Demand for water resources has increased dramatically as a result of population and economic expansion. Consequently, 36% of the world's population now lives in water-stressed areas. Rapid urbanization, particularly in low- and middle-income nations, has caused a slew of water-related issues, such as degradation of water quality, insufficient water supply and sanitation facilities, and the rise of suburban and informal settlements. Good water quality is essential for human health, socio-economic development and ecosystems. However, as the population grows and the natural environment deteriorates, it becomes increasingly difficult to ensure adequate and safe water supply for all. A predominant part of the answer is to lessen pollutants and enhance wastewater control practices. Water must be properly managed throughout the water cycle, from freshwater withdrawal, pretreatment, distribution, usage, collection, and post treatment to the usage of treated wastewater and its eventual return to the environment. Population expansion, increased urbanisation, and economic development are all contributing to an increase in the volume of wastewater created globally, as well as the total pollutant load.

Recently, there was a great boom on the need for revolutionary environmental technology to make certain the sustainability of the water sector. Depending on how the waste is discharged and the nature of the components present in it, the remedy may also comprise one or more of the following processes: equalisation, neutralisation, physical remedy, chemical remedy, organic remedy. Conventional wastewater technologies are limited to treating these pollutants, which could exacerbate the problems the world already faces with drinking water. Consequently, there is an urgent need to develop new methods to mitigate the effects of wastewater on the already degraded environment. To date, more than 100 techniques have been documented for organic and inorganic wastewater treatment. Several of these techniques have emerged and range from chemical and physical methods to biological methods. The need for research, financing, and technological deployment to provide long-term solutions for poor and middle-income nations is relevant.

Taking these into consideration, the special issue titled ‘Technologies for Water Quality and Wastewater Management in Developing Countries’ is dedicated to endorsing papers that provide know-how in particular on novel standards and equipment for water fine tracking and assessment, sustainable tactics for remediating wastewater and formulating guidelines and policies for powerful water and wastewater control structures for city regions of developing nations. In this special issue of Water Science & Technology, 56 papers were selected from 19 different countries that contribute to a broad discussion and demonstration of state-of-the-art in novel technologies in the field of water and wastewater management. This special issue makes a contribution to fixing water-demanding situations through generating precious analytical insights that make sure water security, shield the water environment, and engage water management. Furthermore several papers in this issue emphasize water and wastewater management nexus such as sustainable wastewater remediation methods and techniques, wastewater reuse strategies, design and operation of wastewater treatment facilities, use of membranes in wastewater treatment, novel characterization and quantification techniques for urban water, water quality monitoring and assessment, water conservation and protection, energy recovery, valorization of wastewater.

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