Patent Publication Number: US-6982033-B2

Title: Aerobic treatment plant with filter pipe

Description:
This application claims the benefit of U.S. Provisional Application No. 60/305,170 filing date Jul. 13, 2001 

   BACKGROUND OF THE INVENTION 
   This invention relates to the treatment of sewage. More particularly, this invention relates to the treatment of sewage discharged from houses and other buildings which are not connected to a municipal sewer system such that, after the sewage has passed through the Aerobic Treatment Plant with Filter Pipe (“ATPFP”), it has been cleaned to a level acceptable for discharge into the environment so that it will not contaminate the ground water. Thus, the ATPFP provides an alternative to septic systems for buildings constructed outside of a local municipal sewer system. 
   There are several versions of the conventional sewage treatment system which use aerobic microorganisms to break down sewage. One such device is seen in U.S. Pat. No. 5,549,818. This conventional sewage treatment device consists of a cylindrical tank which encompasses a funnel-shaped clarifier. The clarifier divides the cylindrical tank into an outer chamber, between the outer wall of the tank and the clarifier, and an inner chamber, inside the clarifier. Air is introduced into the outer chamber by multiple air droplines, which are connected to an air compressor and which pump air bubbles into the sewage in the outer chamber. Sewage flows into the outer chamber where it comes in contact with the air bubbles. The introduction of air facilitates the breakdown and digestion of the sewage by aerobic microorganisms present in the sewage. The aerated sewage then proceeds into the clarifier through an opening at the bottom of the funnel-shaped clarifier. Inside the clarifier is a quiescent zone. This area of calm in the inner chamber of the device allows for settling to occur, with the solids falling back out of the clarifier and collecting on the bottom of the treatment tank. Accordingly, the waste water becomes cleaner as it progresses upward in the funnel-shaped clarifier, continuing to allow gravity to separate the solids from the water. So, by the time the sewage has progressed up through the clarifier, it has been substantially cleaned. This treated effluent exits near the top of the clarifier and is discharged. This aerobic clarification process has also been combined with a second, post-treatment stage in an earlier invention by the present inventors, as seen in U.S. Pat. No. 6,228,258. 
   A common problem with such current devices has been that they often do not effectively remove floating debris from the effluent. This may result in a less than satisfactory effluent for discharge to the environment. It may also prevent the use of a pump to discharge the effluent, since the presence of debris would interfere with the operation of the pump mechanism, clogging the pump and requiring an undue amount of maintenance. These problems are amplified in systems which do not include a pre-treatment tank designed to trap trash. Thus, a need has arisen for a compact two-tank sewage treatment plant which effectively overcomes these concerns. 
   The present invention of the Aerobic Treatment Plant with Filter Pipe (“ATPFP”) improves upon the basic aerobic clarification process for sewage by adding an integrated filter cleaning stage after aerobic clarification of the effluent in order to produce a better effluent, more suitable for discharge to the environment. The filter stage also acts to capture floating debris of the type which would hamper the effectiveness of a pump mechanism. Thus, the ATPFP is able to treat sewage more thoroughly than conventional devices, while also providing the benefits of pump-driven discharge of effluent (as for example, when the effluent is used for landscape hydration in an attached sprinkler system). In effect, the filter pipe of the ATPFP acts as both a filter mechanism and a trash trap mechanism simultaneously, allowing a single compact unit to address both of these important functions. 
   In the ATPFP, the sewage first proceeds through an aerobic tank, passing through an aeration chamber followed by a settling chamber in a clarifier. Then, in the second stage, the sewage enters a post-treatment area, where it is filtered and may also be chlorinated before discharge. Through this multi-step process, the ATPFP produces a cleaner effluent. The filter traps small floating particles left after the aerobic clarification process, so that the effluent being discharged to the environment is relatively free of debris and particulates. In addition to producing a cleaner effluent, this produces an effluent which can more easily be pumped out of the post-treatment area. The use of chlorine in the post-treatment tank also disinfects the effluent before discharge, ensuring that no disease carrying organisms, which could contaminate the ground water, are discharged from the ATPFP. 
   SUMMARY OF THE INVENTION 
   The ATPFP is a single device utilizing a multi-stage procedure for treating sewage. The ATPFP is comprised of an aerobic tank, in which the sewage is aerated to allow aerobic microorganisms to break down the sewage and then clarified as the heavier particles separate from the effluent, and a post-treatment tank, which filters and often chlorinates the effluent before discharge. The filter mechanism, in addition to further cleaning the effluent, also allows the ATPFP to effectively use a pump to discharge the cleaned effluent from the post-treatment tank, by trapping floating debris and trash which survived aerobic clarification and would clog the pump device. The two tanks are joined into a single unit, allowing for convenient installation. 
   The aerobic tank is a vessel with sidewalls and a bottom, and the top is sealed by a removable cover. The tank encompasses a funnel-shaped clarifier. The clarifier is wide near the top of the aerobic tank and narrows towards the bottom of the tank, and there is an opening in the bottom of the clarifier. There are many methods which could be used to hold the clarifier in place inside the aerobic tank. The ATPFP preferably uses a clarifier design with a lip that overhangs the sidewalls of the aerobic tank. Thus, the clarifier actually hangs down from the top of the sidewalls. The lip of the clarifier is held firmly in place between the top of the aerobic tank sidewalls and the cover for the aerobic tank. The funnel-shaped main body of the clarifier is offset slightly down from the top of the tank, so that there is a gap between the top of the clarifier and the top of the aerobic tank. This offset provides clearance for the air feed conduit. The clarifier hangs down inside the vessel, not reaching down to the bottom of the aerobic tank but leaving an area of clearance between the bottom of the clarifier and the bottom of the aerobic tank. Thus, the aerobic tank is divided into two chambers by the clarifier. Between the outer sidewalls of the aerobic tank and the clarifier is the outer chamber, where aeration of the sewage occurs, while the volume inside the clarifier is the inner chamber of the aerobic tank, where solid particles are gravity separated from the effluent. 
   Running down into the outer chamber of the aerobic tank from the top of the aerobic tank are droplines. These droplines are typically distributed in the outer chamber such that they provide for aeration throughout the upper part of the outer chamber, above the plane of the bottom of the clarifier. These droplines are conduits which are typically capped at the bottom end and which have small holes for emitting air. The top end of these droplines are connected to an air feed conduit which directs air from the compressor, so that the droplines will emit air bubbles into the outer chamber, aerating the sewage passing through the outer chamber of the aerobic tank. The inner chamber, located inside the clarifier, is screened from the aerating effect of the droplines by the walls of the clarifier, so this inner chamber is a non-turbulent, quiescent zone. Near the top of the inner chamber with its opening located inside the clarifier is an outlet drain leading to the post-treatment tank. Typically, the outlet drain is comprised of an outlet conduit, extending from the clarifier of the aerobic tank to the post-treatment tank, and a T-Baffle, which controls the flow of effluent into the outlet conduit. The T-Baffle is comprised of two T-joints. The first T-joint connects to the outlet conduit and extend upwards and downwards from the outlet conduit. The second T-joint connects to the bottom of the first T-joint, so that its two openings extend out perpendicularly from the openings of the first T-joint. The uppermost opening of the first T-joint extends above the fluid level within the clarifier, acting as a vent for the T-Baffle. Both of the openings for the second T-joint are beneath the fluid level within the clarifier. Thus, the effluent enters the T-Baffle through the two lower openings and then flows into the outlet conduit, out of the clarifier of the aerobic tank and into the post-treatment tank. Because a film of scum can form atop the liquid in the aerobic tank, the T-Baffle acts to drain effluent from beneath the surface of the fluid to provide for a cleaner effluent discharge from the aerobic tank. 
   The sewage enters the aerobic tank through an inlet port located near the top of the aerobic tank. The sewage moves into the outer chamber of the aerobic tank and descends downward through the outer chamber as additional sewage enters the aerobic tank through the inlet port. As the sewage descends, it passes through the air bubbles emitted from the drop lines. This excites the sewage, causing turbulent motion, as it aerates the sewage. Injecting air into the sewage activates and stimulates the aerobic microorganisms in the sewage. This causes the aerobic microorganisms to multiply and increases the amount of sewage that they digest. This aerobic process eliminates sewage contaminants to a great extent, cleaning the sewage. After passing through the aeration zone of the outer chamber of the aeration tank, the sewage enters a relatively calm zone below the air holes in the drop lines. Here, settling begins to occur, with heavier solids falling towards the bottom of the aerobic tank. The sewage in the quiescent zone is displaced upwards and through the opening in the bottom of the clarifier and into the inner chamber of the aerobic tank as more sewage enters the outer chamber of the aerobic tank. The sewage in the inner chamber is in a relatively calm state, and so contaminants, acted upon by gravity, will continue to settle downwards. In this way, the clarifier acts to screen out solid contaminants from the effluent. This continuous process results in a very clean effluent at the top of the inner chamber, where it is drained off by the T-Baffle and flows out of the aerobic tank through the outlet conduit and into the post-treatment tank. 
   The post-treatment tank has sidewalls and a bottom, and the top is sealed with a removable cover. Typically, the post-treatment tank has an approximately rectangular cross-section and is generally the same height as the aerobic tank. The outlet conduit enters the post-treatment tank near the top of the tank. There, it connects to a filter pipe, through which the effluent passes into the storage space of the post-treatment tank. By design, the filter pipe is removably connected to the outlet conduit, typically using a removable pin, so that the filter pipe can be easily detached for regular cleaning in order for the filtering process to remain effective. Optionally, the outlet conduit may be connected to the filter pipe via a chlorinator. In that case, the filter pipe is generally rigidly attached to the bottom of the chlorinator, and the chlorinator-filter pipe assembly is removably attached to the outlet conduit using a removable pin which is inserted through matching holes in the filter pipe assembly and the outlet conduit. Then, the effluent is chlorinated when passing through the chlorinator, generally by flowing across one or more chlorine tablets, before finally being filtered in preparation for discharge. Typically, the filter pipe has apertures through which the effluent flows into the post-treatment tank. Any debris or particulate matter in the clarified effluent which is larger than these apertures will be trapped inside the filter pipe and will not pass into the post-treatment tank. So, in the final stage of the ATPFP, the effluent has been aerobically clarified, filtered, and chlorinated, producing a substantially clean effluent suitable for direct discharge to the environment in accordance with various state health and environmental regulations. The cleaned effluent is typically held in the post-treatment tank until it rises to a level which activates a float switch, triggering a pump, which can be either internal or external, discharging the cleaned effluent. 
   For convenience, the ATPFP connects the post-treatment tank to the aerobic tank, creating a single unit which performs this multi-stage cleaning process for sewage. The top of the two tanks are capped to make the ATPFP a closed system. The cover cap for the aerobic tank is generally convex in shape (dome-shaped). This strengthens the aerobic tank from collapsing under the weight of the earth beneath which it is buried. The cover cap for the post-treatment tank may not be convex, since it is primarily a riser which extends above the earthen surface and so does not need reinforcement. Rather than individual cover caps for each tank, however, a single cover for the entire ATPFP device is preferred. This single cover needs to be formed so that it seals each tank individually, so that there can be no sewage gas transfer between the tanks. In addition, chlorine cannot be allowed to flow from the post-treatment tank to the aerobic tank (if an optional chlorinator is employed), as that would kill the aerobic microorganisms which are crucial to the cleaning process. The single cover is also preferably formed to incorporate a convex section over the aerobic tank for strength purposes. A portion of the cover for each tank can have a service hatch for maintenance. Generally, there is a riser extending from the top of the aerobic tank, allowing for inspection and cleaning of the aerobic tank. Also, there is generally a larger high riser on the post-treatment tank which allows for venting of air from the system. This larger riser also allows access for maintenance and regular cleaning of the filter pipe-chlorinator unit within the post-treatment tank. The accessability and ease-of-removal of the filter pipe assembly is important to the proper functioning of the ATPFP, since the filter pipe will need to be regularly removed for cleaning if the filter pipe is to continue performing its filtering/cleaning process effectively and if the unit is to function properly as a whole. Here, the compact design of the filter pipe itself, which combines a slender profile with a large surface area for trapping particles, is particularly helpful, in that it facilitates the convenient removal of the filter pipe from the post-treatment tank through the service hatch atop the riser. 
   The ATPFP can be made of any non-toxic, solid material, such as concrete, plastic, fibreglass, metal, or ceramic materials for example, but a strong, light-weight, non-corrosive material is preferable for convenience in installation and operation. Preferably, the ATPFP is formed of fibreglass reinforced plastic, keeping the weight of the ATPFP to that reasonable for simple installation without the need for lifting machinery. The tanks are typically joined together by a laminating process. Generally, the tanks are sized so that they do not have to be pumped clean very often, on average requiring cleaning once every two to five years. In addition, the sizes of the tanks are dependant upon the expected amount of sewage generated by the buildings they service on a daily basis. The aerobic tank must also be sized so that the sewage remains in it long enough for the aerobic microorganisms to effectively process the sewage. The ATPFP is typically installed below ground, buried in the yard of a residence, so its compact design simplifies installation and minimizes the amount of damage to the yard. 
   It is an object of this invention to clean sewage in preparation for discharge. In doing so, this invention uses an aerobic processes to break down the sewage, separates the contaminants from the sewage water through a gravity separation process, and filters and chlorinates the effluent. It is still another object of this invention for it to be easy to install and for it to be durable, requiring very little maintenance. It is yet another object of this invention to employ a filter pipe to trap particles floating in the effluent after aerobic clarification in order to produce a better quality effluent for discharge to the environment. It is yet another object of this invention to employ a filter pipe to trap trash and other debris so that the effluent may be pumped out of the post-treatment tank. It is yet another object of this invention to utilize a filter pipe design which facilitates regular removal and cleaning of the filter pipe in order to ensure that the filter pipe functions properly over time. It is yet another object of this invention to utilize a filter pipe design which maximizes the functional operating life of the filter element between regular cleanings by providing a filter with a large surface area. It is yet another object of this invention to provide a multi-stage sewage cleaning process in a single, compact unit. It is yet another object of this invention to discharge water which meets or exceeds state water quality requirements. It is yet another object of this invention to allow for inspection of the tanks and to allow for cleaning and maintenance of the invention. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     Reference will be made to the drawings where like parts are designated by like numerals and wherein: 
       FIG. 1  is a cut-away side view of the ATPFP. 
       FIG. 2  is an overhead plan view of the ATPFP. 
       FIG. 3  is a combined overhead and side view of the filter pipe of the ATPFP. 
       FIG. 4  is a perspective view of the T-Baffle of the ATPFP. 
       FIG. 5  is a side view of the chlorinator of the ATPFP. 
       FIG. 6  is a cut-away side view of the clarifier of the ATPFP. 
       FIG. 7  is an overhead view of the clarifier of the ATPFP. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
   Referring now to the drawings in more detail, the preferred embodiment of the ATPFP is generally designated by the numeral  10 , and is shown generally in  FIG. 1  and  FIG. 2 . 
   The ATPFP  10  is comprised of two tanks which are rigidly joined together into a single unit. The main sewage treatment tank, which is generally the largest, is the aerobic tank  40 . Although it may be any shape, the preferred embodiment is cylindrical with a closed bottom. Also, although the size of the aerobic tank  40  can vary depending upon the amount of sewage that the ATPFP  10  will likely receive in a given day, the aerobic tank  40  generally is sized to handle from 500 to 1500 gallons of sewage per day. The preferred embodiment of the ATPFP processes 500 gallons of sewage per day (as for a typical residence) and has a diameter of approximately 66 inches and a height of approximately 76 inches. The post-treatment tank  60  is generally smaller than the aerobic tank  40 . The post-treatment tank  60  typically ranges in size from 37 to 300 gallons. In the preferred embodiment it holds approximately 166 gallons of effluent and has an approximately rectangular cross-section which is 24 inches by 26 inches. Again, the post-treatment tank  60  can have any shape so long as it has sidewalls and a bottom (so that it can contain the sewage), but in the preferred embodiment the post-treatment tank  60  is roughly rectangular in cross-section. The post-treatment tank  60  is rigidly attached to the aerobic tank  40 , and in the preferred embodiment, the post-treatment tank  60  spans the entire height of the aerobic tank  40 . Although the aerobic tank  40  and the post-treatment tank  60  can be made of any non-toxic, solid material, in the preferred embodiment of the ATPFP  10  both tanks  40  and  60  are formed of fibreglass reinforced plastic, with the post-treatment tank  60  laminated onto the aerobic tank  40  to create a single, one-piece ATPFP  10 . 
   Each of the tanks in the ATPFP  10  must be covered. The cover can be an integrated part of the tank, but generally the cover is a separate, distinct component to simplify both construction and maintenance. The top of the tanks can be sealed by having a separate cover for the aerobic tank  40  and for the post-treatment tank  60 , or a single cover can seal both tanks at once. In the preferred embodiment, a single cover  56  is used to cap the aerobic tank  40  and the post-treatment tank  60 . The cover  56  must seal each tank from the other to prevent any flow of gases between the two stages of the ATPFP  10 . Also, in the preferred embodiment the cover  56  has a convexly curved portion over the aerobic tank  40 , as this convex design strengthens the cover  56  so that it can resist the downward forces applied on it when it is buried beneath the ground. 
   Sewage enters the aerobic tank  40  through an inlet port  25  generally located near the top of the aerobic tank  40 . Within the aerobic tank  40  of the ATPFP  10 , is a funnel-shaped clarifier  46 . The clarifier  46  is wide near the top of the aerobic tank  40  and narrow near the bottom of the aerobic tank  40 , with a hole in the bottom of the clarifier  46 . The preferred embodiment uses a clarifier  46  design with a lip  46   b  that overhangs the sidewalls  41  of the aerobic tank  40  (see  FIG. 6 ). Thus, the clarifier  46  actually hangs down from the top of the sidewalls  41 . The lip  46   b  of the clarifier is held firmly in place between the top of the aerobic tank sidewalls  41  and the cover  56  for the aerobic tank  40 . The funnel-shaped clarifier main body  46   a  is offset slightly down from the top of the tank, so that there is a gap between the top of the clarifier main body  46   a  and the top of the aerobic tank  40 . This offset  46   d  provides clearance for the air feed conduit  57 . Also, in the preferred embodiment, the clarifier main body  46   a  is set slightly in radially from the sidewalls  41  of the aerobic tank  40 , providing a rim  46   c  on which the air feed conduit  57  may lie. The clarifier  46  hangs downward in the aerobic tank  40 , but does not extend all the way to the bottom of the aerobic tank  40 ; instead there is a gap between the bottom of the clarifier  46 , which is the narrow end of the funnel, and the bottom of the aerobic tank  40 . Thus, the clarifier  46  divides the aerobic tank  40  into two chambers. 
   The outer chamber  42  of the aerobic tank  40  is located between the sidewall  41  of the aerobic tank  40  and the clarifier  46 . The inner chamber  47 , is located inside the funnel-shaped clarifier  46 . Located in the outer chamber  42  of the aerobic tank, are one or more air droplines  44  which hang down into the sewage from the top of the aerobic tank  40 . These droplines  44  are conduits, generally capped at the bottom ends, with holes for emitting air bubbles. In the preferred embodiment, the droplines  44  are cylindrical conduits. The top ends of the plurality of droplines  44  are connected to an air feed conduit  57  which leads to an external air compressor. Thus, when the air compressor is operating, air flows through the air feed conduit  57 , into the droplines  44 , and bubbles out into the sewage in the outer chamber  42  of the aerobic tank  40 . For best results, the droplines  44  should not emit air bubbles beneath the plane of the bottom of the clarifier  46 . While this may be accomplished by restricting the length of the droplines  44  so that they do not extend down beneath the plane of the bottom of the clarifier  46 , the preferred embodiment uses droplines  44  which extend down past the bottom of the clarifier  46  but which only have holes in the area above the bottom of the clarifier  46 . There should be enough droplines  44  to adequately aerate the sewage in the upper part of the outer chamber  42 , with two through eight generally required. The preferred embodiment uses four such droplines  44  which are evenly spaced in the area of the outer chamber  42 . 
   Located near the center of the inner chamber  47  near the top of the aerobic tank  40  is the T-Baffle  53 . The T-Baffle  53  functions to draw cleaned effluent from near the top of the liquid surface level in the inner chamber  47  and to transport it through the outlet conduit  55  and into the post-treatment tank  60 . The T-Baffle  53  is comprised of two T-joints  53   a  and  53   b  rigidly linked together (see  FIG. 4 ). The lower T-joint  53   b  is located near the surface level, beneath the cleaned effluent so that cleaned effluent will enter through the two openings in the T-joint  53   b.  This lower T-joint  53   b  is rigidly attached to a branch of the upper T-joint  53   a.  One of the other branches of upper T-joint  53   a  extends up out of the effluent and acts as a vent. The third branch of the upper T-joint  53   a  is rigidly attached to the outlet conduit  55  which extends outward radially from the central location of the T-Baffle  53 , through the outer sidewall  41  joining the aerobic tank  40  to the post-treatment tank  60 , and into the post-treatment tank  60 . Thus, the T-Baffle  53  and connected outlet conduit  55 , which together are termed the outlet drain, transport effluent from the inner chamber  47  of the aerobic tank  40  into the post-treatment tank  60 . 
   In the post-treatment tank  60 , the outlet conduit  55  from the aerobic tank  40  is connected to a filter pipe assembly  80 . Although the filter pipe assembly  80  could be merely comprised of a filter pipe  82 , in the preferred embodiment the filter pipe assembly  80  is comprised of an optional chlorinator  62  and a filter pipe  82 . The filter pipe assembly  80  could connect these elements in a variety of ways and could utilize various specific types of chlorine dispersal units and filter units for trapping debris; the preferred embodiment set forth in detail below is intended to be merely illustrative and is not intended to limit the application or scope of this invention in any way. A person skilled in the art field will recognize and appreciate such equivalents, which are included within the scope of the ATPFP  10 . The purpose of the chlorinator  62  is to distribute chlorine into the effluent. In the preferred embodiment, the chlorinator  62  distributes chlorine by physical contact of the effluent with chlorine tablets. The chlorinator  62  is comprised of a cross  62   a,  an external feeding conduit  62   b,  a restraining mechanism  62   c,  and a tablet droptube  62   d  (see  FIG. 5 ). The restraining mechanism  62   c,  which is a rod (typically a ¾ inch PVC tube) affixed in the center of the bottom of the cross  62   a  in the preferred embodiment, acts as a stop to hold the tablet droptube  62   d  in place in the chlorinator  62 , so that the effluent from the outlet conduit  55  will flow properly through the chlorinator  62  and will be effectively chlorinated before passing into the filter pipe  82 . One branch of the cross  62   a  is removably connected to the outlet conduit  55  from the aerobic tank  40 . Typically, this removable connection is accomplished by sliding said branch of the cross  62   a  onto the outlet conduit  55  and fixing the connection with a removable pin  83 , which is inserted into matching holes in the cross  62   a  and the outlet conduit  55 . Another branch of the cross  62   a  extends outward horizontally into the post-treatment tank  60 . This branch of the cross  62   a  is open and acts as an overflow relief mechanism, in case the filter pipe  82  should ever become clogged by debris (as for example, if the filter pipe  82  was not timely cleaned, so that it filled completely with debris). The remaining branches of the cross  62   a  extend in the vertical plane, one branch extending upwards while the other extends downwards. To the upper branch of the cross  62   a  is connected an external feeding conduit  62   b  which extends upwards out of the post-treatment tank  60 . It is through this external feeding conduit  62   b  that the chlorine tablets are administered. 
   Attached to the lower branch of the cross  62   a  is the filter pipe  82 , which extends downward into the post-treatment tank  60 , so that the effluent from the outlet conduit  55  may pass through the chlorinator  62  and through the filter pipe  82  before entering the post-treatment tank  60  in preparation for discharge to the environment. The filter pipe  82  may be either rigidly attached (with an adhesive, for example) or removably attached (with pins, for example) to the chlorinator  62 . The restraining mechanism  62   c  is typically located near the interface between the chlorinator  62  and the filter pipe  82 , so that the droptube  62   d  cannot enter the filter pipe but is held in its proper location so that the effluent may be effectively sanitized by the chlorinator  62 . The chlorine tablets are loaded into the chlorine droptube  62   d,  which is a straight conduit that has a small enough diameter to fit into the external feeding conduit  62   b.  The chlorine droptube  62   d  is then placed in the external feeding conduit  62   c,  loading the chlorine into the chlorinator  62 . The chlorine droptube  62   d  has holes or slots in it to allow effluent to pass through the sidewall of the chlorine droptube  62   d,  making contact with the chlorine tablet before exiting out the chlorinator  62 . 
   The filter pipe  82 , shown in  FIG. 3 , is a filter cleaning mechanism for trapping small particles and floating debris and trash still remaining in the effluent after the aerobic clarification cleaning process. The filter pipe  82  is designed to primarily trap hair, lent, and other such floating solids which have made it through the aerobic clarification process, while also reducing the small solid particulates in the effluent. In general design, the filter pipe  82  utilizes small apertures through which the effluent flows in order to trap solid particles floating in the effluent. These particles are held within the filter pipe  82 , so that they may not pass through into the post-treatment tank  60 . In the preferred embodiment, the filter pipe  82  is comprised of a slotted tube which is capped at the bottom end by a removable cap  84 . Although various sizes and types of tubes could be utilized, the preferred embodiment employs a filter pipe  82  which is 4 inch PVC pipe with horizontal slots of approximately 0.050 inches in width cut along its length. In the preferred embodiment, four such slots are spaced evenly around the circumference of the filter pipe  82  at each location along its length, with slots being spaced evenly along the vertical length of the filter pipe  82  and typically having approximately ¼ inch of vertical distance between layers of slots. And in the preferred embodiment, the filter pipe  82  essentially spans the length of the post-treatment tank  60 , such that when it is in place, it rests on the bottom of the post-treatment tank  60  for additional support. This particular design provides maximum filter surface area and effective radial distribution of effluent. Also, the design&#39;s length allows the ATPFP to be utilized for extended periods between cleanings. Finally, the design provides a slender profile for easy extraction of the filter pipe  82  when cleaning does become necessary. And if additional filtration is desired, it may easily be added to the ATPFP  10  by simply incorporating additional filter pipes  82  of varying radii which encompass the original filter pipe  82 . These additional filter pipes  82  could have either the same size slots as the original filter pipe  82 , or they could have narrower slots for more refined filtration. Thus, the filtration system of the ATPFP  10  can readily be modified as needed by simply adding radial layers of filter pipes  82 . 
   Regardless of the number of layers of filter pipes  82 , the basic filtration process remains the same. The effluent enters the top of the filter pipe  82  and flows out into the post-treatment tank  60  through the slots along the length of the filter pipe  82 . Any particulate matter and debris in the effluent larger than the slots in the filter pipe  82  will be trapped inside the filter pipe  82  and will be unable to flow into the post-treatment tank  60  for discharge. Instead, the particulates will fall to the bottom of the filter pipe  82  and collect in the cap  84  at the bottom of the filter pipe  82 . In this manner, the filter pipe  82  acts as both a filter and a trash trap. Thus, the greater the length of the filter pipe  82 , the longer the permissible period of time between cleanings, since the filter pipe  82  will have additional space to store the trapped debris while still having ample unblocked slots for effluent to flow through on its way to the post-treatment tank  60 . When it is time for the filter pipe  82  to be cleaned, the pin  83  can be removed, the cross  62   a  can be slidably disengaged from the outlet conduit  55 , and the entire filter pipe assembly  80  can be easily removed through the service hatch  67  atop the riser  68  of the post-treatment tank  60 . Then, the actual cleaning of the filter pipe  82  can quite easily take place by simply removing the cap  84  from the bottom of the filter pipe  82  and flushing the particulate matter and debris out of the filter pipe  82 . Because of the length of the filter pipe  82 , clogging should not become an issue so long as the standard six month regular maintenance schedule is observed and the system is not severely abused. 
   The single cover  56  which acts to seal both tanks  40  and  60  of the ATPFP  10  has various openings, risers, and hatches built into it. Over the aerobic tank  40 , an inspection riser  59  extends up above ground level. Over the post-treatment tank  60 , a post-treatment tank riser  68  extends up above ground level. This post-treatment tank riser  68  has a service hatch  67  for regular cleaning and maintenance of the filter pipe  82 . The post-treatment tank riser  68  and service hatch  67  are both sized to allow for easy access to the filter pipe assembly  80  for maintenance and/or cleaning purposes, as well as for installation and maintenance of an internal pump  73 , which may be located within the post-treatment tank  60 . Preferably, a float switch  74  in the post-treatment tank  60  activates an internal pump  73  when the effluent in the post-treatment tank reaches a certain level. In the case of an internal pump  73 , a pump seat  75  can be rigidly attached to the bottom of the post-treatment tank  60  to minimize pump movement and stress on the pump line. The effluent is generally pumped out of the post-treatment tank riser  68  through an outlet port  69  drilled in the post-treatment tank riser  68  at the time of installation. 
   The invention described above employs a multi-stage procedure for cleaning raw sewage. The raw sewage enters the aerobic tank  40  through the inlet port  25 , which has a sealant around it to prevent any leakage. As more sewage enters the aerobic tank  40  through the inlet port  25 , sewage is displaced downward in the outer chamber  42  and passes through the air bubbles emitted from the droplines  44 . These air bubbles aerate the sewage, stimulating the aerobic microorganisms so that the aerobic processing of the sewage is greatly enhanced. As the sewage continues to descend in the outer chamber  42 , the sewage exits this aeration zone where the air bubbles are emitted by the droplines  44  and enters a quiescent zone near the bottom of the aerobic tank  40 . In this quiescent zone, the solid contaminants suspended in the effluent begin to fall towards the bottom of the aerobic tank  40  under the influence of gravity. As more sewage enters the outer chamber  42  from the inlet port  25 , the aerated sewage in the quiescent zone near the bottom of the aerobic tank  40  is pushed up into the inner chamber  47  inside the clarifier  46 . The inner chamber  47  is protected by the walls of the clarifier  46  from the stirring effect of the air bubbles emitted from the droplines  44  in the outer chamber  42 , so the inner chamber  47  is a zone of relative calm. As the sewage continues to rise upward through the inner chamber  47 , the force of gravity continues to pull down the heavier solid contaminants. Thus, the inner chamber  47  acts as a gravity separator, continually segregating the contaminants from the effluent, so that by the time the treated sewage reaches the top of the inner chamber  47 , the effluent has been substantially cleaned. Again, the size of the outer chamber  42  and the inner chamber  47  of the aerobic tank  40  are selected based upon the typical amounts of sewage to be processed so that each chamber has sufficient time to perform its cleaning function. 
   As the treated effluent nears the top of the inner chamber  47 , it enters the two bottom openings in the T-Baffle  53 . The effluent then flows through the outlet conduit  55 , passing out of the inner chamber  47 , through the clarifier  46 , through the outer chamber  42 , through the sidewall  41  of the aerobic tank  40  where it is adjacent to the post-treatment tank  60 , and into the post-treatment tank  60 . At the point where the outlet conduit  55  passes through the clarifier  46  and the side wall of the aerobic tank  40 , a sealant ensures that there is no leakage. In the post-treatment tank  60 , the outlet conduit  55  removably connects to the filter pipe assembly  80 . In the preferred embodiment, the filter pipe assembly  80  is comprised of a chlorinator  62  and a filter pipe  82 . Although a person skilled in the art field will appreciate that there are several different ways in which the filter pipe assembly could join a chlorination unit of some type to a filtering mechanism of some type, in the preferred embodiment, the filter pipe assembly  80  is constructed so that the filter pipe  82  is attached to the bottom of the chlorinator  62 , so that the effluent is chlorinated and then filtered before being released into the post-treatment tank  60 . Thus, the effluent flows into the cross  62   a  of the chlorinator  62 , passes through holes in the chlorine droptube  62   d  to flow across a chlorine tablet, and then flows down through the inside of the droptube  62   d  and through the restraining mechanism  62   c  to exit the chlorinator  62 , chlorinating the effluent before it enters the filter pipe  82 . The effluent then flows into the filter pipe  82  and through the slots in the filter pipe  82  into the post-treatment tank  60 . In the preferred embodiment, the chlorinator  62  uses chlorine tablets designed to ensure that the chlorine content in the effluent passing across it will be at least 1 ppm. Although a variety of means could be used to discharge the cleaned effluent from the post-treatment tank  60 , in the preferred embodiment an internal pump  73  activated by a float switch  74  discharges the cleaned effluent into the environment. The treated effluent is stored in the post-treatment tank  60  until the level of effluent rises high enough to activate a float switch  74  on the internal pump  73 . At that point, the internal pump  73  activates and pumps the treated effluent out of the post-treatment tank  60  through the outlet port  69 , discharging the now cleaned effluent. 
   As stated above, the preferred embodiment uses fibreglass reinforced plastic for the tanks  40  and  60 , the clarifier  46 , and the cover  56 . This material selection allows the ATPFP  10  to be relatively light-weight, for ease-of-installation, yet durable. A strong, lightweight plastic would also be effective. The pipes, conduits, and T-joints in the preferred embodiment can also be made of any non-toxic, solid material, but the preferred embodiment uses commercially available PVC components since they are durable and light-weight and since their ready availability simplifies the manufacturing process. In addition, since each tank needs to be sealed to prevent transfer of liquids or gases between them and to prevent leakage of untreated sewage out of the ATPFP  10 , sealant material is used wherever a conduit, pipe, or port passes through a separating wall. Generally, the tanks are sized appropriately depending on the expected sewage production rate of the buildings serviced by the ATPFP  10 , with the size of the aerobic tank  40  being most critical to the sewage cleaning process since the aerobic microorganisms must be given sufficient time to process the sewage. In the preferred embodiment, the aerobic tank  40  processes approximately 500 gallons per day, while the post-treatment tank  60  holds approximately 166 gallons of effluent for discharge. 
   In the aerobic tank  40 , the size of the gap between the opening in the bottom of the clarifier  46  and the bottom of the aerobic tank  40  should be big enough to allow for a good flow of sewage from the outer chamber  42  of the aerobic tank  40  into the inner chamber  47 . In the preferred embodiment, the gap is approximately 10 inches. In addition, in the preferred embodiment the offset from the top of the aerobic tank  40  to the top of the clarifier main body  46   a  is approximately 2 inches. Also, the clarifier rim  46   c  in the preferred embodiment is approximately 9 inches. 
   Although the size, number, and distribution of air holes in the air droplines  44  can vary, the air holes should be as small as possible without clogging regularly in operation, since this will allow for good air diffusion into the sewage while allowing the ATPFP  10  to operate reliably. In the preferred embodiment the holes are 3/16th of an inch in diameter. Each dropline  44  in the preferred embodiment has three vertical columns of holes spaced ⅜th of an inch apart facing towards the clarifier  46  and running down the length of each dropline  44  from near the top of the aerobic tank  40  and ending just above the plane of the opening in the bottom of the clarifier  46 . In the preferred embodiment, there are 13 holes in each dropline  44 , with the holes in each column spaced ¾th of an inch apart.