Three methods of physical separation of soil have been used, sieving, sedimentation and densitometry. Sieving separates soil particles based strictly on size and is used primarily for aggregate separations of non-disrupted soil samples.

When water is added to soil, it can replace the oxygen that is naturally in the soil, and make the soil darker. This means wetter soil will have less oxygen compared with drier soil. When enough water is added, soil can become saturated and the water will start to form a layer on top of it.

A laboratory procedure that simulates coagulation/flocculation with differing chemical doses. The purpose of the procedure is to estimate the minimum coagulant dose required to achieve certain water quality goals. Samples of water to be treated are placed in six jars.

Jar testing is a pilot-scale test of the treatment chemicals used in a particular water plant.It simulates the coagulation/flocculation process in a water treatment plant and helps operators determine if they are using the right amount of treatment chemicals, and, thus, improves the plant’s performance.

To accomplish this, the water is treated with aluminum sulfate, commonly called alum, which serves as a flocculant. Raw water often holds tiny suspended particles that are very difficult for a filter to catch. Alum causes them to clump together so that they can settle out of the water or be easily trapped by a filter.

The jar test involves exposing same volume samples of the water to be treated to different doses of the coagulant and then simultaneously mixing the samples at a constant rapid mixing time. The microfloc formed after coagulation further undergoes flocculation and is allowed to settle.

These include: (1) Collection ; (2) Screening and Straining ; (3) Chemical Addition ; (4) Coagulation and Flocculation ; (5) Sedimentation and Clarification ; (6) Filtration ; (7) Disinfection ; (8) Storage ; (9) and finally Distribution. Let’s examine these steps in more detail.

Chemicals (coagulants) are added to the water to bring the nonsettling particles together into larger, heavier masses of solids called floc. Aluminum sulfate (alum) is the most common coagulant used for water purification.

Depending on the charge and chemical composition of your wastewater, flocculants can either be used on their own or in combination with coagulants. Flocculants differ from coagulants in that they are often polymers, whereas coagulants are typically salts.

Gypsum can coagulate or bridge clay particles, which accelerates settling. Flocculants should be used to prevent damage to sensitive water resources such as ponds, lakes and trout streams or whenever turbidity control is required. The best thing to do is a jar or bucket test using slightly varying rates of gypsum.

Flocculants, or flocculating agents (also known as flocking agents), are chemicals that promote flocculation by causing colloids and other suspended particles in liquids to aggregate, forming a floc. Flocculants are used in water treatment processes to improve the sedimentation or filterability of small particles.

Ferric chloride (FeCl3) is the most common iron salt used to achieve coagulation. Its reactions in the coagulation process are similar to those of alum, but its relative solubility and pH range differ significantly from those of alum. Both alum and ferric chloride can be used to generate inorganic polymeric coagulants.

1. Alum (aluminum sulfate), Al2(SO4)3. Still, the most common coagulant in the United States, it is often used in conjunction with cationic polymers.

In comparison between two species , let FeCl3 and AlCl3 ; more is the deficient of electron to complete octate or stable form more is the acidic strength. As AlCl3 have vacant orbital to fulfil octate ,where as FeCl3 have already octate form so AlCl3 is more acidic than FeCl3 ……

Flocculation is synonymous with agglomeration and coagulation / coalescence. Basically, coagulation is a process of addition of coagulant to destabilize a stabilized charged particle. Meanwhile, flocculation is a mixing technique that promotes agglomeration and assists in the settling of particles.

Chemical Coagulants Used In Water Treatment

• Aluminum Sulfate (Alum) – One of the most commonly used water treatment chemicals in the world.
• Aluminum Chloride – A second choice to Alum as it is more expensive, hazardous and corrosive.
• Polyaluminum Chloride (PAC) & Aluminum Chlorohydrate (ACH)

The key difference between flocculation and deflocculation is that flocculation is the formation of flocs by the clumping of fine particles, whereas deflocculation is the dispersion of flocs to form a stable colloid. Flocculation refers to the formation of clumps from fine particles in a colloid.

Polymers (long-chained, high-molecular-weight, organic chemicals) are becoming more widely used. These can be used as coagulant aids along with the regular inorganic coagulants. Anionic (negatively charged) polymers are often used with metal coagulants.

A polymer is a very large organic molecule; it is a chain of monomer subunits. In wastewater treatment processes, polymers are used to coagulate suspended solids and produce large curds of solid materials (floc).

A flocculant is a chemical that can be added to the water to help colloids and any other suspended solids bind together and form heavier particles. The heavier particles then settle to the bottom of the container/tank and the water on the top is drained off.

How to choose flocculant?

1. the molecular structure:the molecular structure of flocculant depends on the dewatering performance be required.
2. the molecular weight::The choice of molecular weight depends on the types of dewatering equipment, and molecular weight are also said the length of the polymer chain.

The best coagulant is therefore a pre-hydrolysed species with a high basicity. PACl has been found to be very suitable for lime softening applications. The advantage of a low basicity coagulant is even more pronounced in full softening applications, and the non-sulphated PACl is the coagulant of choice.

What is the first step in clarification? Explanation: Finely divided particles suspended in surface water repel each other because most of the surfaces are negatively charged. Coagulation is the first step to neutralize the charged particles and form flocs.

Carbon dioxide gas

It is aluminium potassium sulfate which can be readily available in the grocery shop. Mainly potash alum is used for longer food life, enhancing food taste, flavor & texture. It is also used in water purification treatment to improve the sedimentation of drinking water. It is also used in leather tanning, aftershave.

KAl(SO₄)₂·12H₂O

Uses of Alum

• purification of drinking water as a chemical flocculant.
• in styptic pencil to stop bleeding from minor cuts.
• the adjuvant in vaccines ( a chemical that enhances the immune response)
• deodorant “rock”
• pickling agent to help keep pickles crisp.
• flame retardant.
• the acidic component of some types of baking powder.