The Sagunto locality is situated in the region of the Camp of Morvedre in Spain. In recent years, a strong industrial growth has been anticipated in the zone. This has provoked a growing requirement for water in the Municipal Region of Sagunto. For this situation, the Sagunto Council planed to cover part of the future hydraulic deficit for short and long term with the construction of a Seawater desalination plant.
The combined cycle power plant (1200 MW) of Union Fenosa Generacion SA, in the vicinity offered its collaboration so that they could use the potential synergies derived from its project, in the design and construction of the Desalinating Plant.
The joining of the desalinating plant of Sagunto to the installations of inlet and draining of the Combined Cycle Power Plant implied some inconveniences. The characteristics of the water in the inlet of the desalinating plant are principally worse than those considered in case of making the inlet through wells excavated at the side of the coast. For this a very powerful pre-treatment before desalination is specified. The pre-treatment has to eliminate dissolved or suspended solids, Sand or dissolved mud as well as the corrosive products, scaling, for treatment, additives and organic materials present in water.
Besides, the raw water coming from the inlet can contain a considerable quantity of grease, oils and cargo oils due to its location, which must be treated through a physico-chemical process (coagulation-flocculation-floating) before desalination.
The pre-treatment of raw water is provided to perform the following functions:
- To eliminate turbidity and excess solids in suspension
- To eliminate oil & grease contents in the raw water
- To inhibit biological growths in the system
- To adjust and control pH
- To inhibit or control the formation of compounds that can precipitate on membranes
- To achieve SDI < 5 of the supply water to the membranes
The Pretreatment after the intake pumps consists of the following scheme:
Dosing of Hypochlorite
Coagulation and flocculation
2 stage filtration on anthracite & sand media.
Filtration on cartridges
The desalination of sea water is achieved through reverse osmosis process with spirally wound type membrane elements. The sea water RO streams have been designed for a recovery of 47% in single stage configuration. An interpass suckback tank is installed per RO stream.
Also, to achieve boron limits of < 0.5 ppm in the permeate water at all temperature conditions between 14 deg cel to 25 deg cel, a second pass permeate RO is provided. A provisión to bypass part of the flow in low temperature application and use the entire flow at high temperature applications is also provided in event of lower Boron content in the feed water.
Before pumping the 1st pass RO permeate to the second pass RO, pH of the water has to be raised to achieve good rejection of boron to below desired limits.
The piping and valves of high pressure feed and reject lines are made of Duplex stainless steel 2205. The product collector pipes, connections of product for the modules and general piping for conduction of the product to the tanks are of PRFV & those of small diameter of PP or polyester.
Energy Recuperation Systems for Brine using Pressure Exchangers
For the recuperation of energy, pressure exchanger based device is offered. These are atented units and they are supplied as per manufacturer’s standards.
Post treatment consists of carbon dioxide dosing followed by lime dosing. Dis-infection with hypochlorite is done prior to supply.
Treatment & Disposal of Effluents of Effluents Generated
The sludge from the floatation system shall be taken to the sludge tank from where it will be pumped by means of submersible pumps to the coagulation and flocculation chamber. This will be followed by a sludge thickner which will be used to thicken the sludge to a higher concentration. The overflow from the thickner shall be disposed along with the excess reject and the filter backwash waste.