Impact of artificial monolayers on water quality, potable water treatment, human health and lake ecology

Abstract

Water conservation strategies offer a feasible alternative to the unpopular commissioning of new reservoirs, and to the high infrastructure and running costs of desalination plants (McJannet et al., 2008). Increasing temperatures and decreasing rainfall constrain the feasibility and profitability of the provision of potable water and irrigated agriculture. Of the estimated 7,000 GL of water stored in a million or so small on-farm storages (< 10 ha capacity), up to 20% may be lost to evaporation (Craig et al., 2008). Strategies for reducing evaporative loss include physical floating covers, suspended physical covers, re-engineering the storage to reduce the surface to volume ratio, and applying an artificial monolayer. Of these options, only monolayer (a mono-molecular surface film) application is considered cost-effective for storages larger than 10 ha. The management of artificial monolayers to retard evaporative loss is an old concept (La Mer, 1962) that has not been adopted commercially due to extreme variability in field performance (Barnes, 2008). Recent research highlights deficiencies in the original products that in part account for variable field performance (Pittaway and van den Ancker, 2010b). The promise of improved field performance has encouraged managers of urban water utilities to consider monolayer application as part of their water conservation strategy (McJannet et al., 2008). In contrast to privately owned farm irrigation storages, the adverse effects of monolayer application on the ecology and water quality of the storage must be considered, as well as the potential for monolayer compounds to adversely affect potable water treatment processes. This literature review explores: the mechanisms by which artificial monolayers retard evaporative loss; how the application of an artificial monolayer may adversely affect the physical, chemical and biological processes that occur at the air/water interface; and the potential for monolayers to adversely affect aquatic food chains, potable water quality, and potable water treatment systems