Manufacturing processes & Wastewater characteristics for Thermal power plants

Manufacturing processes & Wastewater characteristics for Thermal power plants

Manufacturing processes & Wastewater characteristics for Steel plants

Manufacturing processes & Wastewater characteristics for Steel plants

Manufacturing processes & Wastewater characteristics for Textile industry

Manufacturing processes & Wastewater characteristics for Textile industry
Two types of wastes are generated in textile industries.
1. Process chemicals and
2. Process wastes
The nature of the waste generated depends on:
1. Type of textile facility
2. Processes and technologies and
3. Types of fibers and chemicals

Little or no wastewater is generated during the process of fiber preparation and yarn spinning
During slashing and sizing operations, the wastewater generated contains BOD, COD, metals, cleaning waste and size.
During weaving, knitting and tufting processes little or no wastewater is generated
Wastewater from desizing operations contains BOD from water soluble sizes, synthetic size, lubricants, biocides and anti-static compounds.
Wastewater from scouring operations contains disinfectants and insecticide residues, NaOH, detergents, fats, oils, pectin, wax, knitting lubricants, spin finishes and spent solvents
Bleaching process wastewater mainly contains hydrogen peroxide, sodium silicate and organic stabilizer and has a high pH
Singeing process yields little or no wastewater.
Mercerizing process in textile mills yields wastewater containing high pH and NaOH.
Little or no wastewater is generated during heatsetting processes
The dyeing process generates wastewater containing metals, salts, surfactants, toxics, organic processing assistants, cationic materials, colour, BOD, COD, sulphide, acidity, alkalinity and spent solvents
Printing process in textile industry produces wastewater containing suspended solids, urea, solvents, colour, metals, BOD, heat and foam
Finishing process in textile industry contains BOD, COD, suspended solids, toxics and spent solvents.
Finally, product fabrication produces little or no wastewater

Wastewater from the textile industry is classified into:
1. Dispersible wastes
Such wastes are highly dispersed and mixed with other wastes
2. Hard to treat wastes
Such wastes resist treatment and contain non biodegradable or inorganic substances that cannot be removed by conventional biological treatment methods
3. High volume wastes
Such wastes mainly contain wash water, alkaline waste and warp sizes
4. Hazardous or toxic wastes
Such wastes are a sub-group of hard-to-treat wastes. They contain metals, chlorinated solvents and non-degradable surfactants.

Acute toxicity of textile dyes leads to skin irritation, vomiting and diarrhea. Reactive dyes cause respiratory and skin problems.
The BOD/COD ratio of composite wastewater is around 0.25 implying that the wastewater contains a large amount of non-biodegradable organic matter.


In the primary treatment, the following sequence of operations is carried-out:
1. Screening
2. Sedimentation
3. Equalization
4. Neutralization
5. Chemical coagulation and
6. Mechanical flocculation
Screening and sedimentation helps remove organic color, suspended solids along with primary reduction of BOD and COD.
The conventional treatment is a physico-chemical treatment followed by a biological treatment system.
Sedimentation is sometimes combined with the equalization process.
Textile effluents are highly variable in terms of pH and extent of impurities
Individual process effluents affect the secondary treatment process due to the extreme variation in chemical characteristics from effluents from other processes. Hence, they are collected in a big tank and stirred continuously by rotating agitators or blowing compressed air from below. The tank has a conical bottom for enhancing the settling procces. Dilute sulphuric acid and boiler flue gas which is rich in carbondioxide is commonly used for neutralisation of alkaline effluents from neutralization. Chemical coagulation and mechanical flocculation are used to remove finely divided suspended solids and colloidal particles that cannot be removed by simple sedimentation by gravity.
Secondary treatment consists of aerated lagoon, trickling filter, activated sludge process and an oxidation pond. In this process, the dissolved and residual organic matter is removed in the aerobic or anaerobic mode. This is achieved by the digestive action of bacteria under suitable conditions. This helps to reduce the COD, BOD and toxicity.
Sometimes, an activated adsorption system along with an ozonation unit is used instead of biological treatment process.
The tertiary treatment process involves the following techniques:
Oxidation
Electrolytic precipitation and foam fractionation
Membrane technologies
Electrochemical processes
Ion exchange
Photocatalytic degradation
Adsorption and
Thermal evaporation

Adsorption is the most commonly used method for dye removal. It can also be used to remove toxic chemicals such as pesticides, phenols, cyanides and organic dyes.
It is an expensive process and the adsorbent should be re-activated resulting in 10 – 15 % loss of sorbent.
Other techniques used are:
1. Ion exchange
2. Membrane filtration
1. Activated carbon filter
2. Micron filter
3. Reverse osmosis
4. Post carbon filter
5. Ultraviolet light
Electrodialysis
Distillation
Advanced oxidation processes
Ozonation / UV radiation
Hydrogen peroxide / UV radiation

Hydrogen peroxide and ozone

Environmental legislation related to industrial effluents and hazardous wastes

Environmental legislation related to industrial effluents and hazardous wastes
The Hazardous Wastes (Management and Handling) Rules, 1989 came into effect on 28th July, 1989. These rules shall apply to hazardous wastes as specified in schedule and exclude waste water and exhaust gases as covered under the provisions of the Water act of 1974 and Air act of 1981. It also excludes wastes arising out of the operation from ships beyond five kilometres and  radio-active wastes. The following are the salient features under this act:

1. The occupier generating hazardous wastes specified in the Schedule in quantities equal to or exceeding the limits mentioned, shall take all practical steps to ensure that such wastes are properly handled and disposed of without any adverse effects which may result from such wastes and the occupier shall also be responsible for proper collection, reception, treatment, storage and disposal of these wastes either himself or through the operator of a facility.
2.  The occupier or any other person acting on his behalf who intends to get his hazardous waste treated shall give to the operator of a facility, such information as may be specified by the State Pollution Control Board.
3. The State Pollution Control Board may cancel an authorisation issued under these rules or suspend it if the authorised person has failed to comply with any of the conditions after giving the authorised person an opportunity to show cause and after recording reasons thereof.
4. Packaging, labelling and transport of hazardous wastes shall be in accordance with the provisions of the rules issued by the Central Government from time to time.
5.  The State Government shall undertake a continuing programme to identify the sites and compile and publish periodically an inventory of disposal sites within the State for the disposal of hazardous wastes.
6. The State Government shall undertake a continuing programme to compile and publish an inventory of sites within the State at which hazardous wastes have at any time been stored or disposed of and such inventory
7. The occupier generating hazardous waste and operator of a facility for collection, reception, treatment, transport, storage and disposal of hazardous waste shall maintain records of such operations in forms specified
8. The occupier and operator of a facility shall send annual returns to the State Pollution Control Board in forms specified
9. Where an accident occurs at the facility or on a hazardous waste site or during transportation of hazardous wastes, the occupier or operator of a facility shall report immediately to the State Pollution Control Board about the accident in forms specified.
10. The CPCB also sets guidelines regarding import of hazardous wastes.

Under the Air (prevention and control of air pollution) Act, 1981, 

1. State boards may lay down standards for emissions of air pollutants from industrial units
2. State boards should examine manufacturing process and pollution control equipment to verify if they meet standards prescribed
3. State board can advise the state government to declare heavily polluted areas as pollution control areas
4. Operation of Industrial unit is prohibited in heavily polluted areas without the consent of the central board.
5. Violation of this law is punishable with imprisonment a term which may extend to three months or fine upto Rs. 10,000 or both.

Water act came into effect in 1974 to prevent pollution of water by industrial, agricultural and household water.

Under the Water (prevention and control of air pollution) Act, 1984,

1. The water act is designed to assess pollution levels and punish polluter
2. The central government and state governments have set-up pollution control boards to monitor water pollution.
3. Central and state boards have been created under this act for preventing water pollution The act empowers the board to take:           -  water samples for analysis, govern discharge of sewage, trade effluents, study or inspect appeals, revision of policies, set minimum and maximum penalties, publication of names of offenders, offences by companies or government departments, establish or recognize water testing laboratories and standard testing procedures. Prevention and control of water pollution is achieved through a 'permit' or a 'consent administration' procedure

In addition to the above, the government has also enacted the water pollution cess act in 1977 requiring industrial consumers to pay cess depending on the type of use as listed below:

1. Industries using water for industrial cooling, spraying in mine pits or as boiler feed
2. Domestic purposes
3. Processing (pollutants are biodegradable. Eg: water from slaughter houses)
4. Processing (pollutants are not biodegradable and are toxic. Eg: water from tannery waste, industrial wastewater from electroplating industries)

Industries that have a treatment plant installed for treating their effluents can get a rebate of 70% on the cess payable.

Issues related to rehabilitation and resettlement of displaced communities

Issues related to rehabilitation and resettlement of displaced communities

Preparation of EIAs of road project, industry and dam

Preparation of EIAs of road project, industry and dam

EIA for road project
As per the EIA notification of 14th September 2006 and its amendment dated 1st December 2009,

highway projects are divided into two categories as mentioned below :

1. Highways New National Highways & Expansion of National Highways greater than 30 km,involving additional right of way greater than 20m involving land acquisition and passing through more than one State come under category A.
2. All state highway projects State highway expansion projects in hilly terrain (above 1,000 m AMSL) and or ecologically sensitive areas come under category B.

Any project or activity specified in category B will be treated as category A, if located in whole or in part within 10 km from the boundary of:

• Protected area identified by wildlife act
• Critically polluted areas as identified by CPCB
• Eco-sensitive areas identified by Environment (Protection) Act

The environmental clearance process for all projects will comprise a maximum of four stages. These four stages in sequential order are:

1. Screening that entails the scrutiny of an application seeking prior environmental clearance to determine whether or not the project or activity requires further environmental studies for preparation of an Environmental Impact Assessment (EIA) for its appraisal prior to the grant of environmental clearance depending upon the nature and location specificity of the project.
2. Scoping’ refers to detailed and comprehensive TOR addressing all relevant  environmental concerns for the preparation of an EIA report.
3. “Public consultation” refers to the process by which the concerns of local affected persons and others. After completion of the public consultation, the applicant shall address all the material environmental concerns expressed during this process, and make appropriate changes in the draft EIA and EMP.
4. Appraisal involves detailed scrutiny of the application and other document like the Final EIA report, outcome of the public consultations including public hearing proceedings, submitted by the applicant to the regulatory authority concerned for grant of Environmental Clearance (EC).

In terms of the EIA notification of the MOEF dated 14th September 2006, the structure of the EIA document shall be as listed below:

• Introduction
• Project Description
• Analysis of Alternatives (Technology and Site)
• Description of the Environment
• Anticipated Environmental Impact & Mitigation Measures
• Environmental Monitoring Program
• Additional Studies
• Project Benefits
• Environmental Cost Benefit Analysis
• Environmental Management Plan
• Summary & Conclusion
• Disclosure of Consultants engaged

EIA for building industry

The EIA Notification, 2006 is to set procedures of environmental clearance before establishment of identified nature and size. The suitability of site for a proposed development is one of the main concerns in awarding an environmental clearance to a project.

A project is considered B category if the built-up area is between 20,000 and 150,000 sq. m. or a township area greater than 50 ha or built-up area greater than 150,000 sq. m.

Any project or activity specified in category B will be treated as category A, if located in whole or in part within 10 km from the boundary of:

Protected area identified by wildlife act

Critically polluted areas as identified by CPCB

Eco-sensitive areas identified by Environment (Protection) Act

The prior environmental clearance granted is valid for a period of five years. The regulatory

authority concerned may extend this validity period by a maximum period of five years provided

an application is made to the regulatory authority by the applicant within the validity period

The structure of the EIA document listed below:

1. Introduction
2. Project Description
3. Description of the Environment
4. Anticipated Environmental Impacts & Mitigation Measures
5. Analysis of Alternatives (Technology and site)
6. Environmental Monitoring Programme
7. Additional Studies
8. Project Benefits
9. Environmental Management Plan
10. Summary & Conclusion
11. Disclosure of Consultants engaged

EIA for dam
An EIA for a dam project should discuss the following:

1. Location of the project, characteristics of the dam, total land area required, catchment area above the dam site,storage capacity and total cost of the project
2. It should clearly state  the need for the project
3. Based on facts and the guidance manual provided by the MoEF, the project should be classified as category A or category B enabling the decision makers to opt for a Rapid EIA (REIA) or a Comprehensive EIA (CEIA)
4. The study comprises of the following five stages
1. Determination of baseline conditions
2. Identification of differ

Preparation of EMP