lec 4-3 industrial wastewater treatment1.pdf

Chapter 1......Introduction.
Chapter 2......Description Of Main Treatment
Technology.
Chapter 3......Sludge Treatment And Disposal.
Chapter 4......Model For Industrial Wastewater
Treatment Plant.
CONTENTS

● 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.

● 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.

Important Contaminants Of Concern In
Wastewater Treatment
Suspended solids
● Lead to the development of sludge deposits and anaerobic
conditions when untreated wastewater is discharged into the aquatic
environment.
Nutrients (P, N2&C)
● When discharged into the aquatic environment, these nutrients can
lead to the growth of undesirable aquatic life. When discharged in
excessive amounts on land, they can also lead to the pollution of
groundwater.
Priority pollutants
● Organic and inorganic compounds selected on the basis of their
known or suspected carcinogenicity, or high acute toxicity. Many of
these compounds are found in wastewater.

Refractory organics
● These organics tend to resist conventional methods of wastewater
treatment. Typical examples include surfactants, phenols, and
agricultural pesticides.
Heavy metals
● Heavy metals are usually discharged to wastewater from
commercial and industrial activities and have to be removed if the
wastewater is to be reused.
Dissolved inorganics
● Inorganic constituents such as calcium, sodium, and sulfate are
added to the original domestic water supply as a result of water use
and may have to be removed if the wastewater is to be reused.

Characteristics Of Industrial Wastewater
1 Physical Characteristics
1.1 Total Solids
● Analytically the total solids content of a wastewater is defined
as all the matter that remains as residue upon evaporation at 103
to 105°C.
● Composed of:
1.Floating matter.
2.Settleable matter.
3.Colloidal matter.
4.Matter in solution.
Classification of total solids

1.2 Odors
● Industrial wastewater may contain either odorous compounds or
compounds that produce odor during the process of wastewater
treatment.
1.3 Temperature
●
The temperature of water is a very important parameter because
of its effect on
-
Chemical reactions and reaction rates in treatment process
.
-
Aquatic life
.
1.4
Color
●
Color of industrial wastewater varies according to the type of
industry
.
●
Most colored matter is in a dissolved state
.
.

1.5 Turbidity
● Turbidity, a measure of the light-transmitting properties of
water, is another test used to indicate the quality of wastewater
discharges and natural waters with respect to colloidal and residual
suspended matter.
2 Chemical Characteristics
2.1 Organic Matter
● The presence of these substances has complicated industrial
wastewater treatment because many of them either cannot be or
are very slowly decomposed biologically.
● Typical examples include:
- Fats, Oils, and Grease.
- Surfactants.
- Phenols.
- Volatile Organic Compounds (VOCs).
- Pesticides & Agricultural Chemicals.

2.1.1 Parameters Of Organic Content
2.1.1.1 Biochemical Oxygen Demand (BOD5)
● The determination of the BOD5 involves the measurement of the
dissolved oxygen used by microorganisms in the biochemical oxidation
of organic matter.
2.1.1.2 Chemical Oxygen Demand (COD)
● It oxidizes organic matter through a reaction with a mixture of
chromic and sulfuric acid at high temperatures.
● The COD of wastewater is, in general, higher than that of the
BOD5 because more compounds can be chemically oxidized than can
be biologically oxidized.
● This can be very useful because COD can be determined in 3
hours, compared with 5 days for the BOD5.

2.2 Inorganic Matter
● Nitrogen & Phosphorus.
● Sulfur.
● Heavy Metals.
3 Biological Characteristics
● Some industries have certain pathogenic organisms like
slaughterhouses others have molds and fungi as starch and yeast
factories.
● Biological information is needed to assess the degree of treatment
of the wastewater before its discharge to the environment.

Common Types Of Wastewater
Treatment Methods
1 Physical Unit Operations
● Treatment methods in which the application of physical forces
predominates.
● Screening, mixing, flocculation, sedimentation, flotation,
filtration, and gas transfer are typical unit operations.
2 Chemical Unit Processes
● 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.

3 Biological Unit Processes
● Treatment methods in which the removal of contaminants is
brought about by biological activity.
● Biological treatment is used primarily to remove the biodegradable
organic substances (colloidal or dissolved) and nutrients (nitrogen &
phosphorus) from wastewater.
● Basically, these substances are converted into gases that can
escape to the atmosphere and into biological cell tissue that can be
removed by settling.

Description
Of
MAIN
TREATMENT
TECHNOLOGIES

Mechanical Processes
1 Screening
● The first unit operation encountered in wastewater-treatment
plants is screening. A screen is a device with openings, generally of
uniform size that is used to retain the coarse solids found in
wastewater.
● According to the method of cleaning, screens are designated as
hand cleaned or mechanically cleaned.
● According to the size of openings, screens are designated as
coarse or fine. Coarse screens have openings of ¼ inch or more, and
fine screens have openings of less than ¼ inch.

2 Oil Separation
● It is a process in which Floatables, namely non-emulsified oil and
organics separates from wastewater.
2.1 API (American Petroleum Institute ) Separators
● The design of the separator is based on the specific gravity
difference between the oil and the wastewater and between the
suspended solids and wastewater .
● In general, this separator can handle very large flow. However,
its disadvantage is the long retention time required for efficient oil
separation.

2.2 CPI (Corrugated Plate Interceptors ) Units
● They consist of stacks of plates or bundles of slanted tubes,
usually at 60 degrees, in a vessel or tank. It has been found that if
the plates are tilted at 60 degrees, the solids will slide down the
plates and be collected at the bottom.
● A CPI units can be placed in a small space but cannot take shock
loads and high flows.
● They are usually more efficient than API separators and primary
clarifiers in removing oil and solids, as more surface area can be
provided.

3 Flow Equalization
● Flow equalization is used to overcome the operational problems
caused by flow variations, to improve the performance of the
downstream processes, and is also used as an emergency tank to
equalize wastewater effluent in case of any process failure in the
treatment process.
● The design must provide for sufficient mixing to prevent solids
deposition and concentration variations and also to provide aeration
to prevent odor problems.
● The best location for equalization facilities to be at existing and
proposed treatment plant sites. In some cases, equalization after
primary treatment and before biological treatment may be
appropriate.

Physical Treatment
1 Sedimentation
● Sedimentation is the separation from water, by gravitational
settling, of suspended particles that are heavier than water.
● Sedimentation is used for separation of grit and particulate
matter in the primary settling basin, separation of biological-floc in
the activated-sludge settling basin, and separation of chemical-floc
when the chemical coagulation process is used. It is also used for
solids concentration in sludge thickeners.
● Sedimentation basins are constructed in a variety of shapes and
sizes, circular tanks or rectangular tanks.
● The basin is comprised of four zones according to function:
1-The inlet zone. 2-The settling zone.
3-The sludge zone. 4-The outlet zone.

● The inlet zone is a region where the incoming suspension is
distributed uniformly over the cross-section of the tank.
● In the settling zone, the particles settle at the same rate as
they would in a quiescent.
● In the outlet zone, the clarified liquid is collected uniformly over
the cross-section of the basin.
● The solids collect in a sludge zone at the bottom of the tank.
Rectangular basin Circular basin

Rectangular basin Circular basin

2 Flotation
● Flotation is a unit operation used to separate solid or liquid
particles from a liquid phase.
● Separation is brought by introducing fine gas (usually air bubbles)
into the liquid phase. The bubbles attach to the particulate matter,
and the buoyant force of the combined particle and gas bubble is
great enough to cause the particle to rise to the surface to form a
scum blanket, which is removed by a skimming mechanism. Grit and
other heavy solids that settle to the bottom are raked to a central
sludge for removal.
● Principal advantage of flotation over sedimentation is that very
small or light particles that settle slowly can be removed more
completely and in a shorter time.

2.1 Types Of Flotation Systems
2.1.1 Air Flotation
● In this system, air bubbles
are formed by introducing
the gas phase directly into
the liquid phase through a
revolving impeller through
diffusers.
2.1.2 Vacuum Flotation
● This process consists of
saturating the wastewater
with air either directly in an
aeration tank or by permitting
air to enter on the suction
side of a sewage pump.
Air
Flotation
Vacuum Flotation

Chemical Treatment
1 Neutralization
● Industrial wastes often contain acidic or alkaline components which
require neutralization before discharge or treatment.
● For wastes that are discharged to receiving waters, a pH between
6 and 9 is frequently specified by regulatory agencies. For wastes
entering biological treatment processes, the pH should be maintained
between 6.5 and 9 for optimum growth of the microorganisms.
● Acidic wastes are commonly neutralized with waste alkaline
streams, lime, dolomite, ammonia, caustic soda, or soda ash.
● Lime is the most widely used alkaline material for neutralization
acid wastes because of its low cost. Lime may be slow to react and
may form insoluble precipitates.
● alkaline wastes usually require treatment with a waste acidic
stream, sulfuric acid or hydrochloric acid.

2 Oxidation/Reduction
● Oxidants are used in wastewater treatment as a first step in the
removal of heavy metals to oxidize organics or as a last step in a
treatment process, to oxidize odoriferous compounds such as
hydrogen sulphide or to oxidize inorganics such as cyanide and for
disinfection.
● 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).

3 Chemical Precipitation
● Chemical precipitation in wastewater treatment involves the
addition of chemicals to alter the physical state of dissolved and
suspended solids and facilitate their removal by sedimentation.
Chemical Precipitation

3.1 Coagulation
● 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
precipitants. 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).
3.2 Flocculation
● The purpose of flocculation is to form aggregates or flocs from the
finely divided matter. The flocculation of wastewater by mechanical or
air agitation.

Coagulation & Flocculation Process
**Chemical Precipitation for Improving Plant Performance
● From 80 to 90 percent of total suspended matter, 50 to 80
percent of BOD5 and 80 to 90 percent of bacteria can be removed
by chemical precipitation. In comparison, when plain sedimentation is
used, only 50 to 70 percent of total suspended matter, 25 to 40
percent of BOD5 and 25 to 75 percent of bacteria can be removed.

Physio-Chemical Treatment
Dissolved Air Flotation (DAF) System
● In dissolved air flotation (DAF), air is intimately contacted with
an aqueous stream at high pressure, dissolving the air. The pressure
on the liquid is reduced through a back pressure valve, thereby
releasing micron-sized bubbles that sweep suspended solids and oil
from the polluted stream to the surface of the air-flotation unit.
● Solids having a specific gravity greater than water tend to settle
to the bottom and are removed by a rotating scraper arm. Attached
to the same shaft is a rotating skimmer blade that removes the
floating matter from the surface of the vessel into a skimming
hopper.
● Clean water passes underneath a skirt and then must leave the
vessel through a launder, which is located in the peripheral region.

DAF system without recycling
Chemical Treatment Physical Treatment

● A portion of the effluent water is recycled for pressurization.
Compressed air is introduced into the discharge of the recycle
pump, and intimate contact with the water is achieved in the
aeration tank.
DAF system with lamella, type flocculate &
recycling
Chemical Treatment Physical Treatment

Biological Treatment
1 Aerobic Biological Treatment
1.1 Activated-Sludge Process
1.1.1 Conventional Activated Sludge
● The conventional activated sludge system contains a tank for
wastewater aeration followed by a settler and a solids recycle line.
● The wastewater flows through under constant aeration in the
presence of activated sludge and exits at the end of the tank after
4-8 hours of residence time. The oxygen concentration in the
reactor should be 0.5-2 mg/l throughout, where values over 2 mg/l
are considered lost energy.

Preliminary Operations
● Preliminary Operations are used to provide a relatively constant,
homogenous feed to sludge-processing facilities.
1 Sludge Grinding
● Sludge grinding is a process in which large and string material
contained in sludge is cut or sheared into small particles to prevent
the clogging of or wrapping around rotating equipment.
2 Sludge Degritting
● In some plants where separate grit removal facilities are not used
ahead of the primary sedimentation tanks or where the grit removal
facilities are not adequate to handle peak flows and peak grit loads,
it maybe necessary to remove the grit before further processing of
the sludge.

3 Sludge Blending
● Sludge from primary, secondary, and advanced processes are
blended to produce a uniform mixture to enhance plant operability
and performance.
● Blending tanks are usually equipped with mechanical mixers and
baffles to ensure good mixing.
4 Sludge Storage
● Sludge storage is particularly important in providing a uniform feed
rate ahead of the following processes: lime stabilization, heat
treatment, mechanical dewatering, drying, and thermal reduction.
● If sludge is stored longer than two or three days, it will
deteriorate and will be more difficult to dewater.

Sludge Dewatering
● Dewatering is a physical (mechanical) unit operation used to reduce
the moisture content of sludge.
1 Chemical Conditioning
● The use of chemicals to condition sludge for dewatering is
economical because of the increased yields and greater flexibility
obtained. Chemical conditioning can reduce the 90 to 99 percent
incoming sludge moisture content to 65 to 85 percent, depending on
the nature of the solids to be treated.
● Chemicals used include ferric chloride, lime, alum, and organic
polymers.

2 Mechanical Dewatering
2.1 Belt Press
● Belt filter presses are continuous-feed sludge-dewatering devices
that involve the application of chemical conditioning, gravity
drainage, and mechanically applied pressure to dewater sludge.
Belt Press

Sludge Disposal and Utilization
1 Beneficial Uses of Sludge
● The fertilizer value of biological sludge, which should be evaluated
where the sludge is to be used as a soil conditioner, is based
primary on the content of nitrogen, phosphorus, and potassium.
2 Sludge Disposal
2.1 Landfilling
● There are two types of landfills for industrial sludge: those which
accept non-hazardous wastes and those that accept hazardous
wastes.
● Landfills are designed to prevent the contamination of ground
water and to prevent the migration of the wastes from the landfill.

Short Notes About Wastewater
For Textile Industry
● wastewater generated from textile industries characterized as
follows:
-High level of PH.
-Increase in total suspended solid (TSS).
-Increase in biological oxygen demand (BOD5).
-Increase in chemical oxygen demand (COD).

Sampling analysis
● Assume that the wastewater sample analysis for Textile industry
was as the following:
Analysis Result
COD 1800
mg/l
BOD 900
mg/l
TSS 1250
mg/l
TDS 1300
mg/l
pH 10

Wastewater Discharge
● Assume that Textile industry will discharge the wastewater after
treatment to Sewer System, so the target now is achieve Egyptian Law
93/62 (as modified by Decree 44/2000).
Parameters
(mg/l unless otherwise noted
(
Max. value according to law
44/2000
COD 1100
mg/L
BOD 600 mg/L
TSS 800 mg/L
TDS -
pH 6.5-9

Unit Processes For Textile
Industry
● All treatment technologies described earlier in chapter (2) can be
used to develop a model for sequential treatment of industrial
wastewater which can be described as follows and shown in the following
Figure.
● According to wastewater analysis for textile industry propose the
following unit processes.
-Screening (as a preliminary treatment).
- Coagulation and Flocculation Process (as a primary treatment).
- Sedimentation (as a primary treatment).
- Activated Sludge Process (as a secondary treatment).
- Sedimentation (as a secondary treatment).
- Sludge drying beds (Sludge treatment).

Block Diagram For
Textile Industry

Flow Chart For
Textile Industry

lec 4-3 industrial wastewater treatment1.pdf

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lec 4-3 industrial wastewater treatment1.pdf