The document discusses various chemical treatment methods for wastewater management, emphasizing the importance of treating wastewater before discharge to prevent environmental pollution and health hazards. It covers key processes such as coagulation, neutralization, precipitation, and oxidation, explaining the purpose and application of each method, along with the types of chemicals used. Additionally, it highlights the significance of coagulants like alum and the role of neutralization in adjusting pH levels for safe disposal.

1. CHEMICAL TREATMENT
METHODS
DONE BY: MAHASWARI JOGIA
WASTE MANAGEMENT TECHNIQUES (HCE 24)
SEMINAR ON:

2. CONTENTS
 INTRODUCTION
 CHEMICAL TREATMENT
 COAGULATION
 NEUTRALIZATION
 PRECIPITATION
 OXIDATION
 REFERENCES
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3. INTRODUCTION
● Industries use water that obtained from the water treatment system for a variety
of purposes, such as:
- For manufacturing goods.
- For heating.
- For cooling.
- As carrier of raw material.
- As carrier of waste matter.
- As a solvent.
● The resulting water is then classified as a wastewater.
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4. ● The indiscriminate discharge of these wastewater streams into the environment
can
- Render soils "sick ".
- Pollute the receiving bodies of water.
- Cause air pollution by generating obnoxious gases.
● Discharge untreated wastewater into the domestic sewer system makes the task
of treating domestic sewage, a very difficult and costly exercise.
● To prevent any health hazards caused by discharging wastewater into the
environment and protect domestic sewage , the wastewater must be treated
before discharge.
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5. CHEMICAL TREATMENT
• Treatment methods in which the removal or conversion of contaminants is
brought about by the addition of chemicals or by other chemical reactions.
• Precipitation, adsorption, and disinfection are the most common examples used in
wastewater treatment.
• Basically the treatment includes:
- Coagulation
- Precipitation
- Disinfection
- Oxidation
- Neutralization, scale control
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6. Very fine suspended particles present in wastewaters cannot be removed in
sedimentation due to settling velocity is very low.
Fine colloidal or dispersed particles contain electric charges and continuously in
motion known as Brownian motion and they are not settled down by gravity force.
Very fine suspended particles can be removed by increasing their size(flocculated
particles). Certain chemical compounds called coagulants are added to the wastewater
which on thorough mixing form a gelatinuous precipitate called floc.
COAGULATION
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7. After which they pass through sedimentation tank and settle down.
It takes place in rapid mix, or flash mix basins which are very rapid. The primary
function of rapid mix basin is to disperse the coagulant so that it contacts all of the
wastewater.
Over the years a number of different substances have been used as coagulants.
The most common ones
-Alum(Al2(SO4)3.18H2O).
-Ferrous Sulfate(FeSO4.7H2O).
-Lime Ca(OH)2.
-Ferric Chloride (FeCl3).
-Ferric Sulfate (Fe2(SO4)3).
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8. Principle of Coagulation
In coagulation, individual particles combine together. When a coagulant is used in
water, it forms a spongy gelatinous precipitate which absorbs fine size particles in
water and binds them together. The whole process results into bigger particles
which are heavier and easily settle able.
Properties of common coagulants
• React quickly
• Cheap
•Easy to handle and store
• React in longer range of pH
• Electrolyte ( positively charged)
• High valance ions for high efficiency
•Not detoriate
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9. Coagulation & Flocculation Process
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10. ALUM [Al2(S04)3 18H2O]:
Alum is the most widely used coagulant in water treatment. It reacts quickly
giving excellent stable flocs. It is cheap and can be easily stored and handled. The
alum when added to raw water, reacts with natural alkalinity in water (if that is
insufficient, lime may be added) so as to form a gelatinuous precipitate of
aluminium hydroxide. It increases the sulphate hardness and corrosiveness of
water to a small extent.
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11. NEUTRALIZATION
If a waste stream is found to be hazardous due to corrosivity, neutralization is the
primary treatment used. It is used as a pretreatment system before a variety of
biological, chemical, and physical treatment processes.
It is the process of adjusting the pH of water through the addition of an acid or a
base, depending on the target pH and process requirements. Some processes such as
boiler operations and drinking water standards need neutral water at a pH of 7.
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12. Water or wastewater is generally considered adequately neutralized if:
(1) its damage to metals, concrete, or other materials is minimal; (2) it has little
effect on fish and aquatic life; (3) it has no effect on biological matter (i.e., biological
treatment systems).
PARAMETERS WHICH AFFECT NEUTRALIZATION:
-pH
-alkalinity/acidity
-Hardness
-Buffers
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13. Fig: continuous neutralization tank
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14. PRECIPITATION
•It is used for removing dissolved metals from waste water solution containing toxic
materials. To convert this dissolved metal into solid particles, a precipitation
reagent is added. A chemical reaction occurs where dissolved metals form solid
particles.
•Filtration can be used to remove the particles from the mixtures. How well the
process takes place depends on the types of metal present, its concentration, and
reagent used.
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15. •Example : in hydroxide precipitation, calcium or sodium hydroxide is used as a
reagent to create solid metal hydroxides.
But the main difficulty being the mixture of metals in waste water making it
difficult to precipitate.
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16. OXIDATION
•It is a waste water treatment which involves the use of oxidizing agents such as
ozone, hydrogen peroxide, permanganate, chloride, chlorine, oxygen etc.
•The electrons move from the oxidant to the pollutants in waste water. They
undergo structural modification becoming less destructive compounds.
•Alkaline chlorination uses chlorine as oxidizing agent against cyanide. But it can
lead to production of toxic chlorinated compounds hence require further steps.
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17. APPLICATIONS:
•Reduce concentration of the residual organics
•Controls odors
•Remove ammonia
•Reduce microbial content
Common oxidation agents used in wastewater treatment:
-Oxygen(O2).
-Chlorine (Cl2).
-Sodium hypochlorite (NaClO).
-Calcium hypochlorite (Ca(ClO)2).
-Potassium permanganate(KMnO4).
-Hydrogen peroxide(H2O2).
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18. •www.thomasnet.com/articles/chemicaltreatment
•https://frtr.gov/matrix2/section4/4-50.html
•https://www.slideshare.net/chemicalwatertreatment/industrial+wastewater+treatment
•Centralized water treatment prepared by Innocent L Swai, Bsc EHS
•Flow equalization and neutralization by Ramesh K. Goel, Joseph R.V. Flora,
and J. Paul Chen
•wastewater engineering– objectives of wastewater treatment, primary treatment of
wastewater by Dr. Asha Gupta
•Waste water engineering treatment and reuse by metcalf and eddy
REFERENCE
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