An apparatus and method for the treatment of sewage

The present invention relates to an apparatus and method for the treatment of sewage and, more particularly, to a transportable sewage treatment unit for converting raw sewage into reclaimed water through various stages of treatment.

BACKGROUND OF THE INVENTION

In the following description, the terms sewage and wastewater are used to describe waste from sanitary installations such as toilets, urinals and wash basins, as well as other installations which involve the disposal of waste, for example, kitchens. The current applicant is the owner of a number of co-pending patent applications involving transportable buildings for use in portable camp sites. The apparatus of the present invention is adapted for use in such camp sites, however, it is to be understood that the scope of the present invention is not to be limited to use only in this area. For example, the sewage treatment apparatus may well be used in small communities, holiday camps, caravan parks, and even marine vessels which often require a sewage treatment system that is compact in nature.

Sewage or wastewater treatment plants are generally known. Typically, sewage treatment plants include an aeration chamber and a settling or clarifying chamber, each of which has a distinct function.

Sewage is adapted to be received in the aeration chamber which is oxygenated. Oxygenation, which is typically achieved through the diffusion of air through the liquid at very high rate, causes the sewage and bacteria populations (activated sludge) present in the chamber to mix. This biological treatment of the sewage causes a mixed liquor to form as a result of the transformation of organic compounds in the sewage into carbon dioxide and water. In addition, circulation of sewage in the aeration chamber is undertaken in such a way so as to maintain organic compounds in suspension. This maximizes access to the organic compounds so that they may be readily broken down. If the organic compounds settle to the bottom of the chamber and if aeration is not uniform, they become less accessible.

Mixed liquor from the aeration chamber is then transported to the settling chamber. The primary function of the settling chamber is for solids separation, that is, any solids present in the mixed liquor settle out as sludge. The sludge may also be removed and treated to be used as fertiliser. This process of removing the activated sludge and suspended particles from the liquid

leaves clear, highly treated water usually at the top of the chamber. It is this clear, odourless liquid at the top of the tank that is typically discharged (decanted) from the system. Sewage also contains oil which needs to be removed. In conventional systems, oil is typically removed during aeration.

The type of treatment undertaken after the settling chamber is dependant upon the class of water that is required to be produced. Many countries have in place some form of Guideline or Regulation which typically includes a reclaimed water classification system. For example, the South Australian Reclaimed Water Guidelines include a classification system defining 4 classes of reclaimed water. These classes together with their prescribed uses are as follows:

Class A: Primary contact recreational use such as garden watering, toilet flushing, car washing, path/wall washing, and unrestricted crop irrigation;

Class B: Secondary contact recreational use such as ornamental ponds with public access, irrigation of pasture and fodder for grazing animals, washdown and stockwater, and fire fighting;

Class C: Passive recreational use such as restricted crop irrigation, and irrigation of pasture and fodder for grazing animals; and

Class D: Restricted crop irrigation, irrigation for turf production, silviculture, and non-food chain aquaculture.

The following specification refers to the above classification system in describing the quality of reclaimed water. It is to be understood that this is meant only as a guide and that water classifications in other jurisdictions may well differ from that in place in South Australia.

The water that is decanted from the settling chamber would normally be classified under classes C or D. If one wished to achieve say class B reclaimed water, a secondary treatment would need to be applied to the decanted water which may be in the form of an effluent balance tank or disinfection chamber which disinfects the water typically by chemical means and/or by ultraviolet light or radiation. Class A reclaimed water that is free from harmful micro-organisms may be achieved through a tertiary treatment. Tertiary filtration typically involves the use of a filtration means following the disinfection chamber such as a well known sand filter.

The present inventor is involved in the manufacture and commissioning of remote camps that are assembled using a number of transportable buildings. Some of the buildings are used as sleeping quarters, others as the kitchen and dining room facility and other still as recreational areas. It is not uncommon for a camp to consist of sixty to eighty buildings than can accommodate several hundred people. These camps are completely self-contained in that the transportable buildings provide all of the facilities for a small remote community that may be needed in a particular area. Accordingly, these camps include all of the modern day facilities such as electrical power, water, communication and, of course, sewerage.

During construction of infrastructure across a vast area, such as roads or pipelines supplying water or gas, the abovementioned camps are also made to be portable. This is because as the pipeline is progressively constructed, a particular location for a camp housing the construction workers may only be viable for several weeks or months. Thus, a new camp is typically constructed approximately one hour ahead of the current construction location or generally up to several hundred kilometres away from the existing camp so as to accommodate the workers as the pipeline is progressively constructed. Alternatively, construction work on the particular project can stop for two to three weeks whilst the one camp is relocated.

The applicant has recognised a need for an improved sewage treatment plant that overcomes the problems and drawbacks associated with hitherto known systems and, in particular, to a sewage treatment plant that is configured for particular use in association with portable camps. The effectiveness of any sewage treatment system can be measured by the quality of the effluent produced, and whether the treatment process can be controlled and managed at various stages so that uniformity in the system is assured and different classes of reclaimed water can be retrieved. This is especially important in remote camps where all classes of reclaimed water can be put to good use. Insofar as the applicant is aware, there exists no sewage treatment plant that addresses these issues.

It is therefore an object of the present invention to overcome at least some of the aforementioned problems or to provide the public with a useful alternative.

SUMMARY OF THE INVENTION

Therefore in one form of the invention there is proposed an apparatus for the treatment of sewage, said apparatus including: a means to treat said sewage aerobically;

a means to treat said sewage anaerobically; a means to filter out suspended solids from the aerobically and anaerobically treated sewage to thereby produce filtered liquid; a means to disinfect the filtered liquid; wherein all of said means of treating, filtering and disinfecting the sewage are contained within a compact, transportable structure.

Preferably the apparatus is of a longitudinal box-shape structure including four spaced apart, transversely extending walls defining five areas within the structure, and an internal longitudinal wall which splits the three middle areas into six individual areas, to thereby define eight internal chambers.

In preference at least one of said chambers includes at least one of said treating, filtering or disinfecting means.

In preference the means to treat said sewage aerobically involves activation of bacteria within the sewage by way of oxygenation. This serves to break down organic matter in the sewage.

Preferably the means to treat the sewage anaerobically involves removing nutrients such as nitrates from the sewage.

Preferably the volumetric feed of sewage through the aerobic and anaerobic treatment means within a predetermined amount of time is controllable.

In preference said predetermined amount of time is approximately 4 hours.

In preference the suspended solids form at least part of a filtered sludge which is collected in the filtering means, said filtered sludge adapted to be controUably reintroduced into the aerobic treatment means so that bacteria present in the sludge may become reactivated.

Preferably sewage which has undergone aerobic treatment, anaerobic treatment, and filtering, is further treated through said disinfecting means which involves the introduction of a disinfectant such as chlorine.

In preference said apparatus further includes a tertiary treatment means for producing potable water.

Preferably said tertiary treatment involves the use any one of reverse osmosis, sand filtration, bag filtration, air blowers, or any combination thereof.

In preference said filtering means is in the form of a mesh screen configured to filter out particles of approximately 10-15 micron.

In a further form of the invention there is proposed a sewage treatment apparatus including: a light aeration chamber; a first heavy aeration chamber; an anaerobic chamber; a second heavy aeration chamber; a third heavy aeration chamber; a settling chamber; and a disinfecting chamber; wherein said sewage is adapted to be treated through each of said chambers sequentially.

Preferably said apparatus further includes a tertiary treatment chamber.

In preference each of said aeration chambers include an array of aeration devices in a base area thereof, said diffusers adapted to diffuse oxygen through the sewage contained therein.

Preferably said anaerobic chamber includes a submersible impeller for agitating liquid to thereby prevent solid particles from settling to the bottom of the chamber.

In preference the settling chamber includes a mesh screen adapted to filter out solid particles.

Preferably the mesh screen includes three angled mesh surfaces which, together with an entry wall of the settling chamber, form a substantially inverted frusto-pyramid shape.

Alternatively the mesh screen includes a mesh surface of an inverted frusto-conical shape.

Preferably sludge which is filtered out by the mesh screen is recycled through the apparatus by being controllably re-introduced into the light aeration chamber.

In preference bacteria in the recycled sludge is reactivated upon re-entry into the light aeration chamber.

In preference sludge which is filtered out by the mesh screen is further pumped to pressurised injectors associated with said mesh screen for cleaning thereof.

Preferably liquid which has been filtered through the mesh screen is sprayed as a fine mist over the surface of liquid in the heavy aeration chambers to thereby prevent the formation of foam and excess scum thereon.

In preference the re-introduction of sludge, the supply of liquid to the pressurised injectors, and the spray of fine mist over the surface of liquid in the heavy aeration chambers are each controllable by way of associated valves.

hi preference the disinfection chamber includes a chlorinator adapted to disinfect liquid fed therein.

Preferably sewage is controllably fed from the light aeration chamber to the first heavy aeration chamber by way of a pump and associated timer.

In preference the retention time of the sewage in the aeration chambers prior to entry into the disinfection chamber is approximately 4 hours.

Preferably all pumps and valves associated with said apparatus are controllable via an electronic control unit.

In a still further form of the invention there is proposed a method for the treatment of sewage, said method comprising the following steps:

a) lightly oxygenating raw sewage in a light aeration chamber wherein raw bacteria in the sewage mixes with the oxygen to thereby break down organic compounds;

b) processing said lightly oxygenated raw sewage in an anaerobic chamber for ridding the sewage of nutrients such as sulphate;

c) heavily oxygenating the sewage from the anaerobic chamber wherein further oxygenation produces wastewater that is substantially free of organic compounds;

d) filtering said aerated wastewater of suspended solids in the form of sludge; and

e) controllably recycling filtered out sludge back into the light aeration chamber.

Advantageously, said filtered and aerated wastewater is further disinfected and treated to produce potable water.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several implementations of the invention and, together with the description, serve to explain the advantages and principles of the invention. In the drawings:

Figure 1 illustrates a detailed perspective view of the sewage treatment apparatus of the present invention;

Figure 2 illustrates a detailed plan view of the sewage treatment apparatus of Figure 1 ;

Figure 3 illustrates a detailed front view of the sewage treatment apparatus of Figure 1 ;

Figure 4 illustrates a detailed rear view of the sewage treatment apparatus of Figure 1 ;

Figure 5 illustrates a front perspective view of the filtering means inside the settling chamber of the sewage treatment apparatus of Figure 1;

Figure 6 illustrates a side perspective view of the filtering means inside the settling chamber of the sewage treatment apparatus of Figure l;and

Figure 7 illustrates a perspective view of a filtering means according to a second aspect of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description of the invention refers to the accompanying drawings. Although the description includes exemplary embodiments, other embodiments are possible, and changes may be made to the embodiments described without departing from the spirit and scope of the invention. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts.

The present invention relates to an apparatus 10 and method for the treatment of sewage. The apparatus 10 is adapted to progressively treat a body of liquid 12, which is introduced as raw sewage but whose composition changes upon undergoing different stages of treatment. The apparatus 10 includes a generally longitudinal outer body comprising a base 14, longitudinal front and rear walls 16 and 18, a roof 20, and side walls 22 and 24. Although not shown there is at least one hatch on the roof 20 to gain access inside the apparatus 10.

Divided within the apparatus 10 and sharing a common base are eight chambers, a light aeration chamber 26, a first heavy aeration chamber 28, an anaerobic chamber 30, a second heavy aeration chamber 32, a third heavy aeration chamber 34, a settling chamber 36, a disinfection chamber 38, and a tertiary filtration chamber 40. The chambers are separated by a plurality of internal walls, namely, four transversely extending walls 42, 44, 46 and 48, and one central longitudinal wall 50 which extends between walls 42 and 48 and through walls 44 and 46.

Those skilled in the art should immediately realise that the overall structure of the apparatus makes it easy to manufacture, assemble and transport. The apparatus 10 does not include multiple parts, or chambers that must be connected to one another during assembly, it is a single integral unit. It may therefore well include a base chassis (not shown) or the like which allows it to be transported using one or more heavy duty forklifts. The idea of a large transportable building having a chassis that is moveable using a single forklift is the subject of a coexisting patent application owned by the present inventor, and may well be applied to the sewage system of the present invention. Thus, the plant may be assembled on or off site, and once assembled may be quickly and easily transported around a camp site or other similar type environment.

The apparatus 10 is configured such that liquid is pumped from the light aeration chamber 26 into the first heavy aeration chamber 28, then by gravitational flow and the use of further pumps (later described), the liquid travels through pipe 52 into the anaerobic chamber 30, then through pipe 54 into the second heavy aeration chamber 32, through pipe 56 into the third aeration chamber 34, and then through pipe 58 into the settling chamber 36. From the settling chamber 36, filtered liquid is pumped into the disinfection chamber 38 where it can either be pumped away for use, or it may undergo further treatment in the tertiary filtration chamber 40. In undergoing further treatment in chamber 40, the sewage can be converted into class A reclaimed water (as defined in the South Australian Water Guidelines).

Therefore in the case of camps, wastewater from a plurality of buildings may be pumped into the light aeration chamber 26 where it may be stored, or treated through the remaining chambers. It is to be understood that the flow of liquid through the system is not continuous but variable, that is, it involves a controlled 'push through' of a predetermined volume of fluid within a predetermined period of time. There is a pump 60 and associated timer 62 in the light aeration chamber 26 which allows for this to occur.

The pump 60 and timer 62 are preferably set so that a controlled amount of liquid is introduced into the first heavy aeration chamber 28 through pipe 64. It has been found that in order for effective treatment to occur, the time taken for a body of liquid to travel from the light aeration chamber 26 through chambers 28, 30, 32 and 34, and into the settling chamber 36 should be set to approximately 4 hours. This of course may vary depending on the quality of water that is required at the end of the process, and other factors, but 4 hours should be sufficient to ensure that at least effluent B is produced by the time the liquid reaches the disinfection chamber 38. Different environments around the world may require different retention times, for example, the hotter climates would require less aeration time.

Each of the various stages of treatment which occur in each chamber will now be explained in more detail.

As mentioned, the light aeration chamber 26 acts as a storage chamber and is used to hold raw sewage. The light aeration chamber 26, and the first 28, second 32 and third 34 heavy aeration chambers, each include diffuser arrays 66, 68, 70 and 72 respectively. Air is pumped through the diffuser arrays 66, 68, 70 and 72 via associated pipes 74, 76, 78 and 80 respectively, which extend vertically along the rear wall 18 and then branches off into two horizontal pipe sections along the base 14 in each chamber. The way in which air is supplied to each pipe is considered well known to those skilled in the art and so will not be described here in any detail. The diffusers serve to diffuse the air travelling through the associated pipes into the liquid in each chamber.

Human waste contains different types of bacteria, some of which require little air to become activated, others requiring more air to become activated. This is one of the reasons for having multiple aeration chambers whereby chamber 26 is only slightly aerated while chambers 28, 32 and 34 are heavily aerated. This arrangement of aeration chambers ensures that more bacteria is activated and that maximum break down of organic compounds occurs prior to entry

into the settling chamber 36. Of course, the level of aeration may be adjusted in each chamber to suit different requirements, for example, different types of waste may require lighter or heavier oxygenation.

A further reason that light aeration is required in the first chamber 26 is that sludge which settles in the settling chamber 36 is returned to the light aeration chamber 26 via pipe 82 and the bugs present in the sludge require only light aeration to become re-activated. This process and its benefits will be described in more detail in the description of the settling chamber 36 below.

When raw wastewater enters the light aeration chamber 26, oils, greases and other buoyant solid particles (not shown) rise to the surface of the liquid, this also being helped by the aeration process, and can be cleaned away manually through an access hatch (not shown) in the roof 18 of the chamber 26. Liquid is therefore pumped into the first heavy aeration chamber 28 from the bottom of the light aeration chamber 26 through pipe 64. This ensures that wastewater entering the first heavy aeration chamber 28 is free from grease and/or oil.

Aerobic bacteria populations may be introduced into the light aeration chamber 26, as well as the first, second and third heavy aeration chambers 28, 32 and 34. This is not essential but may need to be done in circumstances where the raw wastewater may not contain the necessary amounts of bacteria to adequately mix with the sewage to cause breakdown of organic compounds in the liquid.

Each of the heavy aeration chambers 28, 32 and 34 also include respective sprinklers 84, 86 and 88 located centrally above the body of liquid inside each chamber. The sprinklers are adapted to spray a fine mist of filtered water, which is pumped from the settling chamber 36 through pipe 90, over the surface of the liquid in the chambers. This serves the purpose of both further triggering bacteria in the aeration chambers and for preventing the formation of foam or excess scum which may form at the surface.

Before reaching the second and third heavy aeration chambers 32 and 34, the liquid is processed through an anaerobic chamber 30. The benefits of anaerobic treatment should be well known to those skilled in the art. Anaerobic digestion stabilises insoluble organic matter and converts these solids to end products such as liquids and gases. Thus, the anaerobic chamber 30 is used to remove scum and nutrients from the wastewater that would otherwise not be removed by way of aerobic treatment. An anaerobic environment is also necessary for dentrification, that is, the process of reducing nitrates present in the water to nitrogen gas. The anaerobic chamber

30 is also slightly agitated by a submersible impeller 92 at the base of the chamber which ensures that no sludge settles to the bottom.

The settling chamber 36 is a key component of the sewage system of the present invention. The chamber 36 includes a mesh screen structure 96 mounted therein for filtering out solid particles. The mesh screen 96 can be seen most clearly in figures 5 and 6.

The mesh screen 96 together with the wall 46 of the chamber 36 form an inverted frusto- pyramid shape whereby the wall 46 forms a side of the pyramid that is perpendicular with the base of the pyramid. Only the three angled sides 98, 100 and 102 are constructed of mesh material and extend from an upper periphery of the chamber 36 downwards and inwardly toward the base of the chamber 36 as shown. Although not shown, the mesh screen 96 should include a frame which supports the screen in the position shown. The mesh screen 96 is shaped like so to direct sediment toward the base of the chamber, and preferably filters out particles of approximately 10-15 micron. The sludge which settles in the settling tank is also of a quality where it may also be discharged into rivers.

Coagulant (not shown), typically in the form of aluminium sulphate, may be spread over the surface of the water in the settling chamber 28 to assist with the settling of the sludge.

Thus, the mesh screen 96 essentially separates the chamber into two bodies of liquid, the unfiltered liquid 104 which is the liquid which enters the chamber into the space within the mesh screen 96, and the filtered liquid 106 found on the other side of the mesh screen 96 substantially at the base of the chamber 36. There are two pumps at the base of the chamber 36, that is, pump 108 which is located in the unfiltered area 104, and pump 110 located in the filtered area 106. Pump 108 is used to pump sludge from the settling chamber 36 back into the light aeration chamber 26, while pump 110 is used to supply filtered liquid to the sprinklers 84, 86 and 88.

Pump 108 serves a further purpose, that is, to supply liquid through pipe 112 to injector array 114 which horizontally lines the three angled sides 98, 100 and 102 of the mesh screen 96 adjacent the top of the chamber, as well as injector array 116 which lines the three angled sides 98, 100 and 102 of the mesh screen 96 approximately halfway down the screen. The injectors 114 and 116 provide a pressurised spray of liquid directly onto the mesh to thereby clean the mesh of solid particles and other matter which builds up. In an alternative embodiment which is not shown, filtered liquid may be sprayed onto the mesh using pump 110.

It is to be understood that the shape of the mesh screen inside the settling chamber 36 may vary. For example, illustrated in Figure 7 is a mesh screen 118 according to a second embodiment of the present invention. The mesh screen 118 in this case includes a mesh surface 120 of an inverted frusto-conical shape and includes a circular injector array 122 lining the upper internal surface of the screen 118.

At this stage of the process, the water 106 is clear and odourless and is likely to be classified as class C or class D reclaimed water. This water may contain aerobic bacteria which were carried through from the aeration chambers. Although not shown, this water may well be pumped away at this stage and used accordingly.

The water 106 travels through pipe 124 by way of gravitational flow into the disinfection chamber 38. A chlorinator 126 is associated with pipe 124 such that the water 106 passing through pipe 124 is exposed to chlorine tablets (not shown) contained within the chlorinator and which dissolve. It is however to be understood that the disinfection chamber 38 may contain other chemicals which serve to disinfect the water, for example, the application of ultraviolet or ultraviolet radiation is known to be an effective disinfectant. The quality of reclaimed water following disinfection may be classified as class B reclaimed water, but may potentially even be class A reclaimed water at this stage of the process. Again, although not shown, this water may be pumped out and used without any further treatment.

The water may then be made to undergo tertiary treatment to produce potable water. This is preferably achieved using a series of treatment devices. Predetermined amounts of liquid may be pumped from the disinfection chamber to any one or through all of the treatment devices. In the embodiment shown, the treatment devices are in the form of two air blowers 128 and 130, and a bag filter 134. However, other treatment devices such as sand filters or a reverse osmosis machine may be used.

The process of treating the liquid in the tertiary treatment chamber 40 may be controlled via an electronic control box 136, that is, the amount of liquid that is processed through the tertiary treatment chamber as well as the level of treatment may be controlled. The electrical control box may also be linked to the other pumps and timer in the system so that the entire system can be controlled inside the tertiary treatment chamber 40.

It can be seen that lines 82, 90 and 112, each have associated therewith their own manual control valves 138, 140 and 142 respectively. Thus, the amount of sludge that is returned to the light aeration chamber 26 and to the injector arrays 114 and 116, as well as the amount of water fed to the sprinklers 84, 86 and 88 may all be controlled. These valves may also be linked to the electrical control box 136 so that they too may be controlled electronically. The tertiary treatment chamber also includes an irrigation pump 144 which may be used to pump water from any one of the chambers out of the system through pipe 146.

Although not shown, it is to be further understood that the present system may include a backwash system whereby the system may be flushed by way of a series of pipes (not shown) connecting the base of longitudinally aligned chambers which will force liquid in each chamber out through the pipes by way of pressurised flow when a flush valve (not shown) associated therewith is opened.

The present invention therefore provides a number of advantages over known systems. The apparatus as a whole is configured to be a truly portable unit suitable for use in camps and the like. The apparatus is preferably constructed to be approximately six metres long which is suitable for camps of up to 150 people, and 12 metres long which is suitable for camps of up to 250 people. Further, all aspects of the system are controllable, in particular the variable flow of sewage therethrough and the recycling of sludge. This level of control ensures that uniformity within the system may be maintained. In fact, the continuous recycling of effluent as proposed in the present invention ensures that no suspended solids are present in the effluent, very low nutrients such as nitrates and the like remain in the water, and in terms of control, the system allows for improved effluent management.

Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope and spirit of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus.

In any claims that follow and in the summary of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprising" is

used in the sense of "including", i.e. the features specified may be associated with further features in various embodiments of the invention.