Zero Liquid Discharge Systems Research Articles

Zero liquid discharge management: optimizing sustainable reverse osmosis desalination practices

This study introduces a Zero Liquid Discharge (ZLD) scheme for Reverse Osmosis (RO) desalination, integrating ultra-filtration pretreatment and Electrodialysis (ED) for brine concentration. The scheme divides brine reject into fractions, directing them to an electrolyser and evaporator powered by renewable energy sources. Notable findings include the treatment plant's capability to produce 792 cubic meters of fresh water daily, while decreasing salt concentration from 4,660 ppm to 30 ppm, showcasing efficient desalination. Additionally, recycling fractions of RO unit waste to various components enhances resource efficiency. The study highlights the daily production of 2,269.27 kg of hydrogen, coupled with minimal electricity consumption of 74,885.91 kWh, thereby improving overall energy efficiency. Furthermore, the utilization of solar energy significantly reduces reliance on fossil fuels, thereby promoting sustainability and mitigating the environmental impacts associated with traditional energy sources. Solar energy is a clean, renewable resource that helps decrease greenhouse gas emissions and other pollutants, contributing to cleaner air and a healthier planet. This shift towards renewable energy is crucial in addressing climate change and ensuring a sustainable future for generations to come. In the context of desalination, emphasizing environmental preservation and water security is paramount. Desalination processes, while providing essential fresh water in arid regions, often produce brine as a byproduct. The brine, with a high salt concentration of 13,648 ppm, poses a disposal challenge that can negatively impact marine ecosystems if not managed properly. This is where Zero Liquid Discharge (ZLD) systems come into play. With a ZLD index of 2.7%, these systems ensure that all wastewater is treated and reused, leaving no liquid waste behind. ZLD technology captures and recycles every drop of water, converting waste into reusable resources, thus minimizing environmental harm. The model showcased a significant decrease in brackish water extraction from 1,200 cubic meters per day to 871.52 cubic meters per day, marking a notable 27% reduction. These results highlight the promising effectiveness of the proposed ZLD scheme in enhancing the efficiency of brackish water treatment, demonstrating its potential to significantly reduce the demand for fresh water resources while achieving sustainable desalination practices. This article will present a detailed yet a simple description of reverse osmosis and ZLD, how do they correlate and how these two technologies represent the future of water treatment.

A comprehensive assessment of the economic and technical viability of a zero liquid discharge (ZLD) hybrid desalination system for water and salt recovery

Brine, a by-product of desalination and industrial facilities, is becoming more and more of an environmental issue. This comprehensive techno-economic assessment (TEA), focusing on the technical and economic aspects, investigates the performance and viability of a novel hybrid desalination brine treatment system known as zero liquid discharge (ZLD). Notably, this research represents the first instance of evaluating the feasibility and effectiveness of integrating three distinct desalination processes, namely brine concentrator (BC), high-pressure reverse osmosis (HPRO), and membrane-promoted crystallization (MPC), within a ZLD framework. The findings of this study demonstrate an exceptional water recovery rate of 97.04%, while the energy requirements stand at a reasonable level of 17.53 kWh/m3. Financially, the ZLD system proves to be at least 3.28 times more cost-effective than conventional evaporation ponds and offers comparable cost efficiency to alternatives such as land application and deep-well injection. Moreover, the ZLD system exhibits profitability potential by marketing both drinking water and solid salt or solely desalinated water. The daily profit from the sale of generated water varies from US$194.08 to US$281.41, with Greece and Cyprus attaining the lowest and highest profit, respectively. When considering the sale of both salt and water, the profit rises by 8% across all locations.

Electrodialysis of moderately concentrated solutions: Experiment and modeling based on a simplified characterization of ion-exchange membranes

Electrodialysis (ED) is a cost-effective and environmentally friendly process; it is considered a key step in Zero Liquid Discharge systems. However, the ED process producing a fairly concentrated solution is not well understood. An ED process where 10 L of 0.5 M NaCl was circulated in diluate stream (DS) and 0.1 L of initially 2.0 M NaCl circulated in concentrate stream (CS) was studied. The concentration of concentrate increased up to 3.5 M. The electrodialyzer's design eliminated current leakage. Ion-exchange membranes, MK-40, MA-41 (Shchekinoazot) and CJMA-3 (Chemjoy Polymer Materials), were characterized prior to ED. Based on the concentration dependences of membrane conductivity and diffusion permeability, the “true” (ti⁎) ion transport numbers in the membranes were found; the water transport number (tw) was found from volumetric measurements. It was shown that the current efficiency, η, found using ti⁎ is quantitatively consistent with η found in the ED experiments. To calculate the time dependences of solution concentration and volume in CS, a mathematical model was built. For the first time, ti⁎ and tw determined in independent experiments, were used as parameters. The only fitting parameter was the osmotic permeability coefficient. A good agreement with experimental results is obtained.

Multistage membrane-integrated zero liquid discharge system for ultra-efficient resource recovery from steel industrial brine: Pilot-scale investigation and spatial membrane fouling

Zero liquid discharge (ZLD) strategy provides significant potential for industrial brine treatment. Still, the application has been constrained by the inadequate water recovery and membrane fouling of its membrane-based brine concentration system. Herein, a pilot-scale system was established that integrated pretreatment, reverse osmosis (RO), nanofiltration (NF), and disk tube reverse osmosis (DTRO), and demonstrated over a 6-month operation for the first application in treating steel industry brine. Meanwhile, novel insights were offered into the spatial evolution of DTRO membrane fouling. The overall ZLD system reached ultra-efficient water recovery at 91% with relatively low energy consumption (7.27 kWh/m3). The RO and NF units concentrated the brine and selectively separated ions of different valences, simultaneously eliminating various contaminants. The DTRO unit enriched the highly saline NF permeate with a remarkable 7.5-fold concentration effect, producing an extremely hypersaline brine salinity (138,472 ± 34,804 mg/L, Cl−/SO42− mass ratio of 56) that ultimately yielded ultra-pure NaCl salt. Additionally, DTRO special fouling patterns revealed a distinctive "W"-shaped fluctuation in humic acid along the device water flow, with concurrent reduction in iron/aluminum oxides leading to their deposition at the outlet. This synergistic fouling, coupled with silicon, coincides with the transformation of silica colloids into silicate compounds. The multistage membrane-based strategy and the spatial membrane fouling evolution pattern proposed and investigated in this work provide a highly efficient and cost-effective solution for industrial brine treatment with ZLD.

Hybrid desalination system for Baltic Sea water: A preliminary study

The world's water resources predominantly comprise salt water. In the face of forecasts of increasing demand for hydrogen obtained by electrolysis, it is becoming important to investigate the feasibility of seawater desalination. As part of a research project, the possibility of using a hybrid zero liquid discharge (ZLD) desalination system to desalinate seawater from the Baltic Sea was examined. In addition to analysing the operating parameters of the system, a detailed physico-chemical examination of the process water was carried out at each stage of treatment. It was found that the reverse osmosis (RO) and multiple-effect desalination (MED) systems allow sufficient water parameters to be obtained to feed the ion exchange (IX) system, and after deionisation it is possible to achieve the water parameters required by proton exchange membrane (PEM), anion exchange membrane (AEM) and alkaline water (AWE) electrolysers. Furthermore, the possibilities of concentrating brine in the multiple-effect desalination system and extracting salt in solid form in the ZLD system were verified.

Artificial intelligence models for predicting calcium and magnesium removal by polyfunctional ketone using ensemble machine learners

Calcium (Ca2+) and magnesium (Mg2+) are the major scaling ions of reverse osmosis concentrate in zero-liquid discharge systems, causing performance decline. In this study, we predicted the removal of Ca2+ and Mg2+ from simulated reverse osmosis concentrate by functional polyketones (FPKs). Four amines, including 1,2-diaminopropane (DAP), 1-(2-aminoethyl) piperazine (AEP), 1-(3-aminopropyl) imidazole (API), and butyl amine (BA) used to synthesize FPKs. The effects of various factors such as the amount of adsorbent, feed water concentration, and pH were investigated for process optimization. In this study, ensemble learner artificial intelligence models, decision tree (DT), extreme gradient boost (XGB), and random forest (RF) were used to predict Ca2+ and Mg2+ removal by the FPKs. Datasets were collected experimentally using FPKs to remove Ca2+ and Mg2+ from the simulated reverse osmosis concentrate. The predictions were made by XGB, DT, and RF models for the first chosen amine for Ca2+ and then for Mg2+, subsequently, this process was repeated with each amine. The developed DT, RF, and XGB models demonstrated higher coefficients of determination for predicting Mg2+ removal by AEP and DAP (R2 = 0.841–0.935) than by API and BA (R2 = 0.774–0.801) except in the RF and XGB model results (R2 = 0.801–0.846). Overall, the XGB model displayed good results for both Ca2+ and Mg2+ removal but slight changes were observed in the AEP and BA predictions by DT and RF. Therefore, artificial intelligence models may be a viable alternative for further insight in predicting Ca2+ and Mg2+ removal by FPKs from simulated reverse osmosis concentrate.

Efficacies and mechanisms of different cleaning strategies for NF and RO membranes in a full-scale zero liquid discharge system

Membrane fouling conditions can be distinct for multi-step nanofiltration (NF) and reverse osmosis (RO) membrane processes in zero liquid discharge (ZLD) system. Customizing cleaning procedures according to fouling characteristics is imperative to improve the overall cleaning efficiency of the system. Herein, we performed four different “alkaline + acid” cleaning procedures, including alkaline solution (NaOH), acid solution (citric acid), metal chelating agents (Na2EDTA), and surfactants (SDS), on five fouled NF and RO membranes from a full-scale ZLD system for cold-rolling wastewater brine treatment. The“alkaline + acid” cleaning procedures were effective for organic and inorganic combined fouling removal in two-stage NF process, but failed to remove SiAl complex scaling completely for the 2nd RO process. Due to the slight membrane fouling, both performance and surface properties of 1st and 3rd pass RO membranes did not change significantly after the cleaning. The high pH-induced solubilization were the major mechanism for the removal of the SiAl complex. Na2EDTA/SDS addition caused the decrease of foulant-foulant and foulant-membrane interactions. Customizing membrane cleaning procedures based on membrane fouling characteristics can facilitate the stable operation of hybrid membrane system for the practical industrial wastewater ZLD treatment.

Innovative desalination system driven by a solar micro gas turbine for off-grid applications

Past work by the authors has suggested that Solar micro Gas Turbines (SmGTs) can be used cost-effectively to produce electric power and heat for freshwater production through desalination, mainly in off-grid locations. This is further studied in this work, providing an exhaustive modelling procedure and methodology. Additionally, a comprehensive analysis of system performance under both design and part-load conditions is provided along with the complete set of characteristics of the components of the SmGT and the desalination unit. To this end, the SmGT is assessed first, incorporating innovative solutions that enable better off-design performance: Variable Inlet Guide Vanes (VIGVs) in the compressor and Variable Nozzle Guide Vanes (VNGVs) in the turbine. The implementation of these features brings significant advantages in part-load operation, leading to a considerable increase in solar-to-electric efficiency and rangeability, particularly under certain ambient conditions; in particular, using these features yields 5% higher efficiency at the minimum load of the original engine (without variable geometry) and, from this load setting downwards, 15% lower minimum stable load is enabled. Furthermore, a sensitivity analysis to control strategies and ambient conditions has been included, exploring their impact on system performance.The water treatment system is comprised of two elements. A Reverse Osmosis (RO) desalination unit is driven by the electric power produced by the SmGT. Considering the emphasis on flexibility and part-load operation enhancement addressed in this work, a moderate recovery rate is proposed for this unit. The RO unit produces brine with high salt concentration to be partially treated further in a Zero Liquid Discharge (ZLD) unit driven by the exhaust gases of the microturbine (at about 250–300 °C), where the sensible heat of this stream is harvested by the ZLD unit to “dry” and concentrate the effluent. Finally, the potential and the operational limitations of the ZLD system are discussed, complemented with results from an experimental proof of concept where the feasibility of the concept is verified.

Design and applicability of a water recycling system to treat wastewater generated from real uranium-contaminated soil

This study investigated, from practical and engineering perspectives, a systematic design and its ability to remediate real U-contaminated soil, with the aim of assessing the performance of a zero liquid discharge system for treating wastewater from a soil-washing process. Specifically, we carried out a purification process for U-contaminated soil and its wastewater; the proposed method consisted of U(VI) precipitation, solid–liquid separation with a filter-press, and distillation of the filtrate on the basis of U(VI) concentration. Experimental results indicated complete separation of uranium from the contaminated soil. Self-disposal of the treated soil was possible because it contained uranium at a concentration less than 1.0 Bq·g−1, which the International Atomic Energy Agency has suggested as the clearance level for radionuclides. In terms of the zero liquid discharge system, the distillation process enabled not only water reuse of the filtrate after solid–liquid separation but also self-disposal of high-purity Na2SO4 in the residues of the distilled filtrate. According to a comparison of the economic analysis between direct disposal and the application of a remediation process to treat U-contaminated soil, the proposed comprehensive zero liquid discharge system for the treatment of U-contaminated soil is a practical and feasible option. We anticipate that the valuable experimental results and implications in this study will play a significant role in both academia and industry given the demonstration of design and applicability of the proposed zero liquid discharge system to treat wastewater generated from real U-contaminated soil.

Design of a multistage hybrid desalination process for brine management and maximum water recovery.

Hypersaline brine production from desalination plants causes huge environmental stress due to the untenable conventional discharge strategies. Particularly, brine production is expected to drastically increase in the coming few decades due to the increasing desalination capacity in attempts of forestalling water scarcity. Thereby, zero liquid discharge (ZLD) is a worth-considering solution for strategic brine management. ZLD or minimal liquid discharge (MLD) systems provide maximum water recovery with least or zero liquid waste generation and valuable salt production. In this work, a theoretical design of ZLD/MLD system is proposed for reverse osmosis (RO) brine management. Different scenarios are investigated utilizing multistage freeze desalination (FD) and its hybridization with multistage direct contact membrane distillation (DCMD), and eutectic freeze crystallization (EFC) technologies. The design is based on the experimental assessment of the indirect FD process at different feed salinities, i.e., 2g/L to 155g/L. FD experiments showed that ice quality is reduced at greater crystallinity levels and initial concentration. Moreover, a computational fluid dynamics (CFD) model is utilized to assess the performance of DCMD. A single DCMD module could produce 53kg/(m2.h) of pure water operating with 69% thermal efficiency. Eventually, water recovery, water quality, as well as specific energy consumption (SEC) are evaluated for the whole system. Based on different configurations of the hybrid ZLD system, the proposed design can achieve water recovery between 40 and 93% with SEC range of 28-114 kWh/m3. Results also showed that the produced water quality exceeds drinkable water standards ( 500mg/L). This work has provided great evidence in the practicality of ZLD/MLD systems for sustainable brine management.

Sustainable Concept of Zero-Liquid Discharge and Its Impact on Climate Change: Detail Case Studies

In the developed world’s metropolitan areas, proper wastewater treatment and recycling are of the utmost importance. Releasing wastewater into aquatic systems is the biggest environmental risk and the biggest barrier to wastewater regeneration and reuse. The origin of the wastewater also has an impact on its potential for reuse. There are three separate processes at work in the universe: the physical, the chemical, and the biological. The study examines the challenges associated with wastewater consumption, as well as wastewater treatment, reuse, and repurposing. One of the most compelling arguments for exploring the possibility of zero liquid discharge is the possibility of energy recovery from wastewater. Manufacturing operations that aim for Zero Liquid Discharge (ZLD) may recycle or reuse the solid waste they produce. ZLD system design is becoming more popular. To be sure, current ZLD systems have their drawbacks, the most notable of which are the high plant costs and high energy intensity of their crystallizers. Because of the growing public and media awareness of the consequences of wastewater pollution, stricter environmental restrictions are expected to push more polluting businesses onto ZLD. Moreover, climate plays such a significant role in the wastewater treatment plant; climate change may have far-reaching implications on the drainage system.

Techno-Economic Analysis of Brine Treatment by Multi-Crystallization Separation Process for Zero Liquid Discharge

This study analyses the concept of a novel multi-crystallization system to achieve zero liquid discharge (ZLD) for desalination plants using an innovative heat recovery system consisting of a heat transfer fluid and a compressor to reduce energy consumption. The main focus is to recover water and separately extract salts from seawater brines with high purity, including calcite, anhydrite, sodium chloride, and epsomite, which can be sold to the cement industry. The system is compared with a conventional brine treatment system. The energy demand and economic feasibility of both systems are assessed to evaluate profitability at a scale of 1000 kg/h. The results estimate that the utilization of a heat recovery fluid reduces energy consumption from 690 kWhth/ton of feed brine to 125.90 kWhth/ton equaling a total electric consumption of 60.72 kWhe/ton. The system can recover 99.2% of water and reduce brine discharge mass by 98.9%. The system can recover 53.8% of calcite at near 100% purity, 96.4% of anhydrite at 97.7% purity, 91.6% of NaCl at near 100% purity, and 71.1% of epsomite at 40.7% purity. Resource recovery accounts for additional revenues, with halite and water accounting respectively for 69.85% and 29.52% of the income. The contribution of calcite and anhydrite to revenue is very low due to their low production. The levelized cost of water (LCOW) of the multi-crystallization system is 13.79 USD/m3 as opposed to 7.85 USD/m3 for the conventional ZLD system. The economic analyses estimate that the conventional ZLD system can achieve payback after 7.69 years. The high electricity cost, which accounts for 68.7% of the annual expenses, can be produced from renewable sources.

Membrane fouling behaviors in a full-scale zero liquid discharge system for cold-rolling wastewater brine treatment: A comprehensive analysis on multiple membrane processes

The challenge of water scarcity drives zero liquid discharge (ZLD) treatment to maximize reuse of industrial wastewater. Deciphering the characteristics and mechanisms of membrane fouling in the membrane-based ZLD system is crucial for the development of effective fouling control strategies. However, current studies only focused on the membrane fouling of single step, lacking in-depth understanding on the ZLD systems using multiple membrane processes. Herein, membrane fouling characteristics and mechanisms in a full-scale ZLD system for cold-rolling wastewater brine treatment were investigated via a comprehensive analysis on multiple nanofiltration (NF) and reverse osmosis (RO) membrane processes. The membrane fouling behaviors showed distinct characteristics along the wastewater flow direction in the ZLD system. Increasing amounts of foulants were deposited on the membrane surfaces with the sequence of the 1st pass RO, 1st stage NF, and 2nd stage NF processes. The organic fouling and silica scaling were more intensive in the 1st stage NF and 2nd stage NF for treating the brine of the 1st pass RO, as the foulants were rejected and concentrated by previous membrane processes. Severe inorganic fouling, containing amorphous SiO2, Al2O3, and Al2SiO5, occurred on the membrane surface of the 2nd pass RO membrane, due to the recirculated high-concentration silica, high water recovery, and concentration polarization. For the 3rd pass RO process, both the amounts of organic and inorganic foulants decreased dramatically, due to the low foulant concentration in its influent. This work provides a comprehensive understanding of membrane fouling in a membrane-based ZLD system, facilitating the development of membrane fouling control strategies for multiple membrane processes.

Relationship of Photosynthetic Activity of Polygonum acuminatum and Ludwigia lagunae with Physicochemical Aspects of Greywater in a Zero-Liquid Discharge System

Landscape harmony is a key factor in the application of nature-based solutions to provide green areas. The search for plants that meet this requirement is crucial in this context. We evaluated the adaptation, resistance, and performance of Polygonum acuminatum and Ludwigia lagunae, macrophytes from the Pantanal biome, in greywater-fed mesocosms simulating zero-liquid discharge systems. Four irrigation solutions were tested for 212 d. Neither species exhibited stress conditions in the adaptation phase, with photosynthetic activity (Fv/Fm) close to that obtained in Pantanal. However, over time, the mesocosms irrigated with greywater (GW) without nutrient supplementation exhibited stress according to correlation analyses of photosystem PSII and physicochemical parameters; L. lagunae for dissolved oxygen below 3 mg L−1 and P. acuminatum for water temperatures above 27 °C. Supplementation of GW with nutrients resulted in good growth and performance. Both species were able to receive high chemical oxygen demand (COD) loads, averaging 34 g m−2 day−1 for L. lagunae and 11 g m−2 day−1 for P. acuminatum, with an average removal of 85% by both. L. lagunae had better evapotranspiration capacity, with greater potential for use in cooling islands, whereas P. acuminatum showed a more resistant metabolism without nutrient supplementation.

Comparative techno-economic and environmental analysis of minimal liquid discharge (MLD) and zero liquid discharge (ZLD) desalination systems for seawater brine treatment and valorization

Brine from desalination plants has become an environmental issue as the global desalination capacity is increasing. This study presents a techno-economic & environmental analysis of minimal liquid discharge (MLD) and zero liquid discharge (ZLD) systems in the Eastern Mediterranean. In particular, two cases are considered: (i) an MLD system incorporating reverse osmosis (RO) and forward osmosis (FO), and (ii) a ZLD system incorporating RO, FO, brine concentrator (BC) and brine crystallizer (BCr). The results indicated that the energy (6.74 kWh/m3) and cost demands (US$0.72/m3) in case 1 are lower than in case 2, with energy consumption of 10.36 kWh/m3 and cost demands of US$0.79/m3 due to two additional thermal-based technologies. MLD and ZLD systems are both comparable in cost to subsurface water sources; thus, they can be a valuable alternative to subsurface water. Furthermore, both cases are lucrative from the selling of fresh water (from US$195.33/day to US$228.4/day), while the ZLD system is even more lucrative when solid salt is also sold, increasing the profit in case 2 from US$228.4/day to US$247.44/day (8% increase). Overall, the proposed desalination brine treatment systems boost the circular economy and could have significant economic potential in the Eastern Mediterranean and elsewhere.

Techno-economic assessment and feasibility study of a zero liquid discharge (ZLD) desalination hybrid system in the Eastern Mediterranean

The environmental consequences of brine disposal (i.e., marine pollution, soil salinization, and groundwater contamination) are a concern for desalination plants across the world. This techno-economic assessment and feasibility study explores for the first time both the performance and the feasibility of a zero liquid discharge (ZLD) desalination hybrid system for brine treatment and valorization in Eastern Mediterranean countries, namely, Greece, Cyprus, and Israel. The results revealed that the recovery rate (99.19%) is exceptional, while the energy demands are 20.23 kWh/m3, which is reasonable as three different desalination processes (namely, high-pressure reverse osmosis (HPRO), brine concentrator (BC), and brine crystallizer (BCr)) are integrated into the ZLD system. The ZLD system is at least 3.22 times less costly than evaporation ponds, and it is on par with deep-well injection and land application alternatives in terms of cost. Furthermore, the ZLD system is lucrative whether it markets only water or both water and solid salt. The profit gain from desalinated water sales ranges from US$196.36/day to US$285.63/day, with Cyprus and Greece having the highest and lowest profit gain, respectively. In respect of both desalinated water and salt sales, the profit gain increases by 7% for each location.

Zero Liquid Discharge System for the Tannery Industry—An Overview of Sustainable Approaches

The tannery industry is characterized by the consumption of a large quantity of water, around 30–40 m3 for processing 1000 kg of hide or skin. This amount becomes wastewater, containing about 300 kg of different chemicals, mainly refractory organic compounds, with high chemical oxygen demand (COD), total dissolved salts (TDS), chromium, and evolution of toxic gases, such as ammonia and sulfides, etc. The remaining tanning chemicals are released as effluent having high resistance against biological degradation, becoming a serious environmental issue. Usually, end-of-pipe treatment is not sufficient to meet the concerns of environmental issues. In terms of cleaner production options, the redesigning of the existing effluent treatment procedures with alternate or additional treatment techniques, which “supports resource recovery with no added chemicals”, is expected to give a sustainable solution for the management of toxic effluent. The Zero Liquid Discharge (ZLD) system serves to ensure zero water emission, as well as treatment facilities by recycling, recovery, and reuse of the treated wastewater using advanced cleanup technology. The international scenario shows the implementation of ZLD thanks to pressure from regulatory agencies. The ZLD system consists of a pre-treatment system with conventional physicochemical treatment, tertiary treatment, softening of the treated effluent, reverse osmosis (RO) treatment for desalination, and thermal evaporation of the saline reject from RO to separate the salts. By adopting this system, water consumption is reduced. Moreover, ZLD also becomes effective in disaster mitigation in areas where the tannery industry is a strong economic actor. With this review, we aim to give an outlook of the current framework.

Crystallization Process as a Final Part of Zero Liquid Discharge System for Treatment of East Baghdad Oilfield Produced Water

This study investigated the application of the crystallization process for oilfield produced water from the East Baghdad oilfield affiliated to the Midland Oil Company (Iraq). Zero liquid discharge system (ZLD) consists of several parts such as oil skimming, coagulation/flocculation, forward osmosis, and crystallization, the crystallization process is a final part of a zero liquid discharge system. The laboratory-scale simple evaporation system was used to evaluate the performance of the crystallization process. In this work, sodium chloride solution and East Baghdad oilfield produced water were used as a feed solution with a concentration of 177 and 220 g/l. The impact of temperature (70, 80, and 90 °C), mixing speed (300, 400, and 500 rpm), feed concentration (177 and 220 g/l), and time (0.5-9.5 h) on the crystallization performance for oilfield produced water treatment were investigated on evaporation rate and recovery. The recovery increased with increasing temperature and mixing speed while decreasing with an increase in feed concentration. Pure water and salts were recovered from the concentrated produced water, the recovery of pure water at 80 °C, 400 rpm, and 220 g/l feed concentration was 82.22 and 81.35% after 5.5 h for NaCl solution (i.e., simulated oilfield produced water) and oilfield produced water, respectively.

Sustainable cleaner production technologies and treatment of segregated effluent streams with recovery of quality salt, chromium & water

Conventional process and treatment system adopted by Indian and Global Tanneries consist of Segregation of Spent Chrome Stream and discharge of supernatant for combined treatment along with effluent from all sectional operations starting from soaking to finishing, Conventional physiochemical and biological treatment for reduction of Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), etc., Ultra-filtration and Reverse Osmosis (RO) system for recovery of water and Multiple Effect Evaporator (MEE) for the evaporation of RO reject stream and generation of mixed salt in case of Zero Liquid Discharge (ZLD) system and Storage of mixed salt recovered from the MEE system for which no viable disposal system is found. Establishment of treatment system for the mixed stream results in poor performance of biological treatment units, increases the Operation & Maintenance (O&M) cost and accumulation of recovered mixed salt in case of ZLD system. It is estimated that, more than 8-10 tones of mixed salt is generated during the treatment of 1.0 MLD effluent under ZLD system. To address this serious environmental problem, an innovative approach of segregation of saline streams such as soak liquor and chrome liquor are planned to be collected separately with the feasibility of recovering reusable quality salt and chromium in the form cake for regeneration and use in the form of Basic Chromium Sulphate (BCS) by the tanneries. This innovative treatment concept has been developed and is being implemented in many Common Effluent Treatment Plants (CETPs) in India. This will become the first of its kind in Global Leather World. This developmental scheme is in accordance with the guidelines and recommendations of UNIDO in terms of sustainability of ZLD system for leather sector. The technological developments on cleaner productions, centralized chrome recovery reuse system, segregation of saline soak water for separate treatment with recovery of water and quality salt are dealt in this technical paper.

Enhanced anti-wetted PVDF membrane for pulping RO brine treatment by vacuum membrane distillation

Large amounts of lignin, hemicellulose, organic matter and inorganic salts are present in pulping and papermaking wastewater. Therefore, the treatment and discharge of pulping wastewater are important issues. We have designed and developed the world's first zero liquid discharge (ZLD) system for it based on pretreatment-membrane-evaporative crystallization integrated technologies. However, for the treatment of high salt reverse osmosis (RO) brine, there are still challenges that need to be addressed. In this work, the feasibility of using a membrane distillation crystallization (MDC) process to treat high saline RO brine was investigated. Two different coating materials, Hyflon AD 40H and perfluoropolyether (PFPE), were applied to improve the membrane surface hydrophobicity for stable and efficient performance. After modification, the water contact angle was up to 138.4o and 157.7o for Hyflon/polyvinylidene fluoride (PVDF) and PFPE/PVDF composite membranes, respectively. Moreover, the PFPE/PVDF membrane showed a higher repellency toward RO brine, which is better for the following MDC treatment. During the MDC progress using composite PFPE/PVDF membranes, the salt crystals precipitated and gradually accumulated. More importantly, the final NaCl purity can be up to 94%. Therefore, it is hopeful to improve of the existing ZLD system by MDC operation.