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Dew water is water droplets formed due to condensation of atmospheric water vapor on surfaces of temperature below its dew point temperature. Dew water can be seen as a nonconventional source of water and may be exploited in regions where weather conditions favor dew formation and inadequate supply and quality of water is a prevalent problem. There are two main types of dew condenser, the apparatus used to collect dew water, namely radiative (also called passive) and active condensers. Radiative passive collectors rely on exploiting the physical processes responsible for dew formation to collect dew water without any additional energy input. Previous studies indicate that a 1 m 2 radiative condenser yields between 0.3 and 0.6 L/day of dew water in arid and semi-arid regions. Active condensers have been designed as an alternative method of collection that produces higher yields by using additional energy inputs. Several designs of active condensers have been patented for which the yield can reach 20 L/day for portable devices, and up to 200,000 L/day for larger agricultural water devices. Active condensers are also known as atmospheric water generators, dehumidifiers, and air to water devices. Most of the active condensers are based on a regenerative desiccant that attracts and holds large volumes of water from the air or on a means of cooling the condensing surface below the dew point temperature (refrigeration circuit). The larger yields and wider range of environmental conditions in which dew can be collected make active condensers a promising option as an alternative or supplemental source of water in water scarce regions. The aim of this paper was to provide a comprehensive review of radiative and active condensers, including dew formation processes, methods of dew collection, and parameters that influence the dew collection. Subsequently, patents of active condensers were reviewed to ascertain how they can be integrated with different types of renewable energy and to assess the potential use of such integrated systems as a sustainable source of water in regions that suffer water scarcity and/or as a sustainable source of water for agriculture.

An up-to-date review of the statistical approaches utilized for the assessment and redesign of surface water quality monitoring (WQM) networks is presented. The main technical aspects of network design are covered in four sections, addressing monitoring objectives, water quality variables, sampling frequency and spatial distribution of sampling locations. This paper discusses various monitoring objectives and related procedures used for the assessment and redesign of long-term surface WQM networks. The appropriateness of each approach for the design, contraction or expansion of monitoring networks is also discussed. For each statistical approach, its advantages and disadvantages are examined from a network design perspective. Possible methods to overcome disadvantages and deficiencies in the statistical approaches that are currently in use are recommended.