WO2003047782A1

WO2003047782A1 - Treatment of waste materials for disposal

Info

Publication number: WO2003047782A1
Application number: PCT/AU2002/001593
Authority: WO
Inventors: Michael Philip Summer-Pots; Richard John Curtis Lear
Original assignee: Matrix Technology Pty. Ltd
Priority date: 2001-12-05
Filing date: 2002-11-29
Publication date: 2003-06-12
Also published as: AU9704601A

Abstract

A method and apparatus for treating infectious waste comprising shredding the waste to obtain a finely divided particulate material, capturing the aerosols with an oxidising solution, wetting the waste with an aqueous alkaline solution, treating the waste with an alkaline earth oxide or hydroxide, dewatering the waste to collect dewatered waste and excess alkaline solution which can be reuse for wetting the waste.

Description

TREATMENT OF WASTE MATERIALS FOR DISPOSAL

This invention is concerned with the disposal of waste

materials which are or may become biologically active if left untreated,

including, hospital waste materials, clinical waste materials, pathogenic

materials, quarantine wastes, sewerage sludges, and the like which

include pathogenic organisms.

BACKGROUND TO THE INVENTION

Hitherto the disposal of clinical waste materials has been

confined generally to incineration. There are significant costs associated

with incineration, to ensure that gaseous emissions are satisfactorily

controlled. Large volumes of gases including C02, CO, NO_x, S02, can be

discharged to atmosphere as well as chemicals such as halogenated

hydrocarbons, hydrogen chloride and dioxins.

Monitoring emissions to atmosphere from incinerator stacks,

a condition of an environmental licence, is both complex and expensive

and there is significant public disquiet with the use of incinerators in

urban areas.

Incinerators have very high maintenance requirements

especially the refractory linings of combustion chambers. When

overloaded or when operating below optimal temperatures they can

discharge higher levels of pollutants to atmosphere. In addition an ash

waste product is generated which requires routine testing to determine

the concentration of pollutants such as heavy metals prior to stabilisation

and disposal.

Infectious pathogenic wastes are also treated in steam autoclaves to render them sterile. This method is a slower batch process

requiring intermittent loading of the equipment embodying this process.

The end-product of steam treatment is not biologically or chemically inert,

that is it can reinfect and secondly malodorous vapours are discharged during routine operation.

US 5,568,895, filed by the applicants, involved the treatment of waste materials with an oxidising solution, an alkali metal oxide or

hydroxide and a cementitious binder, comprising bentonite and sodium

silicate, which results in a disinfected mass with a fairly high residual

moisture content. The disadvantage with this process is the cost of the

reactants, complexity of the delivery mechanism, processing time, and the

bulk and weight of the resultant mass leading to increased transport and

disposal costs. The resultant disinfected mass contains greater than

50% by weight of additional material mostly excess calcium oxide and

retained water, apart from the addition of the cementitious material.

Apart from incineration, there exists no known process that

produces a reduced, sterile and inert end-product. OBJECT OF THE INVENTION

Accordingly, it is an aim of the present invention to overcome or ameliorate the known disadvantages of disposal of clinical waste materials, including pathogenic organisms and to provide an improved method for safe disposal thereof.

DISCLOSURE OF THE INVENTION

According to one aspect of the present invention there is

provided a method for disposal of clinical waste materials comprising the steps of:- shredding a clinical waste material to obtain a finely divided

particulate material;

disinfecting and containing dust particles and aerosols

produced during shredding by spraying shredded waste material with an

oxidising solution;

treating said shredded waste material with calcium oxide, in

the presence of water at a pH 9 or greater, to form a treated waste

material, said process characterised by;

de-watering the treated waste material to form a compacted

waste and an extracted alkaline aqueous phase;

said process further characterised in that the extracted alkaline

aqueous phase is returned to said waste material for

processing and initial disinfection

Clinical waste may include human tissue, such as hair, teeth,

nails and the like; visibly blood stained body fluids, material and

equipment; laboratory specimens and cultures, including specimen and

culture holders and containers; animal tissue, carcases and other waste

from animals; plastic bags and scrap plastic generally, syringes, needles

and other steel surgical tools and instruments; paper and cardboard.

Preferably said oxidising solution comprises a source of free

oxygen such as ozone, or a peroxide, a source of free halogens or oxy-

halogens such as chlorine, hypochlorites or other oxidants including

metabisulphates, nitrites, formaldehyde or glutaraldehyde. Most

preferably the oxidising solution comprises hydrogen peroxide. Preferably the particle size of the shredded waste is less than

40 mm. More preferably the particle size of the shredded waste is less

than 20 mm.

Suitably treating said shredded waste material with calcium

oxide, in the presence of water at a pH 9 or greater, to form a treated

waste material, results in a heat of hydration of between 60 and 85°C.

Preferably, said water present for the treating of shredded waste

is derived from said extracted alkaline aqueous phase.

Suitably, said extracted alkaline aqueous phase is returned to said

waste material prior to or during shredding.

According to a second aspect of the invention there is

provided an apparatus for carrying out the process according to the

invention, said apparatus comprising:-

a feed hopper;

a shredder with an inlet associated with said feed hopper;

a mixer adapted to receive shredded waste material from said

shredder;

a first meter to introduce an oxidising solution into said feed

hopper as a spray of droplets;

a second meter to introduce calcium oxide into said mixing

means;

discharge apparatus to discharge treated waste material from

said mixer;

a dewatering apparatus into which the discharge treated

material enters and is dewatered before final discharge, resulting in an extracted aqueous phase and a compacted waste; and

a recirculator and meter for returning the extracted aqueous phase

from the dewatering apparatus to one or more of the feed hopper,

shredder and/or mixer.

An apparatus for carrying out the process according to the

invention further comprises a compression device for compressing the

dewatered treated waste material, before final discharge.

Preferably said apparatus comprises a hopper feed

apparatus.

Suitably said hopper feed apparatus includes a meter to

determine the mass of material to be treated.

The shredder may comprise any suitable device to reduce a

waste material to a particulate form.

If required the shredder may comprise a two stage shredding

apparatus having the output of a first shredder in communication with the

input of a second shredder.

Preferably said shredder comprises, counter rotating knives

and hooks.

More suitable the shredder is in association with a filtration

device, for the additional containment of dust particles.

The mixer suitably comprises a high shear mixer.

Preferably the mixer comprises a paddle type mixer.

The first meter and second meter are preferably coupled to

said hopper feed apparatus to permit feeding at predetermined rates and

predetermined ratios of said oxidising solution and said calcium oxide. The discharge apparatus may comprise any suitable

conveyor.

The recirculator may comprise one or more holding tanks,

filters , pumps and associated meter or meters.

The process and apparatus of the invention has many

advantages over the prior art. These advantages include faster

processing and less mechanical and electronic complexity, high level of

safety through the self containment of the apparatus minimising risk of

exposure to pathogens for employees, significantly reduced use of

reactants, and reduction in the bulk and weight of disinfected waste.

While generally effective for its intended purpose of

processing a wide range of wastes, including quarantine materials,

confiscated drugs, putrescible and infectious pathogenic materials, in

practice the process of the prior art US 5,568,895 results in a treated

waste which is bulkier in volume and weight and is more costly. In

addition the bentonite and sodium silicate, used in the US 5,568,895

process are very expensive materials, which whilst effective for their

purpose add significantly to the initial cost of the waste processing.

Within the US 5,568,895 process it was thought at the time

that the only way to deal with trace cytotoxins on disposed dispensing

equipment was through alkaline decomposition caused by the calcium

oxide and binding or encapsulation. The bentonite and aqueous sodium

silicate act well to bind the cytotoxins and prevent them from being leached into landfill sites. The addition of the bentonite served partly to

absorb any excess moisture present in the treated waste to prevent leaching of aqueous phases and otherwise as a reactant with the silicate

to form a stable cemented mass. Calcium hydroxide residues also react

with the silicate. Much of the calcium hydroxide is still active when

silicate is added due to the variability of waste ingredients, as usual

excess lime is added to ensure adequate treatment. The addition of

these reactants to the treated process adds up to >50% by weight to the

final treated waste and increases transportation costs accordingly.

It is important to avoid addition of non-waste material to

landfills, as it increases transport and handling costs in the transporting of

waste and non-waste materials from the processing site to the landfill.

As landfill sites fill there is a need to find new landfill sites this becomes

increasingly difficult with the increase in urban space. As urban areas

expand and landfill sites become more remote it is important to look also

at the longer term costs of transporting wastes to landfill, through the

effects of transport vehicle travel and the flow on effects to air pollution

and consumption of fossil fuel. In addition the filling of a land fill site will

render a parcel of land unusable for many years as it needs to be left

untouched upon sealing under current environmental and town planning

requirements.

The use of bentonite and sodium silicate in the US 5,568,895

process add to the volume and weight of the final treated waste. This

results in the addition of "materials" into landfill that may be avoided.

Through the development of an improved process of the invention,

especially for the treatment of wastes which may become pathogenic

organisms, these disadvantages in costs and bulk of treated product contribute to addressing both the short and long term disadvantages of

the currently known processes.

BRIEF DETAILS OF THE DRAWINGS

In order that the invention may be more fully understood,

reference is now made to various preferred embodiments illustrated with

reference to the accompanying drawings in which:

FIG 1 shows a schematic view of an apparatus for processing

waste materials according to the invention;

FIG 2 shows schematically an electrical control circuit for the

apparatus of FIGS 1 ; and

FIG 3 shows schematically a materials flow chart.

DETAILED DESCRIPTION OF THE DRAWINGS

In Figure 1 , the apparatus comprises a feed hopper 1

associated with a shredder 2 driven by an internal combustion motor or

electric motor 3.

Associated with feed hopper 1 is an elevation mechanism 4

which is adapted to selectively elevate and tip one or more conventional

sized refuse bin(s) 5. Typically the refuse bin(s) are between 80 to 1 1 00

litres in capacity. Bin 5, for the purpose of elevation has a location

position on a weighing apparatus 6 such as a load cell platform or the like

calibrated to determine the load contained in bin(s) 5.

A conveniently located operation panel (not shown) in the

region of bin(s) 5 is provided for authorised operation of the apparatus by

means of a key activated switch or the like.

Upon activation of the operation switch associated with the operation panel, bin 5 containing waste materials is elevated and the

contents thereof are tipped into hopper 1. Preferably the mouth of the

bin(s) 5 is adapted to seal and engage the mouth of hopper 1 to ensure no spillage of contents from the bin(s) 5. Hopper 1 provides a feed chute for a shredder 2. The outlet

port of the shredder 2 may be in communication with the inlet port or feed hopper of secondary shredder 2b.

Feed hopper 1 may comprise a hydraulically or pneumatically

actuated closure door 1a to seal the mouth of the hopper during the

shredding operation. Preferably however, the mouth of the hopper is

sealed by leaving bin 5 sealingly engaged with hopper 1 during the

shredding process to provide a closure to hopper 1 .

During the tipping of refuse from bin 5 into hopper 1 , spray jets (not shown) located within hopper 1 direct an oxidising solution,

typically aqueous spray of 0.1 -10% hydrogen peroxide solution, into the

hopper 1 to disinfect and contain dust particles and/or aerosols from the

waste material being fed into hopper 1 . The hopper 1 is maintained at a

negative pressure by fans drawing air inside the hopper through a

filtration unit (not shown). The filtration unit generally contains filters

similar to HEPA (Trade Mark) in nature, having a 0.3 micron filter capable of removing and trapping microorganisms.

The oxidising solution is sprayed into the hopper 1 such that the droplet size is comparable to the particle size of the shredded waste. Air atomising nozzles may also be present to assist in the droplet formation of the oxidising solution. The extracted alkaline aqueous phase is

also sprayed over the waste mass in the hopper wetting the waste material.

The refuse treated with the oxidising solution and the extracted

aqueous phase then enters the shredding or pulverising means 2. Suitably the shredder may be a two or four shaft rotary knife and hook shredder such as Untha RS50 (Trade Mark), or similar

The shredding apparatus may further comprise a primary

shredder 2a and a secondary shredder 2b to ensure that the feed

material is reduced to a finely particulate matter. Suitably both primary

and secondary shredders 2a and 2b comprise rotary knife and hook

shredders such as Brentwood AZ-15 and Brentwood AZ-7 (Trade Mark)

shredders respectively. The apparatus described with reference to the preferred embodiment has been trialed with conventional hospital waste

comprising fabric bandages, swabs, glass, plastics and even stainless

steel surgical implements accidentally included in the waste.

The waste materials, after treatment with an oxidising solution such as 0.1 -10% hydrogen peroxide to capture aerosols are then wetted

with the extracted alkaline aqueous phase from spray nozzles located immediately above the waste materials and then subjected to shredding. Any pathogenic aerosols created during the shredding process are captured by the oxidant spray and/or the filtration unit. If required, the

oxidant spray may also be selectively directed into bin 5 to wash out the

bin and thoroughly disinfect it.

The shredded wetted waste passes from the shredding apparatus 2

onto a mix feed screw conveyor apparatus 8, to which calcium oxide (burnt lime) from hopper 9, via a conveyor 10, is added. The shredded

oxidised wetted material and calcium oxide then enters a mixer 1 1. The

mixer is a conventional fine clearance twin rotating paddle unit or a unit with

paddles mounted on the inner surface of the cylinder of the mixer.

After thorough mixing with the calcium oxide, the treated

waste material, progresses through the mixer to a screw dewatering press

12 to substantially remove any liquid component and produce a

particulate solid treated waste material. The particulate treated waste

material then fed onto conveyor 13 for either final disposal or enter into a

compactor 14 for compressing prior to entering a collection bin or the like

15.

FIG 2 shows schematically a control circuit from the

apparatus of FIGS 1 .

A microprocessor or programmable logic controller 17 is

provided to control the various aspects of the process such as feed ratios

of water, hydrogen peroxide, and lime; monitoring temperatures and pHs

in the mixer; mixer speed; dewatering step and return of the extracted

alkaline aqueous phase and compression as a function of the feed mass

detected by weighing apparatus 6. Microprocessor 1 7 is

programmable to compensate for differing types of feed material including

moisture content to ensure a thoroughly treated safe material exits from

the apparatus for subsequent disposal.

Metering pumps 18, 19, 20 respectively are employed to feed

water, hydrogen peroxide and calcium oxide to their respective feed or

introduction points in the system. As a function of the nett mass of the waste material

determined by weighing apparatus 6, programmable logic controller 17

determines, for a predefined waste material type such as hospital waste,

the concentration of the oxidant by metering respective sources of 50%

H2O2 and water to obtain approximately a 0.1 -10% H2O2 solution and the

feed rate of the extracted alkaline aqueous phase and the mass or

volumetric ratios of calcium oxide (burnt lime), to obtain a treated waste

material of a predetermined consistency. Preferably the hydrogen

peroxide solution has a concentration of 0.1 -5% H2O2. Most preferably the

hydrogen peroxide solution has a concentration of 0.3-3% H₂0₂. By

controlling moisture content, the moist material so produced issues from

the shredder 2 in the form of small particles less than 40 mm in diameter,

preferably less than 30mm in diameter.

FIG 3 shows a schematic flow chart of the process in

accordance with the invention.

During the shredding operation metered quantities of water

and concentrated hydrogen peroxide (50%) is diluted and fed into the

hopper 1 as a fine droplet spray at a 0.1 -10% concentration to reduce dust

and aerosols The extracted alkaline aqueous phase is also

added to the hopper to moisten the waste and to commence its disinfection

process in the high shear shredding or maceration process.

The shredded waste is then introduced to a paddle mixer

feed conveyor 8 to which lime is added before residing in mixer 1 1 for a

predetermined period. A quantity of lime to be introduced to the mixer is

controlled via an appropriate metering means. The treated waste then enters the dewatering press 12 and is dewatered prior to being

discharged. The discharged treated waste may be compressed in a

compactor 14 prior to final disposal. The alkaline aqueous phase of the

dewatering step is recycled to the hopper 1 and/or mixer 1 1 to start initial

5 disinfection..

The present invention is considered to be unique in that while

it has been known to denature clinical wastes by oxidation with halogens

and oxy-halogens, such material is not chemically inert and can discharge

these sterilising chemicals into the workplace and environment as

10 vapours. The inert particulate calcareous coated product produced from

this process is readily useful to line the perimeter of landfills and will

thereby neutralise the inherent acidity of the ground water/leachate.

The advantages of the process of the invention are manifold

and include; full automation of the process, failsafe computer activated

i s shutdown procedures, can be operated by one or two personnel and

there is no human contact with the waste, virtually no liquid or gaseous

emissions, no chlorine or other environmentally harmful chemicals used

or to be disposed of, no additional heating required, low energy demands

compared to incineration and other technologies, lower greenhouse gas

0 impacts and the final product being stable, reduced in volume and

unrecognisable as clinical waste.

The following examples serve to illustrate the various aspect

of the invention.

EXAMPLE1

5 Utilising the apparatus illustrated in FIGS 1 -3, clinical waste such as swabs bandages, tissue samples, biopsy samples, syringes, drug

containers and the like, are introduced into a single shredder 2 to at a

rate of 1 .5 tonnes per hour and shredded into a particle size of 30 mm or

less. At the same time, aqueous hydrogen peroxide at a concentration of

from about 0.1 -10% is introduced into the top of the shredder as a fine

droplet spray to disinfect the airborne particles and to prevent the

generation of aerosols which could carry toxic matter and contain the dust

from the shredder. The waste mass is then wetted by the alkaline aqueous

phase and HEPA filters remove additional dust and particles generated by

the shredder.

The shredded, initially wetted material then drops into the

mixer feed conveyor 8 whereupon a quantity of calcium oxide is added.

Calcium oxide reacts with the resident moisture to promote initial pHs of 13

or higher and a general heating of the overall admixture.

The intense alkalinity of the calcium oxide aided by the

residual heat of hydration causes the denaturing of microbial proteins and

enzymes, liquification of membranes and saponification of cellular fats

and lipids.

Heating of the overall admixture is generally in the range of 60 to 85°C.

The treated mixture typically has a residence time of 5 to 10 minutes in the mixer 1 1 .

The waste is subsequently mechanically dewatered to

produce a compacted waste of pH greater than 9.

The aqueous discharge from the dewatering step may be

recycled back to the beginning of the process for addition to the waste material in the instance that the waste material is low or very low in

moisture content. The recycling of the aqueous discharge reduces the

amount of lime and hydrogen peroxide required to disinfect the waste

material. The filtrate may be discharged into the sewer or to an off site

treatment facility for control of lime and scaling of equipment.

EXAMPLE2

A series of independent tests were carried out by a suitably

qualified laboratory on a mixed sample of hospital waste material treated

in accordance with the invention

The tests were designed to determine if the process meet the

Californian Department of Health Services (CDHS) guidelines. The

CDHS guidelines are the most stringent in assessing the safety of a

biohazardous or clinical waste. The CDHS guidelines or STAATT 2 report

define the requirements for microbiological testing for assessing

alternative treatment technologies as any proposed treatment method

shall be capable of destroying pathogenic bacteria, pathogenic fungi and

yeasts, spore forming bacteria and viruses, as well as bacteria which are

resistant to heat, antibiotics and disinfectants." The guidelines stipulate a

6 Log-io reduction in the concentration of a Mycobacte um sp., M. bovis

BCG, M. Phlei, or other species of mycobacteria, and a 4 Log-io reduction

in the level of Bacillus spores.

Clinical waste processed by the process and apparatus of the

invention is inoculated with mixtures of the aforementioned organisms.

Testing was conducted on two separate occasions. The first occasion the

waste mixtures were tested for their microbiological content on exiting the process and 24 hours post treatment. The second occasion the waste mixtures were tested for their microbiological content on exiting the process and 1 hour post treatment.

The waste mixtures used in the process included; routine medical waste with very low moisture; anatomical waste blended with routine medical waste with high moisture content; and quarantine waste with low moisture content.

The challenge microorganisms were prepared as freeze dried preparations into a 10% skim milk-base with organic yellow colourant added. On both test occasions, with the three waste types tested, the challenge inoculate were introduced to untreated waste, already with significant microbial population already present

Inocula were prepared by concentration and all testing was performed in duplicate with one replicate at a 'high' and the second at an 'extremely high' initial concentration The 'high' inoculum comprised 1 0 kg of 10⁸/g inoculum per 100kg waste resulting in an initial inoculum level of 10⁶/g of waste material The 'extremely high' inoculum comprised 1 0 kg of 10 /g inoculum per 100kg waste, resulting in an initial inoculum level of 10⁹/g of waste material The results of the test are summarised in Table 1 Significant

levels of microbial reduction were observed in the waste exiting the

process of the invention. It was demonstrated that vegetative bacterial

cells were reduced by 8 log-ι₀ units within five minutes of processing,

whereas mesophilic bacterial spores were reduced by 6 logio units within a similar time frame. The independent testing also evaluated the disinfection test results from the processing, for specified challenge microorganisms, as being acceptable according to the CDHS guidelines. The results are summarised in Table 2. In addition, other microorganisms were included in the challenge inoculum. Selected microorganisms were chosen to represent a range of vegetative bacteria, including those commonly occurring in a hospital waste environment together with typical fungi and yeast species. All of these other microorganisms were reduced to non-detectable levels during the course of processing.

It should also be noted that the microbial reduction continues after the waste exits the process. The independent testing determined time constants for this post processing microbial reduction, with a majority of the reduction occurring almost immediately. Anatomical waste showed a marginally greater rate of microbial reduction and lower final microbial counts than the routine processed medical waste. This is more likely due to the increased moisture level of the anatomical waste.

Table 1 . Summary of biological testing

1. High inoculum, usually at a level of 106 per g of waste material or level as indicated

2. Extremely high inoculum usually at a level of 109 per g waste material or level as indicated

3. Routing medical waste, low moisture

4. Anatomical waste blended with routine medical waste, high moisture

5. Quarantine designated waste from AQIS. very low moisture

6. Numbers correspond directly with waste type tested, eg; 3/4 in column 4 would have results written as those for waste type 3 / and those for waste type 4 as per the appropriate time

7. Not analysed (na)

Example 3

A second set of independent tests were carried out to

determine the temperature and pH of the waste during and/or post

processing. Waste material is treated according to the process of the

invention and the subsequent tests were carried out.

The discharge conveyor carrying treated waste from the

mixer to the 12 cubic metre steel skid tray bin or receival hopper fills it, at

the rate of approximately 4m³ per day during the challenge test as out

lined in the above example. Twenty one sample sites were chosen over

the area of the discharge conveyor. Samples A, B, C, D, E, N, O, P, Q, R,

S, T, were take at a point 300mm from the edge of the discharge

conveyor. Samples G, H, 1 , J, K, L, were take along the midline of the

discharge conveyor. Samples F, M, U, were taken 10mm from the edge

of the discharge conveyor.

Samples B, F, M, U, were measured at 10mm, 100mm and

500mm below the surface. Sample O was measured at 10 mm and 100mm

below the surface. Other samples were measured at 10mm below the

surface. Temperature recordings are summarised in Table 3.

Samples F and U were from the extreme edge of the

discharge conveyor (10 mm from the corner) where a significant air gap is

present which would allow rapid cooling of the waste.

Single location temperature profiling

The temperature change over time for a freshly processed

waste was monitored at sample site B over a period of 1 hour. Chilled waste with an initial temperature of 0.6°C was processed. Initially the probe was located on the surface of the discharge conveyor however as the waste depth built up the probe was set at !mm from 25 minutes onwards. The temperature reading are set out in Table 4.

Table3. Temperature measurements for a range of sample sites on discharge conveyor The processed waste increases in temperature from less than 4°c to reach a core temperature of greater than 60°c in less than 60 minutes, and a minimum core temperature of 80°c in less than 90 minutes.

Table 4: Temperature profile post processing pH Monitoring pH Monitoring

The pH was recorded using an EML pH meter EB1-5, a Schott Handilab 1 unit calibrated using certified pH buffers supplied by Amyl Australia. The pH was measured at sample locations B, K, M, U. The measurements are summarised below in Table 5.

Table 5: pH measurements on post processed waste

It will be readily appreciated by a skilled addressee that the apparatus and method according to the invention provides an effective, economic means for treatment of wastes containing pathogenic organisms. The chemical treatment processes are simple and easy to manage and the self contained apparatus are virtually fail safe in terms of operation.

The resultant disinfected product of the process of the invention disinfects the pathogenic microorganisms through the formation of an environment with a high pH. The resultant pH is between 11 and 13. The product of the process is non-pathogenic, odourless and spadable allowing for easy handling and disposal.

The process of the invention is safe to those people working in the area as it does not off gas vapour, the process is fully automated

Claims

and any dust or aerosols are contained through the use of the hydrogenperoxide overspray and HEPA filters.The hydrogen peroxide is fully consumed in the process andany remaining amounts present in the compacted waste is belowdetectable limits. The addition of lime to the shredded waste not onlyelevates the pH and therefore disinfects any pathogens, the heat of thereaction also assists in the disinfection aspect of the process.None of the chemical residues in the treated product poseany short or long term environmental threat, thus permitting simple andinexpensive disposal in landfill sites.Throughout the specification the aim has been to describethe preferred embodiments of the invention without limiting the inventionto any one embodiment or specific collection of features.We claim:

1 . A method for treatment of waste comprising the steps of:

shredding with a suitable shredding apparatus with a receival hopper a waste

material to obtain finely divided particulate material ;

capturing aerosols with an oxidising solution

wetting said waste with extracted alkaline aqueous solution

following said shredding and wetting steps treating said waste

with an alkaline earth oxide or hydroxide;

and mixing the alkaline earth oxide or hydroxide treated waste in a suitable

mixer the resultant treated waste material comprising a moist particulate

disinfected mass;

2. A method as claimed in claim 1 n wherein the resultant moist particulate mass is conveyed to a pressing apparatus whereby excess alkaline fluid is pressed out of the said mass;

3. A method as claimed in claim 1 wherein the said alkaline fluid is collected

and conveyed back to the said hopper

4 A method as claimed in claim 1 wherein the said alkaline fluid is collected

and conveyed back to the said mixer

5. A method as claimed in claim 1 wherein the alkaline earth oxide comprise calcium or magnesium oxide;

6. A method as claimed in claim 1 wherein the earth hydroxide comprise

calcium or magnesium hydroxide;

7. A method as claimed in claim 1 wherein the oxidising solution comprises an

aqueous peroxide solution

8 A method as claimed in claim 1 wherein the oxidising solution comprises an aqueous hydrogen peroxide solution

9. An apparatus comprising:

a feed hopper;

a shredding system with an inlet associated with said feed hopper; a mixer adapted to receive shredded material from said shredder;

a dewatering press adapted to receive shredded material from said mixer; a first metering system to introduce an oxidising solution; a second metering systtem to introduce excess alkaline fluid collected and returned from said dewatering press; a third metering system to introduce an alkaline oxide or hydroxide into said mixer;

10. An apparatus as claimed in claim 9 including a device to compact the discharged treated waste prior to disposal;

2. A method as claimed in claim 1 wherein the said alkaline earth oxide or hydroxide has a suitable dye added to it such that the waste after said treatment is recognisably coloured by the said suitable dye.