Reuse of car wash wastewater by chemical coagulation and membrane bioreactor treatment processes

Car wash wastewater contains significant concentrations of contaminants such as nutrients, organics, particulate matter, sand, oil, grease, diesel detergents and so on. A range of treatment processes such as a membrane bioreactor (MBR), coagulation and ozonation were investigated to treat car wash wastewater. Ozonation was effective in removing the chemicals and suspended solids; the removal efficiency was greater than the coagulation process. Once the MBR system was acclimatised, 100% of suspended solids, 99.2% of COD, 97.3% of TOC and 41% of ammonia were removed. This study demonstrates that MBR is a potentially promising treatment system for recycling car wash wastewater which could be reused in the same car wash station.

Reclaiming spent liquor from cotton reactive dyebaths using nanofiltration membrane for possible reuse of water and salt

During dyeing, salts are placed in a dyebath to aid the fixation of various dyes on to the fabric while bases are added to raise the pH from around neutral to pH 11. Afterwards, the used dyebath solution, called dyebath spent liquor, is discharged with almost all the salts and bases added as well as unfixed dyes. Consequently, a lot of raw materials are lost in the waste stream ending up in the environment as pollutants. In this study, possibilities of reusing water and salts of dyebathes were investigated, using a nanofiltration membrane. When the salt concentration in the spent liquor was increased from 10 to 80 g/L, the salt rejection by membrane was found to decrease initially; however, the salt rejection increased over the time, which was not expected. The aggregation of dye was also studied and found to decrease in the concentrate when the salt concentration was increased. This may be due to the aggregation of salt in the concentrate, which explains the increase in salt rejection. This information is useful for the textile industry in evaluating the treated water quality for the purpose of reuse.

Preparation of cross-linked nanoporous poly(ethylene glycol) diacrylate membrane in hexagonal lyotropic liquid crystal phases

Cross-linked poly(ethylene glycol) diacrylate (PEGDA) membranes were prepared by polymerization in periodic nanostructured lyotropic liquid crystals (LLC) hexagonal phases under UV light. A series of membranes were prepared under different purification treatment conditions. Polarized light microscope was employed to determine the LLC phase texture of LLC system before and after polymerization. It is found that the LLC hexagonal structure retained to some degree after polymerization. The interior structures of final membranes were investigated with scanning electron microscope (SEM). The results suggested that purification process affect the structure retention.

Nanofiltration for the possible reuse of water and recovery of sodium chloride salt from textile effluent

During the reactive dyeing of cotton, salts such as sodium chloride (NaCI) are placed in a dyebath to aid the exhaustion of various dyes onto the fabric while bases are added to raise the pH from around neutral to pH 11 to achieve fixation. Afterwards, the used dyebath solution, called dyebath spent liquor, is discharged with almost all the salts and bases added as well as unfixed dyes. Consequently, many raw materials are lost in the waste stream ending up in the environment as pollutants. In this study possibilities of reusing the water and salts of dyebaths were investigated using a nanofiltration membrane. When the NaCI concentration in the spent liquor was increased from 10 to 80 g/L, the NaC1 rejection by the membrane was found to decrease initially; however, the NaC1 rejection increased over time, which was not expected. The aggregation of dye was also studied and found to decrease in the concentrate when the salt concentration was increased. This information is useful for the textile industry in evaluating the treated water quality for the purpose of reuse.

Application of submerged membrane bioreactor for aquaculture effluent reuse

Discharging the nutrient rich aquaculture effluents into inland water bodies and oceans is becoming a serious concern due to the adverse effect that brings in the form of eutrophication and subsequent damages to those waters. A laboratory scale biological reactor consisting of a denitrifying compartment followed by a submerged membrane bioreactor (SMBR) compartment was used to treat 40 L d−1 of aquaculture effluent with an average concentration of 74 mg L−1 nitrate (NO3 − ). Sugar was added to the aquaculture effluent in order that to enter into the denitrifying compartment at a carbon: nitrogen ratio (C:N) of 2:1 and 4:1. A hollow fibre membrane with a pore size of 0.4 μm and a filtration area of 0.20 m2 was used in the SMBR and was operated at an average flux of 0.20 m3 m−2 d−1. An intermittent suction period of 12 min followed by a relaxation period of 3 min was maintained in the SMBR throughout the experiment. Different aeration rates of 1, 3, 5 and 10 Lpm were applied to the SMBR to determine the rate of membrane fouling and 5 Lpm aeration rate was found to be optimum with respect to the rate of fouling of membrane at a C:N ratio of 4:1. The average rate of fouling at 1, 3, 5 and 10 Lpm were 1.17, 0.70, 0.48 and 0.52 kPa d−1, respectively. The increase in the rate of fouling when the aeration was increased from 5 to 10 Lpm may be due to the breakage of suspended particles into finer particles which could have increased the fouling of membrane. It was also found that increasing the C:N ratio from 2:1 to 4:1 resulted in more cake being formed on the membrane surface as well as an increase in the reduction of NO3 − from 64% to 78%. Preliminary calculations show that 2.4 to 3.2 g of suspended solids could be accumulated per square meter of membrane surface before physical cleaning of membrane is required (at a transmembrane pressure of 20 kPa).

Performance evaluation of different ultrafiltration membranes for the reclamation and reuse of secondary effluent

This study investigates and compares the performance of two different types of ultrafiltration (UF) membranes in the recovery of water from secondary treated wastewater. Filtration experiments were carried out on a pilot scale cross-flow unit using synthetic wastewater similar to the quality of secondary treated wastewater by varying the operating parameters such as transmembrane pressure (TMP), feed composition and membrane configuration. The filtration experiments demonstrated that the flux recovery through spiral polymeric UF membrane was more sensitive to the variation in TMP compared to the tubular ceramic UF membrane over the range of TMP studied. The resistance in series model was used for the evaluation of the resistance to the permeate flux. The fouling resistance, particularly irreversible resistance compared to reversible resistance plays a major role in the total resistance for the tubular ceramic membrane. In contrast clean membrane resistance is the major contributor for the total resistance of the spiral polymeric membrane. Finally, the effectiveness of the filtration treatment was determined by evaluating the rejection coefficients for various pollution indices of the wastewater. Significant differences in the performance of the membrane types were observed which are likely to impact on the selection, operation and maintenance of the membrane system.

Comparison of the performance of ceramic microfiltration and ultrafiltration membranes in the reclamation and reuse of secondary wastewater

Advanced treatment of secondary wastewater generally has been achieved using polymeric microfiltration and ultrafiltration membranes. Newly developed ceramic membranes offer distinctive advantages over the currently employed membranes and were recently introduced for the purpose. This paper presents results of a pilot study designed to investigate the application of ceramic microfiltration (MF) and ultrafiltration (UF) membranes in the recovery of water from secondary wastewater. Synthetic wastewater similar to the quality of secondary treated wastewater was fed to ceramic MF and UF system in a cross-flow mode. The filtration experiments revealed that the flux recovery through tubular ceramic MF membrane was more sensitive to the variation in TMP compared with the tubular ceramic UF membrane over the range of TMP studied. The resistance in series model was used for the evaluation of the resistance to the permeate flux. The results revealed that for ceramic UF membrane, the contribution to the total resistance of fouling was higher than the inherent of the clean membrane resistance. However, both the clean membrane resistance and the fouling resistance contribute equally in the case of MF membrane. Various wastewater indices were measured to evaluate the effectiveness of the filtration treatment. The ceramic UF membrane consistently met water quality in the permeate in terms of colour, turbidity, chemical oxygen demand and absorbance, suggesting that the permeate water could be made to be reused or recycled for suitable purposes. However, MF membrane appeared to be incompetent with respect to the removal of colour. The unified membrane fouling index (UMFI) was used to measure the fouling potential of both the membranes. The result showed that for UF membrane, the value of UMFI is one order of magnitude higher than MF membrane. The overall results suggest that there were significant differences in the performance of both the ceramic UF and MF membranes that are likely to impact on the operation and maintenance of the membrane system.

Performance of reverse osmosis (RO) for water recovery from permeates of membrane bio-reactor (MBR)

In this study, permeate from a hollow fiber polyethylene (PE) membrane bio-reactor (MBR) system treating synthetic agricultural wastewater was fed into a cellulose acetate brackish water reverse osmosis (BWRO30 2540) membrane system; three different trans-membranes pressures (TMPs) of 1000, 2500, and 4000 kPa were selected to evaluate the system performance in terms of general operating parameters as well as the removal of chosen important potential fouling water quality parameters. The results showed that highest corrected permeate flux rate was at a TMP of 2500 kPa, whereas lowest recorded at a TMP of 4000 kPa. Similar situation prevailed in water recovery rate. But temperature corrected specific fluxes decreased as the applied TMPs increased. In all selected TMPs, more than 96% of salinity was removed. Permeate from MBR as feed to reverse osmosis required frequent chemical cleaning than the microfiltration/ultrafiltration (MF/UF) permeates and granular media filter (GMF) filtered in order to maintain the required rate of product water. One of the reasons for this frequent chemical cleaning is due to higher total organic carbon as well as total nitrogen (TN) in the MBR permeate. This result needs to be further evaluated through field trials.

Effect of feed temperature and membrane orientation on pre-treatment sludge volume reduction through forward osmosis

This study focuses on volume reduction of pre-treatment sludge as well as on dilution of reverse osmosis (RO) concentrate through emerging forward osmosis (FO) technology where RO concentrate draws water from the pre-treatment sludge (feed solution) in order to reduce pre-treatment sludge volume and increase the RO water recovery. Experiments were carried out using two different types of sludge i.e. (1) synthetic pre-treatment sludge (Lab sludge) which has lower salinity and (2) actual sludge from Perth Seawater Desalination Plant, Australia (Perth Seawater Desalination Plant (PSDP) sludge) which has higher salinity. Effect of membrane orientation (FO and pressure-retarded osmosis (PRO) modes) and temperature of pre-treatment sludge on permeate water flux was investigated. There was a significant increase in water flux from 3.2 to 10.2 LMH (i.e. ~3 times higher) when temperature increased from 20 to 40°C for Lab sludge in PRO mode. However, there is no significant effect of temperature on water flux in FO mode for Lab sludge. On the contrary for PSPD sludge, there was no effect on water flux with increase in temperature at PRO mode. Dissolved ions in the porous side increased the severity of concentrative internal concentration polarization; hence, it could reduce the flux. There was no significant change in water flux when temperature increased from 20 to 40°C for PSDP sludge in FO mode. However, higher amount of water has permeated from Lab sludge compared to PSDP sludge in FO mode. © 2014 © 2014 Balaban Desalination Publications. All rights reserved.

Alignment and characterisation of hexagonal lyotropic liquid crystalline nanostructure for membrane synthesis

Weiwei has been devoting to the alignment and characterisation of hexagonal lyotropic liquid crystalline nanostructure to uniform orientation by applying external fields. According to the Synchrotron small angle x-ray scattering results, it has produced distinct progress. This technique is aimed for improving the filtration efficiency of nanoporous membranes.

Wastewater reuse and treatment options for the dairy industry

Milk-processing plants generate significant quantities of wastewater with relatively high organic matter concentrations on a daily basis. In addition to environmental damage that can result from the discharge of these wastewaters into the natural waterways, the presence of products such as milk solids into wastewater streams represents a loss of valuable product for the plants. This paper presents a review of wastewater management practices employed by six milk-processing plants in Victoria, Australia. In all six plants investigated, milk powder represents a major product. During the milk powder production, water is evaporated, condensed and can be reused for various purposes with a significant impact on water usage. Other major products are anhydrous milk fat, cheese, butter, and UHT milk. The effectiveness of the practices was assessed through two main criteria: first through the water to milk intake ratio, and the waste volume coefficient. Both parameters characterise the plant efficiency in regard of water consumption and water reuse, Information on cleaning chemical usage and recovery was also assessed as part of the review. Significant discrepancies emerge between the plants first due to the products manufacturad and water reuse possibilities available in each plant. Second the type of treatment technologies used for condensate and cleaning solution influences the figures. One of the investigated plants is almost self-sufficient for water, emphasising the benefits gained from the use of technologies like membrane separations for condensate and cleaning solution treatment. In some cases, less cost-intensive technologies such as a clarifier are successful to improve cleaning agent recovery.

Cycling performance of lithium metal polymer cells assembled with ionic liquid and poly(3-methyl thiophene)/carbon nanotube composite cathode

A poly(3-methylthiophene) (PMT)/multi-walled carbon nanotube (CNT) composite is synthesized by in situ chemical polymerization. The PMT/CNT composite is used as an active cathode material in lithium metal polymer cells assembled with ionic liquid (IL) electrolytes. The IL electrolyte consists of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) and LiBF4. A small amount of vinylene carbonate is added to the IL electrolyte to prevent the reductive decomposition of the imidazolium cation in EMIBF4. A porous poly(vinylidene fluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) film is used as a polymer membrane for assembling the cells. Electrochemical properties of the PMT/CNT composite electrode in the IL electrolyte are evaluated and the effect of vinylene carbonate on the cycling performance of the lithium metal polymer cells is investigated. The cells assembled with a non-flammable IL electrolyte and a PMT/CNT composite cathode are promising candidates for high-voltage–power sources with enhanced safety.

Effects of backwashing on PVDF membrane fouling by organic foulants

Membrane is usually subject to fouling by various organic foulants, such as yeast, protein and sodium alginate during filtration. Backwashing is a common practice to reduce membrane fouling. It is essential to evaluate the effects of backwashing on fouling in order to optimize operational parameters. In this experiment, poly(vinylidene fluoride) (PVDF) membranes were used to filter organic foulants from suspensions in a dead-end stirred cell. Three types of organic foulants including yeast, protein and sodium alginate which were stained with fluorescent dyes before filtration were used with different combinations in the experiments. After filtration, the PVDF membrane was backwashed.

Consequently, a stack of images, instrumental data and sample data were captured from the fouling layers on the PVDF membrane surface using confocal laser scanning microscope (CLSM) and its associated image acquisition software LAS AF. Then, the quality of the images was enhanced for better visualization and a set of quantitative fouling data were derived by using the software code developed by the project team at Deakin University.

This collection contains raw image data of poly(vinylidene fluoride) (PVDF) membrane’s fouling layer when three types of organic foulants present, which are captured by confocal laser scanning microscopy (CLSM) and its software, and the instrumental and sample metadata, the processed image data and the geometrical structure properties of the fouling layer. By comparing with the same membrane without backwashing, the efficiency of backwashing was computed.

This data collection would be useful to evaluate the backwashing efficiency of PVDF membrane in order to optimize frequency and operational conditions of backwashing by membrane materials researchers and water researchers.

Polycarbonate (PC) membrane fouling by protein and sodium alginate

This data was obtained from an experiment, where polycarbonate (PC) membranes were used to filter two types of organic foulants, including protein and sodium alginate, from suspension in a dead-end filtration cell. These model foulants were stained with fluorescent dyes before filtration. Consequently, a stack of images were captured from the fouling layers on the PC membrane surface using confocal laser scanning microscope (CLSM). This data collection contains 105 2D images of polycarbonate (PC) membranes fouling layer. This data collection would be useful to investigate membrane fouling mechanism by membrane materials researchers and water researchers.