The diagram below illustrates the various stages involved in a modern water purification and distribution system for a city. Summarize the information by selecting and reporting the main features, and make comparisons where relevant.
Band 9.0 Model Answer:
The provided diagram delineates the multi-faceted procedure through which raw water is treated and subsequently distributed to an urban population.
Overall, the system comprises a sequential series of eight distinct stages, beginning with the extraction of water from a natural source and culminating in its delivery to residential and industrial consumers. The process is characterized by a transition from mechanical filtration to chemical disinfection.
Initially, water is drawn from an underground aquifer or a reservoir via a high-pressure intake pump. It then enters a sedimentation tank where large debris and suspended solids are allowed to settle. Following this, the water is channeled through a sand and gravel filtration bed, a crucial step designed to remove finer impurities. Once filtered, the water undergoes carbon activated treatment to eliminate organic contaminants and improve clarity.
In the final phases, the water is transferred to a chlorination chamber where it is chemically sterilized to eradicate pathogenic bacteria. Subsequent to disinfection, the potable water is pumped into a pressurized storage tower, which ensures a consistent flow rate. From this elevated tank, the water is distributed through an underground pipe network to individual households and commercial facilities. Finally, used water is collected and directed toward a wastewater treatment plant for recycled use, thus completing the cycle.
Highlight Vocabulary
- Delineates /dɪˈlɪn.i.eɪts/ (v): To describe or portray something precisely.
- Culminating in (phrasal verb): Reaching a climax or point of highest development.
- Potable /ˈpoʊ.tə.bəl/ (adj): Safe to drink; drinkable.
- Pathogenic /ˌpæθ.əˈdʒen.ɪk/ (adj): (of a bacterium, virus, or other microorganism) causing disease.
- Subsequently /ˈsʌb.sɪ.kwənt.li/ (adv): After a particular thing has happened; afterwards.
- Carbon Activated Treatment (n): A method of filtering water using charcoal to remove chemical impurities.
