In today’s world chemicals are commonly used everywhere in society, with both positive and negative impacts on health, well-being, social & economic aspects and the environment. At international level chemicals management and regulations is still insignificant nonetheless the impacts of chemicals are very significant. Still Serious incidents occur and there are still adverse effects on both human health and surrounding environment, and it is an accepted reality that the environment can be save/conserved by chemical management at workplace. In addition, the proper management of chemicals has continued importance, specially according to the goals approved at the 2002 World Summit on Sustainable Development in Johannesburg to ensure that, by the end of year 2020, chemicals production and usage is in ways that lessen the significant adverse harmful impacts on the environment and people. So, the proper management of chemicals is very important for the safety of people and environment. The person responsible for chemicals management should ensure below points:
Prepare, update, maintain and implement the chemical safety plans
Maintain a record and manifest (if applicable) of hazardous chemicals and notify the regulator of obvious quantities if necessary
Identify the risk of physical or chemical reaction of hazardous chemicals and ensure the stability of dangerous chemical substances
Ensure that exposure standards are not exceeded
Provide health monitoring to workers
Provision of information, training, instruction and supervision for workers
Spill containment system provision for hazardous chemicals if required
Obtaining the latest MSDS (material safety data sheet) from the chemical suppliers
Providing the information in the local language
Ignition sources control and accumulation of flammable substances separately
Supply and availability of fire protection, fire extinguishing and emergency equipment and safety equipment
Prepare an emergency plan if the amount of a hazardous chemical class in a workplace exceeds the amount shown for this hazardous chemical
Keeping in mind the stability and support of pipes and containers for bulk of hazardous chemicals
Commissioning and decommissioning of storage areas and handling
If there is any waste notify the certified contractor for proper handling (reuse or incineration)
ETP treats the waste materials into neutralized molecule or reduces the harmful ingredients. Industrial wastewater treatment covers the mechanisms and processes used to treat waters that have been contaminated in some way by anthropogenic industrial or commercial activities prior to its release into the environment or its re-use.
In textile mills the waste water effluent contains:
Chemicals & Auxiliaries
They directly or indirectly effect the colour, alkalinity, pH, hardness, BOD, COD values of water.
What are the sources of waste water in Textile mills?
The main sources of waste water from textile process are:
Why treat waste water?
Waste water released from textile
processing units is treated in effluent treatment plants due to several reasons
Basic aim is Environmental protection
Corporate social responsibility
Maintenance of clean water
Conservation and protection of water for industrial and agricultural uses
Categories of Effluent Treatment Plant Processes
There are three (3)
Categories by nature of treatment being used in ETP as follows:
By degree of treatment:
There are 4 main types
of treatment in ETP by degree of treatment as follows:
Categories of treatment
in Degree of treatment does have physical, chemical, biological processes in
Preliminary treatment is mostly physical treatment
Primary treatment may contain both physical and
Secondary treatment also known as biological treatment
Tertiary treatment contains both chemical and
treatment processes further contain below mentioned processes in table
Screening Scraper Grit chamber Skimming tank Aeration
Sedimentation Clarification Flocculation Equalization Tank Neutralization tank
Activated Sludge Process Trickling filter Aerated Lagoons Oxidation Pond
Preliminary treatment get
rid of overweight solids and materials that can be easily collected from the
effluent and can harm or choke the pumps and skimmers of primary treatment
clarifiers. These are in-organic materials and insoluble organic pollutants
(i.e. huge floating and suspended solid material, gravel, oil & grease)
which are inert and cause problems to further chemical and biological
treatments. The presence and sequence of preliminary treatment units totally
depend on the characteristics of effluent that is to be treated. All
preliminary treatment consists of physical separation techniques by controlling
flow rate of effluent. The physical separation
techniques are as follows:
The influent sewage water is screened to remove all large objects like fabric parts, plastic packets, or any other container etc. According to size of the solid particles to be removed there are further three main types of screens
The purpose of
a scraper is to remove solids, produce a cleaner effluent and concentrate
solids. Concentration of solids removed from the wastewater reduces the volume
of sludge for dewatering and/or disposal.
chambers are long narrow tanks that are designed to slow down the flow so that
solids particles will settle out of the water. When waste flows into the grit
chamber, particles settle down to the bottom of the chamber based on their
size, their specific gravity, and the speed of roll in the tank
A skimming tank is a
chamber designed so that floating matter rises and remains on surface of the
wastewater until removed, while the liquid flows continuously through outlet or
partition below the water lines. Removes oils, greases, etc.
In this tank air is
used to remove the solid particles and oil and greasy materials.
In Primary treatment, sedimentation
process is used for most of the solids that can be settled are physically
separated or removed from the wastewater. When some chemicals are used in
primary sedimentation tanks, some of the mixture of solids(colloidal) are also
eliminated form waste water.
The process of primary
treatment is used to reduce the pace of the wastewater necessarily to permit
solids to settle and floatable material to surface. That’s why, primary devices
may contain settling tanks, clarifiers or sedimentation tanks. Because of
variations in design, operation, and application, settling tanks can be divided
into following groups:
In this tank as name presents, the solid particles
are allowed to settle down based on gravity. This process does take some time.
This process is also used to slow down the speed of the waste water flow.
A flocculent (chemical
substance) is added in waste water to increase the settling speed. Small
particle based on charge combine together and create large particles known as
flocs and settle down based on gravity.
The function of equalization
tanks is not only to act as holding tanks to help balance flow in
wastewater treatment processes, but to also act as an excellent holding zones
for other liquids, agents and chemicals added in the wastewater treatment
systems. Aeration might be required to maintain the waste water in original
phase during holding time.
most critical stage in most of the industrial waste water treatment processes
is the process of Neutralization. It is critical to neutralize the waste water
before going to biological process otherwise it could kill the bacteria or
process depends significantly on the aerobic organisms which biochemically degrade
the organic materials to inorganic or stable organic solids. It is similar to
the recovery zone in the self-purification of a stream.
removes dissolved and suspended biological matter. This is typically performed
by indigenous, water-borne micro-organisms in a managed habitat. This process
may require a separation process to remove the micro-organisms from the treated
water prior to discharge or tertiary treatment.
Activated Sludge Process:
It is a type of
wastewater treatment process for treating wastewater using aeration and a
biological floc composed of bacteria and protozoa. The method of Activated-sludge,
is a process in which sludge, the stored, bacteria-rich collections
of settling tanks and basins, is spread on the incoming waste water and the combination
is stirred for numerous hours in the presence of appropriate air supply.
Organic matter from
wastewater is removed by using trickling filters. The TF is an aerobic
treatment system that utilizes microorganisms attached to a medium to remove
organic matter from wastewater.
A bed of solid media on
the surface of which bacteria are attached is trickling filer. Wastewater is
irrigated on the solid media. It is also known as biological filter to make it
clear that its not a mechanical process.
The aerated lagoon (or
aerated pool) could be simply effluent treatment system consisting of a pond
with artificial aeration to endorse the biological oxidation of wastewaters. The Aeration process increases the efficiency
of treatment process, that can reduce energy costs in some cases. Lagoons with
aeration system needs less land area and shorter detention times.
Large cement tanks having 3-5 m depth.
Effluent coming from Primary Treatment is stored in these tanks for the
duration of 2-6 days which is then aerated mechanically. After aeration for 2-6
days, a healthy sludge in flocculent form is made, which performs the oxidation
of organic matter. It can removes upto 90% of BOD.
An oxidation pond is a
large shallow pond. Stabilization of organic matter is brought out by bacteria.
Oxygen is required for this purpose of metabolism and is supplied by algae. The
algae utilizes the carbon dioxide released by bacteria for photosynthesis.
Maximum sunlight penetration (for photosynthesis),
Wind action for mixing
Tertiary treatment is
the final treatment, meant for ‘polishing’ the effluent and removal of
pollutants not removed in previous treatment processes. These pollutants may
include soluble inorganic compounds such as phosphorous or nitrogen which may
support algae growth in receiving waters. Tertiary treatment also removes
organic materials that contribute to color, taste, odor, bacteria, viruses, BOD,
COD, or other soluble minerals that can interfere with ultimate re-use of the wastewater.
Preferred when treated water is need to be reuse or discharge is into the
It produces high
quality effluent which can be reuse further for commercial and industrial
applications. Treated water can be reuse for the irrigation of a golf course,
green way or park, construction work, industrial process, etc. If the water is
satisfactorily clean then it can also be used for recharge of groundwater. Sometimes,
the treated water is disinfected by chemicals or physically depending on the location
The Sand Filters are specifically
designed to remove additional Biological Oxygen Demand (BOD) and Suspended
Solids (SS) from sewage and Effluent treatment plants. This low cost and low
maintenance sand filter tertiary treatment technique is an ideal addition for
new and existing (permanent or temporary) process units. Sand filters have the
capacity to produce high-quality water without even using chemicals additives.
Passing flocculated water through a rapid gravity sand filter strains out the
floc and the particles trapped within it, reducing numbers of bacteria and
removing most of the solids. Sand of varying grades is used as the medium for
Activated Carbon Filters
It is used in
treatments plants to remove micropollutants or difficult
contaminants from industrial effluents. Carbon filtering is a method of filtering that utilizes a bed of
activated carbon to remove pollutants and impurities, using chemical
absorption. Each particle/granule of carbon provides a large surface area/pore
structure, allowing contaminants the maximum possible exposure to the active
sites within the filter media.
The killing or removal of pathogenic microorganisms or their
deactivation is known as water disinfection. Destruction or deactivation of
microorganisms results in closure of their reproduction and growth. Physical or
chemicals disinfectants are means through which disinfection can be achieved.
Several acids and bases etc.
Ultraviolet light (UV)
The exchange of irons
between an electrolyte solution, and a complex or between two electrodes is
called ion exchange.
The term ion exchange
is significantly used in case of purification process, decontamination, or separation
of aqueous and other solutions that contain ions with the use of solid or mineral
Through this process it
is possible to regenerate resins. It has low initial cost. Ion exchange method
is extensively used to remove hardness, iron and magnesium salts. But is does not removes bacteria effectively.
This process is most commonly used to recover H2SO4 , Cu, Pb, Hg, Cr, Ni, and also the removal of cyanides after recovery of Cr. from waste water Majorly used for recovery of Cr, Ni, Phosphate and H2SO4, Cu, Pb, Hg and removal of cyanides from wastewater after Cr recovery.