Hydrosphere The hydrosphere is a combination of all kinds of free water on the Earth. From Greek: ὕ δωρ - hydōr, "water" σφα ῖ ρα - sphaira, "sphere" The total mass of the Earth’s hydrosphere is about 1.4 × 10 18 tonnes, which is about 0.023% of the Earth's total mass. Approximately 75% of the Earth's surface is covered by ocean (an area of 361 million square kilometers).
The Structure of Hydrosphere Hydrosphere includes water in liquid and frozen forms in groundwater, glaciers, oceans, lakes and streams. Saline water account for 97.5% of this amount. Fresh water - 2.5% of water Water distribution:
Water pollution Water covers about 70% of the surface of the Earth, but only 0.002% of the water is available for human consumption. Humans need water for drinking, sanitation, agriculture, and industry; and contaminated water can spread illnesses and disease vectors, so clean water is both an environmental and a public health issue. Pollution of water affects drinking water, lakes, river and oceans all over the world. In most of the developing countries the major cause of death is consumption of polluted water.
Water Pollutants Pathogens: disease-causing organisms Solids: suspended particles that make the water turbid Nutrients: such as phosphorus that can cause nuisance plant growth Organic matter: that can rob the oxygen resources of streams Toxic substances: metals and synthetic organic chemicals harmful to humans and wildlife
Toxic Substances Toxic Metals Persistent Organic Pollutants Arsenic Beryllium Cadmium Chromium Lead Mercury PCBs/PBDEs DDT Aldrin/Dieldrin Dioxins/Furans Toxic substances can act as a poison, producing either immediate illness following short-term exposure to high concentrations or delayed (chronic) effects after long term exposure at lower levels. Two classes are typically recognized:
Nutrients The addition of nutrients to surface waters has the effect of stimulating biological activity. Two categories of nutrients: inorganic chemicals such as nitrogen and phosphorus which stimulate plant growth; organic matter which stimulates bacterial growth. Phosphorus is found in fertilizer and in animal (including human) wastes and is discharged to lakes and rivers from point and nonpoint sources. When excessive phosphorus is added to lakes it stimulates the growth of algae and higher aquatic plants. This ‘over- feeding’ is called eutrophication.
Eutrophication Eutrophication leads to green foul smelling water with algae and overcrowded with macrophytes. The plants eventually settle to the bottom of the lake and decompose, consuming oxygen. The loss of oxygen can lead to fish kills.
Pathogens Pathogens are organisms that cause disease. Viruses, bacteria and protozoa are the three types of organisms responsible for most waterborne disease. The contamination of water with fecal matter from humans or other animals is the source of these diseases. Bacteria: E. Coli Viruses: Hepatitus AA Protozoa: Giardia lamblia
Drinking Water Water provided for human consumption requires treatment in order to make it safe (portable) and good tasting (palatable). Our water supply comes from two sources—surface waters (rivers, lakes) and groundwater. Each source presents its own problems. Surface waters often have elevated levels of soil particles and algae, making the water turbid, and may contain pathogens. Groundwater typically has higher levels of dissolved organic matter and minerals such as iron. Both sources may have high levels of calcium and magnesium (hardness) which results in soap scum and scale and both can be contaminated by toxic chemicals.
Drinking Water Treatment At its simplest level, drinking water treatment seeks to remove turbidity (solids) and pathogens. Additional treatment may be applied to deal with specific problems, e.g. hardness and chemical contamination. The drinking water treatment includes five steps: coagulation, flocculation, sedimentation, filtration and disinfection
Coagulation The process in which the negative charge on particles is neutralized, usually by addition of positive charges such as those provided by alum. The neutralization of particles allows them to clump together forming larger particles which are easier to settle. Aluminum sulfate or iron chloride
Flocculation The slow mixing process in which particles that have had their charge neutralized (coagulation) are encouraged to clump together with other particles, creating larger masses that will settle more rapidly.
Sedimentation Settling The water flows to a tank called a sedimentation basin where gravity causes the flocs to settle to the bottom. Large particles settle more rapidly than small particles. The clarified water, with most of the particles removed, moves on to the filtration step where the finer particles are removed.
Filtration The process of passing water through a filter to remove particles. In water treatment, the filter material is typically sand, sometimes with a layer of anthracite (coal) above.
Disinfection The most common disinfection method involves some form of clorine or its compounds. Chlorine is a strong oxidant that rapidly kills many harmful micro-organisms. Ultraviolet light’s disinfection
Wastewater Treatment The purpose of wastewater treatment is to reduce the level of contamination in the water so that it can be safely returned to the environment.
Wastewater Treatment Preliminary treatment removes the materials contained in wastewater that may damage or interfere with later treatment steps. Primary settling removes the solid particles contained in wastewater. The process consists of allowing the water to flow into a large basin or tank, usually concrete or steel. During the 1.5 to 3 hour period the water is in the tank, the settleable contaminants fall to the tank bottom and are removed. Biological treatment utilizes microorganisms to convert most of the remaining contaminants from soluble and non-settling solids into settleable solids. Some portion of the organic materials will also be oxidized to carbon dioxide and water.
Wastewater Treatment Secondary settling is similar to primary settling. The purpose of advanced wastewater treatment is to remove nutrients such as nitrogen and phosphorus, convert ammonia to nitrate, or to increase the efficiency of the plant beyond the typical range of 85 to 95 % removal of pollutants. The purpose of sludge treatment is to destroy the pathogens contained in the sludge and to reduce its objectionable characteristics prior to ultimate disposal. The most common treatment methods are aerobic (with oxygen or air) and anaerobic (without air) biological processes.