United States Patent: 7510649.
Unlike conventional wastewater treatment systems, the apparatus of the present invention uses no chemicals, no motors, no electricity and it has no moving parts. It relies totally on the sun, gravity, wetland plants, bacteria, and a growth media to achieve the desired effluent quality.
Because all of the treatment is accomplished below ground level, surface features are conducive to the creation of ecology parks, recreation areas, and self-educational nature trails.
Although wastewater treatment is the primary objective, economic considerations usually include a selection of plants with resale value, and the production of clean water that can be reused for industrial processes, irrigation, aquaculture or even drinking. An additional benefit of “below ground” treatment is that the technology is much less sensitive to climatic difference than other systems. In northern climates when air temperatures drop to well below freezing, bacterial heat production in the growth media maintains an above freezing environment.
crushed glass in Lumby landfill
The growth media itself also serves as insulation. In addition, to naturally occurring materials like coarse sand a wide variety of other media can be used effectively. These include but are not limited to, peat moss, rockwool, shredded plastics, crushed glass, coffee bean shells, rice shells, coconut fiber, corn husks, African palm shells, and the shells of sun flower seeds.
Unlike other systems, the technology, also provides 100% treatment of the wastewater components. After separation of solids using conventional settling tanks, sludge residuals are removed and treated using “perpetual reed beds”. The liquid fraction of the wastewater undergoes transformations in the roughing and polishing beds that include aerobic microbial breakdown near plant root surfaces and anaerobic microbial breakdown a short distance away from the roots (see FIGS. 6 and 7).
Additionally, there are aerobic and anaerobic chemical processes occurring throughout the growth media matrix. Heavy metals are oxidized and precipitated while others “exchange” on growth media surfaces. Plants absorb wastewater nutrients and other organic materials. The media itself is an excellent sieve or filter, and typically reduces suspended solids concentrations to one or two mg/l. During summer months, the high rate of plant evapotranspiration can reduce effluent flows to near zero.
Referring to FIG. 4, sludge treatment is accomplished using a perpetual reed bed that relies on microbial decay and annelidic consumption (i.e. worms) to biodegrade the sludge at a rate essentially equal to that being applied. As such, there is not measurable accumulation of sludge within the treatment cells once the annelid population has established itself.
The perpetual reed bed is generally includes a base of 2-5 cm drain stone. A layer of coarse sand is located above the base. A layer of pea stone is located between layers and base. Decades of stored sludge is located above the layer and contains worms and the roots of phragmites reeds. Perforated drain pipes are located in the base of drain stone.
A special application of the technology when used for landfill leachate treatment can include the combustion of waste methane gas to heat greenhouses that can be operated year round even in temperate climates. The use of this greenhouse gas (i.e. methane) to produce heat and carbon dioxide not only enhances leachate treatment and plant growth, but it also eliminates the large economic and environmental costs associated with trucking and treating leachate at municipal wastewater plants. When one considers that post landfill closure leachate treatment is usually required for 30-50 years, the economic savings are substantial.
This is a link to: New England Waste Systems – Owner of this patent
In areas of the world where wastewater for irrigation is limited, the use of the treatment system of the present invention can greatly reduce the demand on potable water supplies by farmers. The extremely high quality effluent which can be controlled to retain its nutrients like nitrogen, phosphorus and potassium represents an excellent irrigation source. In other applications it can be recycled into municipal drinking water sources by percolation back into the groundwater.
The extremely low concentration of suspended solids and turbidity make effluent from the treatment system of the present invention an excellent candidate for ultra violet disinfection, thereby reducing public health concerns regarding bacteria and virus contamination of groundwater. By eliminating the need for costly and “environmentally unfriendly” electricity, the technology also offers and excellent long-term solution for wastewater treatment in developing countries.
It is obvious that minor changes may be made in the form, construction and operation of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form here in shown and described, but it is desired to include all such forms as intellectual property that come within the scope claimed.
