WO1997010190A1

WO1997010190A1 - A method and system of processing waste

Info

Publication number: WO1997010190A1
Application number: PCT/AU1996/000578
Authority: WO
Inventors: Gerard Gillespie
Original assignee: ACT DEPARTMENT OF URBAN SERVICES
Current assignee: ACT DEPARTMENT OF URBAN SERVICES
Priority date: 1995-09-13
Filing date: 1996-09-13
Publication date: 1997-03-20
Anticipated expiration: 1998-03-13
Also published as: AUPN541095A0

Abstract

A method/system for processing waste, and the product produced by the method. The method supplies earthworms to a mixture of waste products, such that the earthworms digest the mixture and produce castings. The mixture comprises shredded paper, cardboard or like material, and, sludge, sewage or the like, which may typically contain high levels of heavy metals, such as cadmium. The process is particularly suitable for the processing of organic waste maerial from a sewage or sludge pond. The product may be used as a fertiliser, for example, on broad acre crops, or, as an aquaculture food source.

Description

A METHOD AND SYSTEM OF PROCESSING WASTE

Background of the Invention

The present invention relates to a method and system for processing waste, utilising earthworms or the like. In particular, the present invention relates to a method of processing a combination of organic waste material such as sludge, sewage or the like, and, cellulose fibre. The present invention has particular application to the processing of sewage sludge, typically contained in sludge lagoons or the like, which commonly have high levels of heavy metals, such as cadmium. By utilising the method of the present invention, a useful plant growth fertiliser/additive soil conditioner material is produced, and, in addition, heavy metals are removed from the sludge.

Description of the Prior Art

One of the responsibilities of waste management departments of local Government organisations is to carry out regular garbage collections from domestic and commercial premises. In fairly recent times, such waste material is being sorted by the householder into recyclable and non-recyclable material. The recyclable material is sometimes even sorted into different types of recyclable material such as paper, bottles, etc. Waste organisation/management can then transport the bottles, recyclable paper and other recyclable materials to the appropriate recycling authorities, and discard the remainder at land fills, etc. One ofthe materials which is typically collected by such waste management organisations is 'soiled paper material', such as paper which is contaminated with food remnants or other materials. Such materials are generally classified with those materials which -ire non-recyclable. The present invention seeks to 'recycle' such 'non-recyclable' paper materials and the like as one source of cellulose fibre.

Another ofthe typical responsibilities of local Government organisations, is to manage sewerage treatment works. Typically, such sewerage treatment works comprise ponds containing sludge which are contaminated with a cocktail of heavy metals and organic contaminants. Traditionally, in the reclamation of such sewage ponds, it is necessary to physically transfer the sludge to a different site or attempt to utilise some ofthe sludge by composting. The present invention seeks to provide a method of reclaiming such sewage pond materials. It is also presently known to utilise earthworms in "compost bins" for the breakdown of organic material, including garden clippings and vegetable waste. The worms feed on the organic materials, such that their digestive processes cause the breakdown ofthe organic matter. The present invention seeks to provide a method and system for processing waste, which utilises earthworms or the like.

Summary ofthe Invention

The present invention seeks to provide a waste processing method and system which can turn a combination of waste materials into useful products.

The present invention seeks to provide a waste reduction process whereby a material which is generally considered to be non-recyclable such as soiled paper and cardboard or other cellulose can be processed and effectively recycled.

The present invention also seeks to provide a waste reduction process which processes organic material such as sludge, sewage, and like material.

The present invention also seeks to provide a waste reduction process, wherein, in the processing ofthe sludge sewage and like material, heavy metals are removed from the material.

The present inventions also seeks to provide a waste reduction process which utilises earthworms, or the like.

In one broad form, the present invention provides a method of processing waste, utilising earthworms or the like, comprising the steps of: shredding paper, cardboard or material; mixing said shredded material with organic waste material, such as sludge, sewage or the like; supplying said earthworms or the like to said mixture such that said animals digest said mixture and produce castings.

Preferably, said organic waste material is derived from a sewage or sludge pond or the like.

In a preferred form, said organic waste material may contain heavy metals, such as cadmium.

The process preferably further comprises the steps of: separating said earthworms from said castings; or processing said castings for use as a fertiliser/additive material.

Preferably, said processing step, when processing said castings, comprises: forming a solution utilising said castings; adjusting the pH of said solution to an alkaline solution, preferably having a pH of approximately 8. 5, by adding alkali such as sewage ash, lime, or the like, such that precipitation of heavy metals, such as cadmium, occurs therefrom.

Preferably, a ratio of said mixture is about 50% shredded material and about 50% waste material, but may vary to suit available food sources and worm species used.

Also preferably, in said supplying step, said mixture and said earthworms or the like are provided in conditions having predetermined moisture, temperature and/or nutrient levels.

Preferably, said moisture levels are damp to extremely high, said temperature ranges are from about 1 5 C to 26 C, but preferably about 23 C, and, said nutrient levels are maintained by providing a relatively high level of bacteria.

Brief Description of the Drawings

The present invention will become more fully understood from the following detailed description of a prefeπed but non-limiting embodiment thereof, described in connection with the accompanying drawings, wherein:

Fig. 1 illustrates a schematic flowchart outlining the various steps in a heavy metal extracted process ofthe present invention; Fig. 2 illustrates a 'closed loop' farming/processing system ofthe present invention; and Fig. 3 illustrates a schematic flow chart of a composite worm waste reduction process.

Detailed Description of Preferred Embodiment It should be appreciated that in reading the description hereinafter, preferred but non-limiting embodiments ofthe invention are described. It will be appreciated that numerous variations and modifications will be capable of being made to the invention, without departing from the scope ofthe invention.

The Applicant of the present invention, the ACT Department of Urban Services, is a government authority which is responsible for the routine collection and processing of domestic and commercial waste. Whilst various parts of such household and commercial waste are able to be re-used, by recycling processes, not all ofthe collected garbage, for instance, organically contaminated paper and cardboard material, including paper and cardboard material soiled by foodstuffs, etc., is able to be recycled. The present invention provides a method of reducing waste which can utilise such cardboard and waste material, which is generally considered to be 'non-recyclable'.

The Applicant of the present invention is also responsible for management and reclamation of decommissioned sewerage treatment ponds, including the Coppins Crossing and

West Macgregor ponds in the ACT, Australia. Ponds such as these hold vast quantities of sewage sludge. One ofthe primary reasons for wanting to rehabilitate such sewage ponds is such that the land can be utilised for other purposes, such as residential or commercial purposes.

Past practices of sewage disposal by commercial and industrial entities have resulted in waste fluid products of a variety of forms, being provided into the sewage system. This has resulted in various levels of metal contamination ofthe sludge held in such ponds. Samples from such ponds have been analysed by the inventors revealing a cocktail of heavy metals and organic pollutants. Specific levels of contamination vary between different ponds, but typically, the major contaminants are cadmium, chromium, copper, lead, organic pollutants and zinc.

The present invention seeks to provide a method of reclaiming such sewage ponds by utilising a specific process which incoφorates the use of earthworms or the like. The inventors have discovered that earthworms can be used to reduce the levels of heavy metals in sewage sludge, whilst at the same time rendering the processed material pathogen free and available as a soil conditioner.

The process of the present invention takes advantage of waste material, such as solid papers and cardboard, in the processing of organic material, including such sewage or sludge. The mixture is then suitable for processing using the earthworms or the like.

Fig. 1 describes a preferred embodiment of the invention whereby a sewage or sludge pond may be remediated utilising the system in accordance with the present invention. The organic material from a sewage pond 1, contaminated with heavy metals and the like, is aerated 2 and then mixed 3 with paper or the like 4, primarily to increase the bacteria production and worm food value, but also consequentially to decrease the proportion of metal contamination by, say 50%. The next step 5 is the processing ofthe sewage sludge by worms, to produce castings. As the worms process acidic waste, the mixed material goes through a pH shift, whilst the worms absorb heavy metals into their bodies. The level of cadmium and other heavy metals is then low enough to be used on broad acre crops. The worm castings 6, because of worm gut bacteria, are then readily dissolvable. The next step 7 is to remove the heavy metals. For this puφose, the pH ofthe mix is adjusted to about 8.5 by adding sewage ash or lime. As the material reaches a pH level of about 8.5, as shown in step 7, heavy metals drop out ofthe solution by precipitation.

The solution may then be pumped off for transportation, as shown in step 8, for use on broad acre crops 9, and the castings may be dried as shown in step 10, and processed for the separation of selected metals 11.

A "closed loop" farming/processing system is being another prefeπed embodiment ofthe present invention, is shown in Fig. 2, which starts and finishes with an animal 20 consuming a protein product 21. The excrement 22 from the animal 20 is then supplied into a worm bed 23 for appropriate decomposition by the worms. Excess worms may be washed in a water/alcohol mixture 24, dried and cured in an oven or like device 25, for supply, as protein, back into the feeder 21. The worm castings may be supplied for agricultural puφoses 26 for the growing of grain crops or lucerne crops, again for consequential resupply into the feeder 21.

A preferred embodiment of an overall process ofthe invention, shown in Fig. 3. After collection ofthe garbage from the commercial or residential premises, by a collection vehicle 31, the garbage is sorted by a known sorting conveyor the like 32, such that the organics are separated therefrom. The organics are then shredded as indicated at reference numeral 33, and mixed in a suitable mixing apparatus 34, with paper, cardboard and the like. A suitable aerating agent may additionally be supplied into the mixer 34. Various additional steps may be included as indicated by reference numeral 36, such as re-injection of warm air to encourage rapid breakdown of organics to kill harmful pathogens and assist breakdown. Additional additives may be supplied at this point, depending upon the material being processed.

After output ofthe mixed material 37, it is supplied into worm beds 38 and left until it is at least partially decomposed. After processing of the material 37, excess worms may be supplied for further processing as indicated at reference numeral 39, whilst the worm castings may be supplied for alternative processing as indicated by reference numeral 40.

The processing ofthe excess worms 39 may incoφorate the steps of washing the worms in a water/alcohol mix 41 , drying them in an oven to dry the worm protein 42, and then crushing the dry protein at 43. The crushed dry protein may be then utilised for aquaculture purposes or the like 44.

The worm castings may be processed by firsdy drying and sieving them 45, and preparing them for application, 46 as a fertiliser or other soil conditioner 47, for agricultural puφoses. The following flow cha illustrates an overview of the process in accordance with the present invention, providing an indication of the typical time to perform the process and an estimate of costs experienced/estimated by the Applicant

COMPOSTING/WORM FARM PRODUCTION FROM WASTE STREAM ORGANICS

Collect organics- Castings Contaminants removed- current value at end material shredded of process

$500 per tonne

Total weight 8 Tonne Total value $2000

Notes to the Process

Sewage ponds at Macgregor and other sites were passed on to Waste Management when ACTEW opened its processing plant at Lower Molonglo.

These sewage ponds contain heavy metals of unacceptable levels for location on or near urban development. In total, there are approximately 17,000 cu metres (17,000 tonnes) of this material. Options for remediation are...

1. Processing through Lower Molonglo sewerage treatment works at a total cost of $1.7 million. 2. Bulking with organic waste to reduce cadmium to acceptable levels for agricultural use - Total cost $800,000.

3. Worm farm processing - Total cost $300,000.

Remediation of the sludge ponds would release a large tract of land for urban development. • This process can be applied to any sewage scheme.

Any township of up to 40,000 population can use this process to produce castings for broad acre application from sewage sludge and paper waste especially in locations where recycling in impractical. • The process could be applied to a variety of soil remediation projects including those with arsenic contamination.

The technology would remain the patented property ofthe ACT and has the potential to generate funds in any area which has a sewage scheme.

The following flow chart illustrates an overview ofthe remediation process in processing sewage wastes using worm farming.

REMEDIATION OF SEWAGE WASTES USING WORM FARMING

Notes to the Process

Total processing time for material is 7 weeks.

The weekly total throughout is 40 tonne. This would cost $880 to dispose of in landfill. Once established the farm can process the same quantity of material every day. The value of $500 per tonne is the retail price. If the farm were designed to handle 40 tonne of raw organics per week the weekly throughput would be value at $ 10,000.

This process, when passed by tender to private industry, will sustain at least four employment positions full time. It will therefore be appreciated that the present invention provides a method of processing waste which utilises a mixture of shredded paper, cardboard or like material and organic material such as organic waste material, sludge, sewage or the like. By mixing these ingredients together, and the supply earthworms thereto, the animals digest the mixture and produce castings. The earthworms can be utilised to form a high protein product which may be utilised for stock feed or aquaculture, and the castings may be utilised as a fertiliser additive material or a soil conditioner.

The worm castings may be applied to a broad acre crop plantings by mixing the castings in either a fluid o dried form with paper and other waste products. This combined material would then be partially dried and formed into pellets. The pellets would be spread onto farmlands using a supeφhosphate spreader or other type of machinery.

In such a system, obviously, certain factors are preferred. For example, for the worms to effectively be utilised, and to consume quantities of material, it is necessary that there are adequate moisture levels, adequate ambient temperature ranges, and satisfactory nutrient levels. Various earthworms are suitable for the process ofthe invention, being segmented type worms. Such worms have no lungs to absorb oxygen, but rather, have tiny blood vessels which are abundant in the skin, which the earthworm uses a respiratory organ to obtain oxygen. Because gas exchange must occur across a film of moisture, an earthworm suffocates if the skin dries. Whilst it is critical that the moisture level be maintained, their tolerance level can range from damp to extremely high. Consequently, adequate moisture levels must be prevalent. Worms of varying species have been found to have temperature tolerances up to as high as 38°C. Activities considerably reduce below temperatures of about 11°C. For the puφoses of breeding, the optimum range for earthworm cocoon production is 15 - 25°C. A temperature of 23°C is also optimum for body growth.

The food mixtures for the worms, should contain relatively high levels of bacteria. As the food supplies of worm species are usually acidic in the process in accordance with the present invention, i.e. sewage or sludge, before the food goes into the gut ofthe worm, the pH level must be made more alkaline. To achieve this, the worm has glands in it's mouth which secrete calcium into the food supply before it reaches the gut. The end result of this action is a more alkaline product being produced by the worm. At the same time, this product is also highly water soluble.

The gut bacteria of earthworms also has the ability to eliminate pathogens as part ofthe digestive process. Sewage sludge can be rendered pathogen free and suitable for use as agricultural applications after use as a food supply for worms. The process will also eliminate heavy metals from sludge.

Investigations by the Applicant show that typical levels of cadmium contamination in sewage ponds vary between about 8ppm and 1 8ppm. The levels of other heavy metals are also typically high.

To reduce the levels and cadmium and other heavy metals, non-recyclable type paper products, that is, paper products which have been contaminated by food stuffs, etc., can be pulped or shredded, and this cellulose fibre mixed with the sewage sludge. Research by the

Applicant confirms that a ratio of 50/50 is readily consumed by the worms. The paper component could be further raised by the use of sewage sludge to the higher nutrient level.

By adding 50% by weight of paper to the sewage sludge, the cadmium level has been found to be reduced from 1 8ppm to 9ppm. As the worms process this food supply, it will absorb an amount ofthe cadmium. Worms can absorb concentrations of cadmium as high a 143.7ppm. This ability further reduces the cadmium levels, typically by about 3 ppm, leaving a level of about 6ppm in the remaining castings.

The casting however now have a pH closer to 7 or neutral and are water soluble or readily soluble. By raising the pH level above about 8.5, heavy metals commence to drop out of the solution. If the castings, now of approximate pH level 6, are then mixed into an alkaline solution, the cadmium and all other heavy metals drop out of the solution, rendering the remaining casting solution, suitable for use as an agricultural soil conditioner.

It should be noted that this process can be applied to any heavy metal contaminated material which can be passed through the guts of worms. For example, contaminated soils can be mixed with a worm food mix, and the process used as described.

The present invention has therefore provided a method of processing wastes which has a number of advantages. Such advantages include the very economical method for the removal of heavy metals, the ability to process sewage waste for reuse, the ability to re-use a previously non-recyclable paper product. It will therefore be appreciated that the present invention has numerous commercial advantages.

Recent tests conducted have indicated that the combination of various organic wastes including paper with worm castings could provide a very practical method for returning organic material to soils thus reducing the need for the use of landfill as a waste disposal technique.

Whilst particular preferred embodiments have been hereinbefore described, it should be appreciated that numerous variations and modifications to the invention will become apparent to persons skilled in the art. All such variations and modifications should be considered to fall within the scope ofthe invention as hereinbefore described and as claimed hereinafter.

Claims

THE CLAIMS

1. A method of processing waste, utilising earthworms or the like, comprising the steps of: shredding paper, cardboard or material, mixing said shredded material with organic waste material, such as sludge, sewage or the like; supplying said earthworms or the like to said mixture such that said animals digest said mixture and produce castings.

2. A method of processing waste as claimed in claim 1 , wherein said organic waste material is derived from a sewage or sludge pond or the like.

3. A method of processing waste as claimed in claims 1 or 2, wherein said organic waste material may contain heavy metals, such as cadmium.

4. A method of processing waste as claimed in any one of claims 1 to 3, further comprising the steps of: separating said earthworms from said castings; or processing said castings for use as a fertiliser/additive material.

5. A method for processing waste as claimed in claim 4, wherein said protein product is utilised as an aquaculture food source.

6. A method as claimed in claim 4, wherein said processing step, when processing said castings, comprises: forming a solution utilising said castings; adjusting the pH of said solution to an alkaline solution, preferably having a pH of approximately 8. 5, by adding alkali such as sewage ash, lime, or the like, such that precipitation of heavy metals, such as cadmium occurs therefrom.

7. A method as claimed in any one of claims 1 to 6, wherein a ratio of said mixture is about 50% shredded material and about 50% waste material, but may vary to suit available food sources and worm species used.

8. A method of processing waste as claimed in any one of claims 1 to 7, wherein in said supplying step, said mixture and said earthworms or the like are provided in conditions having predetermined moisture, temperature and/or nutrient levels.

5 9. A method of processing waste as claimed in any one of claims 1 to 8, wherein said moisture levels are damp to extremely high, said temperature ranges are from about 1 5 C to 26 C, but preferably about 23 C, and, said nutrient levels are maintained by providing a relatively high level of bacteria.

10 10. A method of processing waste as claimed in any one of claims 1 to 9, wherein, said product is applie to crops, such a broad acre crops, by mixing in a fluid or dry form, optionally with paper and/or other waste products.

11. A method of processing waste as claimed in any one of claims 1 to 10, wherein said 15 product is provided in a pellet or like form.

12. A product produced from the method claimed in any one of claims 1 to 11.

13. A method of processing waste, substantially as hereinbefore described. 20

14. A product produced from the method of processing waste, substantially as herein described.