Making Water Shouldn't
Waste Water
Trevi’s next generation of forward osmosis brine concentration technologies enables sustainable zero liquid discharge and resource recovery.
Learn More About Our Forward Osmosis Technology
Trevi’s unique forward osmosis solutions are the core of our low energy, high recovery desalination, and MLD/ZLD solutions for resource recovery.
1. Forward Osmosis vs Reverse Osmosis
Osmosis is a natural process and it occurs in the cells of all living things. When liquids of differing solute concentrations are separated by a semi-permeable membrane, the water moves by the process of osmosis from the solution of lower concentration to that of higher concentration. Forward osmosis (FO) utilizes the difference in solute concentration in the two liquids and the natural osmotic pressure as a result of a highly concentrated draw solution on one side of membrane to pull / transport pure water from an impaired water source into the draw solution with everything taking place under low pressure and energy conditions. Reverse osmosis (RO) however, utilizes high hydraulic pressure to push water through a semi-permeable membrane resulting in significant energy expenditure and high pressure conditions.
FO provides a number of advantages over RO for seawater desalination in addition to the energy savings. Lower fouling of the membrane provides longer lifetime and lower maintenance costs. Other advantages of FO include higher maximum feed water recoveries and a reduced level of pretreatment.
2. Trevi's Forward Osmosis Technology
A key element of Trevi’s forward osmosis technology is the company’s proprietary, retrograde thermolytic solute draw solution which has
(1) a high osmotic pressure needed to desalt high concentration saline water through the forward osmosis membrane
(2) a chemistry that allows the draw solute to be separated from the recovered water using low grade thermal heat. Waste heat is used to cause a phase of the draw solute from the water separation (similar to an oil and water layer), producing water and concentrated draw solute. This abrupt phase separation at a very specific temperature is what results in the low energy requirements of Trevi System’s process. The concentrated draw solute is continuously recycled back to the FO membrane and the heat used is passed through heat exchangers to recuperate most of the thermal energy in the process. The product water is passed through a polishing nano-filter to ensure compliance with World Health Organization (WHO), National Science Foundation (NSF) and international water quality specifications. The draw solute is continuously recycled back to the FO membrane to maintain the driving force.
As a result of this proprietary, retrograde thermolytic solute draw solution, Trevi’s forward osmosis system does not require the high pressure (and high energy) pumps and vessels needed in RO systems or the high consumption of electricity required to run them. This is significant as energy costs (and commensurate CO2 emissions), are the single largest expense in operating most competing incumbent water treatment technologies to achieve the same result, including reverse osmosis, evaporators and crystallizer technologies.
3. Trevi's Pressurized Forward Osmosis
Pressurized forward osmosis (PFO) incorporates both the forward osmosis (FO) and reverse osmosis working principles. However, compared to FO, the draw solution is less concentrated than the feed solution and is only utilized to lower the osmotic pressure difference across the modified FO membrane while applying an external pressure to feed clean water through the FO membrane. Thus PFO can be operated at lower applied hydraulic pressures than conventional RO but is operated at higher pressure than conventional FO which permits dewatering of more saline feed streams without exceeding the maximum allowable hydraulic pressure of the FO system, but enables higher recoveries than a typical high pressure RO system when designed properly in stages. Trevi has developed our own proprietary PFO membranes which have been designed uniquely for our draw solution and this application. In addition, thermolytic draw solutions may also be used to make a hybrid FO/PFO system.
Solution Offerings for Different Applications
Trevis’ Solution Offerings for Different Applications makes sense when there is waste heat available, high wastewater salinities and a strong desire to go green and use renewable energy
What Trevi Offers:
1) Forward osmosis (FO) and pressurized forward osmosis (PFO) typically require a lesser degree of treatment than RO. Trevi has the in-house expertise and works with a variety of vendors to ensure that the pre-treatment technologies are affordable, best in class, and meet the requirements of Trevi's FO and PFO technologies.
2) Renewable desalination (Solar power) Trevi's low energy forward osmosis (FO) technology works well when coupled with concentrated solar power (solar CSP arrays, solar ponds, and geothermal) to desalinate seawater/ brackish ground water or produced water. Trevi has 4 renewable desalination projects – Hawaii, Cyprus, India, and Oman. Hawaii’s 500 m3/day renewable solar desalination plant is the largest FO plant to date and provides clean water for agriculture. More information can be found under Projects.
3) Co-generation desalination (Waste Heat) Trevi's low energy forward osmosis (FO) desalination technology works extremely well with waste heat from power plants or any facilities generating waste heat which can be easily captured with simple heat exchangers via hot water. In Kuwait, Trevi has a contract to deliver a 500m3/day co-generation desalination FO plant. More information can be found under Projects.
4) Brine Concentration: Trevi's innovative pressurized forward osmosis (PFO) desalination technology is highly effective at treating high salinity waters to concentrate the brine further. Trevi has a PFO minimum liquid discharge (MLD) pilot, sponsored by the National Alliance for Water Innovation (NAWI), which will be operated in Q1 2024 and will be used to treat RO brine concentrate at various sites in California where wastewater reuse is the name of the game. More information can be found under Projects.
5) Zero / Minimal Liquid Discharge (ZLD & MLD) Trevi is able to combine both our forward osmosis (FO) and pressurized forward osmosis (PFO) technology to enable zero liquid discharge (ZLD) and/or minimum liquid discharge (MLD). In Oman, Trevi is delivering a solar powered MLD forward osmosis plant for produced water where the water recovered will be used for agriculture. More information can be found under Projects.
6) Resource Recovery for Highly Concentrated Brines Given the high recovery rates for Trevi's low energy forward osmosis (FO) and pressurized forward osmosis (PFO) technology, brine concentration for resource recovery is also highly desired by many organizations. Trevi is under contract for brine concentration and resource recovery for the mining industry. Organizations wishing to recover rare earth metals or lithium from natural brine sources should contract Trevi for further information.
7) Technology Consulting
Trevi Systems offers consulting on renewable desalination, brine concentration, zero liquid discharge, and resource recovery for a variety of industries.
Benefits
Green Draw Solution Chemistry
Trevi’s propriety and innovative draw solutions are able to desalinate challenging wastewaters. These can then be separated by low grade waste heat and all draw solutions implemented are FDA approved as food safe, biodegradable, and non-toxic in aquatic environments.
Lower Energy & Sustainable Design
Trevi's FO systems operates under low pressure <60 psi, thereby reducing the need for expensive stainless steel piping and high-pressure, high cost RO membrane vessels. Trevi’s process uses less electrical energy than RO and other evaporative/crystallizer processes and thrives on low grade waste heat. This process opens the door for the use of sustainable renewable energy sources allowing our process to have a net zero carbon footprint.
Challenging Wastewaters with Higher Recoveries
The high osmotic pressure of Trevi’s green draw solutions are able to treat very high salinity wastewaters with minimal fouling due to the overall lower external pressures of the systems. This results in higher recoveries, the ability to do zero/minimal liquid discharge as well as resource recovery with our FO and PFO technologies.
Overall Lower Cost of Water
Less energy, lower pressure, less expensive equipment, higher recoveries, less fouling, and the ability to use low grade waste heat results in an overall lower cost of water for more challenging wastewaters.
The cost competitiveness of Trevi's technology excels when the cost of heat is low and when the cost of electricity is high. The graph above is derived from projections from a 20X scale up of our 500 m3/day solar powered FO seawater desalination plant versus a same sized SWRO plant. It highlights that the LCOW from Trevi's FO plant truly shines when the LCOH decreases and when the cost of electricity is high.
