Component Arrangement For Gravitational Water Desalination

High energy consumption and the negative impacts of hyper saline brine are the two biggest hurdles to a widespread adoption of seawater desalination. Taking advantage of the principal that fluid pressure increases in direct proportion to depth, this invention reduces energy consumption by relocating the process of reverse osmosis at depths where the weight of the water produces the pressure required to drive the reverse osmosis process thereby eliminating the high costs normally associated with raising intake pressure and by simply varying pumping rates, the brine stream can be pre-diluted to levels slightly above the original thereby reducing environmental impact. The simplicity of the design also reduces the costs of building and installation thereby making it likely that seawater desalination will proliferate around the world.

TECHNICAL FIELD

In general, this invention relates to water desalination and more particularly to a component arrangement that allows the generation of the pressure required to drive the process of reverse osmosis to be partly or fully due to gravity.

BACKGROUND

It’s a well-known fact that water scarcity is increasingly becoming problem all over the planet. Even though 70% the planet is covered with water, only 2% is fresh and the rest is salty undrinkable water. Currently, about a fourth of the world population is without easy access to clean drinking water and as world population grows, this water scarcity problem is only projected to get worse. By some estimates, more than half of the world population will live in water stressed communities by 2050. The only alternative to supplementing the available fresh water resources is either thermal or reverse osmosis of sea water desalination. Besides the fact that they both require high capital investments upfront, the ongoing overhead cost of running either of these is very high and that’s because both of these desalination methods are highly energy intensive. That’s why up till now, water desalination has been available only to countries or communities with enough resources to pay for the initial investment costs and the high overhead of running highly energy intensive desalination plants. This automatically eliminates developing countries and poor communities which happen to be located in arid climates.

Therefore, there is a need for a cheaper and much more efficient alternative method of removing salt from water thereby making desalination a viable option for communities in arid regions and the developing world especially those with access to sea or brackish water.

Serendipitously the arrangement of this invention provides for an ecofriendly way of disposing hyper saline brine which is an environmental problem that all desalination plants have to deal with.

SUMMARY

This invention operates on a well known principle in fluid dynamics that pressure is directly proportional to depth. Herein, the process of reverse osmosis lowered to such depths that the weight of the water produces the pressure required to drive the reverse osmosis. Traditionally the energy required to run the process of reverse osmosis broadly falls in two categories 1stpumping the water into and or out of the plant, 2ndpressurizing the water to force it thru the membrane. Most of the energy consumption is towards the later and that’s what this invention is seeks to reduce either in part of fully.

AdvantagesReducing the cost of building/constructing a water desalination plantMinimizing the cost of running the process of reverse osmosisMaking water desalination more of a viable option to developing countries and communities in arid desert areasReducing the greenhouse gases, the byproducts of the highly energy intensive process of water desalination plantsReducing the footprint of water desalination plantsProviding a new process of water purification to city and municipality water treatment plantsCutting the cost of water treatment for city and municipality governmentsProviding a cheap means of augmenting supplies for agriculture and other water intensive industriesProviding a solution to reducing the salinity of brine by simply adjusting flow rates Other objects and advantages will become obvious in the process of reading this disclosure and practicing the examples herein. It is also worth noting that this disclosure only mentions information that relates to the process of reverse osmosis. Other information like pre-filtration and post treatment are left out as they are well documented in prior art.

DETAILED DESCRIPTION

FIG.1shows an exemplary set up of arrangement. Vertical tube2is installed into the ground6. Pump12supplies salt water from filter or reservoir (not shown) to Tube2through water line10. From line10water goes through salt separation membrane assembly4and continues through water line24via Pump18. The remaining brine is evacuated by pump20through waterline22. Also shown in here is computer control module16in communication with water level sensor 8 and water pumps12,18and20through wires14. In order to reduce the salinity of the rejected water (if so desired), water line22may be pre-diluted prior to disposal by calibrating computer control16to run pumps12and20at a higher flow rate than pump18.

FIG.2shows more detailed look of the arrangement (pumps, wires, sensor and computer not shown). Water line10with salt water10’ connected ant the top of water tube2installed in ground. Water10’ fills up tube2via gravity. The pressure of the water at the bottom of tube2forces the water through membrane assembly4. Normally it takes around70bar (1,000 psi) to force water through membrane assembly4. To generate that amount of water pressure using gravity, the membrane assembly4must be at depth26which is around 723 meters, therefore water tube2is longer than 723 m deep in order to collect rejected brine. The Salt free water24' after membrane assembly4flows through water line24either for further treatment or ready for use. The rejected brine22’ flows through water line22for disposal.

FIG.3Ais an even more detailed look at the bottom of the water tube2. Salt water10’comes in from the top and forced through membrane assembly4in direction28. At that point salt-free water24’ and continues through water line24. The rejected brine 22’ collects at the very bottom of water tube2and sucked up by water line22as indicated by direction30.

FIG.3Bis an offshore variation ofFIG.3Awhere the brine is disposed at the bottom of tune2in direction32through opening34.