Capacitive Deionization for RO brine recovery in NEWater production

Treatment and disposal of RO brine is an important part in sustaining the water reclamation practice. RO brine generated from water reclamation contains high concentration of organic and inorganic compounds. Cost-effective technologies for treatment of RO brine are still relatively unexplored. Thus, this study aim to determine a feasible treatment process for removal of both organic and inorganic compounds in RO brine generated from NEWater production. The proposed treatment consists of biological activated carbon (BAC) column followed by capacitive deionization (CDI) process for organic and inorganic removals, respectively. Preliminary bench-scale study demonstrated about 20% TOC removal efficiency was achieved using BAC at 40 mins empty bed contact time (EBCT) while the CDI process was able to remove more than 90% conductivity reducing it from 2.19 mS/cm to only about 164 microS/cm. More than 90% cations and anions in the BAC effluent were removed using CDI process. In addition, TOC and TN removals of 78% and 91%, respectively were also attained through this process. About 90% water recovery was achieved. This process shows the potential of increased water recovery in the reclamation process while volume for disposal can be further minimized. Further studies on the sustainable operation and process optimization are ongoing.

Integrated pretreatment with capacitive deionization for reverse osmosis reject recovery from water reclamation plant

Extended field investigations of ozone-biofiltration advanced water treatment for potable reuse

Ozone-biological activated carbon as a pretreatment process for reverse osmosis brine treatment and recovery

Identification of transformation products during advanced oxidation of diatrizoate: Effect of water matrix and oxidation process

Reverse Osmosis (RO) Brine is waste generated from the desalination process using the RO method. RO Brine is generally directly thrown back into the sea, even though it has the potential to be reprocessed because it still contains a variety of ions in it. The best method in RO Brine processing is Electrodialysis. But it has a problem of decreased membrane performance caused by the formation of fouling. The fouling problem can be overcome by doing a pretreatment process to eliminate impurities contained in RO Brine, one of which is Ca2+. The existence of Ca2+ can trigger the formation of CaSO4 deposits. Therefore, it needs excess reagent Na2CO3 with a certain amount to eliminate the whole Ca2+. Currently, it isn’t yet known the best pretreatment conditions that can eliminate impurities ions and produce high concentrations of NaCl. Pretreatment trials are needed in various variations of reagents amount to reduce impurities. The purpose of this study is to find out the best RO Brine pretreatment process that will later be used for the electrodialysis process to produce high NaCl recovery. The best results were obtained in the pretreatment process with variations NaOH excesses by 15% and Na2CO3 by 30% from the ideal stoichiometry.

Objectives : This article provides a comparative analysis of boron removal for brackish water reverse osmosis (BWRO), boron selective ion exchange (IX), or capacitive deionization (CDI) processes. Permeate of 1st-Pass RO process has to be post-treated for additional boron removal. Hence, we experimentally analyzed the performance of boron removal and specific energy consumption (SEC) of three aforementioned processes and investigated whether the processes are suitable for 2nd pass process of RO desalination.Methods : Raw feed water was prepared using NaCl and B(OH)3. Semi-pilot scale RO and IX systems (over 1 m3/hr capacity) and bench scale CDI system (over 2.5 L/min) were tested for performance comparison. Boron concentration was measured using Azomethine-H method for feed and product water. Energy consumption was monitored by using power quality analyzer.Results and Discussion : Each process has its own operating conditions. The RO process required high pH of feed water for high boron removal rate, the IX process was operated below breakthrough point considering adsorption capacity of boron selective resin, and the CDI process didn’t remove boron because chloride ion has higher ion selectivity for carbon electrode than boron. In terms of SEC, the pressure-driven RO process showed the highest SEC among three processes. The CDI process based on electrical adsorption of carbon electrode showed a considerable energy consumption as well. On the other hand, the IX process was operated at low energy consumption because its removal is just based on adsorption-desorption mechanism.Conclusions : The RO and CDI processes have received a lot of attention as leading and emerging technology while the IX process was regarded as a stubborn process because of regeneration of resin and its several segmentalized steps. However, we found that the IX process has a better performance for boron removal and energy consumption.

Electrodialysis reversal for industrial reverse osmosis brine treatment

Objectives:The purpose of this study was to suggest a more efficient operation condition for the BAC(biological activated carbon) process by evaluating the change in the concentration of biopolymers in the effluent of the BAC process and the head loss of the BAC filter layer according to phosphate (PO4-P) and hydrogen peroxide (H2O2) input.Methods:During the experiment period (Feb. to Aug. 2020), the O3 dosage was fixed at 1 mg･O3/mg･DOC. Four columns with an inner diameter of 20 cm and a height of 250 cm were prepared. Empty bed contact time (EBCT) was fixed at 20 minutes and backwash was performed once a week. The four BAC columns are conventional BAC(control-BAC), enhanced BAC with hydrogen peroxide (H2O2+BAC), enhanced BAC with phosphate (PO4-P+BAC), and enhanced BAC with phosphate and hydrogen peroxide together (PO4-P+H2O2+BAC). In the case of enhanced BAC with PO4-P added, PO4-P was added with a concentration of 0.010 mg/L in the influent, and in BAC with H2O2, H2O2 was added with a concentration of 1 mg/L to the influent.Results and Discussion:According to the change of water temperature, the average head loss in control-BAC was 4.4 (25~28℃)~7.7 cm(8~12℃). In addition, PO4-P+BAC, H2O2+BAC and PO4-P+H2O2+BAC were 3.9~5.8 cm, 2.5~3.5 cm, and 2.6~3.5 cm, respectively. The head loss was reduced by the input of PO4-P and H2O2. During the low water temperature period, in control-BAC, the effluent biopolymers (BP) concentration was higher than the influent concentration, indicating that a large amount of EPS (extracellular polymeric substances) was produced and released from the attached biofilm. In PO4-P+BAC, H2O2+BAC and PO4-P+H2O2+BAC processes, the BP concentration ratio (Cout/Cin) was about 36~57% lower than that of the control-BAC during the low water temperature period. The BP concentration ratio was high when the water temperature (8~12℃) was low, and the BP concentration ratio gradually decreased as the water temperature increased. These results were very similar to those of the head loss change in the control-BAC process and the enhanced BAC process, and the BP concentration ratio and the head loss showed a very high correlation (r2=0.82~0.87). To evaluate the stability of the biofilm during the operation period, the total cell counts (TCC) in BAC treated waters were investigated. In control-BAC, PO4-P+BAC, H2O2+BAC and PO4-P+H2O2+BAC process, the average TCC was 46.8×106 cells, 30.3×106 cells, 21.8×106 cells, and 18.8×106 cells, respectively. Compared to the control-BAC, it was found to be 35~60% lower in the enhanced BAC processes. In addition, live cell count (LCC) ratio (LCC/TCC) was 0.84~0.89 in the enhanced BAC processes compared to 0.53 in the control-BAC. These results indicate that the biofilm stability of the enhanced BAC processes is higher than that of control-BAC.Conclusions:During the experiment, compared to the conventional BAC process, the enhanced BAC processes in which PO4-P and H2O2 were added showed a clear effect of reducing the head loss. In particular, the effect of reducing the head loss was higher when H2O2 was added than when PO4-P was added. A rapid head loss increase occurred in the conventional BAC process compared to the enhanced BAC processes in the low water temperature season is the result of the production of large amounts of EPS in the attached biofilm. The input of PO4-P or H2O2 reduces the head loss by improving the stability of the attached biofilm and reducing EPS production.

The paper introduced a new idea of culturing Chlorella with combined reverse osmosis (RO) brine concentrate and primary effluent from sewage treatment plant as culture medium. This method was expected to reuse wastewater resource and lower the cost of Chlorella cultivation. The biomass of Chlorella at different temperature and different proportion of RO brine (0-90% by volume) were measured. Results showed that Chlorella had an ability to grow in RO brine blended with primary effluent. The biomass of Chlorella in 30% of RO brine blended was the most. At a low temperature of 10℃, the effect of RO brine on Chlorella biomass was obvious, high temperature (30℃) inhibited the growth of Chlorella, 20℃ was the most favorable temperature for growth.

Treatment of RO brine from CSG produced water by spiral-wound air gap membrane distillation — A pilot study

Schemes for salt recovery from seawater and RO brines using chemical precipitation

The mining industry is facing problems of clean production in terms of mineral processing, pollution, water consumption, and renewable energy. An interesting outlook can be to combine the mining industry with membrane-based desalination in the logic of mining from the sea. In fact, several of the drawbacks found in both mining and desalination can be minimized or overcome, which includes hindering mineral depletion, water production instead of water consumption, smart usage of brine instead of disposal, and low energy consumption, etc. Recently, membrane crystallization (MCr) has been developed to recover minerals from highly concentrated solutions. This study suggests MCr for the treatment of nanofiltration (NF) retentate and reverse osmosis (RO) brine leaving membrane-based desalination system. Thermodynamic modeling has been carried out to predict at which water recovery factor and which amount of minerals can be recovered. Theoretical results deviate only 2.09% from experimental results. Multivalent components such as barium, strontium, and magnesium are easier to recover from NF retentate with respect to RO brine. KCl and NiCl2 might be recovered from both NF retentate and RO brine, whereas lithium can only be recovered from RO brine. Moreover, copper and manganese compounds might also be recovered from desalination brine in perspectives.

Objectives:In this study, we compared the properties of the attached biofilm with the ability to remove biodegradable dissolved organic carbon (BDOC) in the conventional BAC (biologically activated carbon) process and the enhanced BAC process with phosphorus and hydrogen peroxide added. The enhanced BAC process was designed to increase the operational efficiency of the old O<sub>3</sub>/BAC process by evaluating the applicability of large-scale water treatment facilities located downstream of the Nakdong River.Methods:The granular activated carbon which was used for 2 years in the O<sub>3</sub>/BAC process in the water treatment plant located downstream of the Nakdong River was used in this experiment. During the experiment period, the ozone dosage was fixed at 1 mg･O<sub>3</sub>/mg･DOC. Four acrylic columns with an inner diameter of 20 cm and a height of 250 cm were prepared. Empty bed contact time (EBCT) was fixed at 20 minutes and backwash was performed once a week. The four BAC columns are conventional BAC (control-BAC), enhanced BAC with hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>+BAC), enhanced BAC with phosphorus (PO<sub>4</sub>-P+BAC), and enhanced BAC with phosphorus and hydrogen peroxide together (PO<sub>4</sub>-P+H<sub>2</sub>O<sub>2</sub>+BAC). In the case of enhanced BAC with PO<sub>4</sub>-P added, PO<sub>4</sub>-P was added with a concentration of 0.010 mg/L in the influent, and in BAC with H<sub>2</sub>O<sub>2</sub>, H<sub>2</sub>O<sub>2</sub> was added with a concentration of 1 mg/L to the influent.Results and Discussion:As a result of evaluating the recovery ability of the damaged biofilm, there was no difference in the biomass recovery rate in the H<sub>2</sub>O<sub>2</sub>+BAC compared to the control-BAC, but the biomass was rapidly recovered in the PO<sub>4</sub>-P+BAC. Considered the biomass and activity of the attached biofilm after the ability to remove organic substances reached a steady state, the biomass and activity in the entire filter layer of the PO<sub>4</sub>-P+BAC increased by 20 to 86% and 7 to 14%, respectively, compared to the control-BAC. In the H<sub>2</sub>O<sub>2</sub>+BAC, only the activity increased by 3~11% and In the PO<sub>4</sub>-P+H<sub>2</sub>O<sub>2</sub>+BAC, biomass and activity were high, about 27 to 87% and 8 to 20%, respectively. In the H<sub>2</sub>O<sub>2</sub>+BAC, the BDOC removal rate was higher than the control-BAC by 20%, and in the PO<sub>4</sub>-P+BAC, the BDOC removal rate increased by more than 100%. Detached total cell counts (TCC) in the control-BAC effluent was 41.7×10<sup>6</sup> cells/mL on average, and in the H<sub>2</sub>O<sub>2</sub>+BAC, TCC was reduced by 49% compared to control-BAC and decreased by 67% and 85% in the PO<sub>4</sub>-P+BAC and the PO<sub>4</sub>-P+H<sub>2</sub>O<sub>2</sub>+BAC effluent. It means the biofilm of the enhanced BAC process was evaluated more stably than control-BAC.Conclusions:The biomass and the activity of the attached biofilm in the BAC process, are one of the important factors that determine the ability to remove contaminants. The enhanced BAC process combined PO<sub>4</sub>-P with H<sub>2</sub>O<sub>2</sub> was very effective in enhancing the biomass and the activity of the attached biofilm. The PO<sub>4</sub>-P added enhanced BAC was more effective in terms of biomass, BDOC removal rate, and biofilm stability than the H<sub>2</sub>O<sub>2</sub> added enhanced BAC. The enhanced BAC combined PO<sub>4</sub>-P with H<sub>2</sub>O<sub>2</sub> showed a slight increase additional efficiency compared to the PO<sub>4</sub>-P added BAC.

Block copolymer coated carbon nanotube membrane anodes for enhanced and multipurpose hybrid capacitive deionization