Water Resources: Management, Uses, and Wastewater Treatment
Technical Measures to Meet Growing Water Demand
The management of water resources is becoming a very important issue for governments as water, an essential resource, is becoming more scarce due to environmental problems that its use is unleashing.
As a result of population and economic growth, needs increase, as does water consumption. This creates problems of overfishing and pollution, which results in loss of both quantity and quality of available water.
Supply management has been based on human intervention in the hydrological cycle through a series of technical measures and a pricing policy that rewards consumption.
The measures are:
- Promoting management pricing policies that enhance or do not penalize the consumer.
- Using scientific and technological knowledge to increase the available water.
- Monitoring water quality in addition to these measures.
Common Uses of Water by Humans
a) Consumptive uses: These involve a disappearance of the volume of water or at least a loss of quality, which makes it unusable again directly. There are three main consumptive uses:
- Urban domestic use or for survival, sanitation, cooking, services, etc.
- Industrial use for refrigeration, preparation of solutions, cleaning, storage of hazardous wastes, etc.
- Agricultural use for irrigation and livestock.
b) Non-consumptive uses: These are those that do not consume water.
c) Water as an energy resource: Since the water cycle depends on the sun, the various forms of exploitation of the mechanical energy of water are renewable. So far, these are: hydro, tidal, and wave.
El Niño and La Niña Explained
The cyclical El Niño phenomenon acts on the eastern coast of Central and South America, causing hurricanes and heavy rains. In the normal situation (called La Niña), the trade winds push water towards the west Pacific surface, thus causing dryness on these shores and bringing cloudiness to the western coasts of Asia. At the same time, this causes the upwelling of a stream of cold, deep water, and the thermocline breaks down, fertilizing the coast of South America, especially Peru, whose fisheries resources are extraordinary.
Phases of Wastewater Purification
Wastewater treatment aims to minimize the impact of water pollution on natural ecosystems. In other words, it tries to help nature in the process of purification to avoid impacts and potential risks.
The pollutants in wastewater are of three types: physical, chemical, and biological agents, and this requires complex treatment combining treatments of the three classes. It should be noted that this purification involves not only expensive investments in technological equipment and qualified personnel but also energy, which will be greater the higher the degree of purification you want to achieve. This will be related to the type and degree of contamination of water, whose origin can be domestic, agricultural, industrial, or combinations of these types of water. Basically, the following phases are distinguished:
- Pre-treatment: This is the separation of suspended solids and floating solids, not fat, by grinding or retention processes through bars of sand removal and degreasing.
- Primary treatment: Sedimentation processes are performed in settling tanks or pools, which are prepared by gravity or solid particles in suspension of greater density. After flocculation, chemicals are used to add and remove colloidal materials by further sedimentation. Subsequently, another chemical treatment is used to neutralize the pH of the water, whose control is needed in the next phase. These processes produce a series of sludges, which are collected to be further processed.
- Secondary treatment: This is a biological treatment to remove organic matter. Wastewater is transported to a tank, injecting oxygen so that bacteria in the water oxidize organic matter under aerobic conditions and under the control of pH and temperature. To avoid risks to human health, before the water is returned to rivers or seas, chlorination or ozonation processes are used for disinfection.
- Tertiary treatment: Sometimes, if water is contaminated with substances such as nitrates, phosphates, heavy metals, salts, etc., which could not be separated by the above procedures, and if it will even be reused for irrigation or cleaning, the concentration of these substances is very high. It is necessary to remove these substances by specific chemical treatments that raise the cost of water purification a lot.
- Sludge treatment: As a result of some of the above processes, slurry or sludge is obtained. After removal of its water, it is stabilized by the oxidation of residual organic matter via some tanks called anaerobic digesters. The result is a material rich in humic components that can be used as compost for agricultural fertilizer, provided that it does not contain toxic substances like heavy metals.
- Gas recovery: The gas from the anaerobic digestion of sludge is rich in methane and can be reused to provide energy to the treatment plant itself.