20 october 2017

Technology Corner

Reverse Osmosis

Among the various processes, membrane desalination via reverse osmosis (RO) has become the most widely used solution.
Tech Corner RO schema

Comprehensive know-how and technological solutions for each stage of RO desalination (see below)

40 years of expertise in membrane desalination
With numerous membrane desalination references – ranging from modular equipment to large turnkey projects producing up to 392,000 m3 of drinking water per day – Veolia
Water Technologies is the world’s undisputed industry leader. Ever since the first seawater reverse osmosis (SWRO) desalination plant in the late 1970s, Veolia has played a major role in the development of technologies and their improved cost-effectiveness through the experience gained on the projects and its research & innovation teams.
Technological developments have made it possible to reduce the plants’ energy consumption by a factor of 4, lower operating costs and environmental impacts, optimize the pre-treatment of raw water (indispensable to avoid damaging the membranes), improve production costs and the efficiency of the membranes.

Membrane desalination

Membrane desalination is based on the principle of reverse osmosis. It consists in pushing water under high pressure through semi-permeable membranes, in order to beat osmotic equilibrium. The salts and other impurities are retained on the side of the saltwater supply. RO is efficient for low or high concentrations of salts and can thus be used to treat brackish water as well as seawater. The saline solution to be treated is separated into two phases: the permeate (freshwater free of salts and impurities) and the concentrate stream (brine enriched with the dissolved salts retained).

Proven adaptability with a wide variety of contract models
Beyond the technological aspect, Veolia also provides engineering to its customers, adapting its level of response and intervention to their financial constraints, governance choice, economic/social/ environmental situations, the number of project partners, etc. This widely recognized adaptability is an additional asset for clients. High-growth countries, such as the Arabian Gulf countries, have launched into major programs to expand their water and/or power production capacities. These projects are divided into two categories – Independent Water Projects (IWP) and Independent Water and Power Projects (IWPP) to attract investors and benefit from top private-sector expertise. Taking part in this type of complex projects which involve numerous players is a challenge which requires total coordination and comprehension among all parties involved, skills that Veolia has developed over the years. Recognized for its contract management expertise, our company stands out as a subcontracting partner, supplier of EPC equipment, or provider of wider expertise in a growing number of these unconventional installations.

Fujairah 2

The Fujairah 2 hybrid desalination project in the United Arab Emirates was the world’s second biggest IWPP when its construction was completed in 2010. It was entrusted to a consortium made up of the Abu Dhabi Water and Electricity Authority (60%), International Power (20%) and Marubeni (20%), who chose Veolia Water Technologies for its engineering and construction and for the supply of equipment for all MED and RO desalination aspects. The operation and maintenance of the RO facility was entrusted to Veolia under another specific contract.


Comprehensive know-how and technological solutions for each stage of RO desalination

1. Seawater intake

Veolia adapts the type of intake to local natural constraints and has experience with beachwells, offshore intakes and colocated intakes. As the quality of the raw water varies, depending on whether it was pumped directly from the sea or from beachwells, the subsequent treatments and equipment used will vary accordingly.

2. Pre-treatment
RO membranes are highly sensitive to variations in water quality, temperatures, algae, etc. Selecting the appropriate raw water pretreatment system is a key factor in the design of a sustainable RO desalination plant.
  • Actiflo®: compact high-speed lamellar clarification process, particularly efficient on turbidity, organic compounds, color and algae
  • Spidflow®: Rapid and compact DAF system to treat wate with low-density particles, algae or humic matter
  • FiltrafloTM TGV: high-speed gravity filtration through a granular medium, particularly efficient in eliminating turbidity
  • SpidflowTM Filter: a compact bundle involving both rapid DAF and high-speed gravitaty filtration through a granular media.
3. Reverse osmosis
For a selection of RO membranes suited to the applications requested by customers, Veolia Water Technologies relies on a dedicated center of expertise within Veolia Research & Innovation (VERI). Independently from manufacturers, this entity assesses the equipment available on the market, defines ideal operating conditions according to situations, and tests the equipment over the long term to optimize the processes.

4. Post-treatment - remineralization
The freshwater extracted via the RO process must be treated in accordance with the type of end-use and legal requirements.
  • Injection of CO2 to remineralize the water
  • Calcite filter to neutralize the pH of the water produced and minimize its corrosiveness
  • MultifloTM  clarification for the production of limewater