Reverse Osmosis Concentrate Research Articles

Optimization of electrolytic system type for industrial reverse osmosis concentrate treatment to achieve effluent quality and energy savings

This study demonstrated the remarkable potential of electrolytic system type for industrial reverse osmosis concentrate (ROC) treatment on effluent quality and energy requirements. Following their individual system optimization, the required current density decreased from 20 mA cm−2 for the batch system during 4 h of electrolysis, to 5 mA cm−2 for a continuous-flow system (CFS) without effluent recirculation (CFS-A), and 3 mA cm−2 for a CFS system with a rear (CFS-B) or front (CFS-C) buffer tank for effluent recirculation (R = 1). The final or effluent chemical oxygen demand (COD) and NH4+−N levels were 31 and 0.4 mg L−1 (Batch), 24 and 0.56 mg L−1 (CFS-A) and 5.7–8.1 and 0.24–0.34 mg L−1 (CFS-B or -C), respectively. Besides the highest pollutant removal, the optimized CFS-B and -C systems also achieved the highest treatment capacity and energy efficiency, and the lowest effluent toxic organic byproduct levels due to the homogeneous diffusion characteristic of CFS systems, and the reutilization of long-lived active chlorine species (ACS) oxidants in CFS-B/C electrolytic effluent. As compared with the optimized CFS-B system, the optimized CFS-C system at an identical recirculation ratio further achieved the lowest effluent ACS level due to the ACS consumption in the front buffer tank (rather than direct discharge in the CFS-B system) and lower flow rate into the electrochemical cell (than that in the CFS-B system), and was finally recommended for future engineering implementation.

Pretreatment of Reverse Osmosis Concentrate from Reclaimed Water for Conventional and High-Efficiency Reverse Osmosis and Evaluation of Electrochemical Production of Reagents

The primary goal of this research was to investigate several water treatment unit operations for converting RO concentrate produced from treated municipal wastewater into potable water. The secondary goal was to evaluate the use of an electrochemical cell for producing the reagents needed to operate a fluidized bed crystallization reactor (FBCR), regenerate ion exchange media, and produce a ferric iron coagulating agent. The effectiveness of the pretreatment processes to prevent membrane fouling were evaluated for conventional and high-efficiency reverse osmosis (HERO). Fluidized bed crystallization removed 93 to >97% of hardness ions, 42% of silica, and 6.5% of total organic carbon. Membrane fouling during HERO was lower than that for conventional RO for pretreatment using fluidized bed crystallization and ion exchange. However, conventional RO with ferric iron coagulation following fluidized bed crystallization and ion exchange showed the least membrane fouling and increased recovery in the second stage RO by 470%. The use of an electrochemical cell for generating the reagents needed for the pretreatment processes was evaluated. Energy costs for operating the electrochemical cell for making acid, base, and ferric iron coagulant were 4.1 kWh per m3 of RO concentrate. The use of electrochemically generated reagents combined with fluidized bed crystallization produces no waste solutions from the pretreatment processes.

Oxidative degradation of bisphenol A in municipal wastewater reverse osmosis concentrate (ROC) using ferrate(VI)/hydrogen peroxide

The combination of ferrate(VI) with hydrogen peroxide (H2O2) was used for the degradation of bisphenol A (BPA) spiked in municipal wastewater reverse osmosis concentrate (ROC). The results showed that the combined Fe(VI) and H2O2 oxidant provided an additive effect to achieve greater degradation efficiencies of BPA in ROC compared to the use of Fe(VI) or H2O2 alone. The degradation efficiency of BPA was studied in detail by assessing the operating conditions, including Fe(VI) dosage, H2O2 dosage, the dosing strategy of Fe(VI) and H2O2, solution pH, and the initial concentration of BPA. It was found that over 99.0% of BPA was degraded (50 µg L−1) by using [Fe(VI)]/[H2O2] at a ratio of 1050:5000 and at pH 8.0. In addition, the degradation was also accompanied by 37.2% of dissolved organic carbon (DOC) removal and 94.0% of UV254 reduction. However, when the excess amount of H2O2 was added, it was found that H2O2 started to inhibit the degradation and the degradation efficiency of BPA in ROC lowered. It was also found that the simultaneous addition of Fe(VI) and H2O2 provided satisfactory BPA degradation. Similar degradation efficiency could be achieved by injecting the second oxidant into the system 10 min after adding the first oxidant at time zero. The apparent second-order reaction rate constant (kapp) obtained was 67.9 × 103 M−1 s−1 at a [Fe(VI)]/[H2O2] ratio of 1050:5000. The overall ecotoxicity of the treated water samples as measured by the Microtox bioassay technique decreased after the Fe(VI)/H2O2 treatment, which indicated that an insignificant amount, if not none, toxic degradation by-products was formed by the oxidative action of the Fe(VI)/H2O2 combined oxidant. The use of Fe(VI)/H2O2 as an alternative treatment option of cost-effectiveness than Fe(VI) alone in water and wastewater industries.

Highly efficient separation of organic substances from high salinity brine by nanofiltration

Efficient separation of organic compounds from the high salinity brines during the treatment of reverse osmosis concentrate (ROC) is highly desirable and also very challengeable for the purpose of zero liquid discharge (ZLD). For the general treatment process, the efficient removal of organic compounds from the NaCl rich solution before the evaporation-crystallization stage is one of the key challenges. In this work, separation of N-(2-hydroxypropyl)morpholine (NMH), 4-morpholineacetate (MHA), the major organic components of ROC in refinery, and monovalent/divalent ions from the high salinity brines by three commercial nanofiltration (NF) membranes, i.e. Desal-5DK, Desal-5DL and NF270 were systematically investigated. The effects of various parameters on the rejection performance of these three NF membranes were experimentally investigated. The results showed that the retentions of NMH and MHA were dominated by flux and pH. Single stage filtration experiments showed that the rejection to NMH and MHA with various operating parameters was high and stable for DK. In comparison, DL and NF270 had higher separation efficiency for monovalent and divalent ions. The experiments determined that the rejections of NMH and MHA were 99.16% and 98.42% under the optimized conditions, respectively, indicating that NF membranes were highly efficient for separating organic compounds from the high salinity brine.

Efficient decontamination of RO concentrate in a sonochemical zero-valent iron/persulfate Fenton-like system: The molecule-size preferred degradation of dissolved organic matters

Interference of real dissolved organic matters (DOMs) in advanced oxidation processes (AOPs) treatment of pharmaceuticals in reverse osmosis concentrates (ROC) has rarely reported. In this study, an ultrasound/zero valent iron/persulfate (US/ZVI/PS) system has been developed to degrade typical antibiotic sulfadiazine in the presence of co-existing ROC DOMs. It was found that common inorganic anions slightly affected the removal of SD, while fulvic acid (FA) and humic acid (HA) would bring medium to strong inhibition. 3D-EEM results evidenced the degradation of DOMs attributed to their competition for the oxidative radicals, suggesting the selective attack liable to larger molecular sizes. Intensive hydroxylation of HA and cleavage of C-C in FA molecule would occur respectively, where benzene ring, carbonyl or conjugated carbonyl group in DOMs would be destructed with oxidation of the nitrogen-containing functional groups. Scaled-up dosages of the agents could achieve efficient decomposition of all the three DOMs in a SD-spiked pristine ROC and all macromolecular structures were transformed into small molecules, suggesting the US/ZVI/PS system would be an good option for treating practical ROCs.

Comparative study on COD removal from reverse osmosis concentrate using two physicochemical combined processes

Reverse osmosis concentrate (ROC) produced from landfill leachate contains a substantial fraction of refractory organics with low biodegradability that is challenging for conventional wastewater treatment methods. To achieve high-efficiency ROC degradation, two physicochemical combined processes, i.e. ceramic membrane/ozone-nanofiltration (CM/O3+NF) and Ca(OH)2 coagulation-ceramic membrane/ozone-nanofiltration (Ca(OH)2+CM/O3+NF) were proposed. In this study, the removal efficiency of organic pollutants in process 1 (CM/O3+NF) and process 2 (Ca(OH)2+CM/O3+NF) was investigated, respectively. The results showed that process 1 and process 2 were both sufficient to eliminate the refractory COD, the permeates have a COD lower than the requirements for discharge. But the process 2 had a better performance than that of process 1. The COD and TOC of ROC decreased from 2500 mg/L and 1050 mg/L to 20.23 mg/L and 8.26 mg/L after process 2 treatment, and the removal efficiency was 1.9% and 4.04% higher than those of process 1, respectively. In process 2, Ca(OH)2 flocculation significantly improves the oxidation effect of CM/O3, effectively shortens the oxidation time by 25%, improves the membrane flux of the ceramic membrane, and reduces the treatment cost of the ROC. Furthermore, the change of the composition of the macromolecular organics in the ROC during the treatment of process 1 and process 2 was compared and explored through analysis by UV254, 3D-EEM, GC-MS. The results indicated that the types of organic matter in the ROC treated by Process 2 decreased from 27 to 8, which was 5 less than that of Process 1. Ca(OH)2 flocculation in process 2 significantly reduces the content of macromolecular humic acid in ROC, especially has a good flocculation effect on lipids, aldehydes, carboxylic acids, ketones and other substances containing carbon-oxygen double bonds. At the same time, Ca(OH)2 provides an alkaline environment and strengthens the decomposition ability of alkanes, alkenes, and aromatics in ROC into more soluble by-products by CM/O3. The remaining pollutants that are difficult to be oxidized are effectively filtered by NF. Overall, the Ca(OH)2+CM/O3+NF process with complementary functions has great potential in realizing effective ROC treatment.

High silica concentration in RO concentrate

Silica scaling is one of the major scaling challenges in Reverse Osmosis (RO). The safe operation practice is to keep the silica concentration below 150 mg/L in RO concentrate. This study addresses the effects of divalent cations such as calcium and magnesium on silica scaling in a seawater RO installation used as a pretreatment to Eutectic Freeze Crystallisation (EFC). Results showed that in the absence of antiscalant and divalent cations a sustained silica concentration of approximately 280 mg/L in concentrate is possible without declining membrane permeability. At a higher concentration of divalent cations, the membrane permeability decreased. Membrane autopsy and analysing destructed membrane showed a relatively low magnesium and a high calcium concentration on the membrane after adding divalent ions into the solutions. It is concluded that in absence of divalent cations and without antiscalant the limits of 150 mg/L silica can be extended to 280 mg/L for 6–8 h.

Titanium Xerogel as a Potential Alternative for Polymeric Ferric Sulfate in Coagulation Removal of Antimony from Reverse Osmosis Concentrate

Titanium Xerogel as a Potential Alternative for Polymeric Ferric Sulfate in Coagulation Removal of Antimony from Reverse Osmosis Concentrate

Potential of Catalytic Ozonation as Advanced Treatment of Reverse Osmosis Concentrate from Coking Wastewater Reuse

Potential of Catalytic Ozonation as Advanced Treatment of Reverse Osmosis Concentrate from Coking Wastewater Reuse

Research and Demonstration on Reclaimation of Chemical Industrial Wastewater with High Salinity and Hardness and Purification of Reverse Osmosis Concentrates

Research and Demonstration on Reclaimation of Chemical Industrial Wastewater with High Salinity and Hardness and Purification of Reverse Osmosis Concentrates

Optimization of Electrolytic System Type for Industrial Reverse Osmosis Concentrate Treatment to Achieve Effluent Quality and Energy Savings

Optimization of Electrolytic System Type for Industrial Reverse Osmosis Concentrate Treatment to Achieve Effluent Quality and Energy Savings

Potential of Catalytic Ozonation as Advanced Treatment of Reverse Osmosis Concentrate from Coking Wastewater Reuse

Potential of Catalytic Ozonation as Advanced Treatment of Reverse Osmosis Concentrate from Coking Wastewater Reuse

Oxidative Degradation of Bisphenol a in Municipal Wastewater Reverse Osmosis Concentrate (Roc) Using Ferrate(Vi) and Hydrogen Peroxide

Oxidative Degradation of Bisphenol a in Municipal Wastewater Reverse Osmosis Concentrate (Roc) Using Ferrate(Vi) and Hydrogen Peroxide

Valorization of Reverse Osmosis Concentrate in the Production of Litopenaeus Vannamei and New Zealand Spinach in an Aquaponic System

Valorization of Reverse Osmosis Concentrate in the Production of Litopenaeus Vannamei and New Zealand Spinach in an Aquaponic System

Use of Reverse Osmosis Concentrate for Mitigating Greenhouse Gas Emissions from Pig Slurry

Use of Reverse Osmosis Concentrate for Mitigating Greenhouse Gas Emissions from Pig Slurry

Improving reverse osmosis concentrate treatment and nutrients conversion to Chlorella vulgaris bioenergy assisted with granular activated carbon

Landfill leachate (LL), especially the reverse osmosis concentrate (ROC), is a societal burden due to high toxicity but may have intrinsic values attributing to copious nutrients and organics. ROC bioremediation by microalgae has attracted much attentions benefiting from its extra advantage of bioenergy production. However, efficient microalgae cultivation with ROC is still a challenging task attributing to notorious ROC characteristics, like high chromaticity and toxicity. To alleviate these negative influences, a technique integrating granular activated carbon (GAC) pretreatment and microalgae bioremediation was proposed, with which nitrogen and phosphorus removal efficiencies achieved 100% along with an optimized microalgal biomass concentration of 1.44 g/L and lipid yield of 482.4 mg/L. Furthermore, a total volumetric energy yield of 33.6 kJ/L was acquired, which was conducive to realize energy valorization. The visualization evidence of three-dimensional fluorescence spectroscopy revealed chromaticity degradation mechanism of ROC as humic acids reduction and transfer to family of soluble microbial by-products. Meanwhile, contributions of GAC adsorption and microalgae assimilation on nutrients removal were analyzed. Together, this work provides a promising method and valuable information for ROC bioremediation with microalgae.

Treatment of reverse osmosis concentrate from industrial coal wastewater using an electro-peroxone process with a natural air diffusion electrode

• Electro-peroxone (EP) treated reverse osmosis concentrate (ROC) for the first time. • The use of natural air diffusion electrode in EP was studied for the first time. • EP could remove refractory substances in ROC within 2 h. • The EP process had high tolerance to wastewater quality. • The combination of peroxi-coagulation (PC) and EP outperformed EP. Reverse osmosis concentrate (ROC) produced in the RO treatment of coal chemical wastewater is highly toxic and difficult to degrade. In this study, an electro-peroxone (EP) process was applied to treat ROC with a natural air diffusion electrode (NADE), which was used as the cathode to efficiently generate H 2 O 2 . The treatment efficiency of EP, electro-Fenton, electro-oxidation (EO), peroxi-coagulation (PC) and ozonation for the removal of total organic carbon, colour and UV 254 in ROC were studied and compared, confirming that EP was the most efficient process. The EP process as well as electric energy consumption (EEC) were optimized, and an optimum reaction conditions (current of 200 mA, pH of 4 and O 3 dose of 6 mg/min) were selected. The production of ⋅ OH in EP was much higher than that in ozonation and EO, as indicated by the EPR measurement. Excitation-emission matrix spectra of ROC after EP treatment verified that all the fluorescent contaminants in ROC was removed within 2 h. Further, the combination of PC and EP processes (2 h + 3 h) significantly reduced EEC by 58% as compared with EP (6 h), realizing complete decolouration. This study declared the potential of using EP and the combined PC-EP process to effectively treat the real ROC wastewater.

Evolution of bacterial communities during the concentration and recirculation of dairy white wastewater by reverse osmosis

The effect of RO concentration on microbial ecosystem changes and the chemical composition of white wastewaters (WW; dairy effluents generated during the hydraulic flush of dairy processes), recovered from two dairy plants (A and B), was evaluated. The WW of dairy plant A was dominated by psychrotrophic bacteria, but no increase of the total number of 16S rRNA genes in the retentate throughout RO was obtained. A thermotolerant lactic acid bacteria genus, Streptococcus, was the most abundant genus in the initial samples of WW from dairy plant B. During WW recirculation in the RO system, the total number of 16S gene copies in the retentates generated by plant B increased significantly after 15 h. An adapted RO treatment with specific parameters is proposed to limit the growth of problematic bacterial genera, so promoting revalorization and reducing the environmental impact of WW dairy effluents.

Highly efficient removal of total nitrogen and dissolved organic compound in waste reverse osmosis concentrate mediated by chlorine radical on 3D Co3O4 nanowires anode

Reverse osmosis concentrate (ROC) from wastewater reclamation has posed significant disposal challenges due to its highly concentrated NH3-N, chloride ion and bio-refractory organics, and developing technologies for their removal are essential. Herein, we developed an efficient electrochemical system to remove total nitrogen and dissolved organic compound (DOC) simultaneously mediated by chlorine radical (Cl•), which is generated by activation of chloride ion existing in ROC on an inexpensive, three-dimensional Co3O4 nanowires. Results showed that the total nitrogen and total organic carbon removal were 98.2% and 56.9% in 60 min for synthetic ROC with 56 mg/L of NH3-N and 20 mg/L of DOC. The utilization of Co3O4 nanowires enhanced NH3-N degradation by 2.58 times compared with Co3O4 nanoplates, which were 1.69 and 17.5 times these of RuO2 and Pt. We found that structural Co3+/Co2+ acts as cyclic catalysis to produce Cl• via single-electron transfer, which convert NH3-N to N2 and lead to faster DOC degradation. This architecture provides abundant catalytic sites and sufficient accessibility of reactants. Small amount of nitrate generated by oxidation of NH3-N was further reduced to N2 on Pd-Cu/NF cathode. These findings provide new insights for utilization of waste Cl– and development of novel electrochemical system for ROC disposal.

Comparative Performance Analysis of Constructed Wetland-Microbial Fuel Cells Operated under Batch and Continuous Mode for Treating Wastewater with RO Concentrate

AbstractComparative analysis of hybridized microbial fuel cell (MFC) with constructed wetland systems (CW) as continuous and batch flow in with/without plant setups has been done. The sewage-genera...