This article throws light upon the top five elemental cycles involved in the treatment of sewage. The elemental cycles are: 1. Calcium Cycle 2. Carbon Cycle 3. Nitrogen Cycle 4. Phosphorus Cycle 5. Sulphur Cycle.
Treatment of Sewage: Elemental Cycle # 1. Calcium Cycle:
The surface run off from rivers, lakes, streams, seas etc. is consumed by plants which in turn are consumed by insects, rabbits, birds and many other animals. In the similar way, the photoplankton and fish are consumed by animals, or on death they revert to soil. The sea spray air borne dust and deaths of plants and animals contribute calcium back to soil and the level of calcium in the soil is maintained.
Treatment of Sewage: Elemental Cycle # 2. Carbon Cycle:
Bacterial decomposition of carbonaceous matter gives rise to CO2. Plants consume carbon from CO2 (stable form of carbon) in the process of photosynthesis and form plant carbohydrates, fats and proteins in presence of light. Animals consume plants and animals, fats and proteins.
Waste products or death of animals form organic carbonaceous matter and in this way cycle of carbon is completed. The organic carbonaceous matter may also be formed by death of plants. The plant life gives off CO2 at night and animal life gives off CO2. These two processes are called respiration.
Treatment of Sewage: Elemental Cycle # 3. Nitrogen Cycle:
Organic nitrogenous matter on decomposition yields ammonia, nitrogen and other gases. As a result of nitrification, ammonia nitrogen gets converted into nitrite and nitrate. This nitrogen is consumed by the plant life and form animal proteins.
Animals consume plants and form proteins. Waste products on death of animals form organic nitrogenous matter and nitrogen cycle is completed. Organic nitrogenous matter can also be formed by the death of plants.
Nitrate is converted to NH3 and N2 by certain bacteria and the process is known as de-nitrification. Free N2 may be directly converted into plant proteins by some bacteria living in the roots of plants. This is known as nitrogen fixation.
Treatment of Sewage: Elemental Cycle # 4. Phosphorus Cycle:
Phosphorus is essential for the growth of algae and other biological organisms. Phosphorus from artificial and chemical sources and also that present in the soil is consumed by plants and when they are consumed by animals, phosphorus is transferred to such animals. The death or excreta of animals and death of plants complete the phosphorus cycle.
Treatment of Sewage: Elemental Cycle # 5. Sulphur Cycle:
H2S is formed by anaerobic decomposition of organic sulphurous matter. By the process of oxidation, H2S is converted into sulphates which are consumed by plant life. As a result, plant proteins are formed. Animals consume plants and from animal protein.
Waste products on death of animals form organic sulphurous matter and sulphur cycle is completed. Organic sulphurous matter is also formed by the death of plants. Similarly, sulphates are converted into H2S by the process of reduction, in the absence of oxygen.
All of the yeasts and similar fungi occur as branched filaments or hyphae, septate or nonseptate masses of interlaced hyphae forming a mycelium Reproduction is by spores.
Three groups of fungi are aquatic:
(1) The Phycomycetes,
(2) Ascomycetes, and
(3) Fungi imperfecti.
Their method of fruiting is a principal distinction. The yeasts are non-filamentous and usually reproduce by budding.
Members of these largest groups of freshwater fungi possess nonseptate hyphate with many nuclei in a single cell. Some are wound parasies on larger aquatic organisms (fish and amphibians), other grow saprophytically on algae, other aquatic organisms, and aquatic debris in general. Reproduction is by motile spores or conjugation. Leptomitus, Saprolegnia, and Achlya are typical representative of this group.
Relatively few of these septate, mono or binucleate organisms are aquatic. Fusarium aqueductum is an example.
(3) Fungi Imperfecti:
So-called because their life cycle is incomplete or not fully known.