Patent Document

This application is derived from Provisional Patent Application Serial No. 60/093,053 filed on Dec. 17, 1997. 
    
    
     The present invention relates to a method of treating waste. 
     BACKGROUND OF THE INVENTION 
     According to municipalities, government agencies, environmentalists and the public in general, odour and potential pollution sources emanating from swine facilities are the main issues that the hog industry needs to address in order to sustain its development. The most intense source of odour from livestock facilities occurs during manure handling and land application. The manure from hogs can generally be classified as low volume, high strength liquid waste. That is, waste of high strength requires high levels of oxygen to biodegrade and may contaminate ground water. Typically, most commercial hog operations feature under-floor manure storage pits. These pits are situated beneath the barns and store the manure until the manure is emptied from the pit and transferred to mid-term storage lagoons. The odour problem that arises when the manure is stored in such a manner is a result of the anaerobic conditions that exist in the lagoon. Typically, aerobic conditions exist only in the layer of manure that is in contact with air and the malodorous gases produced anaerobically beneath this layer gradually diffuse to the surface, which in turn raises the prospect of public annoyance and creates health concerns for the swine herd and the barn workers. Conditions where anaerobic processes under very low dissolved oxygen (&lt;0.5 mg/l) conditions occur are referred to as anoxic conditions. Current methods used in controlling odour production during manure handling and land application have only been capable of suppressing or delaying odour production. Without an adequate treatment, producers are forced to handle manure that is highly non-homogeneous, which can cause a variety of technical and mechanical related problems. Therefore, a method of waste treatment must ensure odour reduction or elimination as well as a reduction in solids content or volume and waste strength. Waste strength is directly related to the Biological Oxygen Demand (BOD) of the waste. The BOD defines the waste strength in that it depicts the amount of oxygen required by the waste in order to biodegrade. Such a method will reduce handling concerns and pollution such as ground water contamination and/or air pollution caused by the malodorous gases. Furthermore, the treated waste produced should be a low strength waste and have high nutrient content (nitrogen, phosphorus, potassium) which is essential for fertilizer value. 
     It is of note that nutrient application to farm land must be balanced with the ability of the crops to utilize the nutrients applied. That is, excess nutrients in the fertilizer that are not absorbed by the soil are likely to contaminate the aquifers and surface water bodies. As a result, the amount of fertilizer that can be applied to a given plot of land is highly dependent upon the local soil conditions, hydrology, geology and geography. However, in many cases, it is not cost effective for swine producers to haul raw manure long distances if the land surrounding the facility is already nutrient rich. Clearly, in cases such as these, it would be preferable to be able to separate the nutrients from the manure, thereby producing a concentrated fertilizer. As a result, the condensed fertilizer could be cost effectively transported and applied to farm land significant distances away from the swine production facility. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention, therefore, to provide a system for treating waste. 
     According to one aspect of the invention there is provided a method of treating waste liquid containing solid content comprising: 
     providing waste liquid containing solid content; 
     heating the waste to a temperature range of 40-70° C. for a time period of 12-36 hours, thereby reducing waste strength and odour of the waste; and 
     separating the treated waste into liquid material and solid material. Heating will eliminate many pathogens within the waste. 
     Preferably, the waste is mixed and shredded during heating. 
     Preferably, the method includes treating the waste with augmenting bacteria and enzymes prior to heating. The addition of bacteria and enzymes promotes anoxic/anaerobic breakdown of the waste in the manure pit. 
     Preferably, the method includes removing gases emitted during heating of the waste and bubbling the gases back into the liquid material and the solid material. As a result of this arrangement, the nutrient content of the liquid material and the solid material is enhanced. 
     The liquid and/or solid material may be used as fertilizer and/or disposed of as a benign waste. 
     Preferably, the waste strength and the odour of the waste are reduced in the absence of added chemicals. 
     Preferably, the nutrient content (nitrogen, phosphorus, potassium) of the waste is maintained. 
     The waste may be homogenized prior to and/or during heating. 
     The method may include heating the waste at a pH range of 8.5 to 9.5, thereby promoting production of gases. Furthermore, the heating may be done at lower than ambient pressure, which will promote liberation of gases, such as ammonia gas, nitrogen gas, methane and carbon dioxide, from the waste. The gases may then be cooled and condensed to liquid form, thereby producing liquid fertilizer. 
     According to a second aspect of the invention, there is provided a waste treatment system for treating waste liquid containing solid content comprising: 
     a reactor tank for reducing waste strength and odour of the waste, thereby producing treated waste, said reactor tank comprising: 
     a reactor inlet arranged to accept the waste; 
     heating means for heating the waste in the reactor tank; 
     a reactor tank homogenizing system for mixing the waste; 
     a shredding system to reduce particle size; and 
     a withdraw port for removing the treated waste from the reactor tank. 
     The waste treatment system may include a clarifier for separating the treated waste into liquid material and solid material, said clarifier comprising: 
     a clarifier inlet arranged to accept the treated waste from the withdraw port; 
     a liquid outlet for removing the liquid material from the clarifier; and 
     a solid outlet for removing the solid material from the clarifier. 
     The waste treatment system may include a flow equalization tank for storing and mixing of the waste, said flow equalization tank comprising; 
     a flow equalization tank homogenizing system for mixing the waste; and 
     a siphon port for supplying the waste to the reactor inlet; 
     Preferably, the heating means may be comprised of a heat exchange system within the reactor tank. 
     The waste treatment system may include de-watering means connected to the solid waste outlet for removing residual liquid from the solid material. 
     Preferably, the waste treatment system includes gas collection means for removing gases emitted from the waste in the reactor tank. 
     The waste treatment system may include gas injection means for bubbling the gases removed by the gas collection means into the liquid and solid material. 
     The storage inlet may comprise a cone-shaped flow distribution baffle. 
     One embodiment of the invention will now be described in conjunction with the accompanying drawings in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is side view in cross section of the waste treatment system. 
     In the drawings like characters of reference indicate corresponding parts in the different figures. 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, a waste treatment system  1  comprises a waste source  10 , a flow equalization tank  12 , a reactor tank  14  and a clarifier tank  16 . 
     The waste source  10  provides waste  18  composed of waste liquid containing solid content for treatment by the waste treatment system  1 . Specifically, the waste strength and the odour of the waste  18  are reduced by the waste treatment system  1  as described below. In this embodiment, the waste source  10  comprises a barn  20  for holding livestock therein. The barn  20  includes a manure pit  22  beneath the barn  20  for collecting the waste  18  from the livestock as described below. The manure pit  22  includes a surface sprayer  24 , a waste outlet  26 , a waste duct  28  and a pump  30 . The surface sprayer  24  is arranged to distribute a microbial additive  32  comprising a mixture of enzyme and bacteria throughout the manure pit  22  for promoting solubilization and odour reduction of the waste  18 . The waste outlet  26  is connected to the waste duct  28  which is in turn connected to the pump  30 . As a result of this arrangement, the pump  30  draws the waste  18  from the manure pit  22  out of the manure pit  22  through the waste outlet  26  and along the waste duct  28 , as described below. 
     The flow equalization tank  12  is arranged for mixing the waste  18  therein, thereby further homogenizing the texture of the waste  18 . The flow equalization tank  12  comprises a top  34 , a base  36 , a waste intake  38 , a storage gas port  40  and a storage homogenizing system  42 . The waste intake  38  is arranged to accept the waste  18  from the waste source  10 . In this embodiment, the waste intake  38  comprises a baffle  43  located proximal to the top  34  of the flow equalization tank  12 . The baffle  43  is arranged to be of variable height relative to the top  34  of the flow equalization tank  12 . It is of note that the baffle  43  is arranged to distribute the waste  18  from the waste source  10  into the flow equalization tank  12  so as to promote mixing of the waste  18  therein. In this embodiment, the baffle  43  has a substantially cone-like shape and the waste  18  is applied directly onto the baffle  43 . As a result, the waste  18  is distributed as a thin film over the baffle  43 , thereby allowing for maximum waste surface area exposure. The storage gas port  40  is arranged to remove gases emitted by the anoxic and anaerobic bacteria during breakdown of the waste  18  from the flow equalization tank  12  as described below. The storage homogenizing system  42  is arranged to mix the waste  18  in the flow equalization tank  12 . SpecIfically, in this embodiment, the storage homogenizing system  42  comprises a withdraw port  44  located at the base  36  of the flow equalization tank  12 , a return port  46  located at the top  34  of the flow equalization tank  12 , a duct  48  interconnecting the withdraw port  44  and the return port  46  and a chopper pump  50  coupled to the duct  48 . Thus, the chopper pump  50  draws the waste  18  out of the withdraw port  44  at the base  36  of the flow equalization tank  12  and shreds the waste  18  before returning the waste  18  to the flow equalization tank  12 , thereby recirculating, mixing and homogenizing the waste  18 . 
     In this embodiment, the storage homogenizing system  42  further includes a siphon port  52  arranged to remove a portion of the waste  18  from the duct  48  and transport the portion of the waste  18  to the reactor tank  14  as described below. 
     The reactor tank  14  is arranged for treating the waste  18 , thereby reducing waste strength and the odour of the waste  18 . The reactor tank  14  comprises a top  54 , a base  56 , walls  57 , a reactor inlet  58 , a heat exchange system  60 , a reactor gas port  62  and a reactor homogenizing system  64 . 
     In this embodiment, the reactor inlet  58  comprises a baffle  43  that is arranged to distribute the waste  18  from the flow equalization tank  12  into the reactor tank  14  so as to promote mixing of the waste  18  therein as described above. The heat exchange system  60  is arranged to heat the waste  18 , thereby reducing waste strength and odour of the waste as well as eliminating pathogens and producing treated waste  66  as described below. The reactor gas port  62  is arranged to remove gases emitted from the treated waste  66  during heating as described below. The reactor homogenizing system  64  is arranged to mix the treated waste  66 . In this embodiment, the reactor homogenizing system  64  comprises a withdraw port  68  located at the base  56  of the reactor tank  14 , a return port  70  located at the top  54  of the reactor tank  14 , a duct  72  interconnecting the withdraw port  68  and the return port  70  and a chopper pump  74  coupled to the duct  72 . Thus, the chopper pump  74  draws the treated waste  66  from the base  56  of the reactor tank  14  and shreds the treated waste  66  before returning the treated waste  66  to the reactor tank, thereby recirculating, mixing and homogenizing the treated waste  66 . Specifically, the combination of heating and shredding of the waste  18  eliminates pathogens and stabilizes the waste such that no further breakdown of the waste occurs and no gases are released, as described below. In essence, the waste is stabilized following treatment. 
     In this embodiment, the reactor homogenizing system  64  further includes a removal port  76  arranged to remove a portion of the treated waste  66  from the duct  72  and transport the portion of the treated waste  66  to the clarifier tank  16  as described below. 
     The clarifier tank  16  is arranged for accepting the treated waste  66  and separating the treated waste  66  into waste liquid  78  and waste solid  80 . The clarifier tank  16  comprises a top  82 , a base  84 , a waste liquid outlet  92  and a waste solid outlet  94 . The clarifier inlet  86  is arranged to accept the treated waste  66  from the reactor tank  14  as described below. The waste liquid outlet  92  is located at the top  82  of the clarifier tank  16  and is arranged for removing the waste liquid  78  from the top  82  of the clarifier tank  16  as described below. The waste solid outlet  94  is located at the base  84  of the clarifier tank  16  and is arranged for removing waste solid  80  from the clarifier tank  16  as described below. 
     The waste treatment system  1  is assembled as follows. The waste duct  28  is connected to the waste intake  38 , the siphon port  52  is connected to the reactor inlet  58  and the removal port  76  is connected to the clarifier inlet  86 . 
     In operation, waste  18  is produced by the livestock in the barn  20  and the waste  18  drops from the barn  20  to the manure pit  22 . At this point, the waste  18  is of highly heterogeneous texture. Specifically, the waste  18  is composed of a mixture of faeces, urine, feed, water, hooves, hair and after-birth. The waste  18  is approximately 50-75% biodegradable, consisting of carbohydrates, proteins and fats, which is an ideal medium for microbial growth. As noted above, the surface sprayer  24  distributes the microbial additive  32  onto the waste  18  at regular intervals. Specifically, the microbial additive  32  is composed of a mixture of enzymes and microbes which will stimulate activity within the waste  18 . In one embodiment, the microbial additive comprises a combination of enzymes and micro-organisms. The bacterial augmentation in the manure pit promotes more anoxicdanaerobic processes than aerobic processes. While aerobic conditions exist in the upper film of the waste in the manure pit due to surface contact with the atmosphere, this aerobic zone is almost insignificant in relation to the majority of the waste in the manure pit which is in an anaerobic condition. Specifically, the aerobic zone is small due to crust build-up on the waste. By using bacterial augmentation in the manure pit, solids are channelled through the bacteria and solubilized in the process. The formulated bacteria are essentially designed to assist the naturally-occurring bacterial populations in swine waste to solubilize the waste more rapidly and efficiently. In speeding up the solubilization process, the crusting is reduced and the odours released by anaerobic breakdown of the waste are reduced. At intervals, the waste  18  is drawn through the waste outlet  26  and into the waste duct  28  by the pump  30 . The waste  18  is then deposited into the flow equalization tank  12  via the waste intake  38 . Therein, the waste  18  is recirculated through the flow equalization tank  12  by the storage homogenizing system  42 . As a result of this arrangement, the waste  18  is mixed and anoxic conditions exist. During this process, gases, for example carbon dioxide, methane, ammonia, nitrogen gas and the like are produced by the anaerobic and aerobic bacteria. As noted above, these gases are removed from the flow equalization tank  12  via the storage gas port  40 . At regular intervals, a portion of the waste  18  is removed from the storage homogenizing system  42  through the siphon port  52  and the portion of the waste  18  is transferred to the reactor tank  14  through the reactor inlet  58 . Therein, the waste  18  is heated by the heat exchanger system  60  to a temperature within the range of 40-70° C. for a period of 12-36 hours, thereby producing treated waste  66 . In this embodiment, the waste  18  is heated to approximately 60° C. for approximately 24 hours. Furthermore, the treated waste  66  in the reactor tank  14  is recycled by the reactor homogenizing system  64  and the gases emitted from the treated waste  66  in the reactor tank  14  are removed via the reactor gas port  62 . It is of note that the heating of the waste  18  combined with the shredding of the waste  18  eliminates pathogens and promotes breakdown of the waste  18 , that is, conversion of the solid content of the waste  18  into colloid and solute fractions. Specifically, the combination of heating and shredding stabilizes the treated waste  66  such that no gases are emitted and the treated waste  66  is stabilized. It is of note that treatment of the waste  18  occurs in the absence of added oxygen. Furthermore, tests indicate that this process is most efficient at the natural pH, which is anticipated to obviate regular chemical additions to modify the pH of the waste  18 . The end result is that the waste  18  is broken down to biomass material, carbon dioxide, nitrate and water and undissolved solids precipitate readily out of solution as a result of the heating and shredding. At regular intervals, a quantity of the treated waste  66  is removed from the reactor homogenizing system  64  through the removal port  76  and transferred to the clarifier tank  16  via the clarifier inlet  86 . Therein, the treated waste  66  separates into waste liquid  78  and waste solid  80 . Furthermore, the removal of the emitted gases also greatly reduces odours associated with treatment of the waste  18  by the waste treatment system  1 . Periodically, the waste liquid  78  is removed via the waste liquid outlet  92  at the top  82  of the clarifier tank  16 . It is of note that the waste liquid  78  may be used, for example, as liquid fertilizer. Similarly, periodically, the waste solid  80  is removed via the waste solid outlet  94  and dried. It is of note that the waste solid  80  may be pelletized and used, for example, as a dry fertilizer or as a feed supplement. 
     The end result of treatment of the waste  18  by the waste treatment system  1  is that a substantial majority of the biodegradable portion of the waste  18  is solubilized. Furthermore, odours produced from the waste  18  are limited by the waste treatment system  1  through the action of the reactor gas port  62  and the storage gas port  40 , which remove the malodorous gases produced by the anaerobic bacteria from the reactor tank  14  and the flow equalization tank  12  respectively. 
     It is of note that, in this embodiment, the waste treatment system  1  is arranged to be a continuous flow system, wherein waste is removed from each of the tanks simultaneously. Alternatively, the waste treatment system  1  could also be run in batch mode. Furthermore, no additional oxygen is added to the waste treatment system. 
     In other embodiments, the waste solid outlet  94  may be connected to a de-watering unit. The de-watering unit is arranged so that the waste solid  80  is deposited onto the de-watering unit by the waste solid outlet  94  which forces residual liquid out of the waste solid  80 , thereby drying the waste solid  80  as described below. Following de-watering, the waste solid  80  may be dried and pelletized and used, for example, as a dry fertilizer or as a feed supplement. 
     In another embodiment, the gases removed via the storage gas port  40  and the reactor gas port  62  may be bubbled into the waste liquid  78  and the waste solid  80  via gas injection means, thereby enriching the nutrient content of the waste liquid  78  and the waste solid  80  by recycling nitrogen. 
     In yet another embodiment, the liquid waste  78  may be stored in an outdoor storage tank and the outdoor storage tank may include gas injection means for bubbling gases removed via the storage gas port  40  and the reactor gas port  62  into the liquid waste  78 , thereby conserving nutrient content, as discussed above. Alternatively, the gas could be deaned and have odours removed by using a gas scrubber or filtration system. 
     In an alternative embodiment, the reactor tank  14  includes a vacuum for generating a lower pressure zone in the reactor tank  14 . As the pH range of the treated waste  66  in the reactor tank  14  is approximately 8.5 to 9.5 and, as noted above, the waste  18  is distributed as a thin film, production of ammonia gas within the reactor tank  14  is maximized. Specifically, the factors that determine the effectiveness of stripping ammonia out of water are pH, relative pressure, temperature and film thickness. In the above-described arrangement, these factors are maximized for the liberation of ammonia gas from the treated waste  66 . In addition, other gases, for example, methane, carbon dioxide and water vapour will be liberated from the treated waste  66  as well. In operation, the gases are forced to move towards the lower pressure zone at the upper portion of the reactor tank  14 . The gases are then drawn out of the reactor tank  14  through the reactor gas port  62 . Once removed from the reactor tank  14 , the gases are transferred to a condensor tank wherein the gases are cooled and condensed back into liquid form. The resulting product is therefore a highly condensed nutrient rich liquid fertilizer. Furthermore, the treated waste  66  remaining in the reactor tank  14  is processed as described above, thereby producing waste liquid  78  and waste solid  80  having a low nutrient content. As a result, the waste liquid  78  and the waste solid  80  may be applied in large volumes without fear of groundwater and surface contamination. Furthermore, the condensed nutrient rich liquid fertilizer can be cost effectively transported and applied to farm land significant distances from the swine production site. 
     An alternative waste source may be human waste or any other high strength waste. 
     Since various modifications can be made in the invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims without department from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

Technology Category: 4