ENVIRONMENTAL IMPACT OF SEAWATER DESALINATION PROCESSES IN CHINA - A REVIEW

The aim of the present review is to report and discuss the relevant literature on environmental impact of sea water desalination in China. China, especially its coastal provinces, is facing a serious shortage of fresh water resources and a water pollution issue, restricting further development. To address the serious imbalance between water resource supply and demand, in addition to efficiently utilizing the regular water resources, China has strived to develop alternative water resources to combat the water crisis, among which seawater desalination plays an important role. This paper reviewed the current situation of the utilization of desalinated seawater in China, including the points outlined below. In order to reduce the detrimental effects of desalination technologies on the environment and to make them sustainable it is of fundamental importance to develop “circular” approaches aimed at valorizing the concentrate streams requiring disposal, with the ultimate goal of zero liquid discharge. It was found that extensive research has been performed on Mg extraction (mainly as brucite) from seawater brines using different technologies; although a few demonstration-scale studies exists on Mg recovery processes both from seawater from industrial brines, most of the recovery technologies are still performed at laboratory scale. In the long term, it is of significant importance to develop desalination technologies to face the challenges of global water crisis. Desalination technologies in China are vital both in the field of freshwater extraction from the sea and the improvement of water environment and ecology. Specifically, emphasis should be put on the following aspects as follows: (1)Technology innovation: Further improve the performance of large-scale SWRO plants. Efforts include the enlargement of single unit capacity, decrease of energy consumption, improvement of system integration, operational stability and reliability, and desalination cost. Further endeavors should be made towards pretreatment and system instrumentation, high-performance RO membranes and elements, high-pressure pumps and energy recovery devices, etc.
(2)Utilization of chemical resources from seawater: The extraction and reuse of chemical resources from seawater desalination is an attractive topic from a scientific point of view. Better technologies need to be explored to recover chemicals and reduce possible cost. Moreover, the extraction of strategic elements such as lithium and uranium is more challenging and needs better technologies.
(3)Green pretreatment methods ; Attention should be paid to the development of green pretreatments involving green antiscaling agents and agent-free biological methods. It is advisable to investigate electrocoagulation and dissolved air flotation techniques.(4)Emerging desalination technologies: Apart from the traditional SWRO desalination technologies, emerging technologies including MD, CDI, and ED desalination processes require more research efforts, from the exploitation of novel membrane materials to the fabrication of core components and equipment. In addition, hybrid systems coupling the traditional technologies and the emerging technologies should be further promoted to make the most of the less-popular technologies.Overall, with the ongoing research and development of desalination, China is believed to play a more and more important role in the international desalination market with remarkable openness and inclusiveness, providing state-of-the-art desalination technologies, facilities and services, benefitting the water-stressed countries and regions in the world.