Coagulation

Coagulation

Coagulation and the flocculation is an essential step for water treatment. All most all the fine suspended and dissolved particles can be removed through this process. In simple words, coagulation can be define as neutralizing the particles in raw water. Color causing substances and turbidity are induced by this process.

Most particles in water are negatively charged. By Dosing a coagulant particles become neutralized and smaller particles adhere to each other & produce settable solids or micro flocks. Coagulant dosage should be uniform, unless residuals can be remain with the water. There should be a proper retention time in the chamber to have accurate and completed step.

pH value of the raw water is an essential parameter in this step, after addition of coagulants rapid mixing should be given to properly disperse.

Commonly used coagulants are Alum [aluminum sulfate - Al2(SO4)3 ] and ferric chloride [FeCl3]. 

 Jar Test

The coagulant process can be identified by conducting a laboratory test call as "Jar test". Jar test equipment consist with six (06) jars filled with raw water in similar capacity (1000 ml). add coagulant in increasing manner to subsequence beakers keeping the first beaker as blank. Increase the mixing rapidly ( rapid mixing - 100-120 rpm). Then reduce to slow mixing (40 rpm). After turning off the mixer keep it to settle (10-15 minutes). Then measure the turbidity. 
We can use the jar test by modifying the process condition such as dosage, pH, flocculation time, settling time etc... and most relevant dosage can be identified.

  

Lets coming back to the coagulation. In most time, to having a rapid mixing Cascade systems are used. Water is falling through a weir into a receiving body, at that moment turbulent space course to rapid mixing and coagulant is dosing. 

Engineers used to add alum while aeration is given through a cascade system because it a success, efficiency method which is cost effective.

 

 

 

 

 

 

 

Screening

Screening is the first step in preliminary water treatment. It removes all the floating and suspended coarse particles and fine particles such as wood chips, fibers, plant leaves, aquatic plants and etc...

The main objective is to prevent pumps/pipes/valves/equipment & other appurtenances in the plant from damages due to clogging of particles. 

We can identify screening as coarse screening and fine screening. course particle size within 6-150 mm and fine particle size < 6mm.

1. Manual Bar Screens

2. Mechanical Bar Screens

Bar Screens use to separate particles. They are installed at the head-work(entrance) of the treatment plant. 

 

This is a very simple diagram which explain screening process. Bar screen is joined to a approach channel. Nowadays both coarse and fine screens are installed in plants. Many industries in everywhere in the world are using different type of bar screens which suits for there requests. Screen manufacturers are used to produce different screens with various bar spaces and which suits for engineers requests. Water treatment plant designers choose a screen with parameters flow rate, particles sizes, Height of the drain, inclination.

Water Treatment

Water is in a vulnerable situation in all most all over the world. Water is everywhere but unfortunately it gives much small contribution for human consumption. Ground water table becomes contaminated day by day due to lots of anthropogenic activities. Therefore requires appropriate treatment to remove disease causes agents from water. Water purification comes up with new technological way to full fill the water requirement all over the world for human consumption. 

Water Treatment Process

This is a simple diagram which indicates the summery of water treatment & theses are common steps of the treatment process. Each steps will be briefly discussed with future articles....

this is my first article

This is content