With the continuous increase in use of medical facilities there is rapid increase in generation of medical wastes disposal of which is a serious threat to environment.
DETAILED DESCRIPTION OF PROBLEM
Biomedical waste is any waste generated during treatment, curing and immunization of humans or animals. In order to treat such wastes one of the technique used is incineration. But this process generates ashes which is subject to landfill. This causes wastage of large area of land. Also heavy metals present in ash leaches towards ground water. Present generation of hazardous waste is 4.16 lakh metric tonnes per annum but we have only capacity of 3.28 lakh metric tonnes per annum. So it becomes very important to search for such alternative which allows use of such ashes in some useful way.
EXPECTED OUTCOME
Present project expect such alternative which reduces the environmental impact due to disposal of treated medical waste. More specifically this project aims in finding the successful use of treated waste ash which is generated during treatment in construction works.
Note :- The format of documentation may be slightly modified as per the need of specific branch.
We, Students here by declare that the above mentioned details are correct/true to the best of our knowledge. If anything is proved to be wrong our team may be cancelled. If admitted, we shall abide by the university rules and regulations.
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ABSTRACT
Advancement in Medical field is an active part of development in science and technology.With the continuous increase in population and increase in use of medical facilities there is sharp rise in generation of medical waste. These wastes are hazardous in nature and have the greatest potential to have impact on living being and environment.
One of the important method of treatment of such waste is incineration but this method also produces ash which is a subject of land filling. This cause wastage of large area of land also leaching of contaminant in ashes cause contamination of ground water.
The purpose of this project is to find some alternative for land filling of incineration ashes.
Key Words: Biomedical waste ash, concrete, leachate, Incinerator ash, Landfill.
INDEX
Sr. No. TITLE Page No.
ABSTRACT (ii)
PART ‘ I
1 INTRODUCTION 1
2 DETAILED DESCRIPTION OF THE PROBLEM 4
3 MATERIALS AND METHODS 7
4 EXPECTED OUTCOME 22
PART ‘ II
5 PREFACE OF POSSIBLE SOLUTION TO THE PROBLEM 23
6 COMPOSITION OF BIOMEDICAL WASTE INCINERATOR ASH 24
7 METHODS OF BIOMEDICAL WASTE ASH TREATMENT 25
8 COMPOSITION AND CHARACTERISTICS OF STABLIZED SLAG 30
9 PROPERTIES AND SUITABILITY OF MOLTEN SLAG 32
10 APPLICATIONS OF MOLTEN ASH SLAG 35
11 CONCLUSION 38
12 REFERENCE 39
PART – I
Chapter ‘ 1
INTRODUCTON
‘
INTRODUCTION
(a) About Industry
Industry / Facility to which this project resembles is M/S En-vision Enviro Engineers Pvt. Ltd.
En-vision Enviro Engineers Pvt. Ltd. Is associated with overall Management of bio-medical waste.
Major steps in Bio-medical waste management includes Segregation, Storage, Treatment & Disposal.
It is the only facility of its kind which concerned with overall Bio-medical waste management throughout South Gujarat.
En-vision is enlisted with Gujarat Pollution Control Board (GPCB) as consultants and pollution control equipment suppliers.
Approved as environmental auditors under the environment audit scheme proposed by the Hon’ble High Court of Gujarat.
Works in adherence with the GPCB norms & rules.
It works on BOOT (Build Own Operate Transfer) basis in affiliation with S.M.C.
(b) Overview of Problem
Medical care is vital for human beings. Population is increasing very fast & with this rapidly
increasing population need of medical facilities is arising at rapid rate.
Also with this increase in medical facilities, generation of wastes is rising sharp. Such type of wastes are termed as bio-medical waste. These wastes are considered to be highly hazardous and have a great potential to imply adverse effect on environment aswell as living beings.
As a matter of great concern, some special treatment methods are employed for treatment of such wastes.
These methods includes incineration, autoclaving, microwaving, shredding, etc.
But these methods lead to the generation of final treated waste which are subject to disposal and landfill.
Landfilling of such wastes gives rise to many adverse impacts on environment. Such as wastage of land resource which is limited in availability, leaching of toxic & heavy metals from disposed waste to ground, contamination of ground water, etc.
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(c) AIMS AND OBJECTIVES
Current project aims in finding alternatives for landfill of hazardous wastes.
To prevent /minimize the wastage of land which is no doubt a valuable resource and limited in availability.
To prevent the leaching of toxic and heavy metals.
To minimize the contamination of ground water.
To utilize treated hazardous wastes in some useful way and thereby saving resource.
The overall aim is to prevent and minimize the adverse impact of such hazardous wastes on environment.
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Chapter ‘ 2
DETAILED DESCRIPTION OF
THE PROBLEM
‘
DETAILED DESCRIPTION OF THE PROBLEM
(a) Incinerator & Incineration
Incineration : ‘Incineration is a controlled combustion process in which waste is completely oxidized & harmful Micro-organisms present in it are destroyed under high temperature.’
Incinerator : ‘It is a closed equipment which is used to accomplish incineration process.’
Incinerators for bio-medical waste treatment involves operation at temperature about 800-1000 C.
Incineration process reduces the volume of waste by 90% and weight by 75%. Various problems are associated with incinerations along with its usefulness.
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(b) The Problem
The incineration process which is one of the steps in treatment of bio-medical waste generates ashes of wastes after combustion.
The incineration process destroys pathogens & reduce the volume of waste by 90% & weight by 75%.
The incineration of hospital wastes not only releases toxic acid gases such as CO, CO2, NO2, SO2, etc. into the environment but also leaves a solid material called ash as residue includes bottom ash and fly ash which increases the leaves of heavy metals, inorganic salts and organic compounds in the environment.
Fly ash settles on post burner equipment such as scrubbers. But bottoms ash is a subjected to landfilling by disposing to some abandoned sites.
Disposal of bio-medical waste ash in landfill without proper treatment may cause contamination of ground water due to leachate as metals are not destroyed during incineration.
Also limited space & high cost for disposal is the part of the problem.
(c) Statistical View of The Problem
In 1947 cities & towns of India generated an estimated 6 milliontones of solid waste, where as in 2006 it was about 48 million tones [SOER 2009].
Surveys showed that 70% of Indian cities lack adequate capacity to transport solid wastes and there is no sanitary landfills to disposal the wastes.
India generates around 7 mt (metric ton) of hazardous wastes every year most of which is concentrated in 4 states Andhra Pradesh, Bihar, Tamil Nadu, Uttar Pradesh.
At present approximately 27.30 lakhs metric tons per annum (MTA) of land disposal wastes is generated which is much more than total waste handling capacity (disposal capacity) which is approx. 15.01 lakhs (MTA) [CPCB 2008].
Particularly in En-vision, average daily incoming bio-medical waste quantity is 2500 kg per day out of which 30-40% are incinerable wastes.
Therefore, roughly 800-1200 kg of wastes is incinerated every day. This may produce disposable ash about 300 kg per day.
Average monthly ash production will be 9000 to 10000 kg.
This is the figure for a single facility. Intensity of the problem can be imagined by applying this much quantity to the facilities throughout the country.
Chapter ‘ 3
MATERIALS
AND
METHODS
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MATERIALS & METHODS
In order to get the clear idea about the problem that this project is concerned, It is very important to have the basic ideas about the sources of generation of wastes, categories of waste, steps in bio-medical waste management process related with the industry (ENVISION).
MANAGEMENT & HANDLING RULES, 1998
‘ It is the duty of every occupier ( a person having control over and institution or premises) of
an institution generating Biomedical waste including a Hospital, nursing home, clinic, medical laboratory, blood bank, animal house, Veternity institution, etc to take all steps to ensure that such waste is handled without any adverse effect to human health and the environment.
‘ Biomedical waste shall not be mixed with other wastes.
‘ Biomedical waste shall be segregated into containers/bags at the point of
generation according to their respective categories.
‘ Biomedical waste shall not be stored for more than 48 hrs.
‘ Every occupier shall make an application to the prescribed authority (GPCB) for
grant of Authorization / undertaking ?
‘ Every occupier shall maintain records related to generation, collection, reception,
storage, transportation treatment and disposal of biomedical waste.
‘ Liquid waste generated from laboratory, Washing, cleaning, housekeeping and disinfecting
activities shall be treated so as to meet the discharge standards stipulated under these rules.
‘ Waste collection bags for waste types needing incineration shall not be made of
chlorinated plastics.
‘ Containers and vehicles containing biomedical waste should hold the symbol
of ‘BIO-HAZARD’.
SOURCES OF BIO-MEDICAL WASTES
Each & every activity related to diagnosis, treatment & immunization of humans or animals contributes to Bio-Medical Waste.
Some of the obvious sources are,
o hospitals;
o nursing homes and extended care facilities
o public health units
o physicians’ offices/clinics
o dentists’ offices/clinics
o veterinarians’ offices/clinics
o veterinary research, teaching and health care facilities
o medical research and teaching establishments
o health care teaching establishments
o clinical testing or research laboratories
o facilities involved in the production or testing of vaccines
o mortuaries and funeral homes
o nursing offices
o blood banks and blood collection center
The Gujarat state has 13 medical colleges, 1,072 primary healthcare centres (PHCs); 7,274 sub centres, 273 community health centres (CHC) and 85 mobile healthcare units. The share of primary care in the total healthcare market of Gujarat is around 80 per cent, secondary and tertiary care account for 17 percent and four per cent respectively. Doctor to patient ratio is 1:10 and nurse to patient ratio is 1:5.
Each and every health care unit described above generate a large amount of hazardous Waste which we say bio-medical waste.
CATEGORY OF BIO MEDICAL WASTE
1) Chief categories are:
2) Human anatomical wastes
3) Animal wastes
4) Microbiological & biotechnological wastes
5) Sharp & pointed wastes
6) Discarded medicines &cytotoxic drugs
7) Soiled wastes
8) Solid wastes
9) Chemical wastes
Category No. 1
Human anatomical wastes
(Human tissues, organs, body parts)
Incineration
Category No. 2
Animal Waste
(animal tissues, organs, body parts, etc.)
Incineration
Category No. 3
Microbiological & Biotechnological Waste
(wastes from clinical samples, pathology, bio-chemistry, blood bank, haematology, laboratory cultures, stocks or specimens of micro-organisms live or attenuated vaccines,
etc.)
Disinfection at source by chemical treatment or by Autoclaving / microwaving followed by mutilation / shredding after treatment final disposal in secured landfill or disposal of recyclable wastes through registered or authorized recycles
Category No. 4
Waste Sharps
(needles, glass syringes or syringes with fixed needles, scalpels, blades, glass, etc. that may cause puncture and cuts. This includes both used and unused sharps.)
Disinfection by chemical treatment or Destruction by needle and tip cutters, Autoclaving / microwaving followed by mutilation / shredding whichever is applicable and final disposal through authorized CBWTF or disposal in secured landfill or designated concrete waste sharp pit.)
Category No. 5
Discarded medicines & cytotoxic drugs
(wastes comprising of outdated, contaminated and discarded medicines)
Disposal in secured land fill or Incineration
Category No. 6
Soiled Waste
(Items contaminated with blood and body fluids including cotton, dressings, soiled plaster casts, linen, bedding, other material contaminated with blood
Incineration
Category No. 7
Infectious Solid Waste
(wastes generated from disposable items other than the waste sharps such as tubing, hand gloves, saline bottles with IV tubes, catheters, glass, intravenous sets, etc.)
Disinfection by chemical treatment or Autoclaving / microwaving followed by mutilation / shredding and after treatment final disposal through authorized or registered recyclers.
Category No. 8
Chemical Waste
(chemical used in production of biologicals, chemicals used in disinfection as insecticides etc.)
Chemical treatment and discharge into drains meeting the norms notified under these rules and solids disposal in secured landfill.
STEPS IN BIO MEDICAL WASTE MANAGEMENT PROCESS
‘ Major steps involved in bio-medical waste management process are;
1) Segregation:-
Segregation means to separate the Bio Medical wastes at the source of generation in accordance with Table given here.
2) Storage & Transportation:-
Waste should be stored seperatly at the source of generationor at the treatment site.
‘ Stored waste is transported through dedicated vehicles.
3) Treatment:-
Treatment is done through autoclaving, incineration, shredding,Microwaving, etc.
4) Disposal :-
Waste after treatment is disposed to land fill sites.
‘ SEGREGATION
‘ Segregation means to separate the Bio Medical wastes at the source of generation in accordance with Table given here.
‘ Untreated Bio Medical waste shall not be mix with other waste.
‘ Segregation is the most important step in Bio Medical waste Treatment & Disposal.
‘ If the proper segregation of the waste is not done at source, then the bio-medical waste might get mixed up with the municipal waste of the hospital.
‘ The un-segregated BMW may jeopardize the entire process of the bio-medical waste treatment.
‘ The un-segregated BMW may endanger human and the animal lives.
‘ It is vital that all the health care units ‘ both in the Government and in the Private Sector ‘ strictly follow the recommended segregation system for bio-medical waste at source.
‘ Waste segregation is the key to waste minimization and efficient waste collection, transportation, treatment and disposal.
‘
‘ Table showing segregation scheme.
‘ Storage & Transportation
a) STORAGE
‘ Waste should not be stored more than 48 hrs.
‘ There should be separate place for storage which is in accessible to common people.
‘ Wastes should be stored on impervious surface.
‘ Storage room for waste should be dark.
‘ Always collect the waste in covered bins.
‘ Fill the bins up to the 3/4th level.
‘ Clean the bins regularly with soap and water/disinfect.
‘ Never over fill the bins.
‘ Never mix infectious and non-infectious waste in the same bin.
‘ Bags containing infectious waste should be sealed properly to avoid leakage.
‘ All the Bags and Container should be labeled properly according to color coding to minimize confusion an easy handling.
b) TRANSPORTATION
‘ Transportation should be carried out through closed vehicles.
‘ Loading & unloading should be carried out very carefully so that there is no damage to bags & bins.
‘ Wastes should be transported via out skirts of city area.
‘ Vehicles carrying such wastes should hold symbol of bio hazard.
‘ Wear appropriate PPE (gloves, clothing cover, safety glasses) when handling non-inactivated waste
‘ Below given image show the dedicated vehicle of ENVISION for transportation
of biomedical waste.
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c) TREATMENT
‘ There are three treatment methods which are based on segregation.
(i) INCINERATION (for yellow bag content)
(ii) AUTOCLAVING (for red bag & sharp wastes)
(iii) SHREDDING (following autoclaving)
i. INCINERATION
“Incineration is a controlled combustion process where waste is completely oxidized and harmful microorganisms present in it are destroyed at high temperature”
Some chief specifications of incinerator used in en-vision are;
‘ Capacity of incinerator used in this facility is 200kg/hr.
‘ Temperature in primary chamber is about 800’?50?? C.
‘ Temperature in secondary chamber ranges1050’?50?? C.
‘ Temperature in venturi chamber should be less than 70?? C
‘ Common fuel used in this incinerator are CNG/LDO
‘ Waste is converted to ash at such a high temperature.
‘ Pollutant gas is made to pass through venturi scrubber which contain 5% caustic solution as scrubbing media.
ii. AUTOCLAVE
“It is a low heat thermal process where steam is brought into direct contact with waste in a controlled manner and for sufficient duration to disinfect the waste’
‘ Optimum condition121??C at 15 psi
‘ Sterilization time:45 min.
‘ Capacity:125 Kg/hr.
Important component of autoclave are steam pulsing system and vaccum pump
.
Vaccum pump : vaccum pump sucks air or air/steam mixtures from the chamber
Steam pulsing unit: serves air dilution by using a series of steam pulses, in which the chamber is alternately pressurized and then depressurized to near atmospheric pressure.
iii. SHREDDING
‘ “Shredding is a process by which waste is cut into pieces”
‘ Treatment after autoclaving is followed by shredding.
‘ Capacity of a typical shredder is about 100Kg/hr.
‘ Combined hook shear blades are employed in shredder.
‘ Shredding is done to minimize the space requirement for disposal and handling of wastes
d) Disposal (THE PROBLEM AREA)
‘ Last step in Bio Medical Waste treatment & handling is disposal.
‘ Such sites should be inaccessible to common people and animals.
‘ Authorized institute must maintain a record of all the pits used for deep burial.
‘ Ground water table level should be a minimum of 6m below the lower level of deep burial pit.
‘ Incinerated ash is disposed at hazardous waste disposal site at BEIL, Ankleshwar.
‘ Autoclaved & Shredded wastes are disposed at Solid waste disposal site of S.M.C.
‘ Disposal of treated wastes to some landfill sites has become a common practice
It has become a conventional step in many treatment processes. Adverse effects associated with land filling are many fold. There are many adverse impacts associated land filling of incinerator ash few of these are:
1. Wastage of large area of land due to land filling practice.
2. There is continuous increase in generation of bio medical wastes and with this there is continuous rise in treated waste (incinerated ash).
3. Leaching of toxic substances and heavy metals in environment.
4. Chances of contamination of ground water.
As there are many direct and sound impacts of landfill activities, disposal of incinerator ash is the main focus of this project.
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Chapter ‘ 4
EXPECTED
OUTCOME
EXPECTED OUTCOME
‘ Present project expect such alternatives which reduces the adverse environmental impact due to disposal of treated medical waste.
‘ More specifically this project aims in finding the successful use of treated waste ash that is generated during treatment in construction work.
‘ But the biggest obstacle in this direction is the presence of toxic substances and heavy metals which cannot be denied.
‘ Ash obtained after incineration of biomedical waste contains a number of toxic substances and Heavy metals such as Ni, Hg, Cd, Pb, etc. Taking the hazardous effect of heavy metals into consideration various regulating authorities and pollution control boards requires strict compliance for use of ash in any other options.
‘ Ultimately land filling has been the last step in management of biomedical waste.
‘ As discussed earlier in this report there are a number of detrimental effects of disposal of ashes on environment, It shows the need of the present time is to search some concrete solution for this problem. The solution will be more effective and beneficial if the ashes can be used in some useful purpose.
‘ This solution will have many fold benefits such as wastage of land caused due to land filling will be minimized as well as raw material requirement in construction works will be minimized.
‘ As an important part of this project report our final conclusion would be eliminating/minimizing the leaching of heavy metals from incinerator ashes.’
PART – II
Chapter ‘ 5
PREFACE OF
POSSIBLE SOLUTION TO THE PROBLEM
‘
PREFACE OF POSSIBLE SOLUTION TO THE PROBLEM :
Problem described in the part 1 of this report can be solved to a greater extent if the final treated ash is utilized in some useful way instead of undergoing conventional landfilling.But the biggest obstacle in this direction is the presence of toxic substances and heavy metals which cannot be denied.
Taking the hazardous effects of heavy metals into consideration pollution control board shows strict requirements for use of ash in any option other than landfilling.If some further treatment is adopted which brings the concentration of constituents up to certain value which is in compliance with permissible value it will open the way of successful application of BMW ash.
As a final part of the project it is of great importance to analyse some measures/processess which can play a significant role in transforming the aim of this project into reality.Some similar processes are presented here.
Though these methods require still further development and research it is notable that successful application of measures presented here will sure lead to benefits to living world, ecosystem and environment as a whole.
Also in order to adopt some methods other than landfilling it is very important to know the composition of ash obtained from biomedical waste incinerator.Assessment of constituents of ash is a very important step to determine the feasibility of application of ash in construction and other activities.
Chapter ‘ 6
COMPOSITION OF BIOMEDICAL WASTE INCINERATOR ASH
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COMPOSITION OF BIOMEDICAL WASTE INCINERATOR ASH:
Physico-Chemical Properties of Biomedical Waste Ash
The quantities of bottom ash from the municipal incinerators in Canada and Massachusetts, USA have some difference in ash characteristics depending on the types of incinerator. The density of fly ash was found in the range 0.37-0.82 kg m-3 and the density of bottom ash was found in the range 0.73-1.04 kg m-3 (Ontiveros et al., 1988)
The elemental composition of the bio-medical waste ash can be determined by scanning electron microscope (SEM) or energy dispersive X-ray (EDX) analysis and revealed the presence of SiO2,Cao, and Al2O3 in ash. Biomedical ash is generally composed of high concentration of toxic heavy metals such as mercury (Hg), arsenic (As), lead (Pb), cadmium (Cd), silver (Ag), iron (Fe), zinc (Zn) etc. Anastasiadou et al., (2011) analyzed the composition of medical waste incineration fly and bottom ash by energy dispersive spectroscopy (EDS) and revealed that;
The major elements of the fly ash were:
CaO- (89.2%),
SiO2- (6.0%) and
Na2O- (2.5%)
While the major elements in bottom ash were:
SiO2- (39.74%)
CaO- (27.77%)
Na2O -(9.13%)
Al2O3 -(5.16%) and
Fe2O3-(4.53%), respectively.
The presence of Siliceous and Argallicious substances in biomedical waste incinerator ash shows the chances of its use in construction activities.However presence of toxic substances such as dioxins and furans and presence of heavy metals such as mercury (Hg), arsenic (As), lead (Pb), cadmium (Cd), silver (Ag), iron (Fe), zinc (Zn) etc. also pose obstruction for the same.So reducing and/or eliminatig the adverse effect of toxins and leaching of heavy metals is the first step in finding the alternative to disposal of biomedical waste incinerator ash.
Chapter ‘ 7
METHODS OF BIOMEDICAL WASTE ASH TREATMENT
Some most promising methods are presented here :
METHODS OF BIOMEDICAL WASTE ASH TREATMENT
1) SOLIDIFICATION/STABLIZATION
The Solidification/Stabilization S/S process refers to those processes that use additive or binder to chemically and/or physically immobilize the hazardous content present in waste
As the name implies the method consists of two processes.
1) Solidification involves the use of agents which solidifies the ashes which are generally in loose form. For solidification, usually binders like cement, lime,etc are used to encapsulate the waste material in order to immobilize contaminates and reduce leachablity. The addition of Portland cement for S/S has already been used in many countries
2) Stabilization means to minimize the solubility and toxicity of contaminates.This can be accomplished by treatment with alkalies.
However, the drawback is that this process is not suitable for treating soluble salts and long-term leaching will be an environmental problem. Also, the volume of waste will be increased (almost doubled) using this method. Thus, this method is much more suitable for treating highly toxic waste material
2) VITRIFICATION PROCESS
Vitrification (from Latin vitreum, “glass”) is the transformation of a substance into a glass.Usually, it is achieved by rapidly cooling a liquid through the glass transition.
‘In a wider sense, the embedding of material in a glassy matrix is also called vitrification.’
An important application is the vitrification of radioactive waste to obtain a stable compound that is suitable for ultimate disposal.
Vitrification is a proven technique in the disposal and long-term storage of nuclear waste or other hazardous wastes in a method called geomelting. Waste is mixed with glass-forming chemicals in a melter to form molten glass that then solidifies in canisters, immobilizing the waste. The final waste form resembles a non-leaching, durable material that effectively traps the waste inside. The waste can be stored for relatively long periods in this form without concern for air or groundwater contamination.
Vitrification is one of the most efficient techniques employed to treat hazardous wastes, is able to fix heavy metals or toxic substances into the amorphous structure of glass. At the same time, the toxic substances such as dioxins decompose when melted above 1,300 ‘C. The vitrified ash is used as road base material, blasting grit, embankments, in the production of construction and decorative materials like ceramic tiles, pavement bricks and water-permeable blocks.
In an experiment it was observed that the domestic waste incinerator fly ash sintered and heated at 950 ‘ C for two hours has good potential to manufacture light-weight aggregates or bricks for engineering applications . Glass-ceramics are fine-grained polycrystalline materials formed when glasses of suitable compositions are heat-treated, and thus undergo controlled crystallization to the lower energy, crystalline state. The mechanical and thermal properties of glass-ceramics are superior to those of the parent glass. Due to its distinct properties, the glass-ceramics find a wide variety of applications. Numerous silicate based wastes have been considered for the production of glass-ceramics .
It has been found that glass produced from the vitrification of incineration ash is suitable for the production of glass-ceramic materials due to its mechanical and thermal characteristics
Vitrified ashes have been successfully used as raw material for production of glass-ceramics and the properties of the glass-ceramics were greatly affected by the heat treatment time and temperature. Yang demonstrated the reuse of MSWI fly ash for glass-ceramic production at a relatively low melting temperature by the use of additives.
Glasses obtained from the vitrification process show lower percentages of metals release and less ion release compared to incinerator ash . However, the exposure of the glass to water may leach toxic substances from the glass matrix. The corrosion behavior of glass and glass-ceramic made of MSWI fly ash was investigated by Park and Heo [135]. It was found that the leaching of heavy metal ions from the glass and glass-ceramic was well below environmental regulations. Similarly leaching of heavy metals from products obtained after vitrification is found to be below regulatory norms.
3) STABILIZATION OF BMW INCINERATION ASH.
This method is similar to process of vitrification.
In this method, melting of the ash is carried out in a combustion chamber at 1200??C. Flow diagram of medical waste incinerator with melting process is presented here.
As shown in this flow diagram the system consists of a waste feeder,a primary combustion chamber (rotary type),a secondary combustion chamber ,a waste heat boiler,dry air pollution control ,and a 24-h gas-emission monitoring device .
The incinerated ash is fed into hopper.Ash is fed into the primary chamber through conveyor belt and ram feeder as high temperature of about 950??C prevails in primary chamber which makes it impossible for manual feeding.The melting of the ash occurs in the secondary combustion chamber at 1200??C..Heat recovery boiler is employed to recover the heat generated while operating at 1200??C.Bag house filter is also used to control air pollution.
Thus the incinerated hospital waste ash is melted at 1200??C and the molten ash is turned into slag by cooling at room temperature.Due to high temperature toxic substances are destroyed and heavy metals get fused.As the ash takes molten state heavy metals gets trapped within the fluidized matter formed.Leaching characteristics of this stablized slag is found to be under regulatory norms.
The slag produced in this way also satisfies the requirement for use in construction purpose.
According to a similar research carried out using the incinerator located at Telok Panglima Garang, Selangor, Malaysia, results obtained were found under regulatory norms.
4) SUGGESTED METHOD:
In conventional vitrification or stabilization high temperature of the order of 1300 C is required.Also there is chance of contamination when vitrified slag comes in contact with water.When only ash is subjected to high temperature though it is found that heavy metals are trapped in the crystal structure of slag formed but vitrification can be made more effective and thus it can be made more suitable for application as aggregates.Following steps may be included as a modification in conventional method.
a) WASHING/PRETREATMENT
Since we know that washing step is able to remove insoluble compounds from ash also impurities like alkali metal chloride are found to be removed from fly ash of municipal solid waste incinerator.The effect of washing pretreatment prior to melting the ash on the microstructure and properties of the glass-ceramics was examined for MSW incinerator and it was found that washing increase network former in fly ash, which results in the increase of peak crystallization temperature of parent glass and strengthening of properties of bending strength and chemical stability of the glass-ceramics.
Based on these findings it may be recommended that washing or treatment of ash prior to vitrification with some chelating agent such as salts of EDTA may prove to be more effective
b) USE OF ADDITIVES:
Some additives or vitrifying agents may be used to enhance the crystal formation.
By combining the incinerated ash with additives such as silica or sand powder,rich Fe2O3 and rich Cao vitrification process may be made more effective.Though the presence of alumina,silica and calcium is found in the composition of biomedical waste incinerator ash, using such ash or slag formed from such ash in construction activities is not a very successful idea because of requirement of strength is not met compared to ordinary Portland cement.
So use of additives can be a good approach to overcome the above said problem also heavy metals are better entrapped in such vitrified product.
Also sodium carbonate can be used as fluxing agent.
Use of additives can give following advantages:
i. Melting temperature of ash mixture decreases.
ii. Thereby cost of production also decreases.
iii. Slag produced is possess more strength
iv. Enhanced crystal structure.
Chapter ‘ 8
COMPOSITION AND CHARACTERISTICS OF STABLIZED SLAG
COMPOSITION AND CHARACTERISTICS OF STABLIZED SLAG
The quantitative analysis from X-ray diffraction (XRD) showed that the slag produced consisted of residual components after the volatilization of low-boiling-point materials from the incinerated ash
Silicon (SiO2), calcium (CaO), and aluminum (Al2O3) were the three main components of the slag. The dominant metals identi’ed in the slag were Cu, Ba, and Ni. Azni and Katayon (2002) characterized the hospital waste incinerator slag by using X-ray diffraction (XRD) and X-ray fluorescence (XRF). The slag contained large amounts of SiO2, CaO, Al2O3, Sn, Ni, Cu, Ba and B. XRD analysis revealed a moderate crystal structure for the melted slag and identified the main crystals as quartz (SiO2), kaolinite (Al2Si2(OH)4), albite (NaAlSi3O8) and gibbsite (Al(OH)3)
It was observed that the crystal structure of the slag assists in preventing the leaching of heavy metals from the slag .The absolute concentration of examined metals in slag is not such as to classify them as toxic and harmful.
1) LEACHING CHARACTERISTICS:
Heavy metals found in biomedical waste ash are As, Ag, Ba, Cd, Cr, Cu, Hg, Ni, etc. Leaching characteristics of molten slag was studied at pH3 and at pH5 and it was found that results satisfied the requirement for application of such slag in construction purpose.
Result obtained after an experiment Is tabulated here
Metals pH 3 pH 5 Standard limit
As 3.14 ?? 0.82 0.08 ?? 0.01 5
Ag 1.25 ?? 0.05 0.09 ?? 0.01 5
Ba 35.1 ?? 5.49 9.73 ?? 1.36 100
Cd 0.02 ?? 0.01 NDb 1
Cr 3.59 ?? 0.96 1.46 ?? 0.03 5
Cu 42.85 ?? 9.17 36.19 ?? 5.53 100
Hg ND ND 0.2
Ni 27.45 ?? 2.14 9.19 ?? 1.43 100
Pb 2.34 ?? 0.05 1.17 ?? 0.03 5
Se 0.01 ?? 0.01 ND 1
Leaching test :
The results of the EPA toxicity test on hospital waste molten slag are given in Table. As shown,the metal concentrations in the leachate at both pH 3 and pH 5 were found to be below the maximum limits specified by the US EPA.The melting method was found to stablize the heavy metals in the waste successfully,and it therefore appears that this is an effective method for ultimate disposal.
2) CHEMICAL COMPOSITION :
The quantitative analysis from XRD showed that the slag produced consisted of residual components after the volatilization of low-boiling-point materials from the incinerated ash.
As shown in Table,silicon (SiO2), calcium(CaO),and aluminum (Al2O3) were the three main components found in slag.
Components Values (Wt.%)
(Mean ?? SD)
Components Values (Mg/Kg)
(Mean ?? SD)
SiO2
53.93 ?? 4.32
As
5.71 ?? 1.12
Al2O3
16.74 ?? 2.85
Ag
0.05 ?? 0.01
CaO
9.82 ?? 1.80
Ba
198.32 ?? 12.26
FeO
5.53 ?? 0.98
Cd
1.56 ?? 0.09
Na2O
4.53 ?? 0.84
Cr
89.65 ?? 8.25
K2O
1.29 ?? 0.15
Cu
520.14 ?? 42.12
TiO2
5.89 ?? 0.76
Hg
0.06 ?? 0.01
MgO
1.37 ?? 0.22
Ni
179.32 ?? 13.54
Other
0.90 ?? 0.07
Pb
13.26 ?? 2.71
Chapter ‘ 9
PROPERTIES AND SUITABILITY OF MOLTEN SLAG
‘
PROPERTIES AND SUITABILITY OF MOLTEN SLAG:
Before thinking about using molten slag in road pavement it must be verified whether the properties of slag is suitable for such application or not.
Such properties include;
o strength of aggregates
o abrasion resistance
o toughness of aggregate
o crushing value of aggregates
o angularity number,etc
Properties of molten slag were studied and were found to be within limits suitable for use as road aggregates and asphalt aggregates.
1).PROPERTIES SUITABLE FOR ROAD AGGREGATES:
The use of the slag as an alternative road aggregate material was investigated and the results are given in Table .The strength of the aggregates to resist abrasion and impact was evaluated using the Los Angeles abrasion test.The abrasion test result was found to be 25.01%,which complies with the standard requirement (30%).The toughness of the aggregate to resist fracture under the impact of moving loads was 29.82% which also reaches the required standard (30%). The aggregate crushing value of molten slag was measured as 15.94%.This value gives a relative measure of the resistance of the aggregate to crushing under a gradually increasing load,and also reaches the required standard (30%).The angularity number or absence of rounding of the aggregate was recorded as 7,which is within the standard range of 6’9.
The angularity number is an important property because it affects the workability and stability of an aggregate’asphalt mixture,which relies on the interlocking of the particles.Aggregates with more angular shapes provide good interlocking,stability and reliability.
Other properties,including water absorption,polished stone value,and soundness,also complied with the standard requirement.In general,the results revealed that hospital waste molten slag fulfills all the requirements for aggregate application.Therefore,hospital waste slag was found to be suitable for use as a replacement aggregate.
Table showing test results,standard requirements and required properties is given below.
PROPERTIES Standard
Requirement Test results
(mean ?? SD)
Water absorption
<2%
0.59 ?? 0.03%
Angularity test
6’9
7.0 ?? 1.42
Aggregate crushing value
<30%
15.64 ?? 2.7%
Aggregate impact value
<30%
29.82 ?? 4.9%
Los Angeles abrasion test
<30%
25.01 ?? 3.7%
Polished stone value
>40
52.27 ?? 8.9
Soundness test
<15%
10.57 ?? 1.8%
2) PROPERTIES SUITABLE FOR USE AS ASPHALT AGGREGATES:
The slag produced was tested as a substitute for asphalt aggregate in road construction.The results for asphalt binder given in Table shows that it complies with the requirements of the standard specification.The penetration of molten slag obtained was 67.7mm which complies with the standard requirement of 63’75mm.The results of this test showed the consistency of the molten slag under certain conditions of time,loading,and temperature.The softening point,or the temperature at which the molten slag gradually under goes a phase-change from a solid to a soft liquid, was measured as 54.25??C.This is within the standard range from 54??to 58??C.
The percentage weight loss was measured using the thin-film oven test.A thin-film oven test was also conducted to indicate the approximate change in weight loss during conventional hot mixing at about 150??C.This test yields a residue which approximates the asphalt condition as incorporated into the pavement.The percentage weight loss was 0.37 which complies with the standard requirement (0.2%’0.5%)
The bulk specific gravity of the molten slag was 1.03,which is within the standard requirement range of 1.02’1.04.Further tests were carried out to determine the proportion of coarse and fine aggregates for the composition of the aggregate mixture.The molten slag produced has been thoroughly tested for compliance with the specifications relating to the requirements for the physical properties of aggregate,and the results are given in Table .These results show that in order to fulfill the requirements for a course surface subjected to medium traffic with an aggregate size of half an inch maximum, the average or optimum asphalt content to be mixed with hospital waste slag is about 5.53%.
Asphalt Physical Properties Standard
Requirement
Test Results
Penetration test
63’75mm
67.7 ?? 8.7mm
Softening point
54’58??C
54.25 ?? 5.9??C
Bulk speci’c gravity
1.02’1.04
1.03 ?? 0.03
Thin ‘lm oven result (weight loss)
0.2’0.5%
0.37 ?? 0.01
Chapter ‘ 10
APPLICATIONS OF MOLTEN ASH SLAG
‘
APPLICATIONS OF MOLTEN ASH SLAG:
Generally to a lay man the word ‘ASH’ stands for a useless thing .However now a days ash obtained from various combustion processes are brought into a variety of uses like substitute for soil or used with some binding agents.But when it comes to hazardous waste ash such as biomedical waste ash there is reluctance in use.This is due to the fact that it comes from hazardous source.
As after undergoing treatment such as incineration there is no or negligible chance of any infection or potential for hazard also as described in this report incinerated ash is again heated at high temperature of about 1200 C to convert into slag form there is no chance of any infections.Such slag can be used in many alternatives instead of conventional landfilling.
Though there is very little advancement in this direction i.e use of biomedical waste ash as raw material for other activities such as construction,some possible applications of molten ash slag are presented here as follows:
1. AS ROAD PAVEMENT:
A typical road pavement consists of several layers, which are composed of different types of materials. Figure here shows the structure of a road pavement.Three main layers of road pavement are:
WEARING COURSE:
The uppermost layer of a sealed pavement is wearing course.
It should be even, durable and highly skid resistant.
The most common materials for wearing courses are bituminous surface dressing and asphalt concrete.
BASE COURSE:
The layer below the wearing course is the base course, which is the main load-spreading layer.
It should be highly sound,hard and durable.Though stabilized molten biomedical waste is crystalline and hard it cannot be used as substitute for asphalt or cement concrete since extremely high intensity load is spread in this layer.
The base may consist of premixed asphalt, cement concrete, graded granular gravel, crushed rock, or materials stabilized with lime or cement.
SUB BASE COURSE:
The layer below the base course is the sub-base, which is usually constructed from natural gravel or from materials stabilized with cement or lime.
SUBGRADE:
The lowest layer is subgrade, which is the soil acting ash a foundation for the pavement.
APPLICATION:
A possible way to use the molten slag is to replace the materials in the base course and sub-base . The reason behind using the biomedical waste slag in base course and sub base course is that these two layers are confined between upper most layer and lower layer.This ensures less or no leaching and percolation of stabilized heavy metals into the ground or in atmosphere.Several road sections have utilized Municipal solid waste incinerator (MSWI) bottom ash and biomedical waste (BMW) molten slag in road construction
A test road was built in Sweden and the bottom ash slag was used as a sub-base material. It was found that substituting gravel in the road base with the bottom ash slag did not affect the release of heavy metals to the environment.
2. IN AGRICULTURE:
Biomedical waste ash has potential for use in agriculture because it contains almost all macro as well as micronutrients except organic carbon and nitrogen. It may act as chemical fertilizer to increase the yield of various agricultural crops. The various doses of ash, cow dung, urea and super phosphate were used for the treatment of Fenugreek and Mustard (Goswami-Giri, 2007). Effect of these fertilizers depends upon the type of crop as well as the type of soil. The positive effect of ash application was observed on average growth of Fenugreek and Mustard. The yield of Fenugreek and Mustard is increased around 54-55% and 35% when compared with control, respectively. For this purpose 1.0 gm and 1.5 gm of ash was applied respectively, in all the treatments.
3. IN CEMENT-BASED MATERIALS AS CONTAINMENT SYSTEM
Waste generation has increased considerably worldwide in the last decades. As a consequence, incineration became an alternative for reducing waste volume, leading to the generation of ash as a new type of waste. The new cement’ ash composite systems have been tested for future applications in building materials. The additions of hospital waste ash in cement matrices to be potentially used as construction elements. This involved the assessment of the effect of the additions (different proportions of ash and metal-spiked ash) on the physico mechanical properties of the building materials and the leachability of metals (Genazzini et al., 2005). Anastasiadou et al., (2011) evaluated the mechanical properties of the medical waste incineration bottom ash using different amounts of ordinary Portland cement (OPC) as a binder. The solidified matrix showed that the cement was able to immobilize the heavy metals found in fly and bottom ash
Cement- based solidification exhibited a compressive strength of 0.55-16.12 MPa. The strength decreased as the percentage of cement loading was reduced; the compressive strength was 2.52-12.7 MPa for 60% cement mixed with 40% fly ash and 6.62-16.12 MPa for a mixture of 60% cement and 40% bottom ash. The compressive strength reduced to 0.55-1.30 MPa when 30% cement was mixed with 70% fly ash and to 0.90-7.95 MPa when 30% cement was mixed with 70% bottom ash, respectively. Filipponi et al., (2003) prepared the different mixes by blending hospital waste incinerator bottom ash with ordinary Portland cement in different proportions and at different water dosages. The solidified products were then tested for the unconfined compressive strength (UCS) at different curing times. Results at curing times longer than 28 days and for waste dosages higher than 50% suggested that bottom ash exhibited weak pozzolanic properties
4. PRODUCTION OF GLASS CERAMICS:
The process of vitrification as discussed earlier yields slag which is glassy in structure when air cooled.This process can be used effectively to produce glass ceramics for use in flooring, roofing ,porcelain articles, decorative articles,etc
Chapter ‘ 11
CONCLUSION
CONCLUSION:
With the continuous development in science and technology there is continuous production and discharge of various types of waste. Good part is that concern for sustainable development is also growing day by day.For achieving the goal of sustainable development some changes are required to be brought into our conventional methods of processing as well as treatment of wastes,some sound steps are required to be undertaken .Project presented here resembles to such a change and such a step.
Though the use of biomedical waste ash in construction activities has not got much attention of researchers but Investigation in this direction is still under active phase also it is notable that if this process is implemented successfully there will be immense benefits to human beings as well as to environment.
Chapter ‘ 12
REFERENCES
‘
REFERENCES
‘ Biomedical Waste Management, GPCB, GandhiNagar.
‘ Information from En-vision Enviro Engineers Pvt. Ltd.
‘ Utilization of hospital waste by Idris Azni
‘ Azni and Katayon (2002)