Paddling across salty water
Control solutions can ensure trouble-free operations for desalination plants, helping meet the increased demand for freshwater.
The Earth seems to be drying up in many spots. While some areas are overflowing with freshwater and even floods, in other areas water scarcity is a reality for many, with about 20% of the world’s population suffering from a shortage of drinking water. A senior water scientist at NASA describing California said “We’re not just up a creek without a paddle … we’re losing the creek too.”
Outside of the US, increased urbanization and development is pushing higher demand for freshwater. The Middle East, Australia and China are some of the areas where demand increasingly outstrips supply.
Of course there’s plenty of water. Our planet is 70% covered by it. Unfortunately 97.5% of it is undrinkable, unusable salt water. But the demand for freshwater has driven a boom in desalination as a source of fresh water. The increased demand stimulated desalination system suppliers to ramp up both research and production, driving down the cost of these systems.
While capital costs fall, operating costs continue to be a concern. Desalination plants, both reverse osmosis (RO) and evaporative (the two main processes), require an enormous amount of energy, making power a prime operating expense.
Energy recovery systems have eased power costs. Many desalination plants are co-located near power generation facilities, or large chemical or oil and gas processing plants to take advantage of the water intake and discharge infrastructure already in place. Residual energy from those facilities can be used as the main energy source at evaporative desalination plants. But reverse osmosis desalination plants – in which high-pressure pumps force the water from seawater or brackish water through a membrane that is mostly impermeable to salt – have huge electric bills.
Many desalination operations managers are turning to advanced control systems to further reduce energy usage. In almost every process, there are opportunities to increase output through fine-tuning. While that’s less true in desalination than in other processes, automation controls can prove valuable in making sure the OEM’s operational specs are maintained. This ensures trouble-free operation while maintaining warranty requirements for new facilities.
Automation controls can also increase total plant output through reduced downtime. Potential troubles are identified earlier, enabling the operator to make preemptive repairs or swap a troublesome RO module out for a spare so it can be inspected prior to unexpected failure.
Another benefit of automation controls is that they make it possible to maximize the time between RO membrane cleanings. ABB is developing new logic for its Symphony Plus automation control system that will give operators a clear picture of the membrane’s health, reducing premature cleanings and unnecessary maintenance.
Naturally occurring freshwater (surface and ground water) is typically less costly than water provided by desalination. But capital costs continue to decline and, aided by automation controls systems, operating costs are falling. Desalination seems well-positioned to play an ever-larger role in quenching the thirst of parched areas around the globe.