ENVS6022 Water Science : Sewage Treatment Process

For this report you are to draw a process diagram showing the trail of water from rain cloud back to rain cloud via the built environment.

 

Your process drawing may fit on a single sheet of A3 but it may not. It will be neat, elegantly formed and skilfully considered and as such will be informative, attractive and a thing of beauty in itself.

 

Your report submission can be hand drawn, computer drawn, coloured or not but must be fully annotated. It must be highly analytical of issues like water usage, water treatment, rainfall, population growth, water-saving measures, water collection, grey water etc etc. You will need to make your own investigations, undertake your own reading and present your work in your own words and using your own drawings.

The sun eamits the heat energy on the earth’s surface. As the water bodies on the earth’s surface heats up, the process of evaporation takes place. The water vapors rise up. As the temperature cools down in the upper atmosphere, water vapor changes into tiny droplets of water and clouds are formed. Sublimation is another process in the atmosphere. This is seen on the mountain slopes where solid changes directly into gaseous form, as a result clouds are formed. When the clouds become too heavy and cannot hold any more water vapor, precipitation takes place. Precipitation can be in the form of rain, snow etc. Precipitation results in surface flow and fills up the lakes, ponds and other water bodies on the earth surface. Some amount of precipitation also percolates downward, sips through the soil and replenishes the aquifers. Some of them flows as a ground water flow and reaches the sea, from where the water cycle starts again. This is the natural water cycle with very less human interventions.

Human being with their built-up environment plays a very important part in the water cycle. As we see from the diagram, the water which is collected in the lake is being transferred into water treatment plant through an intake pipe. There the water go through number of process like pre-chlorination, Coagulation, Flocculation. After this the water passes through the sedimentation basin and filtered through the sand. Eventually we get clear fresh water. Now the water is distributed through the distribution system to household, industries, factories etc.

The water that is distributed in the households is used for drinking, washing, cleaning as well as it passes through the sewage system of the houses. All the dirty water is carried through the sewage system. The water is also necessary for farming, gardening etc. The water which is used in watering the plants or farming, part of it seeps underground through the soil and reaches the ground water flow. It ultimately goes back to the sea from where the water cycle starts again. The water from the plans also changes into vapour through transpiration. These water vapour forms into cloud and the water cycle begin.

The wastewater from flushing the toilet, washing, cleaning goes down the drain and joins a large sewer pipe under the road. These pipes carry the water to the sewage treatment plant where the water passes through four stages before the filtered and the clean water is drained into the water bodies like river lakes etc. So from there water is evaporated when it becomes heated and the water cycle starts again.

References:

Zhang, Q. and Stanley, S.J., 1999. Real-time water treatment process control with artificial neural networks. Journal of Environmental Engineering, 125(2), pp.153-160.

Othmer, D., 1973. Sewage treatment process. U.S. Patent 3,772,187.