Patent Publication Number: US-9884780-B2

Title: Wetland roof technology for treating domestic wastewater

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of environmental technology. More specifically, the present invention relates to wetland roof system for treating effluent of septic tanks in urban areas. 
     BACKGROUND ART 
     There exist many conventional wetland roof (WR) systems around the world because there are real needs for clean environment such as clean water, clean air, and green living areas. However, none provides both domestic waste water treatment from effluent septic tanks and aesthetic decoration for houses in urban cities in developing countries such as Vietnam. 
     The WR system disclosed in CN102518265A is used to treat rainwater to meet the reuse standard. This conventional WR system includes a waterproof layer of roofing construction, laying across the root layer waterproof layer, layer on top of every root laying drainage channels, followed by the laying of eco-filler layer and mix the filler layer drainage channels, the mixed filler layer erection of water distribution supervisor and water distribution pipes. This WR system does not treat domestic waste water and fail to provide aesthetic beauty to houses in urban areas. 
     Yet in another conventional roof wetland system described in CN202391027U does not include any plants. Like the previous WR system, this roof wetland system is used to treat rainwater to meet the reuse standard. This WR system includes a budding roof, a waterproof layer, a root-proof layer, an ecological packing layer, a mixed packing layer, plant vectors. Again, this roof wetland system does not treat domestic waste water for reuse and does not provide any aesthetic values in urban areas. 
     The green roof system described in CN 101538915A only treats rainwater. It collects rainwater and circle such water for irrigation purpose. The green roof system includes roofing, planting layer, a joint all-welded stainless steel waterproof layer on the roof covering, the planting layer on the stainless steel waterproof layer. It does not have any plants for environmental benefits and aesthetic values. In addition, it does not treat domestic waste water. 
     Therefore what is needed is a wetland roof system capable of treating domestic waste water and providing aesthetic and environmental values to houses in urban areas. 
     SUMMARY OF THE INVENTION 
     Accordingly, an objective of the present invention is to provide a wetland roof system and method which provide solutions to the problems described above. Thus, a wetland roof system and method for treating domestic waste water is disclosed, which includes: a container having three sections and a L/W ratio greater than 10, a gravel layer deposited at the bottom of the container at a first thickness, a crushed stone layer deposited directly on top of the gravel layer having a second thickness, a sand layer deposited directly on top of the crushed stone layer having a third thickness, a soil layer deposited directly on top of the sand layer having a fourth thickness, and a plant layer growing from said soil layer at a predetermined density. 
     These and other advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments, which are illustrated in the various drawing Figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
         FIG. 1  is a diagram illustrating a wetland roof system for treating domestic waste water in accordance with an embodiment of the present invention; 
         FIG. 2  is a top view perspective of the wetland roof system for treating domestic waste water illustrating the internal structure and direction of waste water flow of a container in accordance with an embodiment of the present invention; 
         FIG. 3  is a method for treating domestic waste water in accordance with an embodiment of the present invention; 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be obvious to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present invention. 
     Now referring to  FIG. 1  which illustrates a wetland roof system  100  for treating domestic waste water in accordance with an embodiment of the present invention. An essential element of wetland roof system  100  is a container  120  which is placed on a roof of a house (not shown). In a preferred embodiment, container  120  has a length L and a width W and a L/W ratio greater than 10. On the bottom of container  120 , a gravel layer  121  is deposited which has a first thickness t 1 . Next, a crushed stone layer  122  having a second thickness t 2  is deposited directly on top of gravel layer  121 . A sand layer  123  having a third thickness t 3  is deposited directly on top of sand layer  122 . A soil layer  124  having a fourth thickness t 4  is directly deposited on top of soil layer  123 . Finally, plants  125  which has the capability of treating waste water are grown at a predetermined density d 1 . In one embodiment, plants  125  are selected among a group of asteraceae. In the preferred embodiment, plants  125  are  melampodium paludosum  and are maintained at 20-40 mm in height. 
     Continuing with  FIG. 1 , at the input and output sides of container  120 , gravel layer  121  is completely deposited without crushed stone layer  122 , sand layer  123 , and soil layer  124  so that waste water is not clogged there. In addition, container  120  is raised at the input side at an angle α where 
               tan   ⁢           ⁢   α     =     1   100           
so that waste water can seep slowly from the input side to the output side.
 
     Still continuing to  FIG. 1 , in a preferred embodiment, the first thickness t 1  of gravel layer  121  is 50 mm. The second thickness t 2  of crushed rock layer  122  is 120 mm. The third thickness t 3  of sand layer  123  is 20 mm. The fourth thickness t 4  of soil layer  124  is 10 mm. Plants  125  are grown preferably at density around 200 plants/m 2 . Finally, in one embodiment, container  120  has a length of 1.8 m, a width of 0.6 m, and a height of 0.15 m (or 150 mm). However, depending on the roof size, container  120  dimensions can vary to cover the roof as long as the length over width ratio is greater than 10. In one embodiment, container  120  is made from tin, HDPE, plastic, or composite materials. 
     Still referring to  FIG. 1 , container  120  is connected to a septic tank  101  where all the domestic waste water are stored. All home utilities (not shown) that provide clean water to the house are connected to septic tank  101  via aqua duct system (not shown) so that waste water after used are stored in septic tank  101 . At the output side of septic tank  101 , a water pump  102  is used to pump domestic waste water into the input side of container  120  via first connector  110 . In one embodiment, domestic waste water can be input directly into the gravel inlet zone. On the opposite side of container  120 , a second connector  130  leads treated water into a storage (not shown). In one embodiment, water pump  102  is controlled so that the flow rate of waste water inside container  120  is constant. Yet in one embodiment, an effluent valve located at a height of 100 mm to maintain the water level inside container  120  at 100 mm during operation. 
     Referring next to  FIG. 2  which illustrates a top view  200  of container  120  as described in  FIG. 1 . As shown, container  120  has a first wall  200 A and a second wall  200 B dividing container  120  into a first section  120 A, a second section  120 B, and a third section  120 C. First wall  200 A begins at the input side but does not touch the output side of container  120  so that there exists a first gap for water to flow through first section  120 A and second section  120 B. On other hand, second wall  200 B begins at the output side but does not touch the input side of container  120  so that there exists a second gap for waste water to flow through second section  120 B and third section  120 C. In one embodiment, the first gap and the second gap each equals to the width of first section  100 A, a second section  120 B, and third section  120 C. The inclination of container  120  at the angle α described above also contribute to water flow direction  120   f  from first section  120 A, second section  120 B, and third section  120 C. As shown in  FIG. 2 , gravel layer  121  is completely deposited at the input side of first section  120 A and at the output side of third section  120 C. At these two ends, other layers such as crushed stone layer  122 , sand layer  123 , and soil layer  124  are not used. In other words, gravel layer  124  is deposited from the bottom of container  120  all the way to flush with the top surface of soil layer  124  as shown in  FIG. 2 . 
     In operation, domestic waste water is pumped from the last compartment of septic tank  101  to a reservoir (not shown) on the roof. Then, the waste water from the reservoir (not shown) is distributed to first section  120 A of wetland roof system  100  by water pump  102 . In one embodiment, water pump  102  is a dosing pump. Waste water flows  120   f  from first section  120 A through second section  120 B and into third section  120 C. Then, treated water gets out at the output connector  130  (water collecting tube) at the other end of third section  120 C. Finally, treated water is collected in a storage tank (not shown). 
     Now referring to  FIG. 3  which illustrates a method  300  for treating domestic waste water using wetland roof technology. In method  300 , particular deposit layers at specific depths are used and specific type of plants are grown to provide efficient water use and add environmental aesthetic to the neighborhood. 
     At step  301 , a container having a length and width with a L/W ratio of greater than 10 is built depending on the dimension of the roof. In one embodiment, the container is built so that it has three sections. Step  301  is realized by container  120  described above. Container  120  has first section  120 A, second section  120 B, and third section  120 C by virtue of first wall  200 A and second wall  200 B. However, container  120  of the present invention is not limited to three sections as described above in  FIG. 1  and  FIG. 2  above. It is understood by a person of ordinary skill in the art that container  120  can be divided into many odd sections depending on the dimensions of the wetland roof. 
     Next, at step  302 , a gravel layer having a first thickness t 1  is deposited on the bottom of container throughout all the sections. Step  302  is realized by depositing gravel layer  121  on the bottom of container  120  throughout first section  120 A, second section  120 B, and third section  120 C. Please refer to the descriptions of  FIG. 1  and  FIG. 2  above. In one embodiment, the first thickness of gravel layer  121  is 50 mm. 
     Next, at step  303 , a crushed stone layer having a second thickness t 2  is deposited directly on top of the gravel layer throughout all the sections. Step  303  is realized by depositing crushed stone layer  122  directly on top of gravel layer  121  throughout first section  120 A, second section  120 B, and third section  120 C. Please refer to the descriptions of  FIG. 1  and  FIG. 2  above. In one embodiment, the second thickness of crushed stone layer  122  is 120 mm. Yet in one embodiment, the crushed stone layer  122  is not deposited at the input side of first section  120 A and at the output side of third section  120 C. 
     Next, at step  304 , a sand layer having a third thickness t 3  is deposited directly on top of the crushed stone layer throughout all the sections. Step  304  is realized by depositing sand layer  123  directly on top of crushed stone layer  122  throughout first section  120 A, second section  120 B, and third section  120 C. Please refer to the descriptions of  FIG. 1  and  FIG. 2  above. In one embodiment, the third thickness of sand layer  123  is 20 mm. Yet in one embodiment, the sand layer  123  is not deposited at the input side of first section  120 A and at the output side of third section  120 C. 
     At step  305 , a soil layer having a fourth thickness t 4  is deposited directly on top of the crushed stone layer throughout all the sections. Step  305  is realized by depositing soil layer  124  directly on top of sand layer  123  throughout first section  120 A, second section  120 B, and third section  120 C. Please refer to the descriptions of  FIG. 1  and  FIG. 2  above. In one embodiment, the fourth thickness of sand layer  123  is 20 mm. Yet in one embodiment, the soil layer  124  is not deposited at the input side of first section  120 A and at the output side of third section  120 C. 
     At step  306 , plants having waste water treatment capability are grown at a given density. Step  306  is realized by plants  125  described in  FIG. 1  above. In one embodiment, plants  125  are selected among a group of asteraceae. In the preferred embodiment, plants  125  are  melampodium poludosum  and are maintained at 20-40 mm in height. 
     Finally, at step  307 , domestic waste water from septic tank is pumped into the first section of container and stored at a reservoir connected to the third section of container. In the present invention, step  307  is realized by septic tank  101 , dosing pump  102 , input connector  110 , container  120 , and output connector  130 . A reservoir (not shown) is used to store treated water for reuse. The operation of step  307  is described in details in  FIG. 2  above. 
     The foregoing description details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the invention can be practiced in many ways. As is also stated above, it should be noted that the use of particular terminology when describing certain features or aspects of the invention should not be taken to imply that the terminology is being re-defined herein to be restricted to including any specific characteristics of the features or aspects of the invention with which that terminology is associated. The scope of the invention should therefore be construed in accordance with the appended claims and any equivalents thereof.