ABSTRACT
Disasters occur due to both the natural and man-made activities. Hazards and Disasters are categorized into four groups, viz., Natural events, Technological events, Man-made events and Region-wise events. The adverse impacts caused due to the indiscriminate disposal of Hazardous Wastes (HWs) come under the category of Environmental Disasters. Hazardous Waste Management (HWM) is a very important issue and is assuming significance globally. Very few industries in India, mostly in large scale and a few in medium scale, own proper treatment and disposal facilities. A common waste treatment and disposal facility such as Treatment, Storage and Disposal Facility (TSDF) for management of HWs generated from industries, is one of the useful options under such conditions. Few Guidelines issued by Ministry of Environment and Forests under Hazardous Wastes (Management & Handling) Rules, 1989 promulgated under Environment (Protection) Act, 1986 are available in India for selection of best site for TSDF. The planning for HWM comprises of several aspects ranging from identification and quantification of HW to development and monitoring of TSDF.
This report work aims at studying various methods used in managing hazardous wastes which can be effectively applied in developing countries like INDIA.
CHAPTER 1
INTRODUCTION
A hazardous waste is any waste or combination of wastes that poses a substantial danger, now or in the future, to human, plant or animal life and which therefore cannot be handled or disposed of without special precautions. The Hazards and Disasters can be classified into four categories viz., Natural events, Technological events, Man-made events and Region-wise events. The adverse impacts caused due to the indiscriminate disposal of Hazardous Wastes (HWs) come under the category of Environmental Disasters. For example, in 1982, 2242 residents are evacuated after dioxin is found in soil in Missouri, U.S.A. In 1996-97, 265354 tonnes of soil and other dioxin-contaminated material from Times Beach (Missouri, U.S.A) and 26 other sites in eastern Missouri had been incinerated. Release of Methyl Isocyanate (MIC) gas in Bhopal (1984) caused a severe disaster in India. So there is a growing concern all over the world for the safe disposal of hazardous waste generated from anthropogenic sources.
CHAPTER 2
CLASSIFICATION OF HAZARDOUS WASTE
US EPA has designated five categories considered as hazardous:
1. Specific type of wastes from nonspecific sources:a. halogenated &non-halogenated solvents
b. electro-plating sludges
c. cyanide solutions from plating batches
2. Specific types of wastes from specific sources;
a. oven residue from production of chrome oxide green segments
b. brine purification muds from the mercury cell process in chlorine production
3. Specific substances identified as acute hazardous waste:
a. potassium silver cyanide,
b. toxaphene
c. arsenic oxide.
4. Specific substances identified as hazardous wastes
e.g. Xylene, DDT, carbon tetrachloride
5. Characteristic wastes:
Wastes not specifically identified elsewhere exhibiting properties of:
ignitability, corrosivity, reactivity, or toxicity
2.1.CHARACTERISTIC WASTES
Waste that have not been specifically listed may still be considered a hazardous waste if exhibits one of the four characteristics - ignitability, corrosivity, reactivity , and toxicity. · Ignitability - Ignitable wastes can create fires under certain conditions, are spontaneously combustible, or have a flash point less than. Examples include waste oils and used solvents. Test methods that may be used to determine ignitability include the Pensky-Martens Closed-Cup Method for Determining Ignitability, the Set a flash Closed-Cup Method for Determining Ignitability, and the Ignitability of Solids. · Corrosivity - Corrosive wastes are acids or bases (pH less than or equal to 2, or greater than or equal to 12.5) that are capable of corroding metal containers, such as storage tanks, drums, and barrels. Battery acid is an example. The test method that may be used to determine corrosivity is the Corrosivity Towards Steel . · Reactivity - Reactive wastes are unstable under "normal" conditions. They can cause explosions, toxic fumes, gases, or vapors when heated, compressed, or mixed with water. Examples include lithium-sulfur batteries and explosives. There are currently no test methods available. · Toxicity - Toxic wastes are harmful or fatal when ingested or absorbed (e.g., containing mercury, lead, etc.). When toxic wastes are land disposed, contaminated liquid may leach from the waste and pollute ground water. Toxicity is defined through a laboratory procedure called the Toxicity Characteristic Leaching Procedure (TCLP). The TCLP helps identify wastes likely to leach concentrations of contaminants that may be harmful to human health or the environment.
Symbols used for identifying characteristic wastes
CHAPTER 3
BASIC APPROACH IN HAZRDOUS WASTE MANAGEMENT
A logical priority in managing hazardous waste would be to:
1. Reduce the amount of hazardous wastes generated in the first place.
2. Stimulate “waste exchange”:
· One factory’s hazardous wastes can become another’s feedstock; e.g. acid and solvent wastes from some industries can be utilized by others without processing.
3. Recycle metals, the energy content, and other useful resources contained in hazardous wastes.
4. Detoxify and neutralize liquid hazardous waste streams by chemical and biological treatment.
5. Destroy combustible hazardous wastes in special high-temperature incinerators equipped with proper pollution control and monitoring systems.
6. Dispose of remaining treated residues in specially designed landfills.
7. Treatment, storage, disposal facility(TSDF) requirements-
· Treatment: Any method, technique, or process, including neutralization, designed to change the physical, chemical, or biological character or composition of any hazardous waste so as to neutralize it or render it nonhazardous or less hazardous; to recover it; make it safer to transport, store, or dispose of; or make it amenable for recovery, storage, or volume reduction.
· Storage: The holding of hazardous waste for a temporary period, at the end of which the hazardous waste is treated, disposed, or stored elsewhere.
· Disposal: The discharge, deposit, injection, dumping, spilling, leaking, or placing of any solid waste or hazardous waste into or on any land or water so that any constituent thereof may enter the environment or be emitted into the air or discharged into any waters, including ground waters.
3.1.1. Waste minimisation Waste minimisation is the process and the policy of reducing the amount of waste produced by a person or a society. Waste minimisation involves efforts to minimise resource and energy use during manufacture. For the same commercial output, usually the fewer materials are used, the less waste is produced. Waste minimisation usually requires knowledge of the production process, cradle-to-grave analysis (the tracking of materials from their extraction to their return to earth) and detailed knowledge of the composition of the waste. 3.1.2. Waste exchange · Excess unused materials for sale to a third party saves in waste production and in the cost (environmental and financial) of production from new raw materials.
· Rule is “one person’s trash becomes another person’s treasure.”
Ø difference between a manufacturing byproduct (costly to treat or dispose) and a usable or salable byproduct involves opportunity.
Ø knowledge of processes outside the generator’s immediate production line, and comparative pricing of virgin material.
· Waste exchanges serve as information clearinghouses through which the availability and need for various types of materials can be established. 3.1.3. Recycling
· EPA has carefully defined recycling to prohibit bogus recyclers that are really TSDs from taking advantage of more lenient rules for recycling.
· A material is “used or reused” if it is either:
Ø employed as an ingredient to make a product; or
Ø employed in a particular function as an effective substitute for a commercial product.
· A material is reclaimed if it is processed to recover a useful product or if it is regenerated.
3.2. Steps involved in hazardous waste management
· Identification of Hazardous Waste Generation: Identifying the HW generating industries is the first step. The HWs are classified under 18 categories and this information (Refer Table-1) may be used to screen the wastes generated and classifying them as HWs. However there are few observations that- there is a probability of occurrence of wastes in more than one category; and this classification system does not give any information to understand the toxic characteristics of HW. Few suggestions are also given to improve the classification system. The data available with the State Industrial Development Corporation (IDC), District Industries Centre (DIC), State Pollution Control Boards etc. may be utilized to identify the industries with a potential for HW generation.
· Data Collection: After identifying the HW generating sources, the inventory of the data pertaining to HW generation can be developed by conducting surveys through specially prepared questionnaires to each of the identified sources. This should be followed by field visits for data verification. It is essential that, the data that is obtained from the above options is verified from secondary data (either published data or available for another industry producing similar products).
· Waste Characterization: The HW that is generated from the study region should be characterized. For this purpose, it is advisable that the samples may be collected from the waste generation source and analyzed in the laboratory. Literature data may be used in the absence of primary data.
· Quantification of Hazardous Wastes: The HWs are quantified based on their individual characteristics. The several options of compatibility of wastes with different characteristics should be studied and segregated. The quantity of HWs will be expressed in terms of each category for disposal (e.g. Recyclable, Incinerable, or Disposable etc). The wastes that are recyclable are used/waste oil, lead wastes, zinc wastes.
· Identification of sites for disposal: After quantifying the HW, and assessing the probable area requirements for its treatment, storage and disposal, the sites are to be identified. For this purpose, toposheets and/or remote sensing images of the study region may be used. The sites are to be physically verified in the field and to draw observations pertaining to the four different types of attributes (viz., Receptor related-, Pathway related-, Waste characteristics related-, and Waste management practices related-) available for ranking the sites. The site with a minimum score out of the available sites for ranking should be chosen as the site for establishing TSDF.
.
· Conducting EIA: The Environmental Impact Assessment (EIA) should be conducted in the site identified in the above step. The impacts from the project should be identified and public acceptance should be obtained for clearing the site for TSDF.
· Implementing TSDF Programme: The TSDF programme should be implemented at the final designated site. The site should contain adequate provisions for storage, treatment (Stabilization, Incineration etc.) and final disposal. Layouts for collecting the HW from the waste generation sources should be planned. The site should have the laboratory facilities to monitor the function of TSDF from time to time. Landfill is the final disposal option in TSDF. The leachate that has percolated should be treated in Effluent Treatment Plant (ETP) before disposal. Monitoring of ambient environmental qualities and TSDF performance should be done regularly during the postclosure period of landfill (30 years).
Table 1 Categories of hazardous wastes
CHAPTER 4
TREATMENT OF HAZARDOUS WASTE
Treatment when used in connection with an operation involved in hazardous waste management, means any method, technique, or process, including neutralization or incineration, designed to change the physical, chemical, or biological character or composition of a hazardous waste, so as to neutralize such waste or to render such waste less hazardous, safer for transport, amenable for recovery or reuse, amenable for storage, or reduced in volume.
Wastes remain after the implementation of waste minimisation must be treated to detoxify and neutralise them. There are large number of treatment technologies available.
Examples:· Biological oxidation
· Chemical precipitation, oxidation-reduction
· Ion exchange
· Carbon adsorption
· Membrane separation
· Other/new technologies
4.1. BIOLOGICAL TREATMENT
Synthetic chemical compounds are relatively resistant to biodegradation. Microorganisms that are naturally present often cannot produce the enzymes necessary to degrade complex compounds and these compounds are toxic thus killing the biomass. Co-treatment of industrial and domestic waste with the addition of nutrients in biological systems is often a practical system that has been tested in India as a cheap and effective compared to chemical treatments. It consists of the introduction of food they consume, alter and detoxify the waste. This is what is called secondary processing. Table 2 demonstrates that members of almost every class of anthropogenic compound can be degraded by some microorganism the table also illustrates the wide variety of organisms that participate in environmental significant biodegradation.
Table 2- Examples of anthropogenic compounds and microorganisms that can degrade them
4.2. CHEMICAL TREATMENT Chemical treatment of hazardous waste refers to the treatment methods that are used to effect the complete breakdown of hazardous waste into non-toxic gases or, more frequently, to modify the chemical properties of the waste, for example, through reduction of water solubility or neutralisation of acidity or alkalinity. Various chemical treatment methods are chemical oxidation-reduction, acid-base neutralisation, precipitation, hydrolysis, ion exchange, thermal treatment methods, wet air oxidation photolysis and biodegradation. 4.2.1 Oxidation-reduction Oxidation reduction methods provide another important chemical treatment alternative for hazardous wastes. One important chemical redox treatment involves the oxidation of cyanide wastes from metal finishing industry, using chlorine in alkali solution. In this reaction CN- is first converted to a less toxic cyanate. Further chlorination oxidises the cyanate to simple carbondioxide and nitrogen gas.
4.2.2. Ozonolysis
Ozone is a very powerful oxidising agent. Although this process has not been demonstrated in any full-scale facility, its application to Tetrachlorodibenzodioxin(TCDD) and Polychlorinated biphenyl(PCB) is quite promising. With respect to TCDD it was demonstrated that if the dioxins were suspended as an aerosol combined with CCl4, 97% degradation of TCDD was possible. Ozone in conjunction with UV radiation has been shown effective for the destruction of polychlorinated phenols and pesticides. In both the cases the key requirements were to concentrate the TCDD in a medium where they were susceptible to attack and provide a free radical for reaction with dioxin molecule. 4.2.3. Acid-base neutralisation.
Hazardous wastes are categorised as corrosive when their solution pH is less than 2 or more than 12.5. Such wastes can be chemically neutralised . Generally acidic wastes are neutralised with slaked lime [Ca(OH)2] in a continuoulsy stirred chemical reactor. The rate of addition of lime is controlled by feedback control system which
monitors pH during addition. Lime is least expensive and is widely used for treating acidic wastes. Since the solubility of lime in water is limited, solution of excess lime do not reach extremely high pH values.
Alkaline wastes may be neutralised by adding sulphuric acid. It is a relatively inexpensive acid. For some applications acetic acid is preferable since it is non-toxic and biodegradable. Alkaline wastes can also be neutralised by bubbling gaseous carbondioxide forming carbonic acid. The advantage of CO2 is that it is often readily available in the exhaust gas from any combustion process at the treatment site.
4.2.4. Chemical precipitation
This technique can be applied to almost any liquid waste stream containing a precipitable hazardous constituent. By properly adjusting pH, the solubility of toxic metals can be decreased, leading to the formation of a precipitate that can be removed by settling and filtration.
Quite often lime [Ca ] or caustic soda is used for precipitation of the metal ions as metal hydroxides. For example the following reaction suggests the use of lime to precipitate the metal as hydroxide.
4.2.5. Ion exchange:
Ion exchange is judged to have some potential for the application of interest in situations where it is necessary to remove dissolved inorganic species. However other competing processes - precipitation, flocculation and sedimentation - are broadly applicable to mixed waste streams containing suspended solids and a spectrum of organic and inorganic species. These competing processes also usually are more economical. The use of ion exchange is therefore limited to situations where polishing step was required to remove an inorganic constituent that could not be reduced to satisfactory levels by preceding treatment processes.
4.3. CARBON ADSORPTION
The principal use of vapour phase activated carbon in the environmental field is for the removal of volatile organic compounds such as hydrocarbons, solvents, toxic gases and organic based odours. In addition, chemically impregnated activated carbons can be used to control certain inorganic pollutants such as hydrogen sulphide, mercury, or radon.
When properly applied, the adsorption process will remove pollutants for which it is designed, to virtually non detectable levels. In fact one of the first large- scale uses of activated carbon was in military gas masks where complete contaminant removal is essential. Carbon adsorption is equally effective on single component emissions as well as complex mixtures of pollutants.
In the industrial area, the most common applications of activated carbon are for process off-gases, tank vent emissions, work area air purification, and odour control, either within the plant or related to plant exhausts. Additionally, activated carbon is used in the hazardous waste remediation area to treat off-gases from air strippers and from soil vapour extraction remediation projects.
Fig.1. Typical fixed-bed carbon adsorption system
4.4. MEMBRANE SEPARATION: REVERSE OSMOSIS
Reverse osmosis separation technology is used to remove dissolved impurities from water through the use of a semi-permeable spiral wound membrane. Reverse osmosis involves the reversal of flow through a membrane from high salinity, or a concentrated solution to the high purity, or permeate, stream on the opposite side of the membrane. Your water pressure is used as the driving force for this separation. The applied pressure must be in excess of the osmotic pressure of the dissolved contaminants to allow flow across the membrane. Spiral wound membranes are tightly packed filter material sandwiched between mesh spacers and wrapped in a small diameter tube. The membrane's operating conditions are fine-tuned to balance the flux, or the amount of water which passes through the membrane, with the specific rejection rates of Drinking Water Contaminants up to 99.8%. Spiral wound membranes are cost-effective thin-film elements used to remove salts and separate organic material, by molecular weight or particle charge. The technology is also very effective at removing bacteria, pyrogens, and organic contaminants.
Fig 2. Spiral wound reverse osmosis
4.5. INCINERATION
An engineering process that employs thermal decomposition via thermal oxidation at high temperatures (800-1600 C) to convert a waste to a lower volume and non-hazardous material. Products from combustion of organic wastes are carbon dioxide, water vapour & inert ash. Other products can be formed depending on waste composition.
Combustion Conditions of incineration are:
· Actual incineration conditions generally require excess oxygen to maximize the formation of products of complete combustion and minimize the formation of products of incomplete combustion.
· Temperature, residence time, and turbulence are optimized to increase destruction efficiencies. Typical residence times are 0.5 to 2 seconds.
Two types of technology dominate the incineration field (90% of all facilities):
1. Liquid injection and
2. Rotary kiln incinerators.
The majority of incinerators for hazardous waste inject liquid hazardous waste through an atomising nozzle into the combustion chamber. An auxiliary fuel such as natural gas or fuel oil is often used when the waste is not autogenous. Hydrochloric acid generated from chlorinated hydrocarbon wastes is neutralised by the lime in the kiln while slightly lowering the alkalinity of cement products. Cement kilns have been to be very efficient at destroying hazardous waste(Fig 3.).
Fig 3. Rotary kiln incinerator
CHAPTER 5
STORAGE OF HAZARDOUS WASTE
Storage is the holding of waste for a temporary period of time prior to the waste being treated, disposed, or stored elsewhere. Hazardous waste is commonly stored prior to treatment or disposal, and must be stored in containers, tanks, containment buildings, drip pads, waste piles, or surface impoundments that comply with the Resource Conservation and Recovery Act (RCRA) regulations.
5.1. CONTAINERS – A hazardous waste container is any portable device in which a hazardous waste is stored, transported, treated, disposed, or otherwise handled. The most common hazardous waste container is the 55-gallon drum. Other examples of containers are tanker trucks, railroad cars, buckets, bags, and even test tubes.
Fig 4. Hazardous waste disposal container
5.2.TANKS – Tanks are stationary devices constructed of non-earthen materials used to store or treat hazardous waste. Tanks can be open-topped or completely enclosed and are constructed of a wide variety of materials including steel, plastic, fiberglass, and concrete.
Fig 5. Underground storage tank
5.3. DRIP PAD – A drip pad is a wood drying structure used by the pressure-treated wood industry to collect excess wood preservative drippage. Drip pads are constructed of non-earthen materials with a curbed, free-draining base that is designed to convey wood preservative drippage to a collection system for proper management.
5.4. CONTAINMENT BUILDINGS – Containment buildings are completely enclosed, self-supporting structures (i.e., they have four walls, a roof, and a floor) used to store or treat non-containerized hazardous waste.
5.5. WASTE PILES – A waste pile is an open, uncontained pile used for treating or storing waste. Hazardous waste waste piles must be placed on top of a double liner system to ensure leachate from the waste does not contaminate surface or ground water supplies.
5.6. SURFACE IMPOUNDMENT – A surface impoundment is a natural topographical depression, man-made excavation, or diked area such as a holding pond, storage pit, or settling lagoon. Surface impoundments are formed primarily of earthen materials and are lined with synthetic plastic liners to prevent liquids from escaping.
CHAPTER 6
DISPOSAL OF HAZARDOUS WASTE
Disposal is the placement of waste into or on the land. Disposal facilities are usually designed to permanently contain the waste and prevent the release of harmful pollutants to the environment. The most common hazardous waste disposal practice is placement in a land disposal unit such as a landfill, surface impoundment, waste pile, land treatment unit, or injection well. Land disposal is subject to requirements under EPA’s Land Disposal Restrictions Program.
Underground injection wells are the most commonly used disposal method for liquid hazardous waste. Because of their potential impact upon drinking water resources, injection wells are also regulated under the Safe Drinking Water Act (SDWA) and by the Underground Injection Control (UIC) Program.
6.1.DEEP WELL INJECTION
Deep well injection is a liquid waste disposal technology. This alternative uses injection wells to place treated or untreated liquid waste into geologic formations that have no potential to allow migration of contaminants into potential potable water aquifers. A typical injection well consists of concentric pipes, which extend several thousand feet down from the surface level into highly saline, permeable injection zones that are confined vertically by impermeable strata. The outermost pipe or surface casing, extends below the base of any underground sources of drinking water (USDW) and is cemented back to the surface to prevent contamination of the USDW. Directly inside the surface casing is a long string casing that extends to and sometimes into the injection zone. This casing is filled in with cement all the way back to the surface in order to seal off the injected waste from the formations above the injection zone back to the surface. The casing provides a seal between the wastes in the injection zone and the upper formations. The waste is injected through the injection tubing inside the long string casing either through perforations in the long string or in the open hole below the bottom of the long string. The space between the string casing and the injection tube, called the annulus, is filled with an inert, pressurized fluid, and is sealed at the bottom by a removable packer preventing injected wastewater from backing up into the annulus.
Fig 6. Deep well injection
6.1.1. Applicability and limitation
The target contaminant groups for deep well injection are VOCs, SVOCs, fuels, explosives, and pesticides. However, existing permitted deep well injection facilities are limited to a narrow range of specific wastes. Success at expanding existing permits to manage hazardous wastes seems unlikely. Factors that may limit the applicability and effectiveness of these processes include:
· Injection will not be used for hazardous waste disposal in any areas where seismic activity could potentially occur.
· Injected wastes must be compatible with the mechanical components of the injection well system and the natural formation water. The waste generator may be required to perform physical, chemical, biological, or thermal treatment for removal of various contaminants or constituents from the waste to modify the physical and chemical character of the waste to assure compatibility.
· High concentrations of suspended solids (typically >2 ppm) can lead to plugging of the injection interval.
· Corrosive media may react with the injection well components, with injection zone formation, or with confining strata with very undesirable results. Wastes should be neutralized.
· High iron concentrations may result in fouling when conditions alter the valence state and convert soluble to insoluble species.
· Organic carbon may serve as an energy source for indigenous or injected bacteria resulting in rapid population growth and subsequent fouling.
· Waste streams containing organic contaminants above their solubility limits may require pretreatment before injection into a well.
· Site assessment and aquifer characterization are required to determine suitability of site for wastewater injection.
· Extensive assessments must be completed prior to receiving approval from regulatory authority.
6.2. LAND FILL
The EPA defines a landfill as an engineering method of disposing of solid waste on land. As such, landfills are required to protect the environment by spreading waste into thin layers and compacting them into the smallest practical volume. By day’s end, all waste is then covered with earth. Transfer stations have their own regulations. They are required to have their floors clear of all waste by the end of the working day.
6.2.1. Operation
The cell is the basic building block of a sanitary landfill. To build a cell, waste is spread into two-ft layers or less and compacted in thin layers as tightly as practical. At the end of the day, a sufficient amount of cover earth (usually six in.) is spread over waste and compacted. Sometimes an alternative material is approved for daily cover. This may include foam, plastic, or processed landscape waste. The compacted waste and soil constitute a cell. A series of cells that adjoin each other make up a lift. One or more lifts constitute a fill. There are no hard and fast rules for cell height. While four to eight feet is common, landfills handling 250 tons a day or less may have cells less than half this height. Make the width (working face) in front of the cell as narrow as possible to concentrate compaction efforts and reduce cover material requirements. It must be wide enough to prevent congestion of trucks waiting to unload. A typical face ranges from 100 to 250 ft wide.
CHAPTER 7
CONCLUSION
The industry driven economy of India's has resulted in hazardous waste problems, which are difficult to manage in an environmentally friendly manner. The lack of awareness, improper implementation of principles and laws, absence of proper infrastructure and centralized disposal facilities, and lack of technical and financial resources have led to the unscientific disposal of hazardous wastes posing serious threat to human, animal and plant life. All studies related to this matter indicate that the hazardous wastes situation in India is fairly grim. Thus, there is an urgent need for formulating proper hazardous waste management strategies, implementation of hazardous wastes management regulations and establishment of proper hazardous waste treatment and disposal facilities for controlling the unscientific disposal of hazardous wastes .This is now being done in India, but needs more improvement with the aid of better technologies.
1. B. V. Babu and V. Ramakrishna(2007) Hazardous waste management in India, Birla institute of technology & science, Pilani.
2. Hazardous Waste (Management, Handling & Transboundary Movement) Rules(2008), Central pollution control board, Govt. of India.
3. Dr. V. Rajagopalan(2006) Hazardous waste management in India- an overview, India-EU environment forum, CPCB, Delhi.
4. Prof. M. S. Subramanian Chemical methods of treatment, Environmental chemistry and analysis, module 7, IIT Madras.
