Abstract:
A system is provided for treating runoff water in which there is a separator and a filter for cleaning the water. A reservoir is provided to hold large quantities of water during prolonged rainstorms. The output of the reservoir is fed to the filter. The rate of flow from the reservoir to the filter is controlled and limited to flow rates at which the filter can efficiently clean the water.

Description:
RELATED APPLICATION  
       [0001]    I claim the benefit of my prior copending Provisional Application S.N. 60/337,545 filed Dec. 1, 2001, entitled Stormwater Runoff Treatment Train. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention is intended to improve the quality of stormwater runoff from developed impervious surfaces. Stormwater runoff from impervious surfaces like parking lots contains many different contaminants, such as sediments, nutrients, heavy metals, and organic chemicals. In most developed areas of the United States, this runoff is collected in pipes and discharged directly into a stream or other water body. The present invention provides a means by which some of the environmentally detrimental constituents may be removed from the water.  
           [0003]    During the last ten years, a new industry has developed to treat stormwater runoff. To date, the main focus of this industry has been removing suspended solids from the water. Solids can be removed by physical separation, which is most easily achieved by reducing water velocities and allowing the solids to settle out of the water. This is the theory behind the ponds, sediment basins, and hydrodynamic separators that comprise the majority of commercially available stormwater treatment devices. Much of the pollution in stormwater runoff, however, is not suspended, but instead dissolved in the water. These dissolved contaminants require more effective treatment, hence a filter is often used. However, all of the devices now in use become quite inefficient when there is a high rate of flow through them.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention avoids the inefficiency of the prior art by storing the incoming water in a reservoir and limiting the flow rate from the reservoir to the device or devices that clean the water. For example, during a prolonged rainstorm the water collects in a reservoir which has a flow limiting device at its output that limits the flow rate to a rate at which the flow cleaning device (gravity separator, filter, etc.) can efficiently clean the water.  
           [0005]    The invention contemplates that any suitable flow limiting device may be used to limit the rate of flow of water from the reservoir to the fluid cleaning device (gravity separator, filter, etc.) to a rate that the cleaning device can handle efficiently. The prior art teaches many such flow limiting devices, per se. They range from a float (on the surface of the water in the reservoir) controlling a valve in the outlet of the reservoir to a small induction motor driving a pump, which motor during high rates of flow acts as a generator and thereby controls the rate of flow of water. To summarize, the output of the reservoir is preferably held to a relatively constant rate of flow that renders the filter or other cleaning device efficient.  
           [0006]    The present invention involves a single process for the treatment of stormwater runoff. The invention relies on extended detention to remove sediments and associated pollutants (many detrimental pollutants adsorb, or attach themselves, to the surface of suspended sediment particles). Following extended detention, the water is transferred to a filter, which removes dissolved pollutants, as well as any very small suspended particles that escape from the extended detention phase. The present invention includes a pump that regulates flow through the filter unit, as well as mechanisms to clean the filters with excessive maintenance requirements.  
           [0007]    The present invention improves upon the prior art in several significant ways. The prior art relies solely on gravity flow to drive stormwater runoff through the treatment process. The present invention, however, uses a pump or other energy source to drive the water in cases where the elevation differences on the site are not sufficient to impart this energy. This energy sources makes the present invention far more flexible than the prior art in terms of range of applications.  
           [0008]    The prior art also overwhelmingly relies on a single technology to treat stormwater runoff. The present invention, though, incorporates different technologies, each aimed at a different constituent of stormwater runoff. While the application of any one of these technologies is a commonly used treatment method that is generally effective for a single contaminant species, the combination of the several methods allows the stormwater treatment device to remove a broad range of potential pollutants.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a block diagram of the Preferred Form of the Invention.  
         [0010]    [0010]FIG. 2 is a block diagram of a First Modified Form of the Invention.  
         [0011]    [0011]FIG. 3 is a block diagram of a Second Modified Form of the Invention.  
         [0012]    [0012]FIG. 4 is a sectional view of the discharge end of a third modified form of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    The present invention combines several different technologies for the treatment of stormwater runoff into a single train. The invention includes (a) a physical separator to remove suspended particles, with specific gravitates greater or less than one, from water, (b) a filter that removes dissolved containments, as well as small particulate contaminants that escape from the separator, from water, and (c) the associated means and conveyances required to deliver the water to each phase of the treatment device.  
       Preferred Form of the Invention  
       [0014]    The preferred form of the invention is shown in FIG. 1. An inlet means  101  delivers the influent runoff rainwater to the system. The inlet means discharges the contaminated water into a physical separator  201 . This physical separator is a device such as is disclosed in my U.S. Pat. Nos. 5,746,911 and 6,264,835. The separator  201  relies on gravity to separate suspended particles with a density greater than the density of water from the influent water, and the water exiting the separator  201  has a significantly lower concentration of suspended pollutants than the influent water. A conduit  102  accepts the water exiting the separator, and delivers the water to a large reservoir  202 . This reservoir contains a regulated discharge means  103  that controls the flow rate of the water leaving the reservoir. This discharge means may be an orifice or other hydraulic control, a pump, or any other conveyance that has the capacity to regulate the flow rate. A pump, for example, may have a control or other means to limit and control the rate of flow through the pump. The regulated discharge delivers the water to a second conduit  104 , which delivers the water to the filter  203 . The filter  203  is a device such as that described in my prior copending patent application Ser. No. 10/040,611, filed Jan. 9, 2002 and entitled Filtering System for Runoff Water. Intended to remove both dissolved and particulate pollutants from water by use of a filter media, the filter  203  may use any of various types of media to accomplish this removal, and the media may be tailored for the specific contaminants expected in the stormwater runoff. The water passes through the filter  203  and then enters a conduit  105  which delivers the treated water to an outfall such as a river.  
         [0015]    The runoff water may vary from a very low rate to a very high rate. At high rates the filter  203  is inefficient.  
         [0016]    The reservoir  202  is preferably so big that it will hold all the water from a prolonged hard rain, lasting several hours, but the outlet pipe of the reservoir is so small (or has a restriction) limiting the flow, or has other suitable means for controlling the flow, so that the flow rate therethrough is not only within the capacity of the filter but takes at least one hour to drain the reservoir.  
       First Modified Form of the Invention  
       [0017]    The function of the reservoir  202  and the pump  103  (or other flow limiting device) is to take the widely varying incoming flow and convert it to a relatively steady, more constant, flow rate and thereby improve the efficiency of the filter  203 .  
         [0018]    A second form of the invention is shown in FIG. 2, in which the physical separator and reservoir are combined into a single unit  204 . In this case, the inlet conduit  101 , regulated discharge means  103 , conduit  104 , filter  203 , and discharge conduit  105  are as described in the preferred form of the invention, and serve the same purposes.  
         [0019]    In this form of the invention, a single large container  204  acts as both physical separator and reservoir. The container is capable of holding all the water from a prolonged hard rain, and the conduit  104  is sized or designed such that it takes at least one hour to fully drain the tank.  
       Second Modified Form of the Invention  
       [0020]    [0020]FIG. 3 illustrates another form of the invention, in which the filter  203  can be backwashed without additional equipment. In FIG. 3, the inlet conduit  101 , physical separator  201 , reservoir  202 , regulated discharge  103 , conduit  104 , filter  203 , and outlet conduit  105  are as described in the preferred form of the invention, and serve the same purposes. However, an additional backwash water source  205  and backwash water collector  206  are also included. This source  205  may be a container that is part of the system, or it may simply be a connection to which a separate container can be joined. In addition to the backwash water source  205 , four valves are also included in this form of the invention. During normal operation, valves  106  are open, and valves  107  are closed. In this case, the second modified form of the invention functions in the same manner as the preferred form.  
         [0021]    With normal use, filters become clogged, and require maintenance. This form of the invention allows the filter  203  to be backwashed without additional equipment. To do this, valves  106  are closed, and valves  107  are opened. The backwash water source  205  discharges water through the filter  203 . This reverse flow cleans the filter, and the wash water is collected in backwash water collector  206 . The backwash water is removed from the backwash water collector and disposed of.  
       Third Modified Form of the Invention  
       [0022]    [0022]FIG. 4 shows apparatus that may be added to the outlet conduit  105  of the invention. In this case, fluid in outlet conduit  105  does not flow by gravity. Instead, pump  207  imparts the necessary energy to the water to provide effluent flow from the invention. Conduit  105  leads to recharge trench  208 , which allows the treated water to percolate into the surrounding soils, recharging the groundwater. Alternatively, conduit  105  could flow to high-elevation outfall  209 , which is above conduit  105  in elevation. This form of the invention can be used on sites in which elevation constraints limit the choice of treatment methods for stormwater runoff.