin, lidocaine, sulfamethoxazole and Nacetylsulfamethoxazol (NACS)) were investigated in the influents and effluents of two hospital wastewater treatment plants (HWWTPs) in Saudi Arabia. The majority of the target analytes were detected in the influent samples apart from bezafibrate, cyclophosphamide, and erythromycin. Caffeine and paracetamol were detected in the influent at particularly high concentrations up to 75 and 12 ug/L, respectively. High removal efficiencies of the pharmaceutical compounds were observed in both HWWTPs, with greater than 90 % removal on average. Paracetamol, sulfamethoxazole, NACS, ciprofloxacin, and caffeine were eliminated by between >95 and >99 % on average. Atenolol, carbamazepine, and clarithromycin were eliminated by >86 % on average. Of particular interest were the high removal efficiencies of carbamazepine and antibiotics that were achieved by the HWWTPs; these compounds have been reported to be relatively recalcitrant to biological treatment and are generally only partially removed. Elevated temperatures and high levels of sunlight were considered to be the main factors that enhanced the removal of these compounds

Reverse osmosis concentrate treatment by chemical oxidation and moving bed biofilm processes

In the present work, four oxidation techniques were investigated (O3, O3/UV, H2O2/O3, O3/H2O2/UV) to pre-treat reverse osmosis (RO) concentrate before treatment in a moving-bed biofilm reactor (MBBR) system. Without previous oxidation, the MBBR was able to remove a small fraction of the chemical oxygen demand (COD) (5-20%) and dissolved organic carbon (DOC) (2-15%). When the concentrate was previously submitted to oxidation, DOC removal efficiencies in the MBBR increased to 40-55%. All the tested oxidation techniques improved concentrate biodegradability. The concentrate treated by the combined process (oxidation and MBBR) presented residual DOC and COD in the ranges of 6-12 and 25-41 mg L 1 , respectively. Nitrification of the RO concentrate, pre-treated by oxidation, was observed in the MBBR. Ammonium removal was comprised between 54 and 79%. The results indicate that the MBBR was effective for the treatment of the RO concentrate, previously submitted to oxidation, generating water with an improved quality

Evaluating the performance of a sponge-based moving bed bioreactor on micropollutants removal

University of Technology Sydney. Faculty of Engineering and Information Technology.The ubiquitous occurrence of micropollutants and their metabolites in the aquatic environment has posed threats to living organisms to a great extent. However, effective micropollutants removal normally requires longer hydraulic retention time (HRT) when using biological treatment systems. As an ideal and low-cost material for attached-growth microorganisms, polyurethane sponge has exhibited high potential to eliminate micropollutants. In this study, a sponge-based moving bed biofilm reactor (MBBR) was investigated at four different HRTs (24, 18, 12, 6 h), to better understanding of the effect of HRT on micropollutant removal. The MBBR as pretreatment to a membrane bioreactor (MBBR-MBR hybrid system) was also evaluated. Four groups of frequently detected micropollutants in wastewater (total 22 compounds) were selected, namely pharmaceuticals and personal care products (PPCPs), pesticides, hormones and industrial chemicals. The MBBR alone showed stable and effective removals of TOC (92.6% - 95.8%), COD (93.0% - 96.1%) and NH4-H (73.6%-95.6%) at all HRTs while improving PO₄₋P removal at HRT of 18 h. The MBBR showed the highest performance efficiency for removing DOC, COD, NH₄₋N, PO₄₋P and TN at HRT of 18 h, which were 96.1±0.4%, 97.4±0.8%, 91.1±1.6%, 49.9±7.2%, and 72.3±6.9%, respectively. This could be explained by the food to microorganisms (F/M) ratio in the MBBR. In addition, higher NH₄₋N removal at HRT of 18 h could be attributed to the increased population of ammonium oxidation bacteria in the MBBR unit. Moreover, the use of phosphate for biomass growth and the phosphorus uptake by phosphate accumulating organisms (PAOs) could contribute to the high removal of PO₄₋P at HRT of 18 h. In terms of micropollutants removal, MBBR achieved comparable removal compared to other biological treatment such as activated sludge processes and membrane bioreactor. Although the micropollutants were subjected to biodegradation and sorption, the results indicated compound-specific variation in removal at all HRTs, ranging from 10.7% (carbamazepine) to 98.4% (ibuprofen). Among the selected micropollutants, most of them were biodegradable excluding carbamazepine, fenoprop and metronidazole. In addition, the micropollutants removal could remain constantly high even at lower HRTs with more consistent removal efficiency over the experimental period (except for carbamazepine, fenoprop, 17α-ethinylestradiol and 4-tert-octylphenol). Particularly, at HRT of 18 h, the removal of diclofenac was significantly improved by more than 30% and the removals of ketoprofen, gemifibrozil, acetaminiphen, bisphenol A, and pentachlorophenol were also better. Overall, HRT of 18 h was the optimum HRT for biological degradation of the micropollutants in the MBBR. When using an MBBR as pretreatment to an MBR, the MBBR-MBR hybrid system achieved better removal efficiencies for selected micropollutants, such as metronidazole and carbamazepine. Both metronidazole and carbamazepine are nitrogen bearing compounds, where nitrogen is bound to the cyclic structure. The infinite SRT applied in this study could have facilitated the enhanced removal of the nitrogenous compounds. Even MBR can prevent the washout of slow-growing microorganisms like nitrifiers, the impact of MBR removal was minimal at all HRTs. This may probably due to the low MLSS concentration and the large pore size (0.2 μm; two orders of magnitude larger than the molecular sizes of micropollutants) of the MF membrane used in this study. In addition, a longer HRT (e.g. HRT of 24 h or 18 h) can significantly mitigate membrane fouling when compared with a relatively short HRT (e.g. HRT of 6 h). Especially, the TMP value maintained less than 15 kPa for 60 days (HRT of 18 h) and 68 days (HRT of 24 h). The level of EPS were similar at the beginning of all HRTs, then gradually increased to 15.24 mg/L, 16.43 mg/L, 19.88 mg/L and 22.93 mg/L at the end of operation for MBBR unit under HRT of 24 h, 18 h, 12 h, and 6 h, respectively. The SMP concentration varied for different HRTs but showed minor variation under the same HRT. The SMP concentration was lower at HRT of 24 h, while a significantly higher SMP concentration was observed at HRT of 6 h. As a whole, the MBBR-MBR hybrid system showed improvement in both micropollutants elimination and mitigation in membrane fouling