**2. Surface water quality**

domestic and industrial wastes [2, 3]. The biggest threat to sustainable water supply in South Africa is the contamination of available water resources through pollution [4]. Many communities in South Africa still rely on untreated or insufficiently treated water from surface resources such as rivers and lakes for their daily supply. They have no or limited access to adequate sanitation facilities and are a high risk to waterborne diseases [5]. Since 2000, there has been a

Surface water has been exploited for several purposes by humans. It serves as a source of potable water after treatment and as a source of domestic water without treatment particularly in rural areas in developing countries. It has been used for irrigation purposes by farmers, and fishermen get their occupation from harvesting fish in so many freshwater sources. It is used for swimming and also serves as centers for tourist attraction. Surface water, therefore, should be protected from pollution. Major point sources of freshwater pollution are raw and partially treated wastewater. The release of domestic and industrial wastewater has led to the increase in freshwater pollution and depletion of clean water resources [8]. Most quantities of wastewater generated in developing countries do not undergo any form of treatment. In few urban centers, various forms of wastewater treatment facilities (WWTFs) exist but most of them are producing ill‐treated effluents, which are disposed of onto freshwater courses.

In some developed countries of the world, adequate supply of potable water and improved sanitation facilities have been achieved. Strict environmental laws and monitoring for compliance prevent undue pollution to freshwater sources. Good waste management technologies and increased environmental protection awareness have contributed immensely to the success story. This has resulted in fewer cases of waterborne diseases reported compared to

Many people in developing countries of the world still rely on untreated surface water as their basic source of domestic water supply. This is so because either there is an incessant supply of potable water or inadequate water supply systems. This problem is exacerbated in rural areas. Surface water is increasingly under undue stress due to population growth and increased industrialization. The ease of the accessibility of surface water makes them the best choice for wastewater discharge. Wastewater which comprises of several microorganisms, heavy metals, nutrients, radionuclides, pharmaceutical, and personal care products all find their way to surface water resources causing irreversible damage to the aquatic ecosystem and to humans as the aesthetic value of such water is compromised. These pollutants decrease the supply of useable water, increase the cost of purifying it, contaminate aquatic resources, and affect food supplies [9]. Pollution combined with the human demand for water affects biodiversity, ecosystem functioning, and the natural services of aquatic systems upon which society depends on.

Urban areas in most developing countries do have several wastewater management systems some of which are very effective and meet international standards, but many others are plagued with poor designs, maintenance problems, and expansion including poor investment in wastewater management systems. Most rural and poor communities often do not have any form of wastewater management systems. Effluents from large‐ and small‐scale industries are usually channeled to surface water courses, which often result in pollution, loss of biodiver-

sity in the aquatic ecosystem, and possibly health risk to humans.

developing countries.

402 Water Quality

dramatic increase in the episodes of waterborne diseases in South Africa [6, 7].

Surface water is one of the most influenced ecosystems on earth, and its alterations have led to extensive ecological degradation such as a decline in water quality and availability, intense flooding, loss of species, and changes in the distribution and structure of the aquatic biota [14], thus, making surface water courses not sustainable in providing goods and services [14, 15]. For instance, the health of a river system is influenced by various factors, which include the geomorphology and geological formations, physicochemical and microbial quality of the water, the hydrological regimes, and the nature of instream and riparian habitats [15].

Water quality is described by chemical, physical, and biological characteristics of water that determine its fitness for a variety of uses and for the protection of the health and integrity of aquatic ecosystems [16]. Each aquatic ecosystem has the natural tendency to adapt and compensate for changes in water quality parameters through dilution and biodegradation of some organic compounds [17]. But when this natural buffering capacity of the aquatic ecosystem is exceeded due to the introduction of various classes of contaminants from point and nonpoint sources on a continuous basis, water pollution sets in.

In South Africa like most other developing countries in the world, surface water is usually used for domestic, recreational, and agricultural purposes mostly in the rural areas [9, 18]. Water quality is affected by both natural processes and anthropogenic activities. Generally, natural water quality varies from place to place, depending on seasonal changes, climatic changes, and with the types of soils, rocks, and surfaces through which it moves [5, 19]. A variety of human activities such as agricultural activities, urban and industrial development, mining, and recreation significantly alter the quality of natural waters and change the water use potential [16, 19].

Decrease in water quality can lead to increased treatment costs of potable and industrial process water [19]. The use of water with poor quality for agricultural activities can affect crop yield and cause food insecurity [4]. The presence, transport, and fate of heavy metals and organic compounds (which are toxic and persistent) in water bodies are a cause for serious concern globally [4]. Groundwater can be polluted through the release of chemicals contained in wastewater. Riverbeds and wetlands are threatened with increased sediment impoundments and the presence of toxic and persistent chemicals. Such pollution can persist long after their original sources have ceased.

The health of the aquatic ecosystem can be negatively affected by the presence of toxic substances. This is further exacerbated with high population of pathogens in the water. The use of microbiologically contaminated water for domestic and other purposes is detrimental to human health and the society at large [20]. These conditions may also affect wildlife, which uses surface water for drinking or as a habitat. Generally, for measuring water quality, the physical (turbidity, electrical conductivity, temperature, total dissolved solids, color, and taste), chemical (pH, COD, BOD, nonmetals, metals, and persistent organic pollutants, POPs), and biological (fecal coliform, total coliform, and *enterococci* count) analyses are usually performed [19].
