Continuous Wastewater Treatment Research Articles

Biodegradation of tetrahydrofuran by Pseudomonas oleovorans DT4 immobilized in calcium alginate beads impregnated with activated carbon fiber: Mass transfer effect and continuous treatment

A novel entrapment matrix, calcium alginate (CA) coupled with activated carbon fiber (ACF), was prepared to immobilize Pseudomonas oleovorans DT4 for degrading tetrahydrofuran (THF). The addition of 1.5% ACF increased the adsorption capacity of the immobilized bead, thus resulting in an enhanced average removal rate of 30.3mg/(Lh). The synergism between adsorption and biodegradation was observed in the hybrid CA-ACF beads instead of in the system comprising CA beads and freely suspended ACF. The effective diffusion coefficient of the CA-ACF bead was not significantly affected by bead size, but the bead's value of 1.14×10(-6)cm(2)/s (for the bead diameter of 0.4 cm) was larger than that of the CA bead by almost one order of magnitude based on the intraparticle diffusion-reaction kinetics analysis. Continuous treatment of the THF-containing wastewater was succeeded by CA-ACF immobilized cells in a packed-bed reactor for 54 d with a >90% removal efficiency.

A system combining microbial fuel cell with photobioreactor for continuous domestic wastewater treatment and bioelectricity generation

A coupled system consisting of an upflow membrane-less microbial fuel cell (upflow ML-MFC) and a photobioreactor was developed, and its effectiveness for continuous wastewater treatment and electricity production was evaluated. Wastewater was fed to the upflow ML-MFC to remove chemical oxygen demand (COD), phosphorus and nitrogen with simultaneous electricity generation. The effluent from the cathode compartment of the upflow ML-MFC was then continuously fed to an external photobioreactor for removing the remaining phosphorus and nitrogen using microalgae. Alone, the upflow ML-MFC produces a maximum power density of 481 mW/m(3), and obtains 77.9% COD, 23.5% total phosphorus (TP) and 97.6% NH4 (+)-N removals. When combined with the photobioreactor, the system achieves 99.3% TP and 99.0% NH4 (+)-N total removal. These results show both the effectiveness and the potential application of the coupled system to continuously treat domestic wastewater and simultaneously generate electricity and biomass.

Integration of ion exchange and electrodeionization as a new approach for the continuous treatment of hexavalent chromium wastewater

Mining and electroplating wastewaters contain many harmful ions, which are discharged into waterways and water bodies and cause significant environmental damage. Hexavalent chromium (Cr(VI)) is an ion that is commonly present in these effluents, which has been proven as toxic to humans. In the present work, continuous ion exchange and electrodeionization are proposed as a new hybrid technology for the effective treatment of Cr(VI) wastewater as well as the recovery of chromium ions. We have systemically studied a strong basic macroreticular anion exchange resin (Amberlite® IRA900) for the removal of Cr(VI). The ion exchange isotherm and kinetics of the resin were determined, showing that the IRA900 anionic ion exchange resin has a high capacity for ion exchange with hexavalent chromium (116mg Cr(VI) per gram of resin). When the anionic resin was combined with a strong acidic macroreticular cation exchange resin (Amberlite® 200C) and employed in continuous electrodeionization, over 98.5% of Cr(VI) was continuously removed from the dilute compartment with an energy consumption of less than 0.07kWh/m3, while Cr(VI) was recovered in the concentrate compartment.

TiO2/β-SiC foam-structured photoreactor for continuous wastewater treatment

This study of photocatalytic degradation of wastewater was carried out in alveolar cell β-SiC foam-structured photocatalytic reactors working in a recirculation mode. The immobilization of TiO2 on β-SiC foams was efficiently obtained through a sol-gel technique in acidic conditions. In order to optimize degradation yields obtained by the foam-structured prototype reactor for the photocatalytic water treatment, the operating conditions of the photoreactor have been investigated and the efficiency of the process was evaluated by measuring the photocatalytic degradation of Diuron (3-(3,4-dichlorophenyl)-1,1-dimethyl-urea)) under UV irradiation. Kinetic studies were carried out by investigating the influence of different parameters controlling the reaction (TiO2 loading and β-SiC foam cell size). The ageing of TiO2/β-SiC foam photocatalytic materials and the mineralization (TOC, Cl-, NO3- and NH4+) of Diuron were investigated.

Response surface-optimized Fenton’s pre-treatment for chemical precipitation of struvite and recycling of water through downstream nanofiltration

Experimental investigations were carried out on a new membrane-integrated hybrid treatment scheme for removal of hazardous cyanide and phenol from coke wastewater and chemical precipitation of ammonia as a value-added struvite by-product. Fenton’s pre-treatment with response surface optimization ensured very effective removal of cyanide and phenol facilitating subsequent chemical precipitation of over 98% ammonia as pure struvite fertilizer. Integration of micro and nano-membrane filtration with these chemical treatment units raised water quality to reusable level. Largely fouling-free flat sheet cross flow membrane modules could remove over 96–98% of the chemical contaminants while still yielding a high flux of 116l/h/sqm of the membrane surface at a transmembrane pressure of only 15–16 bars. The new integrated scheme embracing the concept of zero emission and value addition is a novel approach in continuous treatment of industrial wastewater for recycling.

Response surface optimization of a dynamic dye adsorption process: a case study of crystal violet adsorption onto NaOH-modified rice husk

The adsorption of crystal violet from aqueous solution by NaOH-modified rice husk was investigated in a laboratory-scale fixed-bed column. A two-level three factor (2(3)) full factorial central composite design with the help of Design Expert Version 7.1.6 (Stat Ease, USA) was used for optimisation of the dynamic dye adsorption process and evaluation of interaction effects of different operating parameters: initial dye concentration (100-200 mg L(-1)), flow rate (10-30 mL min(-1)) and bed height (5-25 cm). A correlation coefficient (R (2)) value of 0.999, model F value of 1,936.59 and its low p value (<0.0001) along with lower value of coefficient of variation (1.38 %) indicated the fitness of the response surface quadratic model developed during the present study. Numerical optimisation applying desirability function was used to identify the optimum conditions for a targeted breakthrough time of 12 h. The optimum conditions were found to be initial solution pH=8.00, initial dye concentration=100 mg L(-1), flow rate=22.88 mL min(-1) and bed height=18.75 cm. A confirmatory experiment was performed to evaluate the accuracy of the optimised procedure. Under the optimised conditions, breakthrough appeared after 12.2 h and the column efficiency was determined as 99 %. The Thomas model showed excellent fit to the dynamic dye adsorption data obtained from the confirmatory experiment. Thereby, it was concluded that the current investigation gives valuable insights for designing and establishing a continuous wastewater treatment plant.

Polyelectrolyte-Promoted Forward Osmosis–Membrane Distillation (FO–MD) Hybrid Process for Dye Wastewater Treatment

Polyelectrolytes have proven their advantages as draw solutes in forward osmosis process in terms of high water flux, minimum reverse flux, and ease of recovery. In this work, the concept of a polyelectrolyte-promoted forward osmosis-membrane distillation (FO-MD) hybrid system was demonstrated and applied to recycle the wastewater containing an acid dye. A poly(acrylic acid) sodium (PAA-Na) salt was used as the draw solute of the FO to dehydrate the wastewater, while the MD was employed to reconcentrate the PAA-Na draw solution. With the integration of these two processes, a continuous wastewater treatment process was established. To optimize the FO-MD hybrid process, the effects of PAA-Na concentration, experimental duration, and temperature were investigated. Almost a complete rejection of PAA-Na solute was observed by both FO and MD membranes. Under the conditions of 0.48 g mL(-1) PAA-Na and 66 °C, the wastewater was most efficiently dehydrated yet with a stabilized PAA-Na concentration around 0.48 g mL(-1). The practicality of PAA-Na-promoted FO-MD hybrid technology demonstrates not only its suitability in wastewater reclamation, but also its potential in other membrane-based separations, such as protein or pharmaceutical product enrichment. This study may provide the insights of exploring novel draw solutes and their applications in FO related processes.

Electricity generation and microbial community in a submerged-exchangeable microbial fuel cell system for low-strength domestic wastewater treatment

A submerged type microbial fuel cell (MFC) system, which consisted of six readily exchangeable air–cathode MFCs, was evaluated for continuous treatment of low-strength domestic wastewater. When supplied with synthetic wastewater (COD 100mg/L), the system showed increasing maximum power densities from 191 to 754mW/m2 as COD loading rates increased (0.20–0.40kg/m3/day). COD removal efficiencies decreased with increased COD loading rates but the effluent COD concentrations met the relevant effluent quality standard (CODMn 20mg/L) at all conditions. The system was then operated with domestic wastewater (c.a. 100mg COD/L) at 0.32 and 0.43kg/m3/day. The system showed much lower power densities (116–149mW/m2) at both loading rates, compared to synthetic wastewater. Anodic microbial communities were completely different when the wastewater type was changed. These results suggest that the newly developed MFC system could be applied to treat low-strength domestic wastewater without requiring any additional organic removal stage.

A novel microbial fuel cell and photobioreactor system for continuous domestic wastewater treatment and bioelectricity generation

A system containing a sequential anode-cathode configuration microbial fuel cell and a photobioreactor was developed for continuous treatment of wastewater and electricity generation. Wastewater was treated by the fuel cell to decrease the chemical oxygen demand (COD), phosphorus and nitrogen and to produce electricity. The effluent from the cathode compartment of the cell was continuously fed to an external photobioreactor to remove the remaining P and N using microalgae. Alone, the fuel cell generated a maximum power of 20.3 W/m(3) and achieved removal of 85 % COD, 58 % total phosphorus (TP) and 91 % NH(4) (+)-N. When coupled with the photobioreactor, the system removed 92 % TP and 99 % NH(4) (+)-N. These results demonstrate both the effectiveness and the potential application of the coupled system to continuously treat domestic wastewater and simultaneously generate electricity.

NaCS–PDMDAAC immobilized autotrophic cultivation of Chlorella sp. for wastewater nitrogen and phosphate removal

The unicellular green microalgae, Chlorella sp., entrapped in sodium cellulose sulphate/poly-dimethyl-diallyl-ammonium chloride (NaCS–PDMDAAC) to create microalgae capsules were used to remove total nitrogen (T-N) and phosphate (PO43−-P) from artificial wastewater. Batch and semi-continuous cultivations with capsules recycling were carried out in shake flasks within an illuminated incubator. Experimental results showed that the NaCS–PDMDAAC capsules have desirable biophysical properties such as good mechanical stability, biocompatibility with the microalgae cells resulting in biomass enrichment within the capsules, and high substrate concentration tolerance. NaCS–PDMDAAC Chlorella sp. capsules displayed a considerable high T-N and PO43−-P removal rate of 12.56 and 10.24mg/g biomass per day respectively. The developed immobilized microalgae system has the potential for continuous wastewater treatment operation with reduced downstream operation cost due to the large size of the capsules being 5–6mm.

Continuous flow electrocoagulation for MSG wastewater treatment using polymer coagulants via mixture-process design and response-surface methods

This study investigates the feasibility of applying a continuous wastewater treatment, which is accomplished using a plate-type electrocoagulator in a zigzag flow pattern in series of bipolar plates. Compared to conventional coagulation-flocculation techniques, the continuous flow electrocoagulation was found to be advantageous for the facile removal of COD and colored pollutants from wastewater. On the other hand, there are more operating cost accompanying the excess energy consumption and the short lifetime of electrodes due to high acidity and salt concentration in the monosodium glutamate (MSG) wastewater used. Hence, electrocoagulation experiments with a co-current feeding of polymer coagulants were conducted to improve the treatment for MSG wastewater. We applied statistical design of experiments in an effective approach for the screening and simulation of the influence of operational variables via mixture-process experiments and response-surface methods. The results of multiple regression analysis suggest crucial effects of applied cell voltage, feed flow rate, and ternary polymer coagulants on the response performance. This approach also led to the optimization of mixture constituents for ternary polymer coagulants under an electric field. Here the maximum removals of color and COD for MSG wastewater treatments were obtained at continuous removal rates of 86% and 68%, appreciably better than those of individual polymer components alone or without polymer used. This study therefore indicates the promising potential of the continuous flow electrocoagulation for wastewater treatments.

Membrane Bioreactors: Results of Low Power Use Design Procedures

Membrane Bioreactors: Results of Low Power Use Design ProceduresThe use of membrane bioreactors (MBR) continues to increase across the world. In dry countries such as Australia, they become the foundation technology for reclaimed water production facilities. However, there is a perception that an MBR uses significantly more energy than a conventional continuous wastewater treatment facility and this is incompatible with greenhouse gas concerns especially in...Author(s)John MessengerGraeme LewisSimon PagePeter ZemekSourceProceedings of the Water Environment FederationSubjectSession 104: Membrane Bioreactors: Optimization of Design and PerformanceDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2011ISSN1938-6478SICI1938-6478(20110101)2011:8L.6691;1-DOI10.2175/193864711802793362Volume / Issue2011 / 8Content sourceWEFTECFirst / last page(s)6691 - 6703Copyright2011Word count194Subject keywordsMembrane bioreactornutrient removalpower consumption

Activated carbon supported TiO 2-photocatalysis doped with Fe ions fo continuous treatment of dye wastewater in a dynamic reactor

Fe-doped TiO 2 coated on activated carbon (Fe-TiO 2/AC, FTA) composites were prepared by an improved sol-gel method and characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, inductively coupled plasma mass spectrometry and BET surface area analysis. Obtained FTA composites were applied to the continuous treatment of dye wastewater in a dynamic reactor. The effects of Fe ion content, catalyst content, UV-lamp power and flowrate of the continuous treatment of dye wastewater on degradation efficiency were analyzed to determine the optimum operating conditions of dye wastewater degradation. Continuous photocatalytic experiments provided interesting results that FTA had a high chemical oxygen demand (COD) removal rate compared with TiO 2, Fe doped TiO 2 (FT) and TiO 2 coated on activated carbon (TA). In particular, when using the FTA catalyst with a Fe ion content of 0.33%, the kinetic content ( k = 0.0376) of COD removal was more than the sum of both TA (0.0205) and 0.33% FT (0.0166). FTA showed a high photoactivity because of a synergistic effect between Fe ions and AC on TiO 2, which is higher than the individual effects of AC or Fe ions on TiO 2. Additionally, for the photocatalytic degradation of dye wastewater, the optimum Fe ion content, catalyst content, UV-lamp power and flowrate were 0.33%, 6 g/L, 60 W (two lamps) and 300 mL/hr, respectively. An investigation of catalyst reuse revealed that the 0.33% FTA showed almost no deactivation in photocatalytic degradation of naturally treated wastewater.

Municipal tertiary treatment: Disc filters enhanced by pleated configuration

How can disc filtration make an impact in continuous wastewater treatment? Miguel Gutierrez of Siemens Water Technologies explains the fundamentals of disc filtration and how it can provide an economical and sustainable solution for municipal tertiary treatment applications.

Decolorization and semi-batch continuous treatment of molasses distillery wastewater by Aspergillus tubingensis DCT6

Large quantities of deeply pigmented molasses distillery wastewater (MDW), are discharged during the production of bio-ethanol from molasses. Conventional biological wastewater treatment is not effective in removing the molasses pigments. In the present study, a MDW treatment system was developed with combination treatment involving biodecolorization and biotreatment by Aspergillus tubingensis DCT6, together with physical decolorization by ozonation after treatment by activated sludge. A. tubingensis DCT6, which was isolated from soil, decolorized 44% of the pigments in MDW without adding any nutrients. The combination treatment with A. tubingensis DCT6 and activated sludge method (fungi-activated sludge treatment) removed about 90% of organic compounds from MDW and appears to reduce the amount of space and water required for treatment. The fungi-activated sludge treatment reduced the time needed for decolorization by ozone by 83%. Replacing fresh seed sludge at regular intervals was useful to maintain the dominance and decolorization ability of A. tubingensis DCT6. The entire treatment obtained a decolorization ratio of 89-94% and removed more than 90% of each of DOC, DTN, and DTP.

Continuous electrochemical treatment of simulated industrial textile wastewater from industrial components in a tubular reactor

The continuous electrochemical treatment of industrial textile wastewater in a tubular reactor was investigated. The synthetic wastewater was based on the real process information of pretreatment and dyeing stages of the industrial mercerized and non-mercerized cotton and viscon production. The effects of residence time on chemical oxygen demand (COD), color and turbidity removals and pH change were studied under response surface optimized conditions of 30 °C, 25 g/L electrolyte concentration and 3505 mg/L COD feed concentration with 123.97 mA/cm 2 current density. Increasing residence time resulted in steady profiles of COD and color removals with higher treatment performances. The best column performance was realized at 3 h of residence time as 53.5% and 99.3% for COD and color removals, respectively, at the expense of 193.1 kWh/kg COD with a mass transfer coefficient of 9.47 × 10 −6 m/s.

Continuous High Rate Anaerobic Treatment of Oleic Acid Based Wastewater is Possible after a Step Feeding Start-Up

Mineralization of a synthetic effluent containing 50% COD as oleic acid was achieved in a continuous anaerobic reactor at organic loading rates up to 21 kg COD m(-3) day(-1), HRT of 9 h, attaining 99% of COD removal efficiency and a methane yield higher than 70%. A maximum specific methane production rate of 1170 +/- 170 mg COD-CH4 g VS(-1) day(-1) was measured during the reactor's operation. A start-up strategy combining feeding phases and batch degradation phases was applied to promote the development of an anaerobic community efficient for long chain fatty acids (LCFA) mineralization. Through the start-up period, the methane yield increased gradually from 67% to 91%, and LCFA accumulated onto the sludge only during the first 60 days of operation. For the first time, it is demonstrated that a step feeding start-up is required to produce a specialized and efficient anaerobic community for continuous high rate anaerobic treatment of LCFA-rich wastewater.

Multivariate statistical monitoring of continuous wastewater treatment plants

In this paper, different multivariate statistical approaches for analysing wastewater treatment process data are presented and compared. For this purpose, all the methods have been tested using one-year operational data in a simulation model benchmark. The general monitoring strategy adopted includes a screening stage to improve data quality, an adaptive model to detect and diagnose abnormal events, and two complementary tools for helping in the diagnosis of the faults. The first one is based on the development of a local model that captures the most recent process behaviour and the second one on the application of fuzzy c-means clustering to the scores of the monitoring model. The results have shown that simple scaling parameters adaptation is sufficient to obtain a model useful for monitoring the process during the whole period. Monitoring the deviations from the average daily behaviour showed clear detections of the disturbances in the Hotelling's T 2-statistic and this feature was useful to determine different operational states (disturbances) in the process by clustering the PCA scores. On the other hand, the proposed procedure for isolation based on a local model improved the diagnosis results in terms of the responsible variables identified and the indication of the beginning of the fault.

Development of a continuous process to adapt the textile wastewater treatment by fungi to industrial conditions

The scale-up of a 10 L air pulsed bioreactor for the continuous treatment of textile wastewater by pellets of the white rot fungus Trametes versicolor has been carried out, based on the geometric similitude with lab-scale bioreactors (0.5 and 1.5 L). Decolourisation experiments of 150 mg L −1 Grey Lanaset G dye solution carried out in the pilot-scale bioreactor showed that in both discontinuous and continuous treatment with an HRT of 48 h, the decolourisation levels were higher than 90%. Some operational changes were carried out in the continuous decolourisation treatment of the dye solution in order to adapt the process to industrial conditions such as, non-sterilization of the dye solution, use of tap water instead of distilled water plus macronutrients and micronutrients and the use of industrial quality co-substrate instead of reagent grade. The pilot system was working continuously during 3 months and over 70 days without sterilization of the dye feeding solution, achieving good decolourisation levels (78% average during the treatment). Continuous treatment of real industrial textile wastewater under non-sterile conditions was carried out during 15 days in the pilot-scale bioreactor, with colour reduction levels between 40 and 60%. These dye concentrations are regarded as environmentally acceptable to be discharged into a municipal wastewater treatment plant if necessary according to the local regulation.

The use of polyetherimide hollow fibres in a submerged membrane bioreactor operating with air backwashing

The performance of a submerged membrane bioreactor (SMBR), containing hollow fibre membranes, was investigated for the continuous treatment of wastewater. The hydrophilic polyetherimide membranes were characterised and tested in 5 days experiments using air backwashing to maintain permeate flux. Permeation and air backwashing cycles were investigated, varying the permeation period (15–30 min) with fixed backwashing time (0.5 min). The effect of different hydraulic retention times (2–5 h) on the reactor performance was also assessed. Operation at low hydraulic retention times, with organic load up to 8 kg COD m −3 d −1, led to a sludge production of 0.05 kg VSS kg COD −1, which is considered low in comparison with conventional activated sludge process. The bioreactor produced an effluent free of turbidity and reached high COD (95–100%) and TOC (92–96%) removals. In a long-term operation assay (101-d), the reactor also maintained high COD (92%) and TOC (93%) removals. Polysaccharides content of the reactor supernatant contributed to produce a thin gel layer on the hollow fibre surface during long-term operation.