10 Wastewater Protozoan-Driven Environmental Processes for the Protection of Water Sources Momba MNB Department of Environmental, Water and Earth Sciences, Private Bag x 680 Arcadia Campus, Pretoria 0001, South Africa 1. Introduction Since the middle of the last century, while the population doubled, water use has tripled. The world’s freshwater reserves are dropping year after year and becoming a scarce commodity. On the one hand, the utilization of synthetic detergents, the increased use of agricultural inorganic fertilizers and the population explosion have led to the acceleration of the process of pollution of lakes and other surface water. Reports have shown an increasing percentage of rivers and streams that are contaminated with chemical and microbial pollutants (Momba et al., 2004; 2005; Bahlaoui et al., 1997; Clarke et al., 2008; Pennil et al., 2008). This is compounded by the alterations in the hydrological cycle, associated with the global climate change that increases the magnitude and frequency of runoff events (Rose et al., 2001). On the other hand, the world is faced with problems related to the management of wastewater due to the extensive industrialization, increasing population density and a highly urbanized society (McCasland et al., 2008). Recycling municipal and industrial wastewater is therefore essential for reducing the negative impact of pollution on the freshwater reserves and also for protecting public health by safeguarding water supplies against the spread of waterborne diseases (Bitton, 1999). The first part of this chapter discusses the importance of wastewater treatment for the protection of water resources. The second part sheds light on the role protozoa play in the excess removal of phosphate and nitrate in wastewater treatment plants, with emphasis on the removal efficiency of two ciliates (Aspidisca, Trachelophylum) and one flagellate (Peranema). The third part reveals the predation potential of these protozoan species on pollution indicators and pathogenic bacteria (Escherichia coli O157:H7, Salmonella typhimurium, & Shigella flexneri spp.). 2. Wastewater treatment for the protection of water resources Before wastewater treatment was required, raw wastewater was discharged directly into streams and lakes. Despite significant and prolonged environment damage, major environment legislation did not take effect until the 1970s (Gerardi & Zimmerman, 2005). To maximize the health and environmental benefits associated with the use and discharge of wastewater, great deals of legislation and several guidelines have been developed. The World Health Organization (WHO) Guidelines for the use of effluents were developed in Source: Biomass, Book edited by: Maggie Momba and Faizal Bux, ISBN 978-953-307-113-8, pp. 202, September 2010, Sciyo, Croatia, downloaded from SCIYO.COM www.intechopen.com