Abstract:
An enzyme containing in-house digester unit for receiving and treating household waste material, which utilizes settling and biological treatment of solids and wastewater by means of organisms which digest the organic materials contained in the household waste thereby eliminating the need for any chemical treatment or processes.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates in general to the disposal of household waste or sewage and, in particular, to the pre-treatment of such materials before they are discharged into a municipal sewer system. 
     More specifically, but without restriction to the particular embodiment and/or use which is shown and described herein for purposes of illustration, this invention relates to a domestic wastewater pre-treatment unit for installation in the home to pre-treat household waste or sewage prior to discharge of these materials into a municipal sewer system. Through pre-treatment of these materials inside the home, advantage is taken of the substantially constant warm temperatures to increase the efficiency of the unit&#39;s operational characteristics. 
     While various apparatus has been developed for use in the pre-treatment, or for the initial treatment, of sewage received at municipal sewage treatment plants from a municipal sewer system, such equipment does not address the problem of inadequate municipal sewer systems. As municipalities have grown, an ever increasing population generates more sewage which must be disposed of, and decreases the amount of land available to absorb melting snow and rainfall as new homes are built to house an ever growing population. These factors are major contributors to the cause of inadequate sewage treatment. Resolving this problem requires that existing sewage treatment facilities be expanded, which is a substantial cost to a municipality, or results in the overwhelming of the collection system by the input from the sewer system and storm system, referred to as combined sewer overflow, resulting in the spillage or overflow of raw and untreated sewage. 
     The first stage, or pre-treatment systems presently employed in municipal sewage treatment facilities, because of the volume of material received, are of a large construction. The present invention is intended for installation in a home to treat the sewage before the sewage leaves the home to be discharged into the municipal sewer system. To this end, the smaller volume of materials to be treated enables the treatment unit to utilize a more simple construction and configuration than a treatment process required to achieve the same result, but intended for use with the increased quantity of sewage and larger scale equipment required in a municipal sewage treatment plant. 
     Installation of the present invention in the home permits more efficient utilization of biological organisms to digest the organic material, rather than requiring the use of physical and or chemical processes to remove undesirable materials such as ammonia and phosphorus, which has been attempted by others as disclosed in J. R. Lira, U.S. Pat. No. 5,468,375 “WASTEWATER PRETREATMENT TANK ASSEMBLY”. In the Lira patent, unlike the present invention, a chemical process is used to strip ammonia by the addition of soda ash to raise the pH level. The chemical environment thereby created strips the ammonia. Water spills over a first weir into a stripping chamber whereat an auger dispenser periodically injects a predetermined quantity of soda ash to chemically prepare any ammonia for removal from the wastewater. 
     In the present invention, by utilizing biological organisms to digest organic material, activated sludge and attached growth filters remove ammonia and phosphorus. There is no need to add chemicals to the tank for treating the wastewater. The use of these biological processes, and the sequential alternation of oxygenation through the chambers of the present invention, which moves the bacteria organisms sequentially between a no oxygen environment and a high oxygen environment, enhances the removal of the phosphorus by the bacteria through incorporating the phosphorus into their cells during growth. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to improve systems for disposing of household wastes. 
     Another object of this invention is to decrease the volume of household waste material or sludge discharged into a municipal sewer system. 
     A further object of this invention is to decrease the volume of household waste material discharged into a municipal sewer system by the utilization of an efficient biological organism digesting process. 
     These and other objects are attained in accordance with the present invention wherein there is provided an enzyme-containing, in-house digester unit for receiving and treating household waste material. The in-house digester utilizes settling and biological treatment of solids and wastewater by means of biological organisms to digest the organic materials contained in the household waste, eliminating the need for the addition of chemicals or chemical treatment. 
    
    
     DESCRIPTION OF THE DRAWING 
     Further objects of the present invention, together with additional features contributing thereto and advantages accruing therefrom, will be apparent from the following description of a preferred embodiment of the invention which is shown in the accompanying drawings with like reference numerals indicating corresponding parts throughout and which is to be read in conjunction with the following drawings, wherein: 
     FIG. 1 is a front elevational view of a preferred embodiment of the invention, with portions removed, to illustrate the interior structure thereof and the flow path of materials being treated; 
     FIG. 2 is an end view of the invention, with portions removed; 
     FIG. 3 is a top elevation of the invention, with portions removed, to better illustrate the chambers thereof; and 
     FIG. 4 is a cross sectional view taken along lines  4 — 4  of FIG.  1 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, there is shown a cross-sectional view of a closed pre-treatment tank  10  which includes a top  11 , a forward end wall  12 , a rear end wall  13 , side walls  14  and a bottom  16  which is sloped for a purpose to be hereinafter described in more detail. The top  11  is closed, and the tank  10  is preferably installed in the basement of a home, with an inlet connected to the down pipe from the household waterclosets. 
     The tank  10  comprises four chambers, a first or primary chamber  30  wherein larger solids materials settle and are gravitationally compacted; a second chamber  40  wherein further settling and digestion occurs; a third settling or anaerobic biological digestion chamber  50  wherein, after digestion, accumulated solids and sludge are believed to settle out from the liquid, and a portion thereof is recycled into chamber  40  to be used in the activated sludge process, and a fourth or attached growth media chamber  60  which biologically treats the wastewater to remove ammonia and phosphorus, and lowers the BOD, prior to discharge of the effluent from the tank. These chambers, and the components thereof, will be further discussed in detail hereinafter. 
     In the main or primary chamber  30 , primary settling occurs and anaerobic digestion begins. Chamber  30  includes an inlet zone  31  whereat mixing and dispersion of the solids material into the liquid occurs, and the flow of solids and wastewater entering the tank is dampened. In the primary chamber suspended solids, such as grease, oil and fats, float on top of the liquid contained therein at a level which is determined by the upper edge of a baffle plate  38  extending between the spaced sidewalls  14 . Beneath the suspended solids is a high-flow zone which accommodates periods of moderate or high flow such as occurs when using a shower, dishwasher or washing machine. 
     As the solids materials settle out of the liquid, the solids begin the anaerobic digestion process. Specially selected and seeded biological digestion organisms, preferably two groups of bacteria, an acid forming anaerobic bacteria and a methane forming bacteria, and an enzyme complex such as Biotol-ST, which consists of protein, starch, cellulose, fat grease and oil digesting enzymes, are added to the tank for sludge digestion. These are available from Biotol Inc. 6595 Edenville Blvd., Suite 155, Eden Prairie, Minn. 55346. The nitrifying organisms or bacteria are available from Bacta-Pure International Ecological Technologies, Inc. P.O. Box 208, North Hatley QC, JOB 2C0, CANADA, which contain the microorganisms Nitrobacter and Nitrosomonas in an aqueous solution. These materials are added to the tank  10  at start-up as set forth below. 
     For a treatment tank having a volume sufficient for a typical household, which generally would be capable of handling approximately 100 gallons of liquid, it has been found that the addition at start-up of approximately 1000 ml of nitrifying organisms and approximately 500 ml of digestion organisms is preferred. Thereafter, on a weekly basis 100 ml of nitrifying organisms and 50 ml of digestion organisms and 50 ml of enzyme complex are added, or if a monthly protocol is preferred, 500 ml nitrifying organisms and 250 ml digestion organisms are added to maintain the system in operation. Either a weekly or a monthly protocol may be utilized. These enzymes and bacteria accelerate and facilitate the digestion and other tank processes. 
     When household waste enters the tank  10  from the household downpipe, the waste passes through the inlet port  17  into the inlet zone  31  of chamber  30 . The waste is accelerated by the vertical drop, and strikes a diffuser plate  36  upon entry into the tank. The diffuser plate  36 , because of the momentum generated by the vertical drop of the falling waste, functions to break up large solid matter, and to reduce the velocity of the waste entering the tank acting as a baffle or turbulence suppressor to minimize the turbulence caused by the entry of the waste into the tank. 
     The material which enters the tank  10  through the inlet opening  17  is not uniformly distributed and, therefor, upon entry into the tank the particles rapidly mix with the liquid contained in the tank forming a suspension of solids material. Because of the quiescent state of the tank contents, most of the suspended particles will either discretely settle, or agglomerate and settle to the bottom of the tank forming a layer of solids material at the tank bottom whereat anaerobic digestion occurs converting the solids material into sludge. 
     Particles which are lighter, or less dense than water, will float to the surface of the liquid in the tank to form a surface scum between the wall  13  and another baffle or weir, settling chamber baffle or weir  38 . The top of baffle  38  is spaced from the inner surface of the tank top  11 , and extends the width of the tank between the side walls  14 . 
     The depth of settling chamber baffle  38 , including an angular portion  38   a  extending away from the inlet  17  and towards the second or activated sludge chamber  40 , defines a zone wherein the liquid which has small quantities of suspended biological solids can pass through a throat  39  defined by the lower edge of baffle  38  and a wall  41  which extends the width of the tank  10  and defines in part the activated sludge chamber  40 . 
     That portion of chamber  30  beneath the floating materials and above the accumulated solids materials at the bottom of the tank which are undergoing the anaerobic digestion process and accumulation for removal from the tank through the outlet  66 , is not defined by tank structure but by a gradient increase in the solids content of the liquid contained in the tank  10  as the solids materials settle to the tank bottom  16 . 
     As a result of the settling, dewatering and digesting of the solids material contained in the liquid, the bottom of the tank will contain both actively digesting solids and digested sludge. The longer the time the solids materials remain in the primary chamber  30  of the unit, the greater the amount of sedimentation that will occur, the more the bacterial and digestive enzymes will be able to reduce the sludge volume and the more of the suspended solids material that will be removed from the liquid. Digested biologic solids materials move to the bottom of the tank  10  because of the downward slope of the tank bottom  16 , and are removed through a digested sludge outlet  66  in the wall  12  of the tank. 
     Two groups of bacteria develop in the sludge creating the digestion process. Acid forming anaerobic bacteria metabolize the organic matter forming organic acids, carbon dioxide and methane. Carbon dioxide and methane are the end products of this digestion. Organic acids are an intermediary byproduct and provide the substrate for the methane forming anaerobic bacteria to grow. Methane-forming bacteria use organic acids to produce carbon dioxide and methane. Periodically these necessary bacteria must be replenished and must be added to the system. 
     In order for the liquid in the chamber  30  to pass into the chamber  40 , the liquid must move through the throat  39  defined by the lowermost edge of baffle  38  and the wall  41 , and over the uppermost edge  42  of the wall  41 . The uppermost edge  42  of wall  41  is positioned at a level below that of the uppermost edge of settling chamber baffle  38  so that the liquid contained in the tank is constrained to flow over the edge of the wall  41  and vertically downward into the activated sludge chamber  40 . The angulation of the lower portion  38   a  of baffle  38  allows for a controlled extraction of the settled or clarified liquid at a controlled rate such that the movement of the liquid does not disrupt the settling or digestion process. The throat  39  prevents large solids from being carried, during high flow periods, into the activated sludge chamber  40 . The downward angled slope of the lower portion  38   a  of the baffle  38  causes any fine solids that might accumulate on the baffle to slide down off the baffle for accumulation in the bottom of the tank. 
     The liquid then enters a second treatment chamber  40 . This chamber is defined by wall  41 , bottom  59  and an angled baffle  45 . Near the bottom of this chamber is a bubbler  80  that introduces a low volume of air into chamber  40 . This introduction of air accomplishes several things: the introduction of air moves the digestion process from an anaerobic state toward an aerobic state, and the natural movement of the bubbles upward through the liquid in chamber  40  cause a counterclockwise circulation within chamber  40 . This circulation of liquid, combined with the natural movement of bubbles upward, causes further breakup of large organic solids to smaller particles. A froth forms in the top of chamber  40  and an activated sludge processes is promoted in chamber  40 . 
     While the liquid is recirculating in chamber  40 , a small portion of the liquid traveling up the baffle or wall  45  is passed through a throat  44  defined by the lowermost edge of the baffle  45 , and a wall  61  which defines in part chamber  50 . The liquid moves upward into the chamber  50 . The angulation of the baffle  45  allows for the extraction of the solids from the chamber  50  at a controlled rate to clarify the liquid and causes any removed solids that might accumulate on the baffle  45  during this process to slide back down through the throat  44  into a portion  48  of the chamber  40 , defined by a bottom well  62  of digestion chamber  60 , discharge outlet  67  and the bottom wall  59 , whereat solids material which accumulates therein is passed out of the tank through the discharge outlet  67 , controlled by a suitable gate valve. A baffle or weir  55  is positioned within the chamber  50  with the top of the baffle  55  spaced from the inner surface of the tank top  11 , and extending the width of the tank between the side walls  14 . The depth of baffle or weir  55 , including an angular portion  55   a  extending away towards the wall  61  of digestion chamber  60 , defines a zone wherein the clarified liquid can pass through a throat  54  which extends the width of the tank  10 . 
     The posterior wall  61  of the biological digestion chamber  60 , which is common with the settling chamber  50 , forms a part of the anterior wall thereof. An overflow outlet  68  is provided in the wall  12  of the tank  10  as a precaution in the unlikely event that for some reason the digestion chamber  60  would become plugged, enabling the liquid to leave the unit through this overflow outlet and be passed into the sewer. 
     The treated liquid passes over the wall  61  onto a series of inclined shelves or plates  57 , best illustrated in FIGS. 1 and 3, one end of each being secured to one of wall  61  or anterior or forward wall  12  and extending between the tank sidewalls  14 , to which they are also secured. Because of the slight incline of the plates  57 , the liquid travels or trickles slowly down each plate  57  before reaching the main tank outlet  69  whereat the liquid leaves the tank and is discharged into a sewer system. In order to maintain a small quantity of liquid on the plates  57  at all times, a solid divider plate  57   a  divides each shelf  67  to maintain moisture in the shelf. 
     To biologically treat the clarified liquid, inert inorganic or biofilter material  70  is used as a substrate for the biologic growth of the organisms that are seeded into the tank  10  upon installation. Such a suitable material, an inert plastic substrate is available from Aquatic Ecosystems, Inc., 1767 Benbow Ct., Apopka, Fla. 32703-7730. Slime forming bacteria create a layer over the inorganic or biofilter material  70  with the inner layer developing anaerobic bacteria, while the outer layer develops aerobic bacteria. Bacteria synthesize organic matter and solids, and the protozoans present consume bacteria. High removal rates of bacteria by protozoans cause increased bacterial growth, and thereby further enhance removal rates of organic matter. Nitrifying bacteria compete for space on the biofilter media. The lower the organic loading to the filter, the greater the rate of nitrification. 
     Each of the shelves  57  holds the inert biological substrate for growth of these desirable organisms. Because of the liquid distribution passing over the wall  61 , all of the clarified liquid is passed over the substrate  70 , and the organisms growing thereon and therein, treating the liquid prior to discharge into the sewer system. The bottom or floor  62  of the digestion chamber  60  is pitched down towards the anterior or forward wall  12  of the tank and the outlet  69  to prevent accumulation of biological material. 
     While this invention has been described and explained with reference to a preferred embodiment, the structure of which has been disclosed herein, it will be understood by those skilled in the art to which this invention pertains that various changes may be made and equivalents may be substituted for elements thereof without departing from the invention. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed in the specification and shown in the drawings as the best mode presently known by the inventor(s) for carrying out this invention, nor confined to the details set forth, but that the invention will include all embodiments, modifications and changes as may come within the scope of the following claims: