Advances in Brine Disposal and Dispersion in the Coastal Ecosystem from Desalination Plants

Recently, the use of filters has come into light for sanitizing water plants. This study investigated the role of heat-tolerant ultrafilters (UFs) for the remediation of reverse osmosis (RO) plants using periodic thermal disinfection. Two completely identical RO plants (RO plants A and B) were installed in 2006 for surgical hand antisepsis in the operating theater. RO water was stored in the 300 L storage tank and recirculated in the 190 meter-long loop delivering water to 12 faucets in each RO plant. Periodic thermal disinfection came into practice periodically when a UF module was retrofitted to the recirculation loop of each RO plant in 2010. Endotoxin was monitored closely before and after thermal disinfection. Before UF modules were retrofitted, endotoxin increased to a maximum of 0.301 EU/mL in RO plant A and 1.446 EU/mL in RO plant B after thermal disinfection, respectively. Since a UF module was retrofitted to each RO plant in 2010, endotoxin has been continuously below 0.025 EU/mL in RO plant A and exceeded this level five times in RO plant B. On one occasion, endotoxin increased in all samples collected simultaneously after solenoid valves were replaced in the recirculation loop near the air conditioner outlet. At this time, the inside of the pipework was exposed to the ventilation airflow. After the valves were replaced again, this time with the workplace isolated using a curing sheet, endotoxin decreased. On the other occasions, endotoxin increased only in one sample and decreased after thermal disinfection. Annually replaced UF modules were examined twice for estimating the amounts of immobilized endotoxin. The estimated amounts decreased in 2013 by the order of 10-3 in comparison with those in 2011 in both RO plants. The present study suggested that UFs acted synergistically with periodic thermal disinfection for the remediation of RO plants.

Automation and reliability are the crucial elements of any advance reverse osmosis plant to meet the environmental and economic demands. Early fault indication, diagnosis and regular maintenance are the key challenges with most of the reverse osmosis plants in the Indian scenario. The present work introduces a modern reverse osmosis (RO) plant status monitoring unit to monitor different plant parameters in real time and early prediction for faults and maintenance. Developed RO plant status monitoring unit consists of a touch screen-based embedded monitoring unit, water quality sensors (pH, TDS), sampling chamber for controlled water flow, flow sensors, pressure and level sensors. The present system has been developed in a modular fashion so that it could be integrated with any capacity of RO plant units. Developed embedded system monitors various parameters of the plant such as input power, efficiency of the plant, level of input and output water tank and also guides operator with instructions for plant operation. Other than this, a dedicated smartphone app interface has been developed for the operator to acquire data from status monitoring unit, storage on smartphone, and transfer it to the cloud. The developed smartphone-based app also provides facility to integrate plant data with Google map with location information for easy understanding and quick action. The system has also a backup facility to transfer data to the server using 2G GSM module during the unavailability of the operator. A dedicated centralized Web server has been developed for real-time visualization of all installed RO plant status monitoring units. Different machine learning techniques have been implemented on acquired sensors data to predict early warnings related to power failure, membrane fouling and scaling, input water shortage, pipe, tank leakage, water quality sensors damage, non-operation or wrong operation of the plant along with different maintenance actions such as membrane water and chemical wash. Developed RO status monitoring unit has been tested with various RO plants having capacity from 500 LPH to 2000 LPH and deployed at various nearby villages of Rajasthan.

Chronic Interstitial Nephritis in Agricultural Communities (CINAC) causes major morbidity and mortality for farmers in North-Central province (NCP) of Sri Lanka. To prevent the CINAC, reverse osmosis (RO) plants are established to purify the water and reduce the exposure to possible nephrotoxins through drinking water. We assessed RO plant maintenance and efficacy in NCP. We have interviewed 10 RO plant operators on plant establishment, maintenance, usage and funding. We also measured total dissolved solids (TDS in ppm) to assess the efficacy of the RO process. Most RO plants were operated by community-based organizations. They provide clean and sustainable water source for many in the NCP for a nominal fee, which tends to be variable. The RO plant operators carry out RO plant maintenance. However, maintenance procedures and quality management practices tend to vary from an operator to another. RO process itself has the ability to lower the TDS of the water. On average, RO process reduces the TDS to 29ppm. The RO process reduces the impurities in water available to many individuals within CINAC endemic regions. However, there variation in maintenance, quality management, and day-to-day care between operators can be a cause for concern. This variability can affect the quality of water produced by RO plant, its maintenance cost and lifespan. Thus, uniform regulation and training is needed to reduce cost of maintenance and increase the efficacy of RO plants.

This paper studies energy consumption management of seawater Reverse Osmosis (RO) desalination plants to maintain and enhance the Voltage Stability (VS) of Power Systems (PS) with Photovoltaic (PV) plant integration. We proposed a voltage-based management algorithm to determine the maximum power consumption for RO plants. The algorithm uses power flow study to determine the RO plant power consumption allowed within the voltage-permissible limits, considering the RO process constraints in order to maintain the desired fresh water supply. Three cases were studied for the proposed RO plant: typical operation with constant power consumption, controlled operation using ON/OFF scheduling of the High-Pressure Pumps (HPPs) and controlled operation using Variable Frequency Drive (VFD) control. A modified IEEE 30-bus system with a variable load was used as a case study with integration of three PV plants of 75 MWp total power capacity. The adopted 33.33 MW RO plant has a maximum capacity of 200,000 m3/day of fresh water production. The results reveal that while typical operation of RO plants can lead to voltage violation, applying the proposed load management algorithm can maintain the vs. of the PS. The total transmission power loss and power lines loading were also reduced. However, the study shows that applying VFD control is better than using ON/OFF control because the latter involves frequent starting up/shutting down the RO trains, which consequently requires flushing and cleaning procedures. Moreover, the specific energy consumption (SEC) and RO plant recover ratio decreases proportionally to the VFD output. Furthermore, the power consumption of the RO plant was optimized using the PSO technique to avoid unnecessary restriction of RO plant operation and water shortage likelihood.

Water is not just the essential ingredient for life, but also a fundamental factor in the economy and security of any country. Coupled with increased population and climate change effect, the availability of food, water, and energy are the biggest challenges that the world faces. There is also the dependency of these essential gradients and basic needs on each other; i.e., water is needed to produce energy and energy is needed to produce water as well as both water and energy are needed to produce food. Over the next two decades water demand will exceed water supply by about 40% according to many scientific studies and reports. Food and energy demands will exceed supply by 50% and have also been described by the UK government's chief scientific advisor, Prof. John Beddington, to create the ''perfect storm'' by 2030. The provision of drinkable supplies through desalination could offer a sustainable solution to the drinking water problem but also presents a technical challenge too as well as all existing methods involve high operating and investment costs. A novel manipulated/forward osmosis (MfO) desalination process has been invented and developed at the Centre for Osmosis Research and Applications at the University of Surrey in collaboration with Modern Water plc (Modern Water). In the MfO process seawater is converted into an osmotic agent's solution by taking advantage of the natural osmosis process. Pure water is then recovered from the osmotic agent's solution using a membrane process, where the agent is reused. The technical obstacles being overcome in this process are the avoidance of all scaling, bio-fouling, high operating pressures, and necessity for pre-treatments and the associated chemical wastes, which result in direct and indirect reduction of cost. The concepts also serve as a platform for applications in power generation and other industrial applications. The pilot plant and Modern Water's commercial plants data in Oman and Gibraltar that follow from the manipulated osmosis (MO) process route offers up to 30% saving in the specific energy consumption over a conventional reverse osmosis (RO) process. The MO process also offers an increase in fresh water recovery rate coupled with minimal membrane fouling propensity and brine disposal. Additionally, the process can be incorporated into existing RO and thermal plants with reasonable modifications. New plant based on the MO principle should also have lower capital costs and smaller footprint. The new technology can be used to obtain clean water from any available water source irrespective of its purity, such as waste streams, seawater, brackish water, river water, etc. The provision of drinkable supplies through desalination could offer a sustainable solution to the drinking water problem but also presents a technical challenge too as well as all existing methods involve high operating and investment costs. A novel Manipulated/Forward Osmosis (MfO) desalination process has been invented and developed at the Centre for Osmosis Research and Applications at the University of Surrey in collaboration with Modern Water plc. In the MfO process seawater is converted into an osmotic agent's solution by taking advantage of the natural osmosis process. Pure water is then recovered from the osmotic agent's solution using a membrane process, where the agent is reused. The technical obstacles being overcome in this process are the avoidance of all scaling, bio-fouling, high operating pressures, and necessity for pre-treatments and the associated chemical wastes, which result in direct and indirect reduction of cost. The concepts also serve as a platform for applications in power generation and other industrial applications. The pilot plant and Modern Water's commercial plants data in Oman and Gibraltar that follow from the MO process route offers up to 30% saving in the specific energy consumption over a conventional RO process. The MO process also offers an increase in fresh water recovery rate coupled with minimal membrane fouling propensity and brine disposal. Additionally, the process can be incorporated into existing RO and thermal plants with reasonable modifications. New plant based on the MO principle should also have lower capital costs and smaller footprint. The new technology can be used to obtain clean water from any available water source irrespective of its purity, such as waste streams, seawater, brackish water, river water, etc.

Tandom reverse osmosis process for zero-liquid discharge

A novel solar-powered thermal desalination unit coupled with a reverse osmosis plant to increase overall water recovery

Operational experience from hybrid RO system at SAFI wastewater re-use RO plant

The Nuclear Desalination Demonstration Project (NDDP) at Kalpakkam aims to demonstrate the safe and economic production of good quality water by desalination of seawater comprising 4,500 m³/d Multi-Stage Flash (MSF) and 1,800 m³/d Reverse Osmosis (RO) plant. The design of the hybrid MSF–RO plant to be set up at an existing nuclear power station is presented. The MSF plant based on long tube design requires less energy. The effect on performance of the MSF plant due to higher seawater intake temperature is marginal. The preheat RO system part of the hybrid plant uses reject cooling seawater from the MSF plant. This allows lower pressure operation, resulting in energy saving. The two qualities of water produced are usable for the power station as well as for drinking purposes with appropriate blending. The post treatment is also simplified due to blending of the products from MSF and RO plants. The hybrid plant has a number of advantages: part of high purity desalted water produced from the MSF plant will be used for the makeup demineralised water requirement (after necessary polishing) for the power station; blending of the product water from RO and MSF plants would provide requisite quality drinking water; and the RO plant will continue to be operated to provide water for drinking purposes during the shut down of the power station. Commissioning of the RO section is expected in 2002 and that of the MSF section in 2003. Useful design data are expected from the plant on the coupling of small and medium size reactors (SMR) based on PHWR. This will enable us to design a large size commercial plant up to 50,000 m³/d capacity. India will share the O&M experience of NDDP to member states of the International Atomic Energy Agency (IAEA) when the plant is commissioned. The development work for producing good quality water for power station from high salinity water utilizing low grade waste heat is presented. About 40 and 100 MWth low temperature waste heat is available in the moderator systems of the 220 and 500 MWe PHWR respectively. A significant part of this waste heat can be utilized for seawater desalination for in-house consumption. The Low Temperature Evaporation (LTE) technology for producing low conductivity water from seawater has been demonstrated at BARC on 30 m³/d scale by using waste heat. This plant is being connected to the CIRUS reactor for demonstration of coupling to a nuclear research reactor. The product water from this plant after minor polishing will meet the make up water requirement of the research reactor.

Design of a 1.4 mgd desalination plant based on MSF and RO processes for an arid area in India

Two seawater reverse osmosis plants operating at high pressure and 50% conversion

Design of a 1.4 mgd desalination plant based on MSF and RO processes for an arid area in India

In the past few years, the commercialization of small scale reverse osmosis (RO) plant for low total dissolved solids (TDS) brackish and contaminated groundwater water desalination offered an alternative solution to obtain drinking water with TDS lower than 500 mg/L. Due to rapid development in membrane technology the technical and economical usefulness of RO process has been improved. In the current research work, a prototype Reverse Osmosis (RO) wastewater treatmentplant has been developed and its performance was evaluated to produce the safe and drinkable water at local small community.Salt rejection and ermeatewater flowrate are the key performance parameters. These performance parameters are influenced by other variable parameters such as applied feed pressure, temperature, recovery and feed water salinity.The RO plant performance has been evaluated through testing different water quality parameters; including physical, chemical and biological analysis of the treated sample. The plant was operated by varying feed water pressures and feed water salinity which indicated that the product water has the highest quality and maximum permeateflow rate at 25 bar of applied feed water pressure for feed water salinity upto 4000 mg/L. The water quality results indicate that permeate obtained after treatment has excellent quality free physical and microbial contaminants.

Hybrid desalting systems

Early discovery of RO membrane fouling and real-time monitoring of plant performance for optimizing cost of water