WO2005016833A1

WO2005016833A1 - Waste water treatment process

Info

Publication number: WO2005016833A1
Application number: PCT/AU2004/001085
Authority: WO
Inventors: Robert John Walker
Original assignee: Aso Holdings Pty Ltd
Priority date: 2003-08-15
Filing date: 2004-08-13
Publication date: 2005-02-24
Also published as: AU2003904356A0

Abstract

A waste water treatment process for treatment of liquid waste derived from animal processing plants, food processing plants, agricultural waste and municipal sewage by separating biosolid byproducts from the waste water preferably by filtration devices and other solids separation means(12). The biosolid byproducts are blended(14) with organic material and the mixture undergoes aerobic composting(16) which is then subjected to vermiculture(18) and converted to a solid component comprising worm castings and compost and a liquid component comprising liquid worm castings.

Description

WASTE WATER TREATMENT PROCESS FIELD OF THE INVENTION

The present invention relates to a waste water treatment process, in particular waste water treatment process for treatment of liquid waste derived from abattoirs, rendering plants, sale yards, live animal transports, piggeries, food processing plants, wineries, fish processing plants, pulp and paper factories, and municipal sewage, wherein separated biosolid byproducts from the waste water treatment process undergo aerobic composting to render them as useful and innocuous compost products. BACKGROUND OF THE INVENTION Increasingly, municipal sewage treatment plants are experiencing poor treated water quality, including excessive biochemical oxygen demand, odour problems, high phosphorous levels, and excessive suspended solids, as a result of hydraulic capacity problems. Without huge capital expenditure to invest in larger volume plants that rely on existing processes, these problems will only increase with concomitant increasing population.

Raw sewage is typically treated by most municipal sewage treatment plants by first undergoing a primary clarification stage, followed by biological treatment, then a secondary clarification stage, followed by chlorination. The primary clarification stage is generally conducted in large settling ponds.

Where relatively smaller volumes of liquid waste are generated, such as in the dairy and fish processing industry, primary clarification of the wastewater can be achieved by means of filtration devices and other solids separation means. Such devices afford better quality water, typically with ~50% solids and a reduced BOD5 of ~40%, than what can be arrived at by utilising large settling ponds. However, although it is conceivable that the primary clarification stage of municipal sewage treatment works could be replaced by a bank of filtration devices that would afford "cleaner" water, the volume of sludge generated as a process byproduct would be of too great a magnitude to dispose of viably.

There currently exists a need for the efficient conversion of the resulting sludge into an innocuous or useful product that is environmentally friendly. Conventional methods of waste disposal such as tipping or burning, although effectively disposing of such waste, generally have a negative impact on the environment. Such negative impact may include the leaching of toxic material or excessive nutrients into the soil and hence groundwater and the release of emissions into the atmosphere. Further, sewage is allegedly responsible for approximately 10% global methane emissions derived from waste. As one tonne of organic biosolids is approximately equivalent to two tonne CO₂ equivalent it is desirable that biosolids are removed from the greenhouse gas cycle and converted to innocuous compost in order to reduce the green house effect.

The present invention attempts to overcome at least in part some of the aforementioned disadvantages and seeks to enhance the efficiency of existing wastewater treatment processes. SUMMARY OF THE INVENTION In accordance with a first aspect of the present invention there is provided a waste water treatment process comprising the steps of: a) separating at least part of any water-insoluble substances from a body of waste water with a filtration means, clarification means, or a separation means; b) blending the water-insoluble substances separated in step a) with organic material and facilitating aerobic composting of the resultant blended material to afford compost; c) introducing earthworms to a the compost resulting from step b), wherein the earthworms consume the compost, and aid in converting at least part of the compost into a solid component comprising worm castings and compost, and a liquid component comprising liquid worm castings; d) clarifying the water separated in step a) by a filtration means, clarification means, or a separation means, and optionally treating at least part of the insoluble residues removed therefrom as in step b); and e) performing chlorination, sterilisation, or reverse osmosis in relation to the clarified water from step d) to provide receiving water. In accordance with a second aspect of the present invention there is provided a waste water treatment system for treating a body of waste water comprising: a) a filtration means, clarification means, or a separation means for separating at least part of any water-insoluble substances from the body of waste water; b) a means for blending the separated water-insoluble substances with organic material; c) an aerobic composting means for facilitating aerobic composting of the resultant blended material to afford compost; d) a means for introducing earthworms to a mixture of compost wherein the earthworms are facilitated to consume the compost, and aid in converting at least part of the compost into a solid component comprising worm castings and compost, and a liquid component comprising liquid worm castings, with means for separating the solid and liquid components; e) a clarification means to clarify the water, and f) a means for performing chlorination, sterilisation, or reverse osmosis in relation to the resulting clarified water to provide receiving water. DESCRIPTION OF THE DRAWINGS The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram illustrating the waste water treatment process and system in accordance with the present invention. DESCRIPTION OF AN EMBODIMENT OF THE INVENTION In relation to the first aspect of the present invention, the waste water treatment process is conducted by separating at least part of the water-insoluble substances from the treated waste water. The water-insoluble substances are then blended with organic material and the blended material undergoes aerobic composting to afford compost. The compost is integrally mixed with earthworms, wherein the earthworms consume the compost, and aid in converting the compost into a solid component comprising worm castings and compost, and a liquid component comprising liquid worm castings.

The separated water is then further treated, and then clarified and treated by chlorination, sterilization or reverse osmosis to afford received water. Any water- insoluble substances separated from the clarified water are fed back into the system to enable the water-insoluble substances to be blended with organic material, aerobically composted, and integrally mixed with earthworms, wherein the earthworms consume the compost and aid in converting at least part of the mixture into a solid component comprising worm castings and compost, and a liquid component comprising liquid worm castings. The reaction steps of the wastewater treatment process of the invention, are as follows: a) separating at least part of any water-insoluble substances from a body of waste water with a filtration means, clarification means, or a separation means; b) blending the water-insoluble substances separated in step a) with organic material and facilitating aerobic composting of the resultant blended material to afford compost; c) introducing earthworms to the compost resulting from step b), wherein the earthworms consume the compost, and aid in converting at least part of the compost into a solid component comprising worm castings and compost, and a liquid component comprising liquid worm castings; d) clarifying the separated water of step a) by a filtration means, clarification means, or a separation means, and optionally treating at least part of the insoluble residues removed therefrom as in step b); and e) performing chlorination, sterilisation, or reverse osmosis in relation to the clarified water from step d) to provide receiving water.

Typically, the waste water is liquid waste derived from abattoirs, rendering plants, sale yards, live animal transports, piggeries, food processing plants, wineries, fish processing plants, pulp and paper factories, and municipal sewage. At least part of any water-insoluble substances is separated from the treated wastewater by a filtration means, clarification means, or a separation means.

Preferably, the water-insoluble substances have a moisture content of about 60 % w/w after separation from the treated wastewater. A simple filtration means, such as a sand filter, glauconite or zeolites may be used, however further filtration may be necessary to decrease the moisture content of the separated material to about 60 % w/w.

Preferably, the filtration means is a cleaning device for waste water having an endless filtering belt, such as described in International Publication Number WO 01/56681. Alternatively, the water-insoluble substances may be separated from the treated wastewater by an appropriate clarification means or separation means.

The separated water-insoluble substances are blended with organic material, and the blended mixture then undergoes aerobic composting to afford compost.

The quality of the resultant compost depends very much on the nature of the blended mixture that is to undergo aerobic composting. Typically, a blend is composed of approximately 40% water-insoluble substances and 60% green waste or biomass such as hay, shredded tree clippings and the like.

Once blended, it is envisaged that the blended mixture will typically undergo aerobic composting in an apparatus arranged to facilitate aerobic composting of the blended mixture contained therein, such as is described by the inventor in International

Publication Number WO 02/20428.

It is envisaged that aerobic composting of the blended material will proceed over a period of five to twenty eight days to enable adequate decomposition of the blended material to afford a substantially odourless compost. The compost is then transferred to worm culture vessels, such as is described by the inventor in International Publication Number WO 02/20428, or windrows that are provided with a collection of worms suitable for the further decomposition of organic material. Preferably, the type of worm used in the present invention is a red worm (Lumhricus rubellus), blue worm (Perionyx excavatus) or Tiger worm (Eisenia fetida). Distribution of the compost to the worm systems may be accomplished by any suitable means, such as common farm equipment, including conveyors, spreaders or feed wagons. Further moisture is added to the or each worm system as required, so as to maintain the moisture level of the compost to at least 60% by weight of the total composition. This further moistening may be accomplished by the use of sprinklers and the like or any other suitable moistening means. The worm systems are to be well drained so as to avoid waterlogging of the worm systems. The progressive addition of moisture to the worm systems results in a vertical compaction of the worm system, as castings generally settle, with moisture, as a fine deposit at the bottom of the worm system. Additional compost may be progressively added to the worm system as the compost in the worm system is converted to castings. The addition of further layers of compost may result in a plurality of feed layers within the worm system. Preferably, the compacted feed layers are of a thickness in the order of between five and ten centimetres.

The castings produced by the worms in the or each worm system may be removed by a screening means. Commercially available screening equipment is available for the separation of castings from worms and compost that are produced by the worms in the worm system.

Alternatively, the step of adding compost may be repeated for each worm system to provide a substantially continuous worm system. Continuous worm systems are commercially available that enable the input of material to be composted and digested in a top portion of the worm system, with an output of castings and compost from a lower portion of the worm system and these may be used for this purpose. A cleaning device for waste water having an endless filtering belt, such as described in International Publication Number WO 01/56681, may also be conveniently used to separate the solid component comprising worm castings and compost from the liquid component comprising liquid worm castings.

The treated water separated in step a) is then clarified by a filtration means, suitable clarification means or a separation means. The clarified water then undergoes chlorination, sterilisation, or reverse osmosis under conventional conditions in order to afford received water.

The remaining insoluble residues may then be further composted and ultimately transferred back to the windrows to undergo vermiculture as described above. Referring to Figure 1 there is provided a waste water treatment system 10 for treating a body of waste water comprising a separating means 12 for separating at least part of any water-insoluble substances from the body of waste water; a blending means 14 for blending the separated water-insoluble substances with organic material; an aerobic composting means 16 for facilitating aerobic composting of the resultant blended material to afford compost; a vermiculture facilitation means 18, wherein earthworms contained therein are facilitated to consume compost, and aid in converting at least part of the compost into a solid component comprising worm castings and compost, and a liquid component comprising liquid worm castings; a treatment means 20 for treating the water separated from the water-insoluble substances with flocculants or other proprietary water treatment chemicals; a clarification means 22 to clarify the water; and a purification means 24 for performing chlorination, sterilisation, or reverse osmosis in relation to the resulting clarified water to provide receiving water.

Typically, waste water derived from abattoirs, rendering plants, sale yards, live animal transports, piggeries, food processing plants, wineries, fish processing plants, pulp and paper factories, or municipal sewage, is pumped to the separating means 12 via conduit 11.

Water-insoluble substances with a moisture content of about 60% w/w are separated from the treated wastewater by the separating means 12. Typically, the separating means comprises a filtration means, clarification means, or a separation means. For example, a simple filtration means, such as a sand filter, glauconite or zeolites may be used, however, further filtration may be necessary to decrease the moisture content of the separated material to about 60 % w/w.

Preferably, the separating means 12 is a cleaning device for waste water having an endless filtering belt, such as described in International Publication Number WO 01/56681.

The separated water is then pumped to the treatment means 20 via conduit 13 for optional treatment with flocculants or other proprietary water treatment chemicals. The treatment means 20 comprises a holding tank for the separated water and any convenient type of spray, sprinkler, or pump for dispensing the flocculants or chemicals to the holding tank as a slurry or a powder. Recirculating pumps or a mechanical agitator are also provided to maintain suspension of the chemicals in the separated water during its residence time in the holding tank. This step may include biological aerobic activated sludge formation. Treated water is pumped via conduit 15 to the clarification means 22 to clarify the water emerging from the treatment means 20. The clarification means 22 comprises a simple filtration means, clarification means, or a separation means, preferable the cleaning device for waste water having an endless filtering belt, such as described in International Publication Number WO 01/56681. Any water-insoluble substances separated from the clarified water at the clarifying means 22 are fed back into the blending means 14 via conveyor 43 to enable the water-insoluble substances to be blended with organic material as an additional feed material. Resulting clarified water is pumped to the purification means 24 via conduit 17 for final purification to afford received water 19. The purification means 24 comprises a chlorination plant, sterilization plant, or reverse osmosis plant. The water-insoluble substances separated in the separating means 12 are then transferred to the blending means 14 by conveyor 21, whereupon they are mixed with organic material, such as green waste or biomass, hay, shredded tree clippings and the like, entering the blending means via conveyor 31. The blending means 14 may be an appropriately sized mechanical agitator.

The resulting blended mixture from the blending means 14 is transferred by conveyor 23 to the aerobic composting means 16. Preferably, the aerobic composting means 16 is as described by the inventor in International Publication Number WO 02/20428. Odours arising in the separating means 12 and the blending means 14 are circulated to the aerobic composting means 16 under negative pressure via duct 32. Air is also pumped into the aerobic composting means 16 via duct 32.

Air is exhausted from the aerobic composting means 16 via duct 33, and is typically scrubbed by a bio-filter 26 to remove any remaining traces of noxious pathogens expelled from the aerobic composting means 16. Typically, exhausted air leaving the aerobic composting means 16 is at a temperature of about 60 -70°C and has a large moisture and CO₂ concentration. Such exhausted air is beneficial for circulation in green house horticulture and hydroponic horticultural systems, and preferably the scrubbed exhausted air is circulated via duct 34 to a hot house 28.

After a residence time of up to 28 days in the aerobic composting means 16, the resultant compost is transferred by conveyor 25 to the vermiculture facilitation means 18 such as is described by the inventor in International Publication Number WO 02/20428, or windrows that are provided with a collection of worms suitable for the further decomposition of the compost.

A cleaning device for waste water having an endless filtering belt, such as described in International Publication Number WO 01/56681, may be conveniently used to separate the solid component comprising worm castings and compost from the liquid component comprising liquid worm castings. It is envisaged that the compost will undergo a preliminary screening, before transfer to the vermiculture facilitation means 18, with appropriately sized sieves 30 in which non-biodegradable materials are removed by conveyor 27 for disposal as landfill waste 40, and large biodegradable objects are transferred back to the blending means 14 by conveyor 29 as an additional feed material for the blending means 14. It is envisaged that about one third of fine compost material passing through sieves 30 will be transferred to the vermiculture facilitation means 18, while the remaining two thirds of the fine compost material is blended with worm castings transferred from the vermiculture facilitation means 18 by conveyor 41 in a second blending means 42 to afford an optimum ratio of 1 part worm castings to 5 parts fine compost material, whereafter the blended material is packed in bags by a fully automated bagging device 44.

Both the liquid and solid component from the vermiculture facilitation means 18 can be used in the adjoining hot house 28. Modifications and variations as would be apparent to a skilled addressee are deemed to be within the scope of the present invention.

Claims

1. A waste water treatment process comprising the steps of: a) separating at least part of any water-insoluble substances from a body of waste water with a filtration means, clarification means, or a separation means; b) blending the water-insoluble substances separated in step a) with organic material and facilitating aerobic composting of the resultant blended material to afford compost; c) introducing earthworms to compost resulting from step b), wherein the earthworms consume the compost and aid in converting at least part of the compost into a solid component comprising worm castings and compost, and a liquid component comprising liquid worm castings; d) clarifying the separated water of step a) by a filtration means, clarification means, or a separation means, and optionally treating at least part of the insoluble residues removed therefrom as in step b); and e) performing chlorination, sterilisation, or reverse osmosis in relation to the clarified water from step d) to provide receiving water.

2. A process according to claim 1, characterised in that the water-insoluble substances have a moisture content of about 60 % w/w after separation from the treated wastewater.

3. A process according to claim 1 or claim 2, characterised in that the filtration means is a first cleaning device for waste water having an endless filtering belt.

4. A process according to any one of the preceding claims, characterised in that the earthworms include a red worm (Lumbricus rubellus), blue worm (Perionyx exc vatus) or Tiger worm (Eiseniafetida).

5. A process according to any one of the preceding claims, characterised in that the moisture level of the compost is maintained to at least 60% by weight of the total composition.

6. A process according to any one of the preceding claims, characterised in that the worm castings are separated from the compost by a screening means.

7. A process according to any one of the preceding claims, characterised in that a second cleaning device for waste water having an endless filtering belt, is used to separate the solid component comprising worm castings and compost from the liquid component comprising liquid worm castings.

8. A waste water treatment system for treating a body of waste water comprising: a) a filtration means, clarification means, or a separation means for separating at least part of any water-insoluble substances from the body of waste water; b) a means for blending the separated water-insoluble substances with organic material; c) an aerobic composting means for facilitating aerobic composting of the resultant blended material to afford compost; d) a means for introducing earthworms to compost wherein the earthworms are facilitated to consume the compost and aid in converting at least part of the compost into a solid component comprising worm castings and compost, and a liquid component comprising liquid worm castings, with means for separating the solid and liquid components; e) a filtration means, clarification means, or a separation means to clarify the separated water; and f) a means for performing chlorination, sterilisation, or reverse osmosis in relation to the resulting clarified water to provide receiving water.

9. A waste water treatment system according to claim 8, characterised in that the separating means is a first cleaning device for waste water having an endless filtering belt.

10. A waste water treatment system according to claim 8 or claim 9, characterised in that the clarification means comprises a second cleaning device for waste water having an endless filtering belt.