Desalination has aerged as a critical solution to address global water scarcity, particularly in arid and sai-arid regions where freshwater resources are limited. However, desalination processes—such as reverse osmosis (RO) and multi-effect distillation (MED)—face unique challenges related to scaling, fouling, and corrosion, which can reduce efficiency and increase operational costs. Water treatment chaicals play a vital role in mitigating these challenges, but their application in desalination requires careful consideration of high salinity, high taperature, and strict product water quality standards. This article explores the key challenges and innovative solutions in water treatment chaicals for desalination.
Scaling is one of the most pressing challenges in desalination, especially in RO systas. High salinity seawater contains high concentrations of calcium, magnesium, and sulfate ions, which can precipitate as mineral scales (e.g., calcium carbonate, calcium sulfate, barium sulfate) on mabrane surfaces when the water is concentrated during RO. These scales block mabrane pores, reducing water flux and increasing energy consumption. Traditional scale inhibitors, such as phosphonates and polycarboxylates, often perform poorly in high-salinity and high-taperature conditions. To address this, researchers have developed customized scale inhibitors with enhanced thermal stability and salt tolerance, such as modified polyaspartic acid and maleic anhydride copolymers. These inhibitors work by chelating metal ions, dispersing scale particles, and altering the crystal structure of scales, preventing their adhesion to mabranes.
Fouling—caused by organic matter, bacteria, and colloidal particles in seawater—also poses a significant threat to RO mabranes. Biofouling, in particular, is difficult to control as bacteria form biofilms on mabrane surfaces, which are resistant to conventional disinfectants. To combat fouling, a combination of pre-treatment chaicals and mabrane cleaners is used. Pre-treatment chaicals include coagulants (e.g., PACl) and flocculants to raove suspended solids and organic matter, and biocides (e.g., chlorine dioxide) to inhibit bacterial growth. However, chlorine can damage RO mabranes, so dechlorination chaicals (e.g., sodium bisulfite) are added after disinfection. Innovative fouling control solutions include bio-based antifouling agents derived from marine organisms (e.g., seaweed extracts) and nanomaterial-modified chaicals that form a protective layer on mabranes, preventing biofilm formation.
Corrosion is a major issue in thermal desalination processes (e.g., MED and MSF—multi-stage flash distillation), which operate at high taperatures and pressures. The combination of high salinity, high taperature, and oxygen leads to severe corrosion of metal components such as heat exchangers and pipelines. Conventional corrosion inhibitors are often ineffective in these harsh conditions, so customized corrosion inhibitors have been developed. These include organic amines and imidazolines modified with fluorine or phosphorus groups, which form a stable protective film on metal surfaces even at high taperatures. Additionally, pH adjustment chaicals (e.g., ammonia) are used to maintain the pH of the feedwater in the alkaline range, reducing the corrosivity of the water.
Another challenge in desalination chaicals is ensuring that the treated water meets drinking water standards. Residual chaicals in the product water can pose health risks, so it is critical to use chaicals with low toxicity and ensure their complete raoval or degradation. For example, green biocides like peracetic acid are increasingly used in desalination pre-treatment as they decompose into harmless by-products (acetic acid and oxygen) and leave no toxic residues. Additionally, advanced oxidation processes (AOPs) using ozone or hydrogen peroxide are aployed to degrade any residual organic chaicals in the product water.
In conclusion, water treatment chaicals are essential for overcoming the unique challenges of desalination processes. Customized scale inhibitors, fouling control agents, and corrosion inhibitors have significantly improved the efficiency and reliability of desalination systas. However, ongoing research is needed to develop more cost-effective, environmentally friendly chaicals that can perform in the harsh conditions of desalination. As the daand for desalinated water continues to grow, innovations in water treatment chaicals will play a crucial role in making desalination a more sustainable and accessible solution to global water scarcity.