**3. Environmental Impact of Desalination Plants**

There used to be a huge controversy about the environmental impact of desalination plants, but measures taken these past few years have improved the situation and people now accept the technology. The actions taken to minimize the environmental impact have been simultaneously studied with the technological developments done to make desalination plants more efficient. Some countries have passed strict environmental regulations for both environment effect investigation and control of compliance with the corrective measures approved, significantly improving this matter.

However, the type of technology used to desalinate, and the environmental regulations of certain countries or regions can still cause significant impacts. Raluy et al [40] studied life cycle assessment of MSF, MED, and RO; Mezher et al [41] analyzed technoeconomic assessment and environmental impacts of desalination technologies such as MSF, MED, RO, and hybrid MSF/MED-RO; Van der Bruggen and Vandecasteele [42] gave an overview of process evolutions in desalination of seawater by distillation versus membrane filtration; Najafi et al [43] developed environmental cost analysis of MSF, MED, MVC, and RO, making a performance comparison between MSF and RO (Table 4).


**Table 4.** Performance comparison of multi-stage flash distillation (MSF) and reverse osmosis (RO).

Source Najafi et al.

In this respect, Saracco [18] warned of the risk of contamination by brine disposal, which is significantly higher using evaporation as compared to osmosis. Saracco also pointed out the substantial damage done to the marine ecosystem in the Persian Gulf area.

Jones et al. [44] reported that according to their estimates, brine production is around 142 Hm3/day, approximately 50% higher than had been foreseen. Brine production in Saudi Arabia, the United Arab Emirates, Kuwait, and Qatar represents 55% of the global total, where there are not even emissaries with diffusers or prior dilution. They warn of the need to establish brine management strategies to limit negative environmental impacts and to reduce the economic cost of its disposal, thus stimulating new developments in desalination plants to safeguard water supplies for current and future generations.

According to AEDYR [21], Table 5 shows the salinity of different types of water, indicating the level of salt reduction that desalination plants must achieve.

Nevertheless, there are already countries that are working on the correction of environmental impacts. Spain, Australia, and other developed countries have applied legislation that guarantees the correction of environmental impacts through follow-up programs whose reports are made public.

The environmental impacts and the corresponding corrective measures must be studied as much during the construction of a plant as during the desalination plant lifetime.

In Spain, Law 21/2013 on Environmental Assessment [45] includes the Directives of the European Union in this regard. This law requires an Environmental Impact Statement to be made for each project, which must be approved by the Ministry of the Environment. In the case of desalination plants, ACUAMED, a public company under the Ministry of the Environment, supervises compliance with environmental impact measures.


**Table 5.** Different salinity water.

Source AEDYR.

Martínez de la Vallina [46], Environment Director of the Public Company ACUAMED in charge of the construction and operation of desalination plants in Spain, presented a technical communication in the National Environment Congress held in 2008, where he explained the adopted measures to minimize and restore the environmental impacts caused by the construction and operation of desalination plants on the coast of the Mediterranean Sea. Among other things, it said:

The environmental impact assessment procedure tries to establish the minimum thresholds under which alterations to the environment caused by an action would or would not be acceptable, paying attention not only to the characteristics of the action involved, but also to the environmental conditions–broadly understood- of the area on which action might be needed.

And in this sense, it has to be underlined that the impact of a desalination plant is not at all more than the residual impact of previous larger human actions, such as the urbanization and extensive occupation of thousands of hectares which lack water resources in quantity and quality enough to meet the demand typical for this accelerated building process.

From the requirements established by ACUAMED and the experience accumulated in the projects developed by the authors, the aspects to consider are indicated.

The most relevant points to bear in mind during construction are:


The most relevant points to consider during the operation of the plant are:


The environmental protection measures adopted in Australia are now outlined here for (a) the construction of large desalination plants compatible with sustainable development, including their corrective measures and (b) the monitoring measures to make sure the compliance and outcome of the measures are followed during the operation of the plant.

In the case of Australia during the tender stage for the award and construction of a desalination plant, all the interested companies were given the report and recommendations from the Environmental Protection Authority (EPA), Report 1302 [47]. Regarding the specific desalination plant mentioned above, the Southern Seawater Desalination Project, the Water Corporation transferred this report from the Environmental Protection Authority in Perth, Western Australia.

The report must set out the key environmental factors identified in the course of the assessment, and the EPA's recommendations as to whether or not the proposal may be implemented. If the EPA recommends that implementation be allowed, the conditions and procedures to which implementation should be subject.

The EPA decided that the following key environmental factors relevant to the proposal required detailed evaluation in the report:


The following principles were considered by the EPA in relation to the proposal:


Having considered the proponent's information provided, the EPA has developed a set of conditions that it recommends be imposed if the proposal by the Water Corporation of Western Australia, to construct and operate an 100 GL per annum reverse osmosis seawater desalination plant at Binningup, and associated infrastructure, is approved for implementation. Matters addressed in the conditions include the following:


For the above-mentioned project, EPA required the set of conditions shown in Table 6.

**Table 6.** Key environmental factors.


Source: Water Corporation.

Water Corporation manages two plants, both located near the open sea. Due to the increased energy, the concentrated seawater discharged during the process mixes very quickly with the surrounding seawater. The discharge and admission pipes on the high seas are designed and located to minimize

the effects on sensitive marine habitats, such as seagrasses and reef systems. With regard to the effluent treatment system, the wastewater not assimilable to urban waste is collected and sent to a thickener and subsequent mechanical dehydration by centrifugal pumps.

Christie and Bonnélye [48], in a conference paper at the world congress of the International Desalination Association, held in Dubai in 2009, presented the results of two years of monitoring the operation and environmental impact of the first large desalination plant using reverse osmosis constructed in Australia, the Perth Seawater Desalination Plant (PSDP), with a production capacity of 45 GL/year, which was completed in November 2006 and handed to the Water Corporation in April 2007.

The following conclusions of the study were extracted:

The unprecedented marine monitoring program has included computer modelling for diffuser design and validation, rhodamine dye tracer tests, extensive far field dissolved oxygen tests, a water quality monitoring program, diffuser performance monitoring program, WET testing and Macrobenthic surveys. All studies have proven that the PSDP is having negligible impact on the surrounding environment. Impacts on seawater habitat are limited by a validated diffuser design and treatment of suspended solids.

The power consumption of RO plants is decreasing due to increasing technological gains in plant design, membrane design and energy recovery. RO plants can also easily be powered (offset) by renewable energies. Energy recovery systems such as that used at the PSDP (ERI) are now extremely efficient at recovering energy from the brine wastewater (greater than 96% efficiency). Sourcing power from renewable energy (albeit offset) is an important sustainability principal employed by the PSDP, which is also now being applied by other large-scale Australian desalination plants.

In 2018, the Water Corporation [49] published the 2018 Performance Review Report, which included the result of the environmental monitoring of SSDP during the previous year:

