Costs distribution during the life of a desalination plant

1.- Abstract.  When a desalination plant is scheduled, the main reason that  must be responded is the final destination of the efluent and also the required needs to be solved not only during its construction but also during its commissioning.  It will be worthless if a desalination plant is  designed and constructed but in the end the return of the investment that has been made in order to build the plant doesn't live to  expectations that is when the water product is sold the enterprise in charge of running the plant does not obtain the corresponding benefits when selling water to the final customer. 

2. Why desalinate water if apparently there are other more economical means.

Obviously, there is a wrong belief, that apparently, there are more economical methods to obtain drinking water. The truth is that already in Spain has raised this situation and it has not always been proven to be effective. I am referring to the severe drought which happened during the late 1980s and early 1990s and kept the country under a critical situation as a result of the scarcity of water. Facing this background, it only could be thought of an urgent solution in order to solve this coming problem. This solution should be both fast and effective at the same time and it would not involve a waste of money during the construction process . Accepted this solution, desalination process versus transfer solution, the dilemma was choosing the ideal system to desalinate the sea at the lowest price.

As the previous experience that happened in the Canaries with the construction of the first desalination plant in Spain using the Vapour Compression system and the following  Las Palmas I and Las Palmas II with the MSF systems, the expectations were a bit dissapointed when the results tried to be carried out on the rest of Spain's territory due to the different sea water intake adapted to the plants needs and characteristics.

From that time on, the Spain's Ministery of Environment Engineers looked at the example of Israel that used the Reverse Osmosis solution due to different reasons:

• Lesser construction time in comparison with a distillation plant
• Lesser cost of cubic meter of desalted water.
• A less required surface for plant layout in comparison with distillation. 
• Less data to be controlled just because most of them can be easily automatized.
• Less personnel to do the desalination plant manteinance tasks. 

3.- Distribution costs in a sea water desalination plant. 

Two different stages can be distinguished:

3.1. Construction. 

Among the many costs involved during the construction of a seawater desalination facility the most important ones who are listed below prevailed :

3.1.1. Civil works:  about 20% of the total budget of a work is earmarked for the construction of the facility. This construction, which can reach about 25% figures if it is that you need to perform tasks of piloting for the settlement of the plant on ground recently gained the sea, is the first step in the construction of the desalination plant of seawater. Apart, with the construction of the infall (to the sea intake) and the outfall (for the discharge of brine) these figures can reach the 30% of the budget.

3.1.2. Equipment:  This part of the budget is about 45 % of the budget for the total work. More specifically, today, with the necessity to incorporate the equipment for remineralisation of the treated water, this part represents the most important bulk of the total amount of work.

3.1.3 Administrative costs:  They represent the 5% total budget for needs of legalization of the facility, environmental impact, costs of expropriation of land, etc.

3.1.4 Costs intended for electrical equipment:  including equipment along with wiring of power and instrumentation. Like the previous case, this part targeted 20% of the budgetted work.

3.2. Operation phase.

During this phase, from the moment in which the plant is delivered to its operator, two different costs that can be distinguised: fixed costs and variable costs.

3.2.1.-Fixed costs:

Within this group aspects such as the return on investment, as well as personnel costs and maintenance of the installation can be introduced.

3.2.2.-Variable costs:

They are derivative of the proper functioning of the desalination facility and derived from the amount of effluent such as membranes replacement of osmosis and cartridge filters and pre-treatment filters sand castings. The addition of chemical reagents for the desalination plant itself and in order to optimize the the water product quality. The above is valid from the theoretical point of view since, from my personal and practical point of view, it is best to leave the desalination facility under a steady state regime hence without adding any chemical reagent so with this determination, the associated costs with chemical reagents  would be saved.

Apart from those expenses,  that can be part of these variable costs aside, there are other factors such as expendable office supplies, insurances, etc that can not be overpassed

4. Conclusions.

As a result of all this information, the current net worth of the investment must be greater than zero which means that cash flows have managed to exceed the initial investment of the project. It is from that moment, when you can be sure the investement will be productive.