Copy optimizing industrial wastewater treatment and management- november 2012- 23 sept [compatibility mode]

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Optimizing The Industrial Wastewater
Treatment and Management.

Water and wastewater management and
innovative solutions for a sustainable
environment Conference,
5-6 November 2012

Industrial Wastewater

The water or liquid carried waste from an industrial process

Optimizing The
Treatment and
Management.

These wastes may result from any process or activity of industry,
manufacture, trade or business, from the development of any
natural resource, or from animal operations such as feedlots,
poultry houses, or dairies
The term includes contaminated storm water and leachate from
solid waste facilities
Waste material (solid, gas or liquid) generated by a commercial,
industrial or nonresidential activity.

Dr. Helalley Abdel Hady Helalley
Chief of Industrial wastewater,
Sludge and Reuse Sector.
Drainage Co.

Alexandria Sanitary
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Water and wastewater management and innovative solutions for a sustainable environment Conference, 5-6 November 2012

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Advanced treatment processes are normally applied to industrial wastewater
only, for removal of specific contaminants. Advanced treatment is commonly
preceded by physicochemical coagulation and flocculation. Where a high

Advanced Cost Effective technology
and practices to treat toxic
wastewater pollutants.

quality effluent may be required for protection of public sewerage system
containing sensitive biological treatment plants, wastewater reuse options
and sludge used as fertilizer where the occurrence of toxic materials should
not be present.

Advanced treatment steps may also be added to the
conventional treatment plant.


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Some most frequently used treatment methods are gathered in
Table 1. Many studies exist about the efficiency of single methods
or in combination. As there is no unit specifically designed to
remove these compounds, the elimination by most WWTPs seems
to beinefficient (Castiglioni et al., 2006; Nakada et al., 2006;
Castiglioni et al, 2006; Xu et al., 2007; Gulkowska et al., 2008).

Advanced Cost Effective technologies


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Advanced Cost Effective technologies
1. Membrane filtration technologies
Membrane filtration can be broadly defined as a separation process that uses semi
permeable membrane to divide the feed stream into two portions: a permeate that
contains the material passing through the membranes, and a retentate consisting of the
species being left behind.
More specifically, membrane filtration can be further classified in terms of the size
range of permeating species, the mechanisms of rejection, the driving forces employed,
the chemical structure and composition of membranes, and the geometry of
construction.
The most important types of membrane filtration are pressure driven processes
including microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse
osmosis (RO).

Table 1. Advances treatment techniques
Process Abbreviation (or unit)
Powdered activated carbon
Granular activated carbon
Membranes
MF, UF, NF, RO
Membrane bioreactors
MBR
Chlorination
(As Cl2)
Ozonation
(As O3)
Advanced oxidation processes
Sonication
US


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PAC
GAC

AOP


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1.a. Ultrafiltration/Nanofiltration.
1.b. Reverse Osmosis.
Reverse osmosis is a membrane separation technology used by industrial
facilities for chemical recovery and water recycling.
Reverse osmosis removes ionic salts and other molecules by selective
filtration. It appears to be a viable treatment for removal of most EDCs/PPCPs
in drinking water, except for neutral low molecular weight compounds.
Reverse osmosis achieved >90% removal of natural steroid hormones in one
study.
A combination of reverse osmosis with nanofiltration can result in very
efficient PPCP removal, including a wide range of pesticides, alkyl phthalates,
and estrogens. Reverse osmosis and nanofiltration foul quickly in the
treatment of wastewater, making them prohibitively expensive.

Water is forced through semipermeable membranes that filter out very small
particulates (ultrafiltration) and dissolved molecules (nanofiltration). A study of 52
EDC/PPCPs in modeled and natural waters found that nanofiltration exceeded
ultrafiltration in EDC/PPCP removal. Nanotfiltration removal efficiencies were
between 44-93%, except for naproxen (0% removal), while ultrafiltration removal
was typically less than 40%.
Nanofiltration retains these compounds on the membrane both through
hydrophobic adsorption and size exclusion, while ultrafiltration retention is typically
due to hydrophobic adsorption.
However, these systems foul quickly when used on wastewater systems, and are
reserved for use in drinking water treatment. These techniques are also highly
effective for the removal of pathogens.


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3. Advanced oxidation technologies
Advanced oxidation processes (AOPs) have been broadly defined as near
ambient temperature treatment processes based on highly reactive
radicals, especially the hydroxyl radical (·OH), as the primary oxidant.
The ·OH radical is among the strongest oxidizing species used in water and
wastewater treatment and offers the potential to greatly accelerate the
rates of contaminant oxidation.

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2. Granulated Activated Carbon (GAC).
Water is passed through a bed of activated carbon granules that adsorb
contaminants. GAC has been shown to be very effective at removing many
pharmaceuticals, except for clofibric acid.
Competition with organic matter in WWTP effluent for sorption sites can
reduce EDC and PPCP removal rates. EDC and PPCP removal depends on the
solubility of the compounds – more soluble, polar compounds are not
removed efficiently.
Powdered activated carbon has greater efficiencies of removal for some
pharmaceuticals, but is typically used in episodically to treat a specific
situation.


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a. Ozonation
Is an attractive and a well established technology for wastewater reuse
purposes. We studied the ozonation of pharmaceuticals in wastewater
from the secondary clarifier of urban and domestic STPs by using
alkaline ozone and a combination of ozone and hydrogen peroxide.
Alkaline ozonation achieved only a moderate degree of mineralization
essentially concentrated during the first few minutes; but the addition
of hydrogen peroxide eventually led to a complete mineralization

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AOPs can be broadly defined as redox methods which are based on the
intermediacy ofreactive oxygen species, such as hydroxyl radicals, •OH,
superoxide radical anions, O2 •-, and perhydroxyl radicals HO2 •, to convert
harmful organic and inorganic pollutants found in air, water and soil to less
hazardous compounds. The most widely used AOPs include ozonation,
electrochemical oxidation, Fenton’s and photo-Fenton’s reagent,
heterogeneous semiconductor photocatalysis, wet air oxidation, and
sonolysis, among others2. A brief description of these technologies is given
below.


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c. Electrolytic Recovery
Electrolytic recovery is an electrochemical process used to recover metal
contaminants from many types of process solutions and rinses, such as
electroplating rinse waters and baths.
Electrolytic recovery removes metal ions from a waste stream by processing the
stream in an electrolytic cell, which consists of a closely spaced anode and cathode.
Equipment consists of one or more cells, a transfer pump, and a rectifier.
Current is applied across the cell and metal cations are deposited on the cathodes.
The waste stream is usually recirculated through the cell from a separate tank, such
as a drag-out recovery rinse.

b. Electrodialysis
Electrodialysis is a process in which dissolved colloidal species are
exchanged between two liquids through selective semipermeable
membranes (11). The technology applies a direct current across a series of
alternating anion and cation exchange membranes to remove dissolved
metal salts and other ionic constituents from solutions.
By using the electrodialysis cell, facilities remove impurities from the process
bath, extending its life. Facilities can treat the removed concentrate stream
on-site, or haul it off-site for disposal, treatment, or metals reclamation.


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d. Ion Exchange (in-process)

Polishing Technologies

Ion exchange is a commonly used technology within MP&M facilities. In
addition to water recycling and chemical recovery applications, ion exchange is
used to soften or deionize raw water for process solutions. Figure 8-6 shows a
typical ion-exchange system.
Ion exchange is a reversible chemical reaction that exchanges ions in a feed
stream for ions of like charge on the surface of an ion-exchange resin. Resins are
broadly divided into cationic or anionic types. Typical cation resins exchange H+
for other cations, while anion resins exchange OH-for other anions (10).


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1. Multimedia Filtration
Sand filtration and multimedia filtration systems typically remove small amounts
of suspended solids (metal precipitates) entrained in effluent from gravity
clarifiers. Sand and multimedia polishing filters usually are designed to remove 90
percent or greater of all filterable suspended solids 20 microns or larger at a
maximum influent concentration of 40 mg/L.

Polishing Technologies

Wastewater is pumped from a holding tank through the filter. The principal
design factor for the filter is the hydraulic loading. Typical hydraulic loadings range
between 4 and 5 gpm/ft2 (9).

These systems also can act as a temporary measure to prevent pollutant
discharge should the primary solids removal system fail due to a process
upset or catastrophic event. The following are descriptions of end-of-pipe
polishing technologies that are applicable to industrial facilities.

Sand and multimedia filters are cleaned by backwashing with clean water.
Backwashing is timed to prevent breakthrough of the suspended solids into the
effluent. Figure 8-16 shows a diagram of a multimedia filtration system.

Polishing systems remove small amounts of pollutants that may remain in
the effluent after treatment using technologies such as chemical
precipitation and gravity clarification.


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3. Reverse Osmosis

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2. Activated Carbon Adsorption

Reverse osmosis is a membrane separation technology used by industrial facilities as
an in-process step or as an end-of-pipe treatment.
In an end-of-pipe application, reverse osmosis typically recycles water and reduces
discharge volume rather than recovers chemicals. The effluent from a conventional
treatment system generally has a TDS concentration unacceptable for most rinsing
operations, and cannot be recycled.
Reverse osmosis with or without some pretreatment can replace TDS concentrations,
and the resulting effluent stream can be used for most rinsing operations.

Activated carbon adsorption is a common method of removing organic
contaminants from electroplating baths. Process solution flows through a filter
where the carbon adsorbs organic impurities that result from the breakdown of
bath constituents.
Carbon adsorption can be either a continuous or batch operation, depending on
the site’s preference. Carbon treatment is most commonly applied to nickel,
copper, zinc, and cadmium electroplating baths but also can be used to remove
organic contaminants from paint curtains.


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4. Ion Exchange

Choosing the right technology for the industry
to meet discharge limits of the local sewer.

Ion exchange is both an in-process metals recovery and recycle and end-ofpipe polishing technology.
This technology generally uses cation resins to remove metals but
sometimes uses both cation and anion columns. The regenerant from endof-pipe ion exchange is not usually amenable to metals recovery as it
typically contains multiple metals at low concentrations.


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Regulations

Many industries discharge to a sanitary sewer that
goes to a municipal treatment plant Industrial
discharges regulated by authority operating the
municipal treatment plant and Industry may be
required to obtain a discharge permit or authorization,
depending on type of waste .


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Choosing the right technology
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EPA considers a number of different sub categorization factors
during an effluent guidelines rulemaking, including the
following:
Manufacturing products and processes.
Raw materials.

Discharge limits of the local sewer.

Wastewater characteristics.
Facility size.
Geographical location.
Age of facility and equipment.
Wastewater treatability.


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Technology Selection for industries to meet
limits of discharge of the local sewer.

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Egyptian
Regulations
of disposal of
industrial
effluent to
public
sewers.


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The general criteria for technology selection comprise:

- Average, or typical, efficiency and performance of the technology.

Technology selection eventually depends upon
industrial wastewater characteristics and on
the treatment objectives as translated into
desired effluent quality. Also the type of
wastewater treatment technology selects
depends on the manufacturing operations
generating the wastewater.

- Reliability of the technology. The process should, preferably, be stable and
resilient against shock loading, i.e. it should be able to continue operation and to
produce an acceptable effluent under unusual conditions.
- Institutional manageability.
- Financial sustainability. The lower the financial costs, the more attractive the
technology.
- Application in reuse schemes. Resource recovery contributes to environmental
as well as to financial sustainability.


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Considerations to be taken into account when determining best available techniques
should bear in mind the likely costs and benefits of a measure and the principles of
precaution and prevention. For instance, consideration should
be taken of:

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The best available technology

The best available technology is generally accessible technology, which
is the most effective in preventing or minimizing pollution emissions. It can

a. the use of low-waste technology

also refer to the most recent treatment technology available. Assessing

b. the use of less hazardous substances;
c. furthering recovery and recycling of substances and waste (where appropriate)
generated and used in the process;
d. comparable processes, facilities or methods of operation which have been tried with
success on an industrial scale;

whether a certain technology is the best available requires comparative
technical assessment of the different treatment processes, their facilities
and their methods of operation which have been recently and
successfully applied for a prolonged period of time, at full scale.

e. technological advances and changes in scientific knowledge and understanding;


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Criteria that influence selection of the wastewater treatment process:
•Reliability
•Resistance to hydraulic shocks
•Resistance to organic loading shocks
•Coordination with local climate
•Coordination with local facilities
•Flexibility in operation
•Simple in operation and maintenance
•Capital cost
•Land requirement
•Operation and maintenance cost
•Sludge disposal cost
•Reach to treatment degree requirement
•Odor generation
•Risk
•Amount of sludge generation
•Environment impacts

f. the nature, effects and volume of the emissions concerned;
g. the commissioning dates for new or existing installations;
h. the length of time needed to introduce the best available technique;
i. the consumption and nature of raw materials (including water) used in the process
and their energy efficiency;
j. the need to prevent or reduce to a minimum the overall impact of the emissions
on the environment and
k. the risks to it;
l. the need to prevent accidents and to minimize the consequences for the
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Important factors that must be considered when evaluating and selecting unit
operations and processes
Factor

Comment

1.Process applicability

The process should be matched to the expected range of flowrate. For example,
stabilization ponds are not suitable for extremely large flowrates in highly
populated areas.

3.Applicable flow variation

Most unit operations and processes have to be designed to operate over a wide
range of flowrates. Most processes work best at a relatively constant flowrate. If
the flow variation is too great, flow equalization may be necessary.

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Introduction to Process Selection

The applicability of a process is evaluated on the basis of past experience, data
from full-scale plants, published data, and from pilot-plant studies. If new or
unusual conditions are encountered, pilot-plant studies are essential.

2.Applicable flow range


The purpose of process analysis is to select the most suitable unit
operations and processes and the optimum operational criteria.

Important Factors in Process Selection
The first factor, ‘process applicability,’ stands out above all others
and reflects directly upon the skill and experience of the design
engineer.
Available resources include performance data from operating
installations, published information in technical journals, manuals
of practice published by the Water Environment Federation,
process design manuals published by EPA, and the results of pilotplant studies.


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8.Process sizing based on
mass transfer rates or
process loading criteria

Reactor sizing is based on mass transfer coefficients, If mass transfer rates
are not available, process loading criteria are used. Data for mass transfer
coefficients and process loading criteria usually are derived from
experience, published literature, and the results of pilot-plant studies.

9.Performance

The types and amounts of solid, liquid, and gaseous residuals produced
must be known or estimated. Often, pilot-plant studies are used to identify
and quantify residuals.

11.Sludge processing

Are there any constraints that would make sludge processing and disposal
infeasible or expensive? How might recycle loads from sludge processing
affect the liquid unit operation or processes? The selection of the sludge
processing system should go hand in hand with the selection of the liquid
treatment system

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Performance is usually measured in terms of effluent quality and its
variability, which must be consistent with the effluent discharge
requirements

10.Treatment residuals


4.Influent
characteristics


wastewater

The characteristics of the influent wastewater affect the types of processes to
be used (e.g.,chemical or biological) and the requirements for their proper
operation.

5.Inhibiting and unaffected
constituents

What constituents are present and may be inhibitory to the treatment
processes?
What constituents are not affected during treatment?

6.Climatic constraints

Temperature affects the rate of reaction of most chemical and biological
processes.
Temperature may also affect the physical operation of the facilities.
Temperatures may accelerate odor generation and also limit atmospheric
dispersion.

7.Process sizing based on
reaction kinetics or process
loading criteria

Reactor sizing is based on the governing reaction kinetics and kinetic
coefficients. If kinetic expressions are not available, process loading criteria are
used. Data for kinetic expressions and process loading criteria usually are
derived from experience, published literature, and the results of pilot-plant
studies


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12.Environmental
constraints

Environment factors, such as prevailing wind directions and proximity to
residential areas, may restrict or affect the use of certain processes, especially
where odors may be produced. Noise and traffic may affect selection of a plant
site. Receiving waters may have special limitations, requiring the removal of
specific constituents such as nutrients.

13.Chemical requirements

What resources and what amounts must be committed for a long period of time
for the successful operation of the unit operation or process? What effects might
the addition of chemicals have on the characteristics of the treatment residuals
and the cost of treatment?

14.Energy requirements

The energy requirements, as well as probable future energy cost, must be
known if cost-effective treatment systems are to be designed.

The best way for Industry to control and treat wastes is subject to Best
Management Practices (BMPs) .BMPs

Goal is to prevent or reduce the discharge of pollutants to public
seawares where Industry can look at:
overall processes
Scheduling of activities
Prohibitions of practices
Maintenance procedures


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1. Zero Exhaust Technology
Zero waste is an integrated system approach that aims to eliminate rather than only
manage waste. By encouraging waste diversion from landfill and incineration, it is a
guiding design philosophy for eliminating waste at source and at all points down the
supply chain. It rejects the current one-way linear resource use and disposal culture in
favour of a closed-loop system modelled on strategies found in nature.

Preferable technologies

Therefore, the zero emission approach represents a shift from the traditional industrial
model in which wastes are considered as the norm, to integrated systems in which
everything has its use. It advocates an industrial transformation whereby businesses
minimise the load they impose on the natural resource base and learn to do more with
what the Earth produces.


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The zero waste approach envisions all industrial inputs being used in final
products and product service systems or converted into value-added
inputs for other industries or processes. In this way, industries will be
organized in clusters in order that each industry's by-products are fully
matched with the input requirements of another industry. Finally, the
integrated whole system produces no waste.
From an environmental perspective, the elimination of waste represents
the ultimate solution to pollution problems that threaten ecosystems at
global, national and local levels. In addition, full use of raw materials,
accompanied by a shift towards renewable sources, means that utilization
of the Earth's resources can be brought back to sustainable levels.

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Zero waste is an Targeting the whole system means striving for:
· Zero waste of resources: Energy, Materials, Human;
· Zero emissions: Air, Soil, Water;
· Zero waste in activities: Administration, Production;
· Zero waste in product life: Transportation, Use, End of Life; and
· Zero use of toxics: Processes and Products.


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2. Clean Production Technology

Cleaner Production results from one or a combination of conserving
raw materials, water and energy; eliminating toxic and dangerous
raw materials; and reducing the quantity and toxicity of all emissions
and wastes at source during the production process.
Cleaner Production aims to reduce the environmental, health and
safety impacts of products over their entire life cycles, from raw
materials extraction, through manufacturing and use, to the
'ultimate‘ disposal of the product.

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2. Clean Production Technology

‘Cleaner Production is the continuous application of an integrated
preventive environmental strategy to processes, products, and services
to increase overall efficiency, and reduce risks to humans and the
environment. Cleaner Production can be applied to the processes used in
any industry, to products themselves and to various services provided in
society.


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All the previous techniques leads to sustainability
Sustainability has been defined as the goal of sustainable development, which is
‘types of economic and social development that protect and enhance the natural
environment and social equity’
(Diesendorf 2000: 23).

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Where practical, waste should be minimized (using cleaner production
protocols and recycling techniques to a maximum practical extent) before
consideration is given to allowing any discharge into the
environment/disposal in the most environmentally acceptable manner. Some
waste may require disposal at an authorized disposal site.
Some of the benefits for adopting cleaner production practices include a
reduction in expenditure for packaging, energy, waste treatment or disposal,
water and materials, increased employee environmental awareness and an
improved public perception of the business.


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Pretreatment technologies of

Conventional technologies of
Industrial Wastewater Treatment

pH neutralization
Temp regulations
Solids separation
Toxic metal removal

Treatment needed will depend on the type and
concentration of pollutants in the wastewater

Oil and grease


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Environment-friendly technology
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The suitable environment-friendly technology
selection to minimize the amount and toxicity of
the industrial waste generated depends on the
manufacturing operations generating the
wastewater and the industrial waste water quality .

Using environment-friendly technology
to minimize the amount and toxicity of
the industrial waste generated.


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Waste Water hierarchy
WASTE WATER MANAGEMENT HIERARCHY

A logical waste management hierarchy would be based on the principal
that pollution should be prevented or reduced at the source wherever
feasible, while pollutants that cannot be prevented should be recycled in
an environmentally safe manner. In the absence of feasible prevention or
recycling opportunities, pollution should be treated. Disposal or other
release into the environment should be used as a last resort.


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1. Pollution prevention
Recent and Preferable friendly options the
The pollution prevention practices and wastewater treatment
technologies are used to prevent the generation of wastewater
pollutants and reduce the discharge of wastewater pollutants .

most economical, feasible and
environmental sound for industries
minimizing toxicity of the industrial waste


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pollution prevention measures include the following:
a. Training and Supervision
Training and supervision ensure that employees are aware of, understand, and
support the company’s pollution prevention goals. Effective training programs
translate these goals into practical information that enables employees to minimize
waste generation by properly and efficiently using tools, supplies, equipment, and
materials.
b. Production Planning
Production planning can minimize the number of process operation steps and
eliminate unnecessary procedures (e.g., production planning can eliminate
additional cleaning steps between process operations).

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Pollution Prevention is generally defined as any in-plant process that reduces,
avoids, or eliminates the use of toxic materials and/or the generation of pollutants
and wastes so as to reduce risks to human health and the environment and to
preserve natural resources through greater efficiency and conservation. The goal
of pollution prevention is to minimize environmental risks by reducing or
eliminating the source of risk (rather than reactively through treatment and
disposal of wastes generated).

There are significant opportunities for industry to reduce or
prevent pollution at the source through cost-effective changes
in production, operation, and raw materials use. The
opportunities for source reduction are not often realized
because existing environmental regulations, and the industrial
resources they require for compliance focus upon treatment
and disposal, rather than source reduction. Source reduction is
different and more desirable than waste management and
pollution control.


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c. Process or Equipment Modification
Facilities can modify processes and equipment to minimize the amount of waste
generated (e.g., changing rack configuration to reduce drag-out).

f. Waste Segregation and Separation
Facilities should avoid mixing different types of wastes or mixing hazardous wastes
with nonhazardous wastes. Similarly, facilities should not mix recyclable materials with
noncompatible materials or wastes. For example, facilities can segregate scrap metal
by metal type, separate cyanide-bearing wastewater for preliminary treatment, and
segregate coolants for recycling or treatment.

d. Raw Material and Product Substitution or Elimination
Where possible, facilities should replace toxic or hazardous raw materials or
products with other materials that produce less waste and less toxic waste (e.g.,
replacing chromium-bearing solutions with non-chromium-bearing and less toxic
solutions, or consolidating types of cleaning solutions and machining coolants).

g. Closed-Loop Recycling

e. Loss Prevention and Housekeeping

Facilities can recover and reuse some process streams. For
example, some facilities can use ion exchange to recover
metal from electroplating rinse water, reuse the rinse water,
and reuse the regenerant solution as process solution
make-up.

Loss prevention and housekeeping includes performing
preventive maintenance and managing equipment and
materials to minimize leaks, spills, evaporative losses, and
other releases (e.g., inspecting the integrity of tanks on a
regular basis; using chemical analyses instead of elapsed time
or number of parts processed as the basis for disposal of a
solution).


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2. Source Reduction
The most desirable option of the hierarchy and the most effective way to reduce risk is
through source reduction. Source reduction is defined as any method that reduces or
eliminates the source of pollution entirely. This includes any practice that:
. Reduces the amount of hazardous substances, pollutants, or contaminants entering a
waste stream or otherwise released into the environment prior to recycling, treatment,
or disposal; and
. Reduces hazards to public health and the environment associated with the release of
such substances, pollutants, or contaminants.

The term source reduction includes equipment or technology
modifications, process or procedure modifications, reformulation or
redesign of products, substitution of raw materials, and improvements
in housekeeping, maintenance, training, or inventory control.

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3.

Improving chemical wastewater treatment plant
efficiency and environmental compliance.

4.

5.


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Improving chemical wastewater treatment
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Applications of chemical unit process in wastewater treatment

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Chemical Unit Processes

Role Of Chemical Unit Processes In Wastewater Treatment
Application of Chemical Unit Processes
Currently the most important applications of chemical unit processes in
wastewater treatment are for:
(1) the disinfection of wastewater,
(2) the precipitation of phosphorus,
(3) the coagulation of particulate matter, (4)oxidation and reduction of
industrial pollutants.


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Fundamentals Of Chemical Coagulation

Colloidal particles found in wastewater typically have a net
negative surface charge. The size of colloids (about 0.01 to 1 m
and is such that the attractive body forces between particles are
considerably less than the repelling forces of the electrical charge.
Under these stable conditions, Brownian motion keeps the
particles in suspension.

μ

Coagulation is the process of destabilizing colloidal
particles so that particle growth can occur as a
result of particle collisions.


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Chemical Precipitation For Improved Plant Performance

In current practice, chemical precipitation is used

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Chemical Precipitation For Improved Plant Performance
Chemical precipitation, as noted previously, involves the addition of chemicals
to alter the physical state of dissolved and suspended solids and facilitate their

(1) as a means of improving the performance of primary settling
facilities,
(2) as a basic step in the independent physical-chemical
treatment of wastewater,

removal by sedimentation.
Since about 1970, the need to provide more complete removal of the organic
compounds and nutrients (nitrogen and phosphorus) contained in wastewater
has brought about renewed interest in chemical precipitation

(3) for the removal of phosphorus, and
(4) for the removal of heavy metals.


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Alum.
The insoluble aluminum hydroxide is a gelatinous floc that settles
slowly through the wastewater, sweeping out suspended material

Lime.
Much more lime is generally required when it is used alone

and producing other changes. The reaction is exactly analogous

than when sulfate of iron is also used where industrial wastes

when magnesium bicarbonate is substituted for the calcium salt.

introduce mineral acids or acid salts into the wastewater.
If less than this amount of alkalinity is available, it must be added.
Lime is commonly used for this purpose when necessary, but it is
seldom required in the treatment of wastewater.


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Independent Physical-Chemical Treatment
In some localities, industrial wastes have rendered municipal
wastewater difficult to treat by biological means.
In such situations, physical-chemical treatment may be an
alternative approach. This method of treatment has met with
limited success because of its lack of consistency in meeting
discharge requirements, high costs for chemicals, handling and
disposal of the great volumes of sludge resulting from the addition
of chemicals, and numerous operating problems.
Because of these reasons, new applications of physical-chemical
treatment for municipal wastewater are rare. Physical-chemical
treatment is used more extensively for the treatment of industrial
wastewater.

Enhanced Removal of Suspended Solids in
Primary Sedimentation

With chemical precipitation, it is possible to remove 80 to 90 percent
of the total suspended solids (TSS) including some colloidal particles,
50 to 80 percent of the BOD, and 80 to 90 percent of the bacteria.
Comparable removal values for well-designed and well-operated
primary sedimentation tanks without the addition of chemicals are
50 to 70 percent of the TSS, 25 to 40 percent of the BOD, and 25 to
75 percent of the bacteria.


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Typical flow diagram of an independent physicalchemical treatment plant

The filter is shown as optional, but its use is recommended to
reduce the blinding and headloss buildup in the carbon
columns.
The handling and disposal of the sludge resulting from chemical
precipitation is one of the greatest difficulties associated with
chemical treatment. Sludge is produced in great volume from
most chemical precipitation operations, often reaching 0.5
percent of the volume of wastewater treated when lime is used.


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Comparison of Chemical Phosphorus Removal Processes

Chemical Precipitation For Removal Of Heavy Metals
And Dissolved Inorganic Substances

Table: Advantages and disadvantages of chemical addition in various sections of a
treatment plant for phosphorus removal

The technologies available for the removal of heavy metals from wastewater
include chemical precipitation, carbon adsorption, ion exchange, and reverse
osmosis. Of these technologies, chemical precipitation is most commonly
employed for most of the metals.
Common precipitants include hydroxide (OH) and sulfide (S2-). Carbonate
(CO32-) has also been used in some special cases. Metal may be removed
separately or co precipitated with phosphorus.


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Table Solubility products for free metal ion concentrations in
equilibrium with hydroxides and sulfides

Precipitation Reactions
Metals of interest include arsenic (As), barium (Ba), cadmium (Cd), copper (Cu),
mercury (Hg), nickel (Ni), selenium (Se), and zinc (Zn).
In wastewater treatment facilities, metals are precipitated most commonly as
metal hydroxides through the addition of lime or caustic to a pH of minimum
solubility.
In practice, the minimum achievable residual metal concentrations will also
depend on the nature and concentration of the organic matter in the
wastewater as well as the temperature.


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Table Practical effluent concentration levels achievable in heavy metals
removal by precipitation

Chemical Oxidation
Chemical oxidation in wastewater treatment typically involves the use of oxidizing agents
such as ozone (O3), hydrogen peroxide (H202), permanganate (MnO4), chloride dioxide
(ClO2), chlorine (C12) or (HOC1), and oxygen (O2)

Advanced oxidation process (AOPs) in which the free hydroxyl radical (HO.) is used as a
strong oxidant to destroy specific organic constituents and compounds that cannot be
oxidized by conventional oxidants such as ozone and chlorine are discussed in later
chapters.


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Table Standard electrode potentials for oxidation half reactions
for chemical disinfection
Oxidation-Reduction Reactions.
While an oxidizing agent causes the oxidation to occur, it is reduced in the process.

Half-Reaction Potentials.
Of the many properties that can be used to characterize oxidation-reduction reactions, the
electrical potential (i.e., voltage) or emf of the half reaction is used most commonly.

The half-reaction potential is a measure of the tendency of a reaction to proceed to the

。

the left.

, tend to proceed to the right as


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, tend to proceed to

。

right. Half reactions with large positive potential, E

written. Conversely, half reactions with large negative potential, E


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Preliminary Treatment of industrial Wastewater Streams

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Table Typical applications of chemical oxidation in wastewater collection,
treatment, and disposal

Preliminary treatment systems reduce pollutant loadings in segregated waste streams prior to
combined end-of-pipe treatment. Wastewater containing pollutants such as Pollution Prevention
and Wastewater Treatment Technologies cyanide, hexavalent chromium, oil and grease, or
chelated metals may not be treated effectively by chemical precipitation and gravity settling
without preliminary treatment.
Proper segregation and treatment of these streams is critical for the successful treatment of
process wastewater. Highly concentrated metal-bearing wastewater also may require
pretreatment to reduce metal concentrations before end-of-pipe treatment. This subsection
describes the following wastewater streams that typically undergo
•Chromium-bearing wastewater;
• Concentrated metal-bearing wastewater;
•Cyanide-bearing wastewater;
• Chelated metal-bearing wastewater; and
• Oil-bearing wastewater


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Chemical treatment
Since lime is a base it is sometimes used in the neutralization of acid wastes.
Coagulation consists of the addition of a chemical that, through a chemical reaction, forms
an insoluble end product that serves to remove substances from the wastewater.
Polyvalent metals are commonly used as coagulating chemicals in wastewater treatment
and typical coagulants would include lime (that can also be used in neutralization), certain
iron containing compounds (such as ferric chloride or ferric sulfate) and alum (aluminum

Consists of using some chemical reaction or reactions to improve the water
quality.
Probably the most commonly used chemical process is chlorination. Chlorine,
a strong oxidizing chemical, is used to kill bacteria and to slow down the rate of
decomposition of the wastewater. Bacterial kill is achieved when vital
biological processes are affected by the chlorine.

sulfate).
Certain processes may actually be physical and chemical in nature. The use of activated

Another strong oxidizing agent that has also been used as an oxidizing
commonly disinfectant is ozone.

carbon to "adsorb" or remove organics, for example, involves both chemical and physical
processes. Processes such as ion exchange, which involves exchanging certain ions for
others, are not used to any great extent in wastewater treatment.

A chemical process used in many industrial wastewater treatment operations is
neutralization. Neutralization consists of the addition of acid or base to adjust
pH levels back to neutrality.


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Chemical Precipitation

Chemical precipitation is a highly reliable technology when properly
monitored and controlled. The effectiveness of this technology depends on
the types of equipment used and numerous operating factors, such as the
characteristics of the raw wastewater, types of treatment reagents used,
and operating pH. In some cases, subtle changes in operating factors (e.g.,
varying the pH, altering chemical dosage, or extending the process reaction
time) may sufficiently improve the system’s efficiency. In other cases,
modifications
to
the
treatment
system
are
necessary.

Chemical precipitation is a treatment technology in which chemicals (e.g.,
sulfides, hydroxides, and carbonates) react with organic and inorganic
pollutants present in wastewater to form insoluble precipitates.
This separation treatment technology is generally carried out in the following
four phases:
1. Addition of the chemical to the wastewater;
2. Rapid (flash) mixing to distribute the chemical homogeneously throughout the
wastewater;
3. Slow mixing to encourage flocculation (formation of the insoluble solid
precipitate); and
4. Filtration, settling, or decanting to remove the flocculated solid particles. These
four steps can be performed at ambient conditions and are well suited
to automatic control.


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Hydrolysis
The primary design parameter considered for hydrolysis is the half-life, which is the time

Hydrolysis is a chemical reaction in which organic constituents react with water

required to react 50% of the original compound. The half-life of a reaction generally

and break into smaller (and less toxic) compounds. Basically, hydrolysis is a

depends on the reaction pH and temperature and the reactant molecule (e.g., the

destructive technology in which the original molecule forms two or more new

pesticide active ingredient).

molecules. In some cases, the reaction continues and other products are
formed.

Hydrolysis reactions can be catalyzed at low pH, high pH, or both, depending on the
reactant molecule. In general, increasing the temperature increases the rate of hydrolysis.
Identifying the best conditions for the hydrolysis reaction results in a shorter half-life, thereby

Because some pesticide active ingredients react through this mechanism,
hydrolysis can be an effective treatment technology for PFPR wastewater.

reducing both the size of the reaction vessel required and the treatment time required.


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Advanced chemical processes

1. Ion Exchange
Ion exchange- although both natural and synthetic ion exchange resins
are available, synthetic resins are used more widely because of their
durability. Some natural zeolites (resins) are also used for the removal of
ammonia from wastewater.

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coagulation
Is an important operation in removing colloidal solids. In wastewater
treatment, chemical such as lime, ferric salts and commercial alum are
used as coagulants. This process removes suspended solids ( 60-80% ),
BOD ( 50-70% ) phosphorus ( over 90%) and heavy metal ( over 80%)
Chemical clarification of wastewater can be combined with the
activated carbon adsorption process to provide complete physical –
chemical wastewater treatment. the use of chemical clarification has
restricted application in developing countries because of its constant
requirement of consumable chemical and consequent higher running
costs.


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2. Electrochemical treatment

3. Electro dialysis
Ionic components of a solutions are separated through the use of semi

Wastewater is mixed with seawater and is passed into a single cell
containing carbon electrodes.

permeable ion-selective membranes. If the electrical potential is
applied between the two electrodes, which in turn causes a migration
of cations toward the negative electrode and migration of anions
towards the positive electrode. Due to the alternate spacing of cation
and anion permeable membranes, cells of concentrated and dilute
salts are formed.


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4. Oxidation and reduction
Oxidation - Chemical oxidation is used to remove ammonia, to reduce
the concentration of residual organics and to reduce bacterial and viral
contents of wastewater. At present on of the few process for the
removal of ammonical nitrogen , found operationally dependable , is
chlorination. Ammonia can be removed chemically by adding chlorine
or

hypochlorite

to

form

monochloramine

and

dichloramine

as

intermediate products and nitrogen gas and hydrochloric acid as end
products. Problem associate with this method is the presence of various
organic and inorganic compounds that will exert chlorine demand.
Chemical oxidation of organic material in wastewater.

. Principle of simple electrodialysis process. Diagram shows the membrane configuration with
alternating cation-selective (1)and anion-selective (2) membranes between two electrodes ((3)
and (4)), one at each end of the stack.


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Optimization of Existing Chemical Precipitation
Treatment System
5. Reduction
Nitrates present in wastewater can be reduced electrolytically or by
using strong reducing agents( e.g. ferrous oxide). The reaction must
Facilities can optimize the performance of an existing chemical precipitation
and clarification system using a variety of techniques such as adding
equalization prior to treatment, conducting jar testing to optimize treatment
chemistry, upgrading control systems, and providing operator training.

usually catalyzed while using reducing agents. The two step processes
using different reducing agents and catalysts are limited by the
availability of chemicals at low cost, and the fact that the treated
effluent and waste sludge may contain toxic compounds derived from
the chemicals used for catalyzing various reactions.


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1. Equalization
Equalization is simply the damping of flow and concentration variations to achieve
a constant or nearly constant wastewater treatment system loading (8).

2. Jar Testing
The purpose of jar testing is to optimize treatment pH, flocculent type and
dosage, the need for co precipitants such as iron or polymers , and solids
removal characteristics. Facilities should conduct jar testing on a sample of
their actual wastewater to provide reliable information.

Equalization improves treatment performance by providing a uniform hydraulic
loading to clarification equipment, and by damping mass loadings, which improves
chemical feed control and process reliability. MP&M facilities implement
equalization by placing a large collection tank ahead of the treatment system. All
process water and rinse water entering this tank are mixed mechanically and then
pumped or allowed to gravity flow to the treatment system at a constant rate. The
size (volume) of the tank depends on the facility flow variations throughout the day.
Operating data collected during MP&M sampling episodes indicate hydraulic
residence times for equalization tanks average 4 to 6 hours.


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3. Control System Upgrades
Typical treatment system controls at MP&M facilities includes pH and ORP

4. Operator Training

controllers on alkaline chlorination systems for cyanide destruction, pH

Having operators trained in both the theory and practical application of

controllers on chemical precipitation systems, flow and level monitoring

wastewater treatment is key to ensuring the systems are operating at their best.

equipment on equalization tanks, and solonoid valves and metering pumps on

Many MP&M facilities send their operators to off-site training centers while

chemical feed systems to provide accurate treatment chemical dosing. A

others bring consultants familiar with their facility’s operations and wastewater

number of MP&M facilities have computer hardware and software to monitor

treatment system to the facility to train operators. Some of the basic elements

and change treatment system operating parameters. For a number of MP&M

of an operator training course should include (1):

facilities, upgrading control equipment may reduce both pH and ORP swings
caused by excess chemical dosing, resulting in consistent effluent metals
concentrations.


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An explanation of the need for wastewater treatment, which emphasizes the
benefits to employees and the community;
An emphasis on management’s commitment to environmental stewardship;
An explanation of wastewater treatment terminology in simple terms;
An overview of the environmental regulations that govern the facility’s
First-time training for new operators may require 4 to 5 days of classroom
and hands-on study. Experienced MP&M wastewater treatment operators
should consider attending at least 1 day of refresher training per year to
update themselves on the chemistry and to learn about new equipment
on the market that may help their system’s performance.

wastewater discharges;
A simple overview of wastewater treatment chemistry;
Methods that can optimize treatment performance (e.g., how to conduct jar
testing);
The test methods or parameters used to verify the system is operating
properly (e.g., control systems); and
The importance of equipment maintenance to ensure the system is
operating at its maximum potential.


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References
ADVANCED TECHNOLOGIES FOR MICRO-POLLUTANTS REMOVAL FROM
WASTEWATER
Marjana Simonič
Faculty of Chemistry and Chemical Engineering, University of Maribor,
.Smetanova 17, 2000 Maribor, email: marjana.simonic@uni-mb.si
Selection of wastewater treatment process based on the analytical
hierarchy process and fuzzy analytical hierarchy process methods
1*A. R. K arimi; 1N. Mehrdadi; 2S. J. Hashemian; 1 G. R. Nabi

Bidhendi; 3R. Tavakkoli Moghaddam
1Faculty of the Environment, University of Tehran, Tehran, Iran
2Institute of Water and Energy, Sharif University of Technology, Tehran, Iran
3Department of Industrial Engineering, University of Tehran, Tehran, Iran

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References
Advanced technologies in water and wastewater treatment. H. Zhou and D.W. Smith
ADVANCED TECHNOLOGIES FOR WASTEWATER TREATMENT. Sixto Malato Rodríguez
Investigation on improving efficiency of pre-precipitation process at Sjölunda
wastewater treatment plant. Qianqian Zhou, February 2009
Reduce, Reuse and Recycle (the 3Rs) and Resource Efficiency as the basis for
Sustainable Waste Management. 9 May 2011, New York
EVALUATION OF OZONE WASTE WATER TREATMENTS AND STUDIES. EVALUATING
THE REUSE OF TREATED EFFLUENTS. Amadeo R. Fernández-Alba. University of
Almeria, Spain
Tools to Promote Sustainable Waste Management. K. Fricke1, T. Bahr1, Commercial
Printing Industry . Compliance & Pollution Prevention Workbook

Received 30 June 2010; revised 19 November 2010; accepted 21 December
2010; available online 1 March 2011


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