Patent Application
20190106343
The present invention relates generally to stormwater runoff treatment systems. More particularly the present invention relates to a linear stormwater treatment system which receives and treats stormwater runoff using plant root treatment, fluid recycle, and computerized flow control and operation.
Stormwater runoff is water generated by rain contacting impervious and semi pervious land surfaces which contains significant amounts of contaminants. These contaminants are routinely transported to and discharged into downgradient wetlands, streams, lakes and coastal waters.
Stormwater pollutants include bacteria, viruses, metals, nutrients, oils and other organic compounds. Throughout the United States, stormwater pollution has resulted in the closure of shellfish beds, the eutrophication of waters, the pollution of drinking water supplies and impacts to ecological habitats.
Numerous studies performed by US EPA have demonstrated that the first flush of runoff contains the majority of the pollutants. This is because many of the contaminants are associated with sediment particles which accumulate on road and parking lot surfaces between storms and are transported during the beginning of the first significant precipitation event. Contaminants such as oils and other hydrocarbons also collect on impervious surfaces and are typically flushed during the beginning of a storm event.
Therefore, what is needed is a device that may effectively utilize plant root systems to treat stormwater runoff.
The subject matter of this application may involve, in some cases, interrelated products, alternative solutions to a particular problem, and/or a plurality of different uses of a single system or article.
In one aspect, a linear stormwater treatment system is provided. The system utilizes a linear and elongate treatment chamber which treats the stormwater as it passes along the elongate length of the chamber. The chamber may have a semicircular cross section with the diameter side being open forming an open face, and being upwardly oriented. As such, this embodiment is formed as an approximately half-pipe shape. This semicircular shape uniquely provides structural support because of the strong half-cylindrical shape, and optimized planting and rooting depths for treatment. A quantity of medium, such as soil, gravel, or other granular material fills or at least partially fills the cavity of the chamber. A quantity of plant growth grows within the medium of the chamber such that root zones (roots) of the plants extend into the medium and in turn into the chamber cavity. A fluid inlet provides fluid flow into the chamber for treatment of stormwater. The inlet is configured to direct this inlet flow to the root zone of the plant growth in the medium. In an ideal configuration, the roots will be present throughout the cross section of the chamber and along the length of the chamber to provide maximum interaction of the stormwater with the roots and medium.
In another aspect, linear stormwater treatment system is provided. The system utilizes a linear and elongate treatment area that treats the storm water as it passes along the elongate length of the treatment area. The defined treatment area is bounded on the bottom and sides by a water-impermeable liner/boundary. A quantity of medium, such as soil, gravel, or other granular material fills or at least partially fills the treatment area. A quantity of plant growth grows within the medium of the treatment area such that root zones (roots) of the plants extend into the medium and in turn extend throughout the treatment area. An inlet provides fluid communication to the treatment area, while an outlet provides a fluid outlet from the treatment area.
The fluid inlet enters into a plurality of chambers which extend lengthwise through the defined treatment area, with each of the plurality of chambers having an arch-shaped cross section and defining an internal area. This arch-shaped structure provides structural support for the system, storage of water, and optimized planting and rooting depths for treatment (being shallow above the peak of the arch shape, deeper at the edges of the arch shaped chamber, and deepest where the chamber is not present). The chambers are oriented such that an open end of the arch shaped cross section is facing downward and is positioned near a bottom of the defined treatment area. A partially permeable layer covers the open area of the chamber to allow a controlled release of a fluid within the chamber. As configured, the stormwater fluid for treatment enters the system via the plurality of chambers and in turn through the partially permeable layer into the medium. The stormwater passes through the root zone, medium, and microorganisms there, which all the stormwater, before reaching the fluid outlet where it exits the treatment area.
The detailed description set forth below in connection with the appended drawings is intended as a description of presently preferred embodiments of the invention and does not represent the only forms in which the present invention may be constructed and/or utilized. The description sets forth the functions and the sequence of steps for constructing and operating the invention in connection with the illustrated embodiments.
Generally, the present invention concerns a stormwater treatment system which utilizes plant growth and root systems, along with other various treatment processes and system controls to process stormwater runoff. The system is generally linear which provides for enhanced processing control and predictability due to the progressive treatment from entry on one linear side to exit or recycle on the other linear side. Toxin and contaminant reduction along the linear path may decrease exponentially or linearly depending on toxin content and type, but can be more easily predicted and estimated in the linear flow structure of the present invention compared to the prior art non-linear structures.
The term “treatment” is defined herein to refer to any process which results in an outlet fluid having less dissolved or suspended material or components than when it enters the system at an inlet. The treatment contemplated herein may be achieved by any number of processes, including, but not limited to, mechanical settlement or separation, filtration, adhesion, absorption, adsorption, chemical reaction, uptake by the root systems of plants, microbial biochemical processing and the like.
Treatment is optimized by a variable planting depths with the deepest areas in the middle of the structure with smaller, shallower rooted plants along the margins.
The system typically includes a drain or drains which receives the stormwater runoff (although in some embodiments runoff may flow directly into the treatment system or to an inlet). A settling/pretreatment tank or structure may be connected to the drains to allow stormwater to flow into it. Sediment may settle out of suspension in the tank, facilitating the stormwater treatment. Fluid may exit the tank through an outlet, which may be controlled by a valve such as a computer-controlled valve, and into the treatment area of the system. The treatment portion is generally substantially linear (although in various embodiments may take other shapes). The treatment portion is formed by a chamber which is water-impermeable. Within the chamber is soil or other media, and plants grow in this soil/media such that roots of the plants extend downward into the media. As the stormwater flows through the treatment area, the soil/media and plant roots both serve to filter the stormwater, removing contaminants that are suspended and/or dissolved effectively.
In many embodiments, a computerized control system may be employed to control operation of the stormwater treatment system. The computer referenced herein may be any computerized controller as is well known to have elements such as a processor, a memory storing a programming, which may be reprogrammable or permanent, an input, an output, and the like. For example, an amount of fluid to be treated (measured by flow or volume sensors, or weather data—past and/or predicted, among other options) may determine a rate that fluid is released into the system, and may determine a rate of recycle of the fluid from entry to release. The weather data may be processed by a weather data module of the computerized controller, and may be received from an external source in communication with the computerized controller, or may be calculated by the weather data module of the computerized controller. In high flow conditions, fluid may need to be recycled more times to ensure complete processing. Or, in another embodiment of operation, practical considerations may necessitate that in high flow conditions, fluid is passed through the system at a high rate, which may result in less than complete processing that what might occur at a lower flow rate with longer residence time in the system (and/or recycle flow). While complete treatment is an optimal goal of the present invention, there may be certain conditions which necessitate more rapid but partial processing.
In one embodiment, the chamber may be a half-pipe design having a semicircular or arched cross section. This shape provides a number of advantages not present in the prior art. One advantage is that the semi-circular shape provides the shortest side to side perimeter (along the semicircular perimeter of the half-pipe cross section) and maximum volume. This ensures that as the plant roots grow, they are able to effectively fill in all around the soil/media. Further, the shape ensures that fluid that is passing through the system at various depths is also exposed to roots maximally. For example, because the depth is shallow at the lengthwise edges of the chamber, roots grow in this shallow portion, and extend laterally as well because they cannot extend downward. Other shapes encourage less uniform and less thorough root growth and thus less uniform contaminant treatment. Further, the downward sloping shape of the half-pipe directs fluid down towards a center bottom of the chamber. Generally, root growth also centers here because it is the deepest area and an area with the most plant growth. Accordingly the shape naturally guides the stormwater to be treated towards the best treatment area-which is the area with the most root growth.
In another embodiment, an inverted half pipe or arched shaped chamber, with the arch shape extending upwardly, may be used within a larger chamber as a fluid storage area that slowly releases fluid into the larger chamber. In such an embodiment, the inverted half pipe may be positioned to maximize root exposure time of the stormwater by releasing it at a bottom with an expected flow directing the stormwater upwardly and along the linear flow. This structure (and any other structure that releases stormwater at a bottom of the chamber and expects an upward flow path) effectively lengthens the fluid flow path and thus extends the exposure time by causing the fluid for treatment to move upward a height of the chamber, and along its length.
In further embodiments, a recycle flow function may recycle stormwater near to the outlet of the system back to the beginning for additional treatment. The recycle flow may work with any embodiment. Recycle flow may simply be a return flow to the inlet of the system or treatment area, or may include treatment or partial filtration of the recycling water during the return direction recycle flow.
Turning now to
Stormwater exits the fluid tank 12 into treatment area chamber 16 through flow path 17. This flow path may be a simple outlet pipe which empties into the early stages of the chamber (adjacent to the settling tank), or may be a pipe or other fluid conveyance that slowly releases fluid along the length of the chamber. Not shown in this view is the soil or other media that fills the chamber, and the plants planted therein and related roots. A recycle system may collect fluid at the exit end of the chamber and return it to the settling tank, or to the inlet end of the chamber, depending on embodiment. This recycle structure is shown in this view as an elongate pipe extending along the length of the chamber 16, though in other embodiments, the recycle structure may vary.
Accordingly, the shape of the chamber 16 ensures adequate root exposure along the width and also the height of the chamber 16. Fluid flowing through any area of the chamber will thus be exposed to the root zone, which captures a substantial amount of contaminants, and is critical for the stormwater treatment by the present invention. Below chamber 16 is gravel or other media 33. This media 33 provides support to the chamber 16, and in some embodiments, may be an area used for recycle flow or post-treatment flow. A water-impermeable liner 32 surrounds a defined treatment area of the system, ensuring that fluid is only allowed to enter via the inlet, and exit the system at a designated outlet area. In the embodiment of
While several variations of the present invention have been illustrated by way of example in preferred or particular embodiments, it is apparent that further embodiments could be developed within the spirit and scope of the present invention, or the inventive concept thereof. However, it is to be expressly understood that such modifications and adaptations are within the spirit and scope of the present invention, and are inclusive, but not limited to the following appended claims as set forth.
