A review of strategies for RO brine minimization in inland desalination plants

Coal seam gas (CSG) is a new major export for Australia. The production of CSG releases a significant amount of brackish water to the surface, known as associated water. Queensland’s Department of Environment and Heritage Protection (DEHP) has predicted that the peak yearly flow of the associated water could range between 100-280 gigalitres (GL) per year. This presents a major challenge to the CSG industry in water and its by-product (brine) management. CSG water quality varies across regions, but is typically high in total dissolved solids, bicarbonate, hardness, and silica. Consequently, CSG water without treatment is unsuitable for beneficial uses. To date, reverse osmosis (RO) desalination processes with suitable pre-treatment steps have been employed to remove elevated salts and other compounds before CSG water can be used beneficially. One type of beneficial reuse of the treated water that has gained acceptance and prominence in recent times is the irrigation of agricultural crops and forestry. RO brine, a highly saline stream, requires a managed response to ensure a socially, environmentally and financially sound outcome. Conventional evaporation in brine ponds is not considered favourably under existing government directions and, consequently, alternative solutions are sought. Thermal processes, such as brine concentrators, have been used in the treatment of CSG RO brine. The resulting high-quality distillate produced by thermal processes can be used in a number of applications along with a greater proportion of water recovered from such processes. This peer-reviewed paper concludes that a thermal process in conjunction with a high-recovery RO membrane plant, configured as a hybrid membrane/thermal configuration, is probably a suitable solution to meet policy direction by improving system recovery as a precursor to advance associated water treatment and brine management. The discussion is generated out of MWH’s experience with CSG water treatment and management processes, which totals a number of significant projects in the CSG industry.

Tanning industry is one of the industries that produces tannery waste water (TWW) which is dangerous to the environment. About 250 kg leather generating 15,000-50,000 of waste water. This increase environmental concerns regarding TWW. In this review, discussed the concept cleaner production (CP) approach at each process stage in the tannery process and the Zero liquid discharge (ZLD) system used in processing tannery liquid waste. The application of CP in the leather tanning industry is by substituting chemicals with environmentally friendly materials, management water, optimizing tanning conditions, and using technology to recycle and reuse liquid waste. The application of the ZLD system is one of the CP approach for recycle and reuse TWW. The ZLD system used in leather tanning is the Thermal-based ZLD system and Reverse Osmosis. Several countries have implemented the ZLD system, are the United States, India, China, European Union countries and Middle East. The ZLD system is an important TWW strategy to be implemented globally, although operating costs and high energy consumption are limitations in its application. Technological advances and exploration of new approaches to overcome the limitations of ZLD technology may make the approach more feasible and sustainable in the future.

Agricultural drainage water (ADW) represents a potential source for fresh water after receiving appropriate treatments to satisfy the water quality requirements. Desalination of ADW with medium salinity and moderate contamination with organic and inorganic chemical pollutants could provide a techno-economically feasible approach for facing water scarcity in arid areas. The current work presents a conceptual zero liquid discharge ADW desalination system proposed to treat 300,000 m3/d. The system is based on pretreatment to remove impurities harmful to desalination by staged reverse osmosis (RO) membrane. The brine from the last RO stage is treated via thermal vapor compression followed by evaporation in solar ponds to recover more fresh water and salts of economic value. The essential technical features of the proposed system components are formulated. The proposed system components and its technical and economic indicators are deduced using available software for water pretreatment, RO membrane, desalination, thermal desalination, and solar evaporation ponds. The system provides total distilled water recovery of about 98% viz. 294,000 m3/d in addition to recovered salts of 245,000 t/y. The net cost of water production amounts to USD 0.46 /m3. The environmental considerations of the system are addressed and advantages of applying zero liquid discharge system are elucidated.

Emerging water regulations and fresh water scarcity are driving the natural gas processing industries in Qatar towards implementing Zero Liquid Discharge (ZLD) systems. ZLD implies that all wastewater produced in the plant is contained within the plant fence and treated industrial and process water (TIPW) is not discharged into the environment. This paper presents an evaluation of technologies, their potential effectiveness and challenges in achieving ZLD. Pre-treatment facilities for TIPW re-use generally consist of neutralisation and filtration packages, Hydrogen Sulfide (H2S) strippers and Dissolved Air Floatation (DAF) and Membrane Bioreactor (MBR) units. A combination of technologies such as Brine Concentrators, Ultrafiltration (UF), Reverse Osmosis (RO), evaporation-crystallisation unit, and other emerging technologies, are considered as viable solutions for ZLD. However, space limitations, capital expenditure, and concentrate management (brine disposal minimisation) are being recognised as significant obstacles for the existing plants. Deep well injections, evaporation ponds (and landfill disposal options) and discharge to the marine environment (with proper mixing) are the only feasible options for disposal of concentrated brine. With restrictive environmental permits and requirements for these disposal methods, industrial facilities find it difficult to economically justify a ZLD system. A combination of re-concentration techniques and a comprehensive utilisation of concentrated brine, with supportive governmental policies, would be one of the most effective ways to fulfill ZLD.

Impact of chemical composition of reject brine from inland desalination plants on soil and groundwater, UAE

Use of evaporation ponds for brine disposal in desalination plants

Zero liquid discharge (ZLD) has shown to be a promising technology to recycle water with good quality. The ZLD objective is to purify the water from all the liquid waste. The ZLD approach is concentrated on reducing wastewater for possible reuse. In conventional ZLD systems, thermal processes are fundamental. The biggest challenge to implement thermal ZLD systems widely is its intensive energy consumption. As a solution, thermal ZLD systems are integrated with membrane-based reverse osmosis (RO) technology to reduce both capital and operational costs. This study, therefore, focuses on the optimizing a RO/thermal ZLD system based on one of the most important parameters of design—the salinity of the reject brine of evaporator. To give more practical aspect to the results, solution is based realistic design data of a petrochemical complex as the producer of ammonia (2050 ton day−1) and urea (3250 ton day−1). Results show that increasing the salinity of brine stream in evaporator reduces the total required heating surface area of the ZLD plant as well as its required power. This decrease is evident at lower amounts of Xb, but the rate is lowered with increasing of this parameter. So, further increase in Xb does not have much effect on reducing the total heating surface area and power consumption. It means that there is an optimum amount of Xb which can be selected for different applications.

Review on the escalating imperative of zero liquid discharge (ZLD) technology for sustainable water management and environmental resilience

Regulatory authorities are making effluent disposal standards more stringent to minimize the effect of pollution load on natural streams and protect the environment. Industries producing wastewater with a high pollution load and refractory organics are forced to have a near-zero liquid discharge (NZLD) system to meet the effluent standards for disposal. In the NZLD process, solids are separated from wastewater, and recovered water is again used in the process. Thermal methods were used to achieve zero liquid discharge (ZLD), but they are not feasible for diluting wastewater streams due to high energy consumption. At present, membrane processes such as reverse osmosis (RO), forward osmosis (FO), membrane distillation (MD), membrane electrodialysis (MED), and capacitive deionization (CDI) are being used for preconcentration of wastewater before feeding to the thermal units to reduce operational and capital cost. The use of RO and NF reduced energy consumption in conventional ZLD systems by replacing the brine concentrator. RO has high feed TDS limitation and is more prone to fouling due to operation at high pressure. Therefore, FO, MD, or CDI can be used for handling the rejection from 1st stage RO. CDI and EDR are applicable for relatively lower feed concentrations and can replace 1st stage RO in the ZLD system. The crystallizer requires a lot of energy and can be replaced with a solar crystallizer or evaporation pond to reduce energy consumption in the NZLD system. This chapter aims to give insight into the application of membrane technology in achieving ZLD and making it economically feasible. The application of recently developed membranes and modifications can improve the efficiency and applicability of membrane-based ZLD systems.

Screening and cost assessment strategies for end-of-Pipe Zero Liquid Discharge systems

To develop various usable water from coal seam gas (CSG) water that needs to be pumped out from coal seams for methane gas production, a feasibility study was carried out, evaluating and analysing a recent report (Coal Seam Gas Water Management Policy 2012) from Queensland State Government in Australia to suggest potential CSG water treatment options for fit-for-purpose usable water production. As CSG water contains intrinsically high salinity-driven total dissolved solid (TDS), bicarbonate, aliphatic carbon, , and so on, it was found that appropriate treatment technologies are required to reduce the hardness below 60 mg/L as by setting the reduction rates of , and Na+ concentrations, as well as TDS reduction. Also, Along with fiber filtration and membrane separation, an oxidation degradation process was found to be required. Along with salinity reduction, as CSG water contains organic compounds (TOC: 248 mg/L, : : ) need to be treated first. Therefore, this study suggests a combined system design with filtration (Reverse osmosis) and oxidation reduction (electrolysis) technologies, offering proper operating conditions to produce fit-for-purpose usable water from CSG water.

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

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

Interplant Water Networks Coupled with Two-Stage Treatment and ZLD Options

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.