Trihalomethanes in developed and developing countries.

The reactions between natural organic matter, anthropogenic contaminants, ions, and disinfectants lead to the formation of disinfection by-products (DBPs) such as trihalomethanes (THMs) in drinking water. The formation of THMs is strongly related to the chlorination of water. The study's central objective was to compare the concentration of THMs in twenty developed and developing countries and their disinfection techniques. The THM concentration in 11 developed and 9 developing countries ranged from 0.5 µg/L (Germany) to 215 µg/L (Russia) and 3 µg/L (China) to 439.2 µg/L (Bangladesh), respectively. The developed country has partially succeeded in reducing THM concentration in drinking water, whereas significant steps are needed in developing countries to reduce the existing high THM concentration. The concentration of THMs in water varies among these countries because of the different water sources, water quality, environmental conditions, and efficiency of water treatment technologies. A meaningful relationship has been observed between the properties of water and the THM formation. The use of chemical disinfectants will result in new forms of DBPs that are undesirable due to their carcinogenic and mutagenic effects on human health. The DBP guidelines by various national and international agencies have helped to control and manage the THM concentration in drinking water. However, these regulatory standards are not continuously monitored. Therefore, the formation of these compounds should be prevented either by removing THMs forming precursors or by using an integrated approach for controlling THM formation by implementing advanced water treatment technology. Extensive research is desirable in domains like THM minimization strategies which are easy to deploy, scalable, and cost-effective.

Identification of environmental stress parameters to study the natural colour change of water in highly saline inland Crater Lake at Lonar, India.

Lonar Lake is a highly saline inland water body created by a crater in Maharashtra, India. A rare occurrence of the colour change of lake water from green to brown and eventually to pinkish-red was observed in Lonar in June 2020. This phenomenon attracted the attention of researchers, academicians and interestingly legal fraternity to understand the causes of colour change. The literature studies coupled the phenomenon of colouration of water to three aspects: the presence of halophilic Halobacterium salinarum or an algal species of Dunaliella (Dunaliella salina) or oxidization of metals (Fe and Mn) present in water. A comprehensive study was done to understand and assess the change in the colour of Lonar Lake water. The green colour of the lake is primarily due to the dominance of chlorophyll-a pigment in the algae population. The stressed condition in June 2020 adversely affected the photosynthesis activity of Dunaliella sp. resulting in the red colouration of the species. This red colour of Dunaliella sp. is due to the formation of a pigment named carotenoid which is similar to that in halophilic bacteria. This pigment completely hides the green chloroplast, and water turns pinkish-red. This study describes detailed investigations of environmental and climatic parameters to determine possible causes of abiotic stress on the algae population of the lake. The major factors contributing to the stressed conditions are high dissolved solids, alkalinity and alkaline pH due to salts in the lake water due to evaporation losses and limited rainfall over the months. The study further verified whether the colour change is a cyclic event and predicted possible lake conditions for the event of colour change to occur in the future.