Desalination plants in Mexico, Operation, Issues and Regulation. Ing. Mario Lpez PrezSubdireccin General TcnicaGerencia de Ingeniera y Normas Tcnicas

The need for the use of desalination processes has been growing as some areas of the world have insufficient reliable fresh water suppliesIt is the separation process of dissolved minerals (salts) of brackish waters or sea to turn them into drinking water, industrial use or irrigation (Sorg, 1978)

Millions of m3/daySource: MedinaWorld Desalination capacity:

1969 11.57 m3/s 104.17 m3/s 219.91 m3/s 2006 694.44 m3/s 21, 000 Plants

Grfico1

61

17

5

5

5

7

Ventas

Middle East61%

Spain5%

Italy5%

Rest of EU5%

Rest of the World7%

Hoja1

Ventas

Medio Oriente61

USA17

Espaa5

Italia5

Resto UE5

Resto Mundo7

Para cambiar el tamao del rango de datos del grfico, arrastre la esquina inferior derecha del rango.

Desalination Processes Phase ChangeMultistage Flash Evaporation (MSF)Multieffect Distillation (MED)Vapor Compression (VC)Selective Membrane Reversible Electrodialysis (ED)Reverse Osmosis (RO)Chemical BondIon Exchange (IE)

Installation and operation of a desalination plant will have the potential to adversely impact air quality, groundwater, marine/aquatic habitats and possibly other aspects.All this must be considered and their acceptability and requirements of mitigation, usually would be matter of national and local regulations and policies

Studies to examine these effects must be done in each potential site, and monitoring programs must be implemented post installation

One of the key limitants in the construction of desalination plants is the availability of appropiate conditions and locations to reject the brine. Brine is a sub-product of the separation of minerals from the desalinated water.

This fluid has most of the minerals and polluting agents of the source water as well as additives added before the treatment process, concentrated.

Minerals and pollutants concentrations in Brine usually are 2 to 10 times greater than the original salt water depending on the recovery rate of the desalination plant.

If chemicals pre-treatmeants are used such as coagulants, antiscalants, polymers or desinfectants, these can be part of the brine and increase the ionic content and residual organic compounds in the plant discharges.

Beside the listed methods, two additional trends for the brine handling are gaining acceptance at world-wide level:

Regional handling brine;Benefic use of the brine

Brine Reject Methods Use Frequency Discharge on surface water 45%Discharge in sewerage42%Deep well injection 9%Evaporative ponds 2%Dew irrigation 2%Discharge without liquids 0%

Brine has huge quantities of minerals that can have commercial value. The most valuable minerals are: magnesium, calcium, bromides and sodium chloride. The magnesium compounds in sea water have industrial, nutritional, chemical, agricultural and construction applications. Calcium sulphate (gypsum) is used as construction material for Tablaroca, plaster, mortar and in construction and road repairs. Technologies for the benefic recovery of minerals can be used to handling the brine of desalination plants of brackish water and sea water . This technologies have the potential to decrease the volume and cost of brine transportation.

Boats with desalination technology on board can produce 200 l/s to 3.5 m3/s of drinking water every day, with Reverse Osmosis treatment

The boat, with the desalination plant on board is located in open sea where water quality is better and with less suspended solids, reducing pretreatment costs related with energy, chemical and waste discharge. Sea water is sucked through the intake with low pumping speed, reducing impact in sea life. The intake is equipped with a passive screen that minimize the entrance of marine life and drag sediments. Brine discharge to the ocean fulfills the most strict environmental requirements of temperature and salinityThese processes have the minimum impact on marine life and were developed with emphasis in preserving the balance in ecology

Source: CONAGUA, Subdireccin General TcnicaOverexploited AquiferHydrologic Administrative Region

Stress Degree over Water ResourceVery strong (>100%)Mid strong (20 - 40%)Strong (40 - 100%)Moderate(10 - 20%)Little (

According with statistics, our country has low availability of fresh water (between 1,000 and 5,000 liters annuals per person, approximately 3 to 15 liters daily), for that reason, knowledge and implementation of sea water desalination techniques are very important

In some zones of the country, in short term, the only available supplies of water to population centers, industries and hotels will be sea and brackish water, which makes impossible to use them in its natural conditions, thats why is necessary to process them to take them out the excess of salts and to supply drinking water, as well as to prevent reject water discharges pollution.

In 2002 there were 171 desalination plantsInstalled capacity 781 l/s

In 2006 there are 435 registered desalination plantsInstalled capacity 3,600 l/sThis represents 5 times more.

The State with more desalination plants is Quintana Roo with 79 plants, followed by Baja California Sur with 71.

Although in Quintana Roo there are several reverse osmosis plants like Xcalak, near Chetumal, Contoy Island and Cozumel are un disuse

Fuente: IDA Desalination Yearbook 2007-2008. International Desalination Association,Global Water Intelligence y DesalData. Ed. Media Analytics, UK. 208 p.

StateDesalination PlantsUnitsNacional %OperateInstalled Capacity(m3/d)Yes NoBaja California23388.74241451,938BCS717316.78532036,971Campeche8194.371455,456Coahuila31337.5923107,668Colima17184.142162,856Edo. de Mxico340.92227,000D.F.14173.9112595,471Durango26265.981313868Guerrero661.38332,355Jalisco340.92312,865Morelos2214.83212110Nuevo Len551.15512,847Oaxaca140.924114,256Q. Roo7912428.51735153,339SLP110.231060Sonora16225.061579,349Tamaulipas440.92225,100Veracruz9153.4511412,167Yucatn110.2312700Nacional Total320435100%282137311,377

In Ensenada, B.C.Capacity 250 l/s, its bidded, its expected to begin the construction in a short time. The cost will be 372 MP.

In Rosarito, B.C.Capacity 2,190 l/s, the expected investment is 1,300 MDP, USA would participate in its construction

In Puerto Peasco, Son.Capacity 4,700 l/s in a 1st phase. Is an iniciative from Sonora State, the water will be used to municipality and agricultural.

Bad qualification .

Lack of consultation of the supplier.

Response time of the qualified personnel. Insufficiency in:Specialized tools stockMembranes Stock Electronic and electric equipment

Reserve pumps

Intake of the desalination plant near industries with high organic, grease and oils concentration discharges. * Dissolved Oxygen (O2)Favors materials corrosion.Favors aerobic bacteria growth which damage membrane life time. * Hydro sulfuric (SH2)In the air produces sulphur precipitates that soil the membrane * Carbon Dioxide (CO2)Indicates organic materials Crosses membranes and makes desalinated water hard, affecting quality of product water

Abandoned and without repairs Desalination PlantsInsufficient specialized tools, electric and electronic equipment stock

Water in the intake with too much sedimentsA big number of sand or multimedia filters. Affecting the economy of the company due the replacement and constant changePersonnel to clean sieves. Bad place to put the intake.

Sea water intake with organic materialsPoor knowledge on desalinationPersonnel in charge with low education levelIntake without previous filtrationBad application of anti-scalants Non suitable acid circuits neither time nor concentrationNon suitable membranes to water quality in the intakeDamages the heart of membranes frame of reverse osmosis

Qualified personnel and a good and suitable administration, with knowledge and faith in desalination success.

A good care of osmosis membranes implies a duration of 6 7 years, for that, acid circuits and anti-scalant applications are made, which favors life time of membranes and decrease the cost of changing membranes each year.

Investment in high definition electronic equipment, assuring correct operation of desalination plant, avoiding productions stops and with that decrease in tanks levels and dead times which means costs to the company

Before the pressure that will be exerted by the implementation of water desalination processes in our country due shortage of freshwater, is essential to have clear rules, of handling and management of this facilities, and the quality products, sub-products and wastes must fulfill, with the intention of fulfill two basic objectives, increasing water supply and not to contaminate.

The National Water Law defines concession like the Title that is granted through CONAGUA or the River Basin Organization that correspond, according to its respective competitions, for the extraction or use of national waters, and their inherent public assets, to persons or companies, public or private, except allocation titles.(Artt. 15 Fracc. III)

And refers that concession for the inner sea water or territorial sea extraction or use wont be required, except for those to be desalinated, which will be object of concession. (Art. 17)

In addition, indicates like public works, concerning to Federation, through CONAGUA, those that allows supply, purification and desalination which construction affects two or more states (Art. 96 BIS 2, Fracc. IV)

The use of techniques for obtaining non-renewable resources such as water desalination should be considered after considering all possible forms of savings in all sectors of water.Quality of water obtained by desalination processes is suitable for any type of human consumption, supply and irrigation. Only some very specific industrial processes require special treatment.Currently, in some countries, desalination is one of the mail source of water, with a large number of desalination plants with a fully satisfactory performance.In Mexico, the most commonly used for water desalination is reverse osmosis, with 76% of the plants according to the inventory, and most of them in the hotel industry.

The desalination plant in Los Cabos is the first installed in Mexico, to supply water to a community of 40 thousand inhabitants, which has made desalination in Mexico one of the options to reduce water shortageIts expected that in the medium term, desalination would be an option to apply to different uses of human consumption, such as irrigation of high value crops in greenhouses. Should not be denied the environmental impact related to desalination plants, the most important are brine discharge, chemical and generation of CO2 y Nox caused by energy consumption. Given this, and finally, appropriate legislation (to the gradual introduction of these plants) can minimize these impacts (of dynamic nature), as opposed to the permanent environmental impact arising from these large hydraulic works

Ing. Mario Lpez Prezmario.lopezperez@conagua.gob.mxSubdireccin General TcnicaGerencia de Ingeniera y Normas Tcnicas

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