How a Water Filtration Plant Works
Water is treated to remove objectionable turbidity, taste, color and odor. Then it is disinfected to kill any harmful bacteria, viruses or protozoa that may be present.
The water is then filtered using rapid rate multi-media gravity filters. The different materials work like a giant strainer, trapping remaining particulates.
Coagulation
The coagulation process is one of the first steps in water treatment and involves adding chemical coagulants to destabilize suspended solids and organic compounds. These chemicals are then mixed with the water to cause them to clump together into larger, more easily removable particles known as flocs.
Coagulants can be either organic or inorganic. Inorganic coagulants are based on metal salts such as aluminum sulfate (alum) and iron sulfate. They can be used alone or in combination with other agents such as an oxidant water filtration plant to break down organic matter in the water. These salts react with the water to form metal hydroxides, which precipitate out of solution as sludge.
Organic coagulants are typically cationic polymers with high molecular weights that produce significantly less sludge. Examples include polyamines, dicyandiamide and melamine formaldehyde. This type of coagulant is able to capture both mineral and organic particles and, when combined with alum in a small-scale plant, can eliminate the need for chemical oxidants. This makes it a popular choice for large-scale drinking water production and wastewater processing applications.
Flocculation
The coagulation process causes the positive charge on solid granules suspended in a water stream to neutralize, allowing them to aggregate into larger particles called flocs. After the coagulation process, the flocculated particles are ready for solids-liquid separation. Flocculants, which are polymers, promote clumping by allowing entanglement & enhanced van der Waal forces. They also help increase the strength of the flocs, which increases their settling weight.
During the flocculation process, the small coagulated particles are stirred by mechanical mixing paddles in a settling tank. This gentle stirring allows the colloidal particles to make additional contacts or collisions, growing them into even larger aggregations known as macro-flocs.
The larger the flocs, the easier they are to separate from the rest of the water. They can then be disposed of by sedimentation or filtration. Flocculants can be natural or synthetic, with synthetic polymers being the most common in water treatment. Natural flocculants are usually more ecologically friendly than synthetics, but they require a higher dosage than their synthetic counterparts. LMI offers a global network of chemical feed experts and high-quality mixers for this critical water treatment application.
Sedimentation
Once the coagulation and flocculation processes have been completed, water is transferred to a sedimentation basin. It stays here undisturbed for about three hours while suspended particles settle to the bottom of the basin forming a layer known as sludge. This removes nearly ninety percent of the suspended material from the water.
The settling process is driven by gravity and forces acting on the particles such as centrifugal acceleration or electromagnetism. It is also accelerated by the addition of chemicals, such as ferric sulphate and polymers. These are called coagulants and have a positive charge that neutralizes the negative charges on the dissolved and suspended solids in the water. This causes them to bind together, or coagulate and create larger particles that are then heavier than the water. These larger particles are called floc.
Floc that is ballasted with fine sand has three times the settling speed of unballasted floc. The sludge from the settling zone is collected in a tank and transported by hydraulic mechanism to a hopper for disposal. It is important to design a sedimentation tank that minimizes energy consumption through the use of optimized geometry and flow patterns.
Filtration
Water travels through ecosystems, gathering particles from the soil, rocks and other surfaces. In nature, this is no big deal, but it can be problematic when the unfiltered water reaches our homes. This is why filtration is a necessary step in the process.
Depending on the water quality needs, treatment experts may use one of a number water filtration plant supplier of filter types. The basic requirements are a filter medium that can separate the solids and a driving force to push the fluid through it. This force can be supplied by gravity, centrifugation or pumping.
In the case of sedimentation, the driving force is the weight of the flocs that settle to the bottom of a filter bed. However, more modern filtration methods do not require this step.
Water filtration involves a wide range of techniques that can eliminate particles, germs and some dissolved chemicals. It is important to consider all options when creating a water cleanliness strategy for your home or business. For example, distillers can remove a broad range of contaminants from water. They are also safe and environmentally friendly.
Disinfection
A water treatment plant uses various processes to remove germs, chemicals, and other contaminants from the water it filters. It also disinfects the water to kill any remaining bacteria and viruses.
One of the most common disinfection methods is chlorination. Chlorine is a strong bactericide that can kill most bacteria and other harmful microorganisms. Water filtration plants use chlorine analyzers to monitor the levels of chlorine in the water. This helps to ensure that the water contains the right amount of chlorine, as too much can be dangerous.
In addition to chlorine, a water filtration plant may use other disinfectants. These include hydrogen peroxide, ozone, and other advanced technologies such as UV radiation with titanium dioxide.
In addition to removing pathogens, water filtration plants also filter out chemicals like pesticides. This is especially important in areas that have high agricultural activity, as water can contain residues from herbicides and pesticides. Other chemical contaminants can be removed by oxidation or activated carbon adsorption. Some water supplies also have radionuclides, specific chemicals, or toxins (such as those made by cyanobacteria). These must be treated using specialized methods.