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Appropriate technologies for the treatment of scheduled wastes

CMPS&F - Environment Australia
Review Report Number 4 - November 1997


Contents

SUMMARY


 

GENERAL

A review has been carried out to determine the current status of the development and availability within Australia of technologies for treating scheduled wastes. The review will be used:

This report is the final review in a series of reports prepared by CMPS&F Environmental. The reports are titled "Appropriate technologies for the treatment of scheduled wastes", and the first report was published in November 1994.

TREATMENT TECHNOLOGIES INCLUDED IN EARLIER REVIEWS

The treatment technologies reviewed in the last report included:

Information was sought on the various processes from the technology suppliers, with a focus on Australian suppliers and applications. In some cases the information obtained was limited, with the intention that future reviews would provide more comprehensive and more up-to-date information.

High temperature incineration has not been considered as a current option for the treatment of scheduled wastes.

TREATMENT TECHNOLOGIES INCLUDED IN THIS REVIEW

The treatment technologies reviewed in this final report, include the treatment technologies detailed in the third report plus the following additional technologies submitted for this review:

Additional updated information was sought from technology suppliers on the various processes reviewed in the last report. Where information was made available it was included in this report.

QUANTITIES AND PHYSICAL FORMS OF SCHEDULED WASTES

The quantities and physical forms of scheduled wastes in Australia are not well defined. Hexachlorobenzene waste forms the greatest single category of concentrated scheduled wastes, and these are held at a single location in New South Wales. Apart from this waste, there are large quantities of wastes with low concentration of scheduled waste, including pesticide contaminated soil, pesticide formulations, and PCB contaminated oil and soil. Other wastes include non-pesticide chlorinated hydrocarbons. In general, the quantities which will require treatment will depend on the scheduled waste threshold concentration and landfill acceptance criteria (yet to be specified for all scheduled contaminants).

In most cases it is the physical form of the waste rather than the scheduled waste constituent which determines the applicability of a particular treatment technology. For the purposes of summarising the current status and the applicability of the various technologies, the wastes have been categorised into several groups in terms of physical form and occurrence: contaminated soil; irregular larger inert solids; organic low volatility liquids free of coarse solids; wastes containing high volatility liquids; solid and semi-solid process materials; and aqueous wastes and sludges.

CURRENT CAPABILITY OF THE TECHNOLOGIES FOR TREATING THE VARIOUS FORMS OF WASTE

Changes in the Scheduled Waste Industry since the Previous Review

Since the previous review on scheduled waste treatment technologies, there have been several changes in the Australian waste industry which affect the ability to treat and dispose of scheduled wastes. The key changes are summarised as follows:

Summary of Findings

The findings of the current review are summarised in Table S1 and Table S2.


Table S1
Summary of Applicability of Available Waste Treatment Technologies



Table S1 lists the various waste categories of particular interest in the treatment of scheduled wastes and the applicability of the various treatment technologies. In most cases it is the physical form of the waste rather than the scheduled waste constituents which determine the applicability of a particular treatment technology.


Table S2
Summary of Waste Treatment Technologies



Table S2 allows a comparison of the various emerging treatment processes with regard to the key operating parameters detailed for each technology.

For each of the waste types the current status of available treatment technologies is as follows:

Soils

There are large quantities (>100000 tonnes) of soils contaminated with scheduled wastes which may require treatment.

Soils containing scheduled waste are not able to be treated in significant quantities at this time in Australia. BCD Technologies has constructed a thermal desorption system in the treatment of soils and have applied for a licence for the unit. However, they are not actively pursuing this as they have not experienced strong demand for a soils treatment system. The PLASCON unit purchased by BCD Technologies may be linked with a thermal desorber for the treatment of contaminated soils.

The Eco Logic facility is able to treat a range of wastes, but a thermal desorption unit suitable for large quantities of soil is not planned to be constructed in the short term. Small quantities of porous soils are able to be treated using the Eco Logic Sequencing Batch Vapouriser (SBV).

ADI have demonstrated the use of the STTP/BCD process as a single stage process, in conjunction with a thermal desorber, for the treatment of contaminated soils. This process has considerable potential for the treatment of contaminated soils and full scale application in New Zealand in the next 3 years is likely.

Tox Free Systems have developed a thermal desorption system that is available on a full scale and has been demonstrated on a pilot scale for the treatment of organochlorine pesticide contaminated soils (particularly DDT).

Other technologies which are potentially applicable to the treatment of soils contaminated with scheduled wastes include Plasma Arc Centrifugal Treatment (PACT), Thermal Desorption System (PCS Technology), Supercritical Water Oxidation (SCWO), ball milling, solvated electron technology, Viking Gasification System (VGS), and solar detoxification. However, pretreatment may be required due to restrictions on the form of the waste which can be treated, such as particle size or the amount of inert material in the waste. These technologies, however are unlikely to be available commercially in the short to medium term (refer Glossary for definitions of short, medium and long term in the context of this report).

Molten media process such as molten metal, molten slag and molten salt can be used for the treatment of soil however in practice the inorganic content of soils means these processes are not economic.

Irregular Larger Inert Solids

Large inert solids such as concrete, timber and metal demolition materials and equipment need to be crushed or shredded prior to treatment, or alternatively washed (using an aqueous or organic solvent wash) with separate treatment of the wash solution.

If the material is impregnated with contaminant then crushing (eg for concrete) or shredding (for metals) is likely to be necessary. Crushed or shredded material will require treatment in a system which is able to accept such material, and comments similar to those regarding the availability and applicability of technologies for soils apply. In general, other than in certain specific cases, large quantities of large solid materials impregnated with scheduled wastes are not able to be treated at this time in Australia.

One such case is PCB capacitors. The Eco Logic system in Western Australia is able to treat capacitor material directly. However capacitors are not suitable for direct treatment in BCD systems because capacitors contain aluminium and there is potential to form hydrogen under alkaline conditions. BCD Technologies in Queensland is currently pretreating capacitors by shredding and dissolving the material in sodium hydroxide at ambient temperature. This dissolves the aluminium and the mixture is then suitable for treatment by the BCD process.

If the material is non-porous (such as metal) then washing can be expected to be a practical option. The BCD treatment plant in Queensland has facilities for solvent washing or extracting solid items with treatment of the wash solution by their BCD treatment system. These facilities are currently licensed and are routinely applied to equipment containing PCBs and to a wider range of scheduled wastes. The Eco Logic treatment facility in Western Australia is able to treat non-porous items in the SBV.

If the equipment material is porous (eg corroded metal, concrete), then the equipment may need to be shredded and treated directly in the BCD process. The proponents of the Solvated Electron Technology process claim it has the potential to treat a range of porous and non-porous wastes, however the process is yet to be established in Australia.

In general, treatment of wash solutions which are free of solids is a relatively easy task and a variety of treatment systems (eg PLASCON, steam detoxification, PACT, molten media, cement kilns) are applicable to the treatment of these waste solutions.

The PACT and STARTECH systems are able to accept a wide range of waste materials, including relatively large solid articles. Although PACT technology has reached commercial application overseas it has not been established in Australia. The STARTECH system is yet to be established in Australia.

Ball milling should be able to accept items of contaminated electrical equipment and damaged or corroded waste containers, but the process is still under development and is unlikely to be commercially available in the short to medium term.

The Molten Metal process can be used for the destruction of contaminated electrical equipment.

Although cement kilns are applicable, treatment of scheduled waste materials by this process is unlikely to occur on a commercial scale in the short term. Some cement kiln operators have expressed the willingness to consider the treatment of scheduled wastes. However, this would be dependent on the resolution of a range of financial, social and political considerations which is unlikely in the short term.

Organic Low Volatility Liquids Free of Coarse Solids

There are large quantities (>100,000 tonnes) of mineral oils contaminated with PCBs which may require treatment. Smaller quantities of PCB fluids and low volatility liquids containing OCPs may require treatment.

Treatment of organic low volatility liquids such as Askarel fluids and mineral oils containing PCBs is a relatively easy task and facilities using the BCD process are currently in operation in Queensland and Victoria. The Queensland BCD facility is licensed to treat a range of wastes and concentrations. A facility at Technosafe in Victoria is licensed to treat PCBs up to 2% concentration. This facility was damaged by fire but is now operational again. The Eco Logic system is also able to treat organic liquids. The establishment of a PLASCON system at the BCD Technologies facility in Brisbane is expected to significantly improve the treatment capability for high strength organic liquids. ADI is currently trialing a BCD liquid treatment facility. While the current trials focus on pesticides, it is likely that the system could equally be applied to other organic liquid wastes.

Other treatment systems such as steam detoxification, solvated electron technology, a catalytic process, PACT, STARTECH, molten media, solar detoxification and VGS can be expected to be applicable to a range of organic liquids containing a range of scheduled waste types. However, most of these are not likely to be commercially available for several years. It is also unclear as to whether the Australian market is sufficiently large enough to support additional facilities if those currently established or proposed for the immediate future, are working near capacity. Cement kilns are also technically able to treat such materials (refer to previous comments regarding other considerations in the case of cement kilns).

PCB Gone, Catalytic Treatment and Stopped Counter Flow adsorption are processes which have been specifically developed for the treatment and regeneration of mineral oils containing PCBs (such as occur in electrical transformers). Of these processes, the PCB Gone treatment system is well established overseas, and the Catalytic Treatment and Stopped Counter Flow adsorption processes are under development in Australia for this purpose. The PCB Gone process is no longer represented in Australia.

Ball milling is likely to be able to treat most waste types but is most effectively applied to concentrated wastes such as concentrated PCBs and DDT. The Supercritical Water Oxidation technology is applicable to the treatment of aqueous waste streams including contaminants such as pesticide wastewater and PCBs. These processes currently remain in the experimental phase in Australia.

Wastes Containing High Volatility Liquids

There are relatively small quantities (<5000 tonnes) of scheduled waste containing high volatility liquids.

Wastes containing high volatility liquids (such as pesticides in toluene) can be treated in the excisting BCD systems (although some additional odour control equipment may be required compared to a BCD configuration designed for PCB treatment). If significant quantities of volatile solvents are involved, then stripping of the solvents may be necessary to ensure that the boiling point of the oil used in the BCD process remains within the desired range. ADI are currently trialing the treatment of solid and liquid OCP wastes in a BCD facility in New Zealand.

The Eco Logic facility in Western Australia has successfully treated three tonnes of OCP waste pesticide materials. The nominal capacity of this unit is significant in terms of the overall market size for this waste category in Australia; however, to date the quantity of wastes treated has been limited by process reliability issues.

The PLASCON unit to be installed at the BCD Technologies facility in Brisbane will add to the treatment capability in Australia for such wastes. PLASCON has successfully treated a waste stream at the Nufarm site in Laverton which contains 40% chlorophenols, 40% chlorophenoxy acetates and 20% toluene. While the Nufarm facility is not being used to treat a scheduled waste, it demonstrates treatment of a similar waste.

The treatment processes Eco Logic, PACT, steam detoxification, solar detoxification and molten media should be suitable to treat waste containing high volatility liquids.

The Catalytic Treatment process is claimed to effectively degrade chlorinated compounds such as DDT, hexachlorobenzene (HCB) and dioxins. Although demonstrations on a pilot scale are currently under way, this process is unlikely to be available on a commercial scale for a year or two. The solvated electron technology is expected to be suitable for treatment of this class of wastes although establishment of the technology on a commercial scale in Australia may be up to 1 to 2 years away.

Ball milling and SCWO technology are likely to be applicable and gasification (VGS) is able to treat a range of organochlorine pesticides, however, these process are unlikely to be available commercially in Australia in the short term. Cement kilns are also likely to be able to treat this type of waste.

Solid and Semi-Solid Materials

There are moderate quantities (>10000 tonnes) of solid and semi solid process materials which may require treatment. In addition, significant quantities of solid OCP wastes (eg obsolete powders) may require treatment.

Solid and semi-solid process materials such as filter cake, tars and powders are variable in nature and treatment requirements. The excisting BCD and Eco Logic treatment systems may be able to treat some of these wastes. The Eco Logic unit has been used to treat powdered OCP wastes using the Sequencing Batch Vapouriser. Large amounts of material will require pre-treatment (eg in a thermal desorption unit), and similar comments regarding the availability and applicability of alternative treatment technologies apply as for soils and larger inert solids impregnated with contaminants.

The TFS thermal desorption system has been used for the treatment of oil industry sludges and may be applicable to solid and semi-solid process materials, depending on their specific characteristics (although the process has been promoted for the treatment of soil contaminated with OCPs). The PCS Technology thermal desorption process can be expected to be able to treat organic and/or inorganic materials contaminated with a combination of organics, halogens and heavy metals provided they can be decomposed by reductive thermal treatment below 600oC, and reduced to a size range of less than 5 mm. Detailed manufacturing designs have been completed for full scale units and full scale demonstrations of the PCS process in Australia are proposed.

The Viking Gasification System (VGS) is claimed to be able to treat solid and semi-solid waste materials, however, VGS technology has not been trialed or demonstrated in Australia. The solvated electron technology may also be applied to the treatment of much of this class of waste and the technology has the potential to be implemented in the short term (1 to 2 years).

Molten media processes may be applicable to this waste type, however, wastes comprising mostly inert material cannot be treated in some processes, or may be uneconomic to treat using others.

Solid and semi-solid process materials may be treated using ball milling, PACT, STARTECH and SCWO; however, these processes are unlikely to be available in Australia on a commercial scale in the short to medium term.

Some materials such as tars may be difficult to handle and may require waste-specific pre-treatment systems. This is the case with HCB waste held at Botany, where large quantities of polymerised and tarry material will require a treatment system which is specifically designed to deal with such material.

Aqueous Wastes and Sludges

There are only small quantities (<1000 tonnes) of aqueous waste sludges which may require treatment.

Waste with a high water content can be treated in the BCD systems if only small quantities are involved. Distillation of the water may be necessary with subsequent treatment of the residual contaminant, if larger quantities are involved. The Eco Logic process is able to accept wastes with a higher water content.

The Viking Gasification System (VGS) may treat sludge from water and wastewater treatment plants, and aqueous wastes such as industrial process wastes. This process is still being developed.

SRL Plasma claims that PLASCON is able to treat liquids, viscous liquids and sludges (Hawkes, 1995). However, pretreatment is required to process any waste stream which is thicker than 30-40 weight motor oil. PLASCON treats the moderately viscous Nufarm waste which has a solids content of 40%. The installation of a PLASCON unit at the BCD Technologies facility in Brisbane will add significantly to treatment capability in this area.

The solvated electron technology is suitable for treating aqueous sludges having a water content up to 25% but this process is not yet available in Australia.

Steam detoxification can be used for the treatment of aqueous wastes and sludges, and given the nature of the process, the water content of such wastes is less problematic than for many other treatment processes.

PACT and STARTECH are applicable to the treatment of this waste type. However, concentrated wastes are preferred by such technologies for economic reasons. Molten media processes are not able to treat wastes comprising predominantly inert material, however, wastes which are reasonably homogeneous and have a significant organic content can be treated.

The PCS thermal desorption process has been designed for the treatment of mixed solid hazardous waste and it is claimed that the process can treat sewage sludge. This process is not suitable, however, for the treatment of liquids.

Ball milling is expected to be applicable to this waste type, however, it is most effectively applied to concentrated wastes. A SCWO unit is being developed in the US to treat sludge from pulp and paper plants in Canada, however, SCWO technology is only in the research phase in Australia.

The PACT, molten media, ball milling and SCWO processes are not likely to be available commercially in Australia in the short to medium term.

Cement kilns are applicable to this waste type however, it is not likely that commercialisation of this process for the treatment of scheduled wastes will occur in the short term.

Sludges with a high solids content involve many of the considerations associated with treating soils and other materials such as tars, and the comments in the above sections dealing with these materials are relevant.

MATERIALS HANDLING CONSIDERATIONS

The practical constraints associated with materials handling in the treatment of scheduled wastes often govern the selection of treatment options. Wastes are often in diverse forms, particularly when contaminated soils, demolition equipment, and process wastes are involved. Such materials can present difficult handling problems, and pre-treatment systems or specific technologies may need to be applied to such materials. In some cases the development of an appropriate materials handling strategy and pre-treatment system can be a more difficult and costly problem than the treatment itself.

The diverse waste forms and packaging (eg small plastic containers of OCP liquids, bagged powders) observed in the case of stockpiles from community chemical collections represent a specific range of materials handling challenges.

Waste treatment companies have focused on the most easily identified and serviced segment of the waste treatment market, that of PCB liquids. The treatment of liquids is readily accomplished using the currently available treatment systems. Treatment facilities with a broader range of application, (eg treatment of capacitors, soils, and polymerised materials) are more complex and are only now being established.

MIXED WASTES

Mixed organochlorine pesticide and inorganic wastes (eg DDT/As and OCP/iron mixtures) represent a specific concern in scheduled waste treatment. Thermal treatment processes producing a slag (eg PACT, Molten Slag, Molten Salt, Molten Metal, STARTECH) are able to treat these wastes. However, for other processes the arsenic passes through the system, and requires separate management of the process residuals. Concern regarding the treatment and disposal of arsenic containing process residuals (eg scrubber blowdown water from the Eco Logic process, or solid residue from the ADI STTP or BCD process). With respect to OCP/iron mixtures the primary concern is associated with interference of the treatment process, rather than disposal of residuals.

To date waste treaters have had sufficient wastes to treat and hence there has been little commercial pressure for waste treaters to accept significant quantities of arsenic containing wastes.

LOCATION AND PORTABILITY OF TREATMENT FACILITIES

The applicability of the various treatment technologies is dependent on the location of treatment systems, and whether wastes can practically be transported to the facility. The Queensland BCD system is portable and can be used in various locations in Queensland (although it is largely operated as a fixed unit). The Eco Logic system is relocatable, and generic approval has been obtained for operation of the Eco Logic system in NSW. In practice, considerable effort would be required to relocate either the Eco Logic or Queensland BCD units. To date each has been largely operated as a fixed unit, receiving wastes nationally, rather than relocating to the waste. An exception to this was the short term relocation of the BCD Technologies treatment system to a navy establishment in Western Australia.

However, interstate transport will depend on the availability of treatment systems within the state in which the waste originates and the economics involved. While it is desirable to minimise transport of scheduled wastes, it is not practical to eliminate transport, as this could preclude, delay or increase the costs associated with the treatment and disposal of wastes.

IMPEDIMENTS IN DEVELOPING AND APPLYING SCHEDULED WASTE TREATMENT TECHNOLOGIES IN AUSTRALIA

In conducting this review, CMPS&F notes the following issues that would appear to be impacting on the development of scheduled waste treatment facilities in Australia. These are based on comments received from waste treatment organisations and waste holders:

For example, the tolerable concentration of a scheduled contaminant in a waste or treatment residual depends on the fate of these materials (eg landfill, reuse) and can be highly site-specific. The establishment of uniform standards may limit the options available on a site-specific basis. Further, such standards may preclude certain technologies when the standards are not necessary in every case.