Question

what is the process of drinking water in a city​

Answer 1

While specific water treatment methods vary from city to city depending on the drinking water source, there are four standard treatment steps that all drinking water undergoes regardless of city specifics. These steps are coagulation and flocculation, sedimentation, filtration, and disinfection.

Answer 2

$\huge\bold{\mathtt{\purple{✍︎A{\pink{N{\green{S{\blue{W{\red{E{\orange{R✍︎}}}}}}}}}}}}}$$\huge \Rightarrow$

The process of drinking water in a city is as follows : $\Downarrow$

• The raw water is delivered to the headworks of the water treatment plant where the first of 5 major unit water treatment processes start the treatment to make the water safe to drink. The 5 major unit processes include chemical coagulation, flocculation, sedimentation, filtration, and disinfection (described below).

$\large\bold \red{Chemical\: coagulation}\Rightarrow$

• The first chemical added to the water while Chemical coagulation is chlorine dioxide it is an oxidanat used to break down naturally occurring organic matter such as decaying leaves and other plant material. A chemical coagulant known as Aluminium sulphate is used as primary coagulant.

$\large\bold \red{Flocculation}\Rightarrow$

• The coagulated water then flows to the next major unit process, the flocculation process. Flocculation is a slow stirring process that causes the small coagulated particles to form floc. The flocculation process promotes contact between the floc particles and the particulates (sediment) in the water. Generally, these contacts or collisions between particles result from gentle stirring created by a mechanical or hydraulic means of mixing. There are two sets of flocculation basins that contain mechanical mixing paddles that the water passes through to gently stir the coagulated water. The floc formed creates a surface in which the particulates in the water adsorb (adhere) to the surface of the floc thus forming larger settleable particles for ease of removal by sedimentation and filtration.

$\large\bold \red{Sedimentation}\Rightarrow$

• The flocculated water then flows to the next major unit process, the sedimentation process. The purpose of the sedimentation process is to remove suspended solids (particles) that are denser (heavier) than water and to reduce the particulate load on the filters. Sedimentation is accomplished by decreasing the velocity of the water being treated below the point where it can transport settleable suspended material, thus allowing gravitational forces to remove particles held in suspension. When water is almost still in sedimentation basins, settleable solids will move toward the bottom of the basin. This process of sedimentation removes almost ninety percent of the solids in the water. The clearer water on the surface is collected in the launder tubes that direct the water to the filter gallery to remove the remaining ten percent of solids.

$\large\bold \red{Filtration}\Rightarrow$

• The settled water then flows from the Pre-Sedimentation Building to the Filtration Facility. Before arriving at the Filtration Facility chlorine is added to the water at the pre-chlorination point to begin the disinfection process. The disinfection process is designed to kill or inactivate most microorganisms in water, including essentially all pathogenic organisms whether they are from bacteria, viruses or intestinal parasites. Pathogenic organisms are the microscopic bugs in the water that can cause waterborne diseases such as gastroenteritis, typhoid, dysentery, cholera, and giardiasis.

$\large\bold \red{Disinfection}\Rightarrow$

• The chlorinated settled water then flows into the Filtration Facility and onto the filters for the last of the major unit processes used to treat the drinking water. Filtration is the process of passing water through material such as a bed of coal, sand, or other granular substance to remove particulate impurities that were not removed during the sedimentation process. The water treatment plant uses rapid rate multi-media gravity filter beds. The filters are comprised of a top layer of anthracite, a middle layer of filter sand and then a bottom layer of garnet sand and one an underdrain system that collects the filtered water. The water enters on top of the filter media and passes down through the filter beds by gravity. The different materials work like a giant strainer and trap remaining particulates. When the filters start to get packed full of particles, the operators clean them using a procedure called backwashing. Potable water is run backwards through the filters releasing the entrapped particulates that are collected in drain troughs. The backwash water is sent to the Backwash Recovery Pond and, after a settling process, the backwash water is returned to the raw water settling pond for re-use.

Use water carefully and save Water.

• Hope it will help you.