Reverse Osmosis Treatment Research Articles

A comprehensive approach to an urban water reuse system to meet irrigation demand and conserve water: City of Cape Coral, FL, USA

ABSTRACT Maximizing the reuse of domestic wastewater is a critical objective, spurred by the pressing need to avoid water loss, reduce environmental discharges, and manage irrigation water demand. In the City of Cape Coral (FL, USA), thousands of old-fashioned and inefficient irrigation systems have been installed over the past 50 years. The city has adopted year-round external water use restrictions, but demands continue to increase. In 2020, peak 24-h irrigation water demands exceeded 177,914 m3. In response to recurrent dry seasons and growing demand over the past 20 years, the city has diversified its water resources. The city uses brackish groundwater with reverse osmosis treatment to produce drinking water and reuses 100% of its wastewater effluent for irrigation by blending the treated wastewater with fresh water from 483 km of freshwater canals. To promote efficient irrigation water use among consumers, a new approach has been adopted to automate private irrigation systems. The Environmental Resource Assessment and Management System Integrated Urban Water Model was used to simulate water management scenarios. The simulation showed that increasing automatic irrigation efficiency can save millions of cubic meters of irrigation water and help the city meet the future build-out peak-day demand of 219,758 m3/d, as estimated by the Blaney–Criddle method.

Efficient desalination and synergistic toxic organics removal in RO concentrates with electrochemical advanced oxidation processes

A novel Ce-doped Ti4O7 (Ti/Ti4O7-Ce) electrode was fabricated and investigated in treatment of reverse osmosis (RO) concentrates with Electrochemical advanced oxidation processes (EAOPs). Characterization results showed that Ce was successfully incorporated into the Ti4O7, leading to an increase on the hydroxyl radical (•OH) generation and electrochemical stability compared with Ti/Ti4O7. Ti/Ti4O7-Ce electrodes achieved efficient desalination and oxidation of toxic organics, which was mainly attributed to the indirect oxidation induced by electro-generated •OH and change of electrochemical properties. The action of electric field had great effect on desalination process, and the anions in reverse osmosis concentrates (ROC) deposited on the cathode through this action by characterization and analysis. In the treatment, about 10.8–11.2 % of desalination efficiencies can be obtained, and the removal efficiency of toxic organics enhanced with the increase of Ce addition and current density. In the experiments, TOC removal efficiencies were 57 %, 66 % and 69 % under 10, 20 and 30 mA/cm2 in the 180 min treatment. Toxic chemicals, such as alkanes, haloalkanes, etc., were the main components in treatment, and the organic pollutants with medium molecular weight (MMW) (1400 g/mol) and low molecular weight (LMW) (40–230 g/mol) in ROC were removed. Although slight decreased durability was observed due to Ce leaching, Ti/Ti4O7-Ce electrode maintained stable desalination performance and total organic carbon (TOC) removal efficiency within 60 cycles. This study indicated that Ti/Ti4O7-Ce was a promising electrode for synergistic toxic organics removal and desalination in EAOPs.

Occurrence, toxicity, and control of halogenated aliphatic and phenolic disinfection byproducts in the chlorinated and chloraminated desalinated water

Seawater desalination is widely used to overcome the freshwater shortage worldwide. However, even after three-stage reverse osmosis treatment, the desalinated water still contained 14.6 μg/L of aliphatic disinfection byproducts (DBPs), 384.2 ng/L of bromophenolic DBPs, 3.5 ng/L of iodophenolic DBPs, 1024.7 μg/L of Br-, 2.8 μg/L of I-, and 2.4 mg C/L of dissolved organic carbon (DOC). After the desalinated water was disinfected with chlor(am)ine, the concentrations of halogenated aliphatic and phenolic DBPs further increased, and bromophenolic DBPs were the toxicity forcing agents. When surface water was mixed with desalinated water and then chlorinated, the yield of aliphatic and phenolic DBPs significantly elevated. Separately chlorinating desalinated water and surface water before mixing could mitigate this adverse situation. Chloramine disinfection was more conducive to reducing the total calculated toxicity of disinfected desalinated waters and mixed waters compared to chlorine disinfection. The treatment of desalinated water with granular activated carbon could effectively remove DOC and UV254, leading to a reduction in the content of total organic halogen after chlor(am)ination. Although anion exchange resin could adsorb Br-, it also released the organic precursors of DBPs, ultimately increasing the yield of DBPs. The results of this study can provide a reference for the seawater desalination industry to improve seawater pre-treatment and desalination processes and thus minimize the DBPs.

Fate of emerging contaminants in an advanced SBR wastewater treatment and reuse facility incorporating UF, RO, and UV processes

A critical factor for widescale water reuse adoption is the capability of advanced wastewater treatment facilities to consistently produce high-quality water by efficiently removing various pollutants, including emerging contaminants (ECs). This study monitored the fate of seventeen ECs (which included pesticides, antibiotics and other pharmaceutically active compounds) over six months in an advanced wastewater reuse facility situated in the United Arab Emirates. The facility integrates a sequencing batch reactor (SBR) based sewage treatment plant (STP) with a water recycling facility featuring ultrafiltration (UF), reverse osmosis (RO), and ultraviolet (UV) disinfection. ECs were detected and quantified at the influent and effluents of the various treatment stages, using an ultra-high-performance liquid chromatography coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry (UHPLC-ESI-QTOF-MS). The STP exhibited variable removal efficiencies, achieving >90 % removal for compounds like caffeine and acetaminophen, while others, such as carbamazepine and thiabendazole, displayed poor removal (<10 %). UF treatment broadly resulted in limited removal, with ECs in permeate typically persisting in the 1–10 ng/L range. Subsequently, after undergoing RO treatment, eight ECs were still detected in the RO permeate, albeit at <1 ng/L, except for imidacloprid (2.5 ng/L). Conversely, the final UV disinfection step led to concentration increases of certain ECs, namely imidacloprid, thiabendazole, sulfamethoxazole, sulfamethazine and caffeine. Overall, the total EC concentration levels decreased considerably from 2300 ng/L in the STP influent to 5.2 ng/L in the RO permeate. However, a subsequent increase to 27.5 ng/L was observed after UV disinfection. While the study underscores the effectiveness of advanced treatment processes, notably RO, in reducing EC concentrations, it also demonstrates the importance of continuous EC monitoring in such facilities as many compounds persist post treatment. Additionally, the potential for processes like UV disinfection to increase certain EC concentrations highlights the need to optimize treatment trains to minimize EC concentration rebound.

Occurrence and Ecological Risk Assessment of Highly Toxic Halogenated Byproducts during Chlorination Decolorization of Textile Printing and Dyeing Wastewater.

Textile printing and dyeing wastewater is a substantial source of highly toxic halogenated pollutants because of the chlorination decolorization. However, information on the occurrence and fate of the highly toxic halogenated byproducts, which are produced by chlorination decolorization of the textile printing and dyeing wastewater, is very limited. In this study, the occurrence of six categories of halogenated byproducts (haloacetic acids (HAAs), haloacetonitriles (HANs), N-nitrosamines (NAs), trihalomethanes, halogenated ketones, and halonitromethanes) was investigated along the full-scale treatment processes of textile printing and dyeing wastewater treatment plants. Furthermore, the ecological risk of the halogenated byproducts was evaluated. The results showed that the total concentration of halogenated byproducts increased significantly after chlorination. Large amounts of HAAs (average 122.1 μg/L), HANs (average 80.9 μg/L), THMs (average 48.3 μg/L), and NAs (average 2314.3 ng/L) were found in the chlorinated textile wastewater, and the results showed that the generations of HANs and NAs were positively correlated with the BIX and β/α index, indicating that the HANs and NAs might form from the microbial metabolites. In addition, HAAs and HANs exhibited high ecological risk quotients (>1), suggesting their high potential ecological risk. The results also demonstrated that most halogenated byproducts could be effectively removed by reverse osmosis treatment processes except NAs, with a lower removal rate of 18%. This study is believed to provide an important theoretical basis for controlling and reducing the ecological risks of halogenated byproducts in textile printing and dyeing wastewater effluents.

Multi-laser nanoparticle tracking analysis (NTA): A unique method to visualize dynamic (shear) and dynamic (Brownian motion) light scattering and quantify nonliving natural organic matter (NNOM) in environmental water

Application of simultaneous multi-laser nanoparticle tracking analysis (NTA) to environmental water samples to investigate nonliving natural organic matter (NNOM) is introduced as an innovative method for observing particles directly in their native media. Multi-laser NTA results of particle visualization, particle number concentration, and particle size distribution elucidated particle dynamics in low and high total dissolved solids (TDS) aqueous environmental samples. A pond water sample and concentrate from a reverse osmosis (RO) treatment process (Stage 1) had 1.3 × 108 and 5.62 × 1019 particles/mL, respectively, (at time = 0) after filtration at 0.45 μm. Beyond the traditional applications for this instrument, this research presents novel evidence-based investigations that probe the existence of supramolecular structures in environmental waters during turbulence or quiescence. The pond water sample exhibited time-dependent aggregation as the volume distribution shifted to greater diameter during quiescence, compared to turbulence. Disaggregation (increased numbers of particles over time) was noted in the >250 nm to <600 nm region, and aggregation of >450 nm particles was also noted in the quiescent RO concentrate sample, indicative of depletion of small particles to form larger ones. Multi-laser NTA and dynamic light scattering (DLS) capabilities were compared and contrasted. DLS and NTA are different (complementary) particle sizing techniques. DLS yielded more information about the physical hydrogel in the NNOM hierarchy whereas multi-laser NTA better characterized meta-chemical and chemical hydrogel characteristics. Operationalization of innovation—moving from fundamental investigations to application—is supported by implementing novel analytical instrumentation as we address issues involving climate change, drought, and the scarcity of potable water. Multi-laser NTA can be used as a tool to study and optimize complex water and wastewater treatment processes. Questions about water treatment efficiencies, membrane fouling, assistance of pollutant transport, and carbon capture cycles affected by NNOM will benefit from insights from multi-laser NTA.

Efficient Sb(Ⅲ) removal from printing and dyeing wastewater using TiCl4 as a potential coagulant instead of polyferric sulfate

With increasing health concerns and the tightening of discharge standards, there is growing demand for more efficient Sb(Ⅲ) removal from printing and dyeing wastewater (PDW). Currently, the most common coagulant used in Sb removal in industry is polyferric sulfate (PFS). However, the residual Fe ions in the effluent cause colorimetric problems and irreversibly damage the membrane components during the subsequent reverse osmosis treatment process. Therefore, identifying novel coagulants to replace PFS in the removal of Sb(Ⅲ) is necessary. In this study, TiCl4 was employed for in-situ hydrolysis to produce flocs for Sb(Ⅲ) removal in simulated and real PDW. TiCl4 exhibited an excellent performance compared to PFS in terms of dosage, turbidity, application pH, and anti-interference properties. Sb(Ⅲ) removal of 97.3 % was realized at a dosage of 30 mg/L and a final pH of 5.0 in slightly contaminated PDW, whereas PFS required a higher dosage, resulting in higher disposal costs. Furthermore, the application of TiCl4 led to lower turbidity and reduced secondary contamination. An investigation of the co-existing ions revealed that TiCl4 was considerably more tolerant than PFS toward PO43–, humic acid, and silicate at a lower concentration. Simultaneously, Sb(Ⅲ) was partially oxidised to Sb(Ⅴ) during removal, but TiCl4 exhibited lower oxidative properties. The results of PDW treatment indicated that TiCl4 could realize 85.6 % Sb(Ⅲ) removal at a dosage of 30 mg/L, and the pre-reduction of Sb(Ⅴ) to Sb(Ⅲ) was a safe, effective treatment. The results of zeta potential measurements and X-ray photoelectron spectroscopy revealed that Sb(Ⅲ) removal was mainly realised via chemical adsorption. Overall, this study provides a promising alternative material for use in practical Sb(Ⅲ) removal from PDW, particularly for reducing coagulation sludge, operational costs, and damage during the possible subsequent reverse osmosis process.

Fouling behavior of nanofiltration membrane during the refining treatment of morphlines-dominant reverse osmosis concentrate

Nanofiltration (NF) has been proven to be with great potential for the separation of morpholines with molecular weight less than 200 Da in refining reverse osmosis concentrate (ROC), but its application is significantly restricted by the membrane fouling, which can reduce the rejection and service time. To enable the long-term operation stability of nanofiltration, this work focuses on the fouling behavior of each substance in the hydrosaline organic solution on nanofiltration membrane, aiming to give insight into the fouling mechanism. To this end, in this work, the effects of salts (i.e NaCl and Na2SO4), organic substances (including N-(2-hydroxypropyl)morpholine(NMH) and 4-morpholineacetate(MHA)) and representative divalent ions (Ca2+ and Mg2+) on the performance and physicochemical properties of DK membrane were systematically investigated. The results show that both salts and organics can induce DK membrane swelling, leading to an increase of the mean effective pore size. After the filtration of Na2SO4–NaCl–H2O, the mean pore size increased by 0.002 nm, resulting in the decrease of the removal ratio of NMH and MHA for 3.82% and 13.10%, respectively. With static adsorption of NMH and MHA, the mean pore size of DK membrane increased by 0.005 and 0.003 nm. The swelling slowed the entrance of more organic molecules into membrane pores. Among them, MHA led to the terrible irreversible pore blocking. As the concentration of Ca2+ increased, gypsum scaling was formed on the membrane surface. During this process, NMH and MHA played different roles, i.e. NMH accelerated the CaSO4 crystallization while MHA inhibited. As a conclusion, the fouling behavior of substances in the high saline organic wastewater on DK membrane were systematically revealed with the fouling mechanisms proposed, which could provide an insightful guidance for membrane fouling control and cleaning in the treatment of high salinity and organic wastewater.

Hybrid and combined electro-oxidation and peroxi-coagulation processes in effective treatment of textile reverse osmosis concentrate

In this study, the treatment of reverse osmosis concentrate from a textile industry by hybrid and combined electrochemical processes was investigated. Firstly, the operating parameters of single electro-oxidation (EO) and peroxi-coagulation (PC) processes were optimized, and then the performances of hybrid EO-PC, PC-EO, and combined EO/PC processes were evaluated in pollutant removal under optimum conditions. Optimum conditions for processes were determined as pH: 5, 22.5 mA/cm2, inter-electrode distance: 3 cm, 120 min. Removal efficiency of chemical oxygen demand (COD) for the optimum conditions of EO, PC, EO-PC, PC-EO, and EO/PC were 78.5 %, 73.0 %, 73.8 %, 82.0 %, and 91.9 %, respectively. Specific energy consumption of EO, PC, EO-PC, PC-EO, and EO/PC processes were 61.9, 74.0, 64.0, 60.9, and 56.8 kWh/kg COD, respectively. The EO/PC process was the most effective and feasible one among applied single, hybrid, and combined processes. With the EO/PC, reverse osmosis concentrate met the receiving environment discharge criteria.

Co-treating flue gas desulfurized effluent and produced water enables novel waste management and recovery of critical minerals

This study reports a novel approach of resource recovery from co-managing two geographically co-located and chemically complementary wastewaters using a pilot-scale treatment process. Designed to treat flue gas desulfurized (FGD) effluent from combustion powerplants and produced water (PW) from energy industries, the process consists of soda-ash softening, nanofiltration (NF), and reverse osmosis (RO). Recovered products are barite, calcite, and low-salinity water. Using field-collected waters, the results show that softening at pH ≈ 8.5 produces calcite (yield: ~30 kg/m3 treated water), a chemical used as SO₂(g) scrubbers. NF treatment under an applied pressure of ~3.5 MPa yields a permeate stream laden with monovalent ions (water recovery ~60 %) and a concentrate stream with a sulfate concentration ~1.8 times of the feedwater concentration. Mixing the NF concentrate and PW at a volumetric ratio of 1.0 precipitates a high-density barite material (4.1 g/cm3, yield: ~7.5 kg/m3 mixture) – a critical mineral commonly used as a weighting agent in drilling. The RO treatment recovers >64 % water as the permeate, which can be readily used as cooling make-up water at the powerplants. The RO concentrate stream can be further processed in a thermal evaporative system for additional water recovery and brine production.

Optimization of Dissolved Silica Removal from Reverse Osmosis Concentrate by Gedaniella flavovirens for Enhanced Water Recovery

Photobiological treatment of reverse osmosis concentrate (ROC) using brackish diatoms is a green and sustainable technology that can enhance water recovery by removing dissolved silica from ROC while producing beneficial biomass. This study aimed to determine the optimum conditions for the photobiological treatment of ROC obtained from a full-scale advanced water purification facility using Gedaniella flavovirens Psetr3. While light color presented minor impacts on the silica uptake rate, the impact of color intensity was significant. The uptake rate improved from 28 ± 1 to 48 ± 7 mg/L/day by increasing photosynthetically active radiation (PAR) from 50 to 310 µmol m−2 s−1. Increasing the PAR further did not improve the performance. The optimum temperature was around 23–30 °C. While the silica uptake was slower at 10 °C, G. flavovirens Psetr3 was unable to survive at 40 °C. Experiments using sunlight as a light source verified the impact of temperature on the silica uptake and the detrimental effect of ultraviolet radiation on this diatom. The sunlight-based treatment effectively removed N-nitrosodimethylamine. The results of this study are being used in subsequent pilot-scale investigations and full-scale technoeconomic analysis and will contribute to the further development of this sustainable water technology.

Development of microbial desalination cells for the treatment of reverse osmosis reject water: A new benchtop approach

To address the growing global demand for usable water, there is an immediate necessity to enhance wastewater treatment systems. A continuous mode adaption of the conventional three-chamber microbial desalination cell (MDC) configuration was used, with gravity facilitating the flow of residential reject water for desalination. Initially, operating in batch mode with a 100 mL treatment volume, the single microbial desalination machine was expanded to 300 mL in continuous mode, capable of treating 5 L of home refuse water over 36 days. The batch mode MDC had a maximum current and power density of 3.81 µA/cm2 and 0.337 µW/cm2, resulting in 76 % desalination and 83.9 % COD eradication rates. Scaling up increased the MDC's performance, reaching a maximum of 0.45 µW/cm2 and 5.31 µA/cm2, which was 1.3 times greater than batch mode operation. The current work demonstrates the feasibility of microbial desalination cells and their novel approach for treating much higher quantities of reverse osmosis (R.O.) saline water in a comparable period of roughly 36 days. It emphasizes the actual limits when dealing with real-world wastewater samples, presenting a unique path for biotechnology by simultaneously generating bio-electricity and tackling future contaminants. Furthermore, incorporating desalination chambers with microbial fuel cells increases efficiency and opens up new options for enhanced wastewater treatment, resource recovery, and bioenergy generation. This pioneering strategy uses innovative membrane technologies and microbial optimization approaches to push the limits of desalination.

Catalytic ozonation of reverse osmosis concentrate from coking wastewater reuse by surface oxidation over Mn-Ce/γ-Al2O3: Effluent organic matter transformation and its catalytic mechanism

Degradation of organics in high-salinity wastewater is beneficial to meeting the requirement of zero liquid discharge for coking wastewater treatment. Creating efficient and stable performance catalysts for high-salinity wastewater treatment is vital in catalytic ozonation process. Compared with ozonation alone, Mn and Ce co-doped γ-Al2O3 could remarkably enhance activities of catalytic ozonation for chemical oxygen demand (COD) removal (38.9%) of brine derived from a two-stage reverse osmosis treatment. Experimental and theoretical calculation results indicate that introducing Mn could increase the active points of catalyst surface, and introducing Ce could optimize d-band electronic structures and promote the electron transport capacity, enhancing HO• bound to the catalyst surface ([HO•]ads) generation. [HO•]ads plays key roles for degrading the intermediates and transfer them into low molecular weight organics, and further decrease COD, molecular weights and number of organics in reverse osmosis concentrate. Under the same reaction conditions, the presence of Mn/γ-Al2O3 catalyst can reduce ΔO3/ΔCOD by at least 37.6% compared to ozonation alone. Furthermore, Mn-Ce/γ-Al2O3 catalytic ozonation can reduce the ΔO3/ΔCOD from 2.6 of Mn/γ-Al2O3 catalytic ozonation to 0.9 in the case of achieving similar COD removal. Catalytic ozonation has the potential to treat reverse osmosis concentrate derived from bio-treated coking wastewater reclamation.

An Evaluation of Microfiltration and Ultrafiltration Pretreatment on the Performance of Reverse Osmosis for Recycling Poultry Slaughterhouse Wastewater

To implement sustainable water resource management, the industries that produce a huge amount of wastewater are aiming to recycle wastewater. Reverse osmosis (RO) is an advanced membrane process that can produce potable water from wastewater. However, the presence of diverse pollutants in the wastewater necessitates effective pretreatment to ensure successful RO implementation. This study evaluated the efficiency of microfiltration (MF) and ultrafiltration (UF) as two pretreatment methods prior to RO, i.e., MF-RO and UF-RO, for recycling poultry slaughterhouse wastewater (PSWW). The direct treatment of PSWW with RO (direct RO) was also considered for comparison. In this study, membrane technology serves as a post treatment for PSWW, which was conventionally treated at Sanderson Farm. The results demonstrated that all of the processes, including MF-RO, UF-RO, and direct RO treatment of PSWW, rejected 100% of total phosphorus (TP), over 91.2% of chemical oxygen demand (COD), and 87% of total solids (TSs). Total nitrogen (TN) levels were reduced to 5 mg/L for MF-RO, 4 mg/L for UF-RO, and 9 mg/L for direct RO. In addition, the pretreatment of PSWW with MF and UF increased RO flux from 46.8 L/m2 h to 51 L/m2 h, an increase of approximately 9%. The product water obtained after MF-RO, UF-RO, and direct RO meets the required potable water quality standards for recycling PSWW in the poultry industry. A cost analysis demonstrated that MF-RO was the most economical option among membrane processes, primarily due to MF operating at a lower pressure and having a high water recovery ratio. In contrast, the cost of using RO without MF and UF pretreatments was approximately 2.6 times higher because of cleaning and maintenance expenses related to fouling. This study concluded that MF-RO is a preferable option for recycling PSWW. This pretreatment method would significantly contribute to environmental sustainability by reusing well-treated PSWW for industrial poultry purposes while maintaining cost efficiency.

Performance investigating of the reverse osmosis treatment system to the water supply in the hemodialysis center of Khoy city in 2022

Performance investigating of the reverse osmosis treatment system to the water supply in the hemodialysis center of Khoy city in 2022

Integrating reverse osmosis to a conventional river water treatment plant as a strategy to produce drinking water after mining dam rupture events: a case study

ABSTRACT Incidents of mining dam failure have compromised the water quality, threatening the water supply. Different strategies are sought to restore the impacted area and to guarantee the water supply. One example is water treatment plants that treat high-polluted waters within the required limits for their multiple usages. The current study assesses the integration of reverse osmosis (RO) to a river water treatment plant (RWTP) installed in Brumadinho (Minas Gerais, Brazil) to treat the water from the Ferro-Carvão stream impacted by the B1 dam rupture in 2019. The RWTP started eleven months after the mining dam rupture and is equipped with eight coagulation-flocculation tanks followed by eight pressurised filters. A pilot RO plant was installed to polish the water treated by the RWTP. Water samples were collected at different points of the water treatment plant and were characterised by their physical, chemical, and biological parameters (160 in total). The results were compared with the historical data (1997–2022) to reveal the alterations in the water quality after the rupture event. The compliance with both parameters was only achieved after the RO treatment, which acted as an additional barrier to 30 contaminants. The water quality indexes (WQI) suggested that the raw surface water, even eleven months after the incident, was unfit for consumption (WQI: 133.9) whereas the reverse osmosis permeate was ranked as excellent in the rating grid (WQI: 23.7).

WITHDRAWN: Concentrate Management of Spent Geothermal Water Treated with Two- Step Membrane Processes for Agricultural Irrigation

This study examines a two-step membrane treatment to improve water quality by targeting electrical conductivity in reverse osmosis (RO) concentrate from spent geothermal water. The process involves RO treatment followed by electrodialysis reversal (EDR). Water samples were collected during different seasons to assess quality under varying conditions.Following the initial treatment by XLE-RO membrane test system, the large-pilot membrane (LPM-RO) concentrate achieved salt rejection of 98.6%, while the mini-pilot membrane (MPM-RO) concentrate achieved salt rejection of 95.6%. Conductivity values were 48.6µS/cm for LPM-RO and 226µS/cm for MPM-RO concentrate. Further passing the product water obtained from XLE-RO membrane through the EDR system improved overall product water quality. Treated LPM-RO product water had conductivities of 3.71µS/cm (5V) and 2.36µS/cm (10V). For MPM-RO product water, conductivities were 11.98µS/cm (5V) and 2.64µS/cm (10V). In this study, an additional experiment investigated the EDR treatment of RO concentrate without undergoing initial RO pretreatment. After the experiment, although the salt rejection reached 97.65%, it was observed that the product water quality at the end of the 90-minute treatment was 74.6µS/cm with lower quality as compared to when the RO concentrate underwent initial RO pre-treatment. Hence, the combination of RO-EDR can be successfully utilized to treat geothermal water concentrate for better quality which could be utilized in irrigation. This two-step membrane treatment shows potential for higher-quality water reclamation for various processes.

Economic Feasibility of Reverse Osmosis (RO) Water Treatment Plants: A Case Study from Dimbulagala, Polonnaruwa, Sri Lanka

Social wellbeing is strongly linked with economic feasibility when it needs to attain with the technological advancements. Installation of Reverse Osmosis (RO) water treatment plants have been considered as a promising solution to provide clean water for human consumption, especially in the areas where the CKDu (chronic kidney disease of unknown etiology) prevails. At present, over 2,000 RO treatment plants were installed in the dry zone of Sri Lanka, yet economic feasibility for operation and maintenance of RO plants has not been assessed so far. The present study was intended to identify economic feasibility of operation and maintenance of RO plants. Investigations were carried out in six community RO plants which provided drinking water for over 17,000 people which accounts for 20% of total population in Dimbulagala Divisional Secretariat over a period of 12 months. Six in-depth interviews and questionnaire survey were caried out with RO plant operators. The operational cost per production of cubic meter of filtered water was computed by considering electricity consumption bills. The maintenance costs and service charges were also obtained from the records available with RO plant operators. The results found that the average electricity consumption to produce 1 cube of filtered water is approximately 9kWh and cost is LKR 734 (based on 2021 rates). The average water selling price ranged between LKR 1.00-2.50 per liter. The average monthly income generation from one RO plant is approximately between LKR 561- 875 per cube of filtered water and it largely depended on the type of water source, climatic conditions. It was found that the income generated from RO plants was sufficient enough to cover the operation cost (monthly electricity bill) and for the subsequent maintenance and service charges whenever required. It can be concluded that the use of RO treated water is an economically viable option to provide portable drinking water. &#x0D; Keywords: CKDu, Economic sustainability, Drinking water, Purification cost

Gas-liquid contact evaporation of concentrate leachate from disk-tube reverse osmosis treatment in waste incineration plant

In order to utilize waste heat such as exhaust steam and hot air passing through air preheater in the waste incineration plant to heat air used for evaporating leachate concentrate (LC) by gas-liquid contact evaporation technology, hot air of 600 °C, 450 °C and 250 °C was used to evaporate LC in a laboratory-scale evaporator to obtain purified condensate used for supplying water for circulating cooling water system. The influence of pH, hot air temperature and evaporation rate on COD and NH3–N in condensate were investigated to identify the optimum operation of this technology. The results showed that COD concentration in condensate obviously decreased with increase in hot air temperature. Higher hot air temperature led to higher initial evaporation temperature, and evaporation rate of water was significantly greater than that of small molecular organic matter with lower boiling point than water with increasing hot air temperature. Reduction in contents of phenol, ketone and benzene was responsible for COD decreasing in condensate. COD in condensate decreased with increase in pH, as the amount of volatile organic matter such as fatty acids escaped from LC to condensate decreased. The pH had little influence on the DOM in condensate according to EEM spectra analysis. Evaporation rate had little influence on COD in the condensate water. NH3–N concentrations in condensate in all experimental groups were far away from the limit value (10 mg/L) in the water quality standard. Under the premise of meeting water quality standard, the lowest temperature (450 °C) of hot air was selected to save energy and use lower grade waste heat. Therefore, the optimum condition was 450 °C of hot air, pH = 7 of LC and CF = 10. At this condition, molecular weight of DOM in the condensate was smaller and humification degree and aromaticity of DOM were lower according to UV–visible absorption spectrum analysis.

Fouling characteristics and flux prediction model of reverse osmosis membrane based on hydrophobic fractions in reclaimed water

During the operation of the reverse osmosis (RO) system, the identification of key fouling components and the prediction of flux changes based on these components are crucial for minimizing the costs associated with flux recovery. In this study, the DAX-8 resin fractionation method was employed to separate the organic matter in secondary effluent (SE) into hydrophobic acid substances, hydrophobic base substances, hydrophobic neutral substances (HON), hydrophilic substances, and hydrophobic substances (HOS). The primary objective was to discern critical membrane fouling components. The results revealed that HOS constituted 50.0%–60.0% of the dissolved organic carbon concentration in the SE, emerging as the pivotal fraction responsible for RO membrane fouling, contributing to 90.0% of the flux drop induced by SE. Additionally, a fouling prediction model employing two parameters quantified the fouling characteristics of distinct hydrophilic/hydrophobic fractions in RO treatment. Model fitting results indicated a flux decrease of 61.3%, 54.3%, and 46.7% caused by SE, HOS, and HON, respectively. Notably, 90.0% of the decrease in RO membrane flux induced by SE was attributed to the presence of HOS, with HON accounting for about 90.0% of this decrease. The results of the extended Derjaguin-Landau-Verwey-Overbeek theory demonstrated higher adhesion energy and cohesion energy between HOS and RO membrane surfaces compared to hydrophilic substances. This finding suggests that hydrophobic pollutants are more closely bound to RO membrane surfaces. Subsequently, an RO membrane flux prediction method based on HOS in reclaimed water was established. Predicting the RO membrane fouling characteristics of SE became feasible by measuring the concentration of HOS in the influent. Furthermore, resin pre-treatment mitigated the membrane fouling by removing HOS, and the HOS concentration was proposed as a new influent quality index for RO system design.