Chapter 05 - Clarification
| Name | Typical Formula | Typical Strength | Typical Forms Used in Water Treatment | Density |
| Aluminum sulfate | Al 2 (SO 4) 3· 14 to 18 H 2 O | 17% Al2O3 | lump, granular, or powder | 60-70 lb/ft 3 |
| Alum | 8.25% Al2O3 | liquid | 11.1 lb/gal | |
| Aluminum chloride | AlCl 3· 6H 2 O | 35% AlCl 3 | liquid | 12.5 lb/gal |
| Ferric sulfate | Fe 2 (SO 4) 3· 9H 2 O | 68% Fe 2 (SO 4) 3 | granular | 70-72 lb/ft 3 |
What is a clarifier in water treatment?
Mar 21, 2021 · Clarification, sedimentation or flotation, are physical water treatment processes using gravity or buoyancy to remove suspended solids from water. Solid particles entrained by the turbulence of moving water may be removed naturally by sedimentation in the still water of lakes and oceans.
What is primary clarifier in wastewater treatment?
Sep 05, 2021 · Clarification, sedimentation or levitation is a physical water treatment process that uses gravity or buoyancy to remove suspended solids from water. Solid particles entrained by the turbulence of moving water can be naturally removed by subsidence in …
What is the purpose of water treatment?
Clarification is an essential step in a water or wastewater treatment process to remove suspended solids through gravity settling, providing a clarified liquid effluent. First, understanding primary and secondary clarification is needed to determine the appropriate technology to meet treatment requirements.
What is clarified water?
Clarification, sedimentation or flotation, are physical water treatment processes using gravity or buoyancy to remove suspended solids from water. Solid particles entrained by the turbulence of moving water may be removed naturally by sedimentation in the still water of lakes and oceans.
What is clarification process?
Clarification consists in removing all kind of particles, sediments, oil, natural organic matter anc colour from the water to make it clear. A clarification step is the first part of conventional treatment for waste and surface water treatment.
What is sedimentation and clarification in water treatment?
Clarification, sedimentation or flotation, are physical water treatment processes using gravity or buoyancy to remove suspended solids from water. Solid particles entrained by the turbulence of moving water may be removed naturally by sedimentation in the still water of lakes and oceans.
What is flocculation and clarification?
In most clarification processes, a flocculation step then follows. Flocculation starts when neutralized or entrapped particles begin to collide and fuse to form larger particles. This process can occur naturally or can be enhanced by the addition of polymeric flocculant aids. Inorganic Coagulants.
What is the principle of a clarifier?
Clarifiers work on the principle of gravity settling. The heavier suspended solids settle in the clarifier due to the quiescent conditions provided in the Clarification zone. The settled solids are swept to the centre well provided for collection of sludge with help of moving scraper blades.
Is clarification the same as sedimentation?
Clarifiers are tanks built with mechanical means for continuous removal of solids being deposited by sedimentation. Clarification does not remove dissolved species. Sedimentation is the act of depositing sediment.
What is screening and straining?
Screening and straining devices trap trash and coarse debris using smaller apertures such as grates or screens.Jan 18, 2022
What is chemical clarification?
Chemical clarification consists of four phases: coagulation, flocculation, sedimentation, and filtration. Coagulation, essentially the addition of chemicals that are rapidly mixed with the water, usually involves the use of polymers and/or the oxides of aluminum, iron, or calcium.
Is alum a flocculant?
Alum, is a short term for aluminum sulfate, it works as a flocculant in your commercial pool, meaning that it attracts and traps suspended particles in the water and then sinks them to the bottom of the pool so that these particles can be vacuumed to waste.Feb 7, 2019
Why is aeration done in clarified water?
Clarified water is then passed through an aerator tank where air is pumped into the water. It helps aerobic bacteria to grow which decompose organic matter like human waste.
How many types of clarifier are there?
Clarifiers Basic Principle: Bridge support, column support and traction are the three main types of clarifiers, Primary and Secondary clarifiers.
What is overflow rate in clarifier?
The weir overflow rate is the number of gallons of wastewater that flow over one lineal foot of weir per day. The typical WOR range for primary clarifiers is 10,000 to 20,000 gallons per day per lineal foot of weir.Oct 24, 2016
What is a clarifier launder?
Extending from the outer tank wall to the effluent weir, the clarifier launder protects the effluent trough, weir, and other parts of your clarifier launder from sunlight. Preventing windblown debris such as dust and leaves from entering clarifier launder channels. Controlling odors in the launder trough. and more.
What is clarification in water?
Clarification refers to the sequence of operations used to remove suspended solids(mineral and organic) from the raw water together with a proportion of the dissolved organic matter ("flocculating"fraction ). Depending on the concentrations of the various contaminants present, there may be the need for increasingly complex operations ...
What is contact filtration?
Also called contact filtration( or in line filtration ), this design is the easiest to use: the coagulant is injected in line (static mixing…) without any coagulation or flotation stage. In some cases, especially with cold water, a flash mixer can be added between reagent injection and filtration; water then arrives at the filters in a coagulated state but flocculation is only completed as the water percolates through the upper layers of filter media (sand…).
What is the objective of clarification?
Frequently, the objective of clarification is the re-duction of color. Swamps and wetlands introduce color into surface waters, particularly after heavy rainfalls. Color-causing materials can cause various problems, such as objectionable taste, increased microbiological content, fouling of anion exchange resins, and interference with coagulation and stabilization of silt, soluble iron, and manganese.
What is an upflow clarifier?
Compact and relatively economical, upflow clarifiers provide coagulation, flocculation, and sedimentation in a single (usually circular) steel or concrete tank. These clarifiers are termed "upflow" because the water flows up toward the effluent launders as the suspended solids settle. They are characterized by increased solids contact through internal sludge recirculation. This is a key feature in maintaining a high-clarity effluent and a major difference from horizontal clarifiers.
Why do particles in water repel each other?
Finely divided particles suspended in surface water repel each other because most of the surfaces are negatively charged. The following steps in clarification are necessary for particle agglomeration: Coagulation. Coagulation can be accomplished through the addition of inorganic salts of aluminum or iron.
What is suspended matter?
The suspended matter can consist of large solids, settable by gravity alone without any external aids, and nonsettleable material, often colloidal in nature. Removal is generally accomplished by coagulation, flocculation, and sedimentation.
What is sedimentation in science?
Sedimentation refers to the physical removal from suspension, or settling, that occurs once the particles have been coagulated and flocculated. Sedimentation or subsidence alone, without prior coagulation, results in the removal of only relatively coarse suspended solids.
Can raw water be used to predict coagulation?
Raw water analyses alone are not very useful in predicting coagulation conditions. Coagulation chemicals and appropriate feed rates must be selected according to operating experience with a given raw water or by simulation of the clarification step on a laboratory scale.
What is flocculation in chemistry?
In most clarification processes, a flocculation step then follows. Flocculation starts when neutralized or entrapped particles begin to collide and fuse to form larger particles. This process can occur naturally or can be enhanced by the addition of polymeric flocculant aids.
Is it better to hire a professional for a treatment plant?
While some treatment plant operators try to maintain clarification systems themselves, it is often easier (and more cost-effective) to hire a professional for the job. When choosing to partner with a trusted solution provider, utilities can be confident the treatment plant is in good hands.
Do chain and scraper systems last forever?
While chain and scraper systems are a solid investment for removing solids, even the best clarification systems do not last forever. To prevent chain and scraper system from failing, follow these helpful tips.
How deep is Lake Tekapo?
The lake is 32 km long and 120 meters deep at its deepest part.” (Earth and Sky, Ltd.) Photo by author.
What does a high SUVA mean?
A high SUVA means that the DOC of the water will tend to control the coagulant dosage and relatively high removals of DOC can be expected…When the SUVA is less than 3 L/mg C·m-1; the effect of the DOC on the coagulant dosage may be negligible. (Water Quality and Treatment, 5thed., pg 6.4) .
Filtration Without Reagents
Coagulation, Followed by Filtration
- In the case of raw water having a slightly colloidal turbidity and/or slight colour and/or containing no more than 1,000 to 2,500 micro-algae per mL (therefore close to the A1 quality grade defined by French decree 2001-1220), based on the preceding scheme, a coagulant and, if necessary, a flocculant are utilised. Low dosages should be used as these reagents will shorten the filtration …
Complete Clarification Treatment
- This treatment approach must be applied to all waters where turbidity, colour, suspended solids, algae and oxidability properties exceed the figures quoted in table 3 without, however containing significant pollution (close to the A2 quality according to French decree 2001-1220, appendix 1 – 3).