EP0604588A1

EP0604588A1 - Waste-water treatment system

Info

Publication number: EP0604588A1
Application number: EP92921095A
Authority: EP
Inventors: Philip B. Hawes
Original assignee: Space Biospheres Venture
Current assignee: Space Biospheres Venture
Priority date: 1991-09-20
Filing date: 1992-09-18
Publication date: 1994-07-06
Also published as: WO1993006050A1; AU2670992A; JPH07508451A; EP0604588A4; CA2119266A1

Abstract

L'invention décrit un système transportable de traitement d'eaux usées. Ledit système comprend des réservoirs de retenue anaérobies servant à la digestion anaérobie des déchets, ainsi que des marécages aérobies (20, 34 et 42) servant à la digestion aérobie des déchets. Le système de traitement possède un volume relativement petit de 1.000 à 2.000 litres environ pour chaque personne utilisant le marécage. La digestion aérobie dans les marécages est stimulée par les plantes aquatiques et par les plantes poussant dans un sol humide, ainsi que par les microorganismes associés auxdites plantes et se développant dans les marécages. Les plantes à croissance sur sol humide sont cultivées dans des couches de terre et de gravier (30 et 46) dans le marécage. La terre et le gravier sont déposés en couches sur la partie inférieure du marécage autour de chicanes (26, 28, 38, 39, 48 et 50) en fonction d'une configuration constituant un canal d'eau ouvert (36 et 44). Les plantes aquatiques sont plantées dans ledit canal. La présence des chicanes permet de canaliser les eaux usées le long d'un trajet sinueux à travers les marécages. L'invention décrit également des moyens de recyclage des eaux usées traitées vers les réservoirs de retenue ou vers les marécages, dans le cas où un traitement supplémentaire est souhaitable.The invention describes a transportable wastewater treatment system. The system includes anaerobic holding tanks for anaerobic waste digestion, as well as aerobic swamps (20, 34 and 42) for aerobic waste digestion. The treatment system has a relatively small volume of around 1,000 to 2,000 liters for each person using the swamp. Aerobic digestion in swamps is stimulated by aquatic plants and by plants growing in moist soil, as well as by microorganisms associated with said plants and growing in swamps. Plants growing on moist soil are grown in layers of soil and gravel (30 and 46) in the swamp. The earth and gravel are deposited in layers on the lower part of the swamp around baffles (26, 28, 38, 39, 48 and 50) according to a configuration constituting an open water channel (36 and 44). Aquatic plants are planted in said channel. The presence of baffles makes it possible to channel wastewater along a winding path through the swamps. The invention also describes means for recycling the treated wastewater to the holding tanks or to the swamps, in the event that additional treatment is desirable.

Description

WASTE-WATER TREATMENT SYSTEM

Field of the Invention

This invention relates to a closed ecological system including humans, which is completely isolated from the Earth's environment insofar as transfer of matter is concerned. In particular, the invention relates to recycling of waste water.

Background of the Invention The Earth comprises a biosphere in which micro-organisms, plants, and animals, including humans, exist in a more-or-less steady state, wherein matter is a finite resource which is continually recycled. There is continual energy input in the form of solar radiation. The quantity of matter gained or lost to space outside the Earth's atmosphere is minute.

It is desirable to provide a microcosm of the biosphere known as Earth to study the interaction of components and for the development of techniques for influencing our environment. Such experiments are difficult at best in the open system provided on Earth, since matter is exchanged between the Earth's environment and the experiment. It is, therefore, desirable to provide a system that is completely enclosed so that no matter is exchanged with the Earth's environment. It is desirable to have humans within this miniaturized biosphere to provide control and to conduct scientific research within a closed system, where conditions can be varied as desired.

Currently, a closed ecological system, referred to as Biosphere 2, is being established near Oracle, Arizona. The system completely encloses about one hectare of land and 175,000 cubic meters of space, isolated from the Earth's environment by an impermeable skin so that no matter is transferred.

The closed ecological system will contain humans, other animals, and plants. It is desirable that the wastes or sewage produced by these organisms, as well as waste from industrial and experimental processes, are treated and recycled to prevent an accumulation of the waste products, and potentially toxic materials, within Biosphere 2. Additionally, water within Biosphere 2 is a limited commodity, and, therefore, it is important that all water is recycled and potable water regenerated.

The method for treating the waste should, in itself, be non-polluting. It is also desirable that the methods used to decontaminate and treat the waste or sewage generate usable by-products, such as plant matter, that can be used as fodder or for other uses. Sewage disposal plants are known in the art and, in a typical sewage disposal plant, the sewage is anaerobically decomposed, largely by methane fermentation. Additional soluble organic compounds in the sewage are converted to carbon dioxide, under aerobic conditions. Aeration is often achieved by spraying the liquid on a bed of loosely-packed rocks over which it trickles slowly, by gravity or by forcing air through the sludge. After a period of time, during which the organic matter is oxidized to a very great extent, sludge is allowed to settle. This sludge is eventually dried and used as fertilizer, either directly or after being ashed. Conventional sewage plants rely on microorganisms to decompose the sewage. Further treatment of the sewage may be by waste-water marshes which incorporate plants which exist in a symbiotic relationship with microorganisms to decompose the sewage. Anaerobic and aerobic bacteria associated with plant roots decompose organic waste through reductive and oxidative processes respectively, producing carbon dioxide, methane, water, biomass, and nutrients. Algae and plants use these nutrients in photosynthesis to generate oxygen and produce organic material in a form more compatible with the environment. Such marshes have also been shown to be effective in the removal of some organic chemicals, such as phenol, from contaminated water.

The dimensions of a typical waste-water marsh, to accommodate the sewage generated by about 3,000 people, are about 40,500 square meters in surface area and about 1.5 meters depth. This accounts for approximately 60 million liters in volume or approximately 20,000 liters per person. These estimates are based on assumptions of each person producing about 378 liters of waste per day.

These large systems are, therefore, not portable. Once in place, they are unable to be moved or relocated to a site where such a system may be of temporary or permanent use. Also, such systems do not provide for recirculation of the "purified waste," since the treated outflow is often of low purity.

Therefore, it is desirable to provide a portable non-polluting means of disposing of human, animal, and industrial waste. Such systems have application in industrial settings where their use is desirable to decontaminate temporary increases in production capacity or temporary changes in output of wastes that would result in an overload on existing purification systems. The portable modules also have application for on-site cleanup of pollutants from water before it is released into the general sewage system. Additionally, the portable modules are non-polluting and compatible with the environment.

The operation of Biosphere 2 demonstrates the feasibility of treating sewage, animal waste, and industrial waste to generate non-polluting products and usable water. The module has applications in supplying a model for the removal of these forms of pollution from the water environments of Earth. Waste recycling is an important methodology for the treatment of an ever-increasing problem faced by the Earth as landfills become filled. Also, the oceans, traditionally thought of as being an infinite "dumping ground" for refuse, are beginning to show signs of being overloaded, resulting in the death of marine life. Biosphere 2 is a working model which shows that recycling and living in harmony with the environment are not only feasible, but also advantageous, especially in desert areas where water is a commodity that can ill afford to be wasted. Therefore, recycling has the dual advantages of removing pollution from the environment and supplying much-needed, clean water.

Summary of the Invention

The present invention relates to a portable waste-treatment system. The waste-treatment system comprises anaerobic holding tanks for anaerobic digestion of collected waste and a plurality of aerobic marshes, connected to an outlet of the holding tanks and connected to each other in series, are provided for aerobic digestion of the anaerobically digested waste.

The marshes comprise a liquid-borne waste and a vented tank air diffuser at an inlet of a first marsh for dispersing the liquid-borne waste and anaerobic fumes from the anaerobic holding tanks. Marsh plants are grown in gravel and soil layered beds, through which the waste flows, and aquatic plants are grown in water channels, through which the waste also flows and which also contribute to the aerobic digestion of the waste. In addition, the marshes contain baffles which direct the waste flow in a sinuous path, thereby increasing the distance it travels and the exposure of the stream to the gravel, soil, and plant roots with microbes. The average residence time of the waste in the marsh is also more consistently regulated, and areas of stagnation are eliminated by the sinuous path.

The aerobically digested waste is collected in a waste sump tank. Also provided are means for recycling the waste among the holding tanks, each of the marshes, and the waste sump tank of the waste-treatment system, as desired.

Brief Description of the Drawings

The features and advantages of the present invention will be better understood when considered with reference to the following detailed description and the accompanying drawings, where:

FIG. 1 is a schematic view of water flow through human waste and animal/industrial waste marsh modules; and

FIG. 2 is a schematic view of the overall layout of waste-treatment modules and the flow among different components of the modules.

Detailed Description

Waste-treatment modules, in one embodiment of the invention, are designed to accommodate waste generated by eight people, in addition to farm animals and industrial waste, from laboratories and a mechanical workshop.

In general, wastes are collected and flushed with water through drains to banks of anaerobic holding tanks. The wastes are cycled from the holding tanks through marshes containing microorganisms and plants which aerobically metabolize contaminants in the water, converting them to usable bio ass and nontoxic compounds.

A major part of the aerobic treatment process of the waste marshes is attributed to microorganisms living on and around the plant root system. Once microorganisms are established on aquatic and marsh plant roots, they form a symbiotic relationship with the plant. This relationship normally produces a synergistic effect, resulting in increased degradation rates and removal of organic chemicals from the waste water surrounding the plant roots.

During microbial degradation of the organic materials, metabolites are produced which the plants absorb and utilize, along with nitrogen, phosphorus, and other minerals, as a food source. Microorganisms also use some or all metabolites released through plant roots, as a food source. This symbiotic relationship of one organism using another's waste allows for the rapid removal of organic materials from waste water.

Aquatic and marsh plants have the ability to translocate oxygen from the upper leaf areas to the roots, producing an aerobic zone around the roots, which is desirable in waste treatment and for the growth of aerobic microorganisms.

Aquatic and marsh plant roots are also capable of absorbing, concentrating and, in some cases, translocating toxic heavy metals and certain radioactive elements, therefore removing them from the water system. In addition, aquatic and marsh plants have the ability to absorb some organic molecules intact where they are translocated and eventually metabolized by plant enzymes.

The plants that are preferred for use in the waste treatment are aquatic plants (plants that will grow without a solid surface in which roots are established) and marsh plants (plants that require soil partially submerged in water to establish a root system) . The plants are selected for their ability to remove the contaminating components of the waste, such as heavy metals and organic compounds, for their usefulness as a food source for animals or for man, or for their usefulness as a compost fertilizer. The plants will grow in the marshes; therefore, their mass will increase and require periodic harvesting to remove plants and allow the regrowth of new plants. Marsh plants suitable for use in the marshes include Iris versicolor. Equisetum hvemale, Typha latifolia. Scirpus validus. Phragmites communis, Sagittaria latifolia, Canna edulis. and Acorus calamus. Aquatic plants suitable for use in the marshes include Azola, Lemna (Duckweed) , Eichornia crassipe (Water Hyacinth) , and Nymphaea odorata (Fragrant Water Lily) . Microorganisms suitable for use in the marsh are the microorganisms that are naturally established on the roots of the plants. These microorganisms are transferred into the marshes as part of the plants' natural flora.

It is also desirable to provide aquatic animals, such as fish, in the open water channels. The fish eat mosquito larvae which may breed in the water, and thus provide a natural, non-polluting means of "pest" control. In addition, the fish act as "gardeners," keeping the roots of the plants free from disease. In one embodiment of the present invention, the treatment systems include a human waste system 10 and an industrial waste-treatment system 12. The systems are separate, in the case of the human waste-treatment system and the industrial waste system, since the requirements for the treatment of each of these wastes are different. For example, the human waste could carry pathogenic organisms. Therefore, potential pathogenic organisms must be killed to prevent the spread of disease. Also, the human waste contains a high concentration of undigested cellulose, which needs to be digested to simpler compounds before it can be processed further.

The industrial waste, in the case of Biosphere 2, is derived from a laboratory and mechanical workshop area. Therefore, heavy metals, such as those contained in welding flux or other metals that are used in such areas, organic or inorganic chemicals or metals that are generated by laboratory experiments, need to be treated in a way that ensures removal of these contaminants. An increase in the concentration of heavy metals in the water of Biosphere 2 would lead to a contamination of the whole of the food chain. Also, other contaminants would eventually contaminate water and the air of Biosphere 2, if not removed.

In contrast, animal waste requires much less treatment before it can be reused. The animal waste collection and anaerobic treatment systems stands separately and can, if desired, be used directly as fertilizer on the agricultural crops of Biosphere 2, or, if desired, may be recycled with the human waste, or, as described in this embodiment of the present invention, it can be combined with the industrial waste, to provide a source of nutrients to supplement the waste from the industrial areas, which are low in the nutrients required to support the growth of the organisms used in the treatment processes. Alternatively, under conditions other than those present in Biosphere 2, the various sources of waste could be combined and treated in a single waste-treatment system. In such a case the conditions for the treatment would have to combine the treatments required for the removal of all the undesirable waste components.

The human waste collection areas 14 include toilets, urinals, showers, kitchen areas, general housekeeping areas, and sinks. Toilets and kitchen areas may be equipped with grinders, to reduce the size of solid waste to a "liquid" consistency. These liquefied solids and liquid wastes are transferred to anaerobic holding tanks. Waste from the human habitat is collected into three anaerobic holding tanks 16, each about 1.8 meters long, about 0.9 meter wide, and about 1.2 meters high, having a capacity of about 1,900 liters. Each of the holding tanks is covered, to aid in the development of an anaerobic environment for digestion of the waste, and vents lead into the sub-soil diffuser at the start of the first marsh module. The human waste is retained in the anaerobic holding tanks for a minimum of 24 hours, allowing microorganisms to anaerobically process the tank contents.

Three tanks are provided for batch processing of waste. As one of the tanks is being filled, a second tank is holding the waste, to allow the anaerobic digestion, and the contents of the third tank is being discharged to the marshes. Only 1,500 liters per day are expected to enter these tanks.

The contents of the anaerobic holding tanks is piped via pipe 18, under gravity flow, to a first marsh 20. The maximum flow rate from the holding tanks is about 19 liters per minute. The maximum flow through the marshes is about 1,500 liter per day. The first marsh is about 4.9 meters long by about 2.4 meters wide. The water level in the marsh varies from a maximum high of about 0.43 meter to a minimum low of about 0.15 meter. High water level is generally preferred, since that means slower flow and longer average residence time in the marshes for digestion of wastes. Two diffusers 22 are provided at the inlet 24 of the first marsh and run for a length of about three meters along the 4.9-meter length of the marsh. The diffusers comprise eight-centimeter-diameter piping, with a plurality of one-centimeter holes along the bottom of the piping. The diffusers are provided to distribute the anaerobic waste as it enters the marshes. This aids in the aerobic decomposition of the contaminants in the waste. The first marsh is sectioned with baffles 26 and 28, which direct the flow of waste, in a sinuous path, through the marsh containers. These baffles result in an average total distance of about 14 meters over which the waste flows, and allow the whole area of the marsh to be used. The baffles inhibit mixing of fresh waste with processed waste and direct channeling between the inlet and outlet.

The first marsh also includes about a 0.3-meter layer of gravel covered with about a 0.1-meter layer of soil, in which the plants are planted. The gravel and soil are spread uniformly over the floor of the marsh to form gravel and soil beds 30. The gravel and soil account for a total volume of about 3,600 and about 1,200 liters respectively. There is no "visible" water region in the first marsh, except for an area at its outlet where a small open water area is present to facilitate the flow of water from the first marsh to the outlet. The water and soil/gravel boundary around this small open water area is maintained by a wire mesh which supports the soil/gravel bed and hinders its collapse into the water area. The mesh also inhibits loss of the soil and gravel from the first marsh by helping to bind it in place. Marsh plants are grown in the soil/gravel beds in the first marsh. The roots of the marsh plants, in addition to aerating the water and removing the waste from the water, also help to bind the soil/gravel beds together.

When the flow of waste has completed its passage through the first marsh, it is then directed out of the first marsh and into the second marsh 34.

The second marsh is the same as the first marsh in its dimensions. However, it differs from the first marsh in that the diffusers are not present at the inlet of the marsh. Also, the gravel and soil layers, rather than forming a uniform and even layer across the floor of the second marsh, are distributed in a pattern that establishes an open water channel 36 between the baffles 38 and 39. The soil and gravel are piled up around the baffles and the edges of the marsh. The open water channel and soil/gravel boundary is maintained by a layer of mesh, as described for the first marsh. This arrangement provides an environment for the growth of marsh plants in the gravel- and soil-containing areas and of aquatic plants in the open water channel.

The volume of gravel in the second marsh is about 1,900 liters, and of soil is about 600 liters. The gravel is layered on the marsh floor, around the baffles and along the edges of the marsh, to a depth of about 0.3 meter, and about 0.1 meter of soil is layered on top of the gravel. The total volume of the second marsh is about 5,100 liters at the high-water mark, although a significant part of this volume, about 2,500 liters, is occupied by soil and gravel.

Flow from the second marsh is directed to a third marsh 42. The third marsh is about 2.4 meters wide and about 2.4 meters long. The third marsh also contains water channel areas 44, and gravel and soil layers.

The gravel and soil layers form isolated islands 46. The "island" structures are stabilized by a layer of mesh, as described for the first marsh. Baffles 48 and 50 are provided to direct the water flow back and forth along the length of the third marsh. The total volume of the third marsh is about 2,600 liters at the high water level. Of this volume, there are about 650 liters of gravel and about 200 liters of soil. Marsh and aquatic plants are grown in the third marsh. In each of the first, second, and third marshes, there are marsh plants such as Iris versicolor, Equisetum h ema1e. Typha latifolia. Scirpus validus. Phragmites communis. Sagittaria latifolia. Canna edulis. and Acorus calamus. Aquatic plants suitable for use in the marshes include Azola, Lemna (Duckweed) , Eichornia crassipe (Water Hyacinth) , and Nymphaea odorata (Fragrant Water Lily) , at an average density of about 40-45 plants per square meter of surface area.

Waste from the third marsh is tested to determine its purity. If the purity is of the required minimum quality, the waste is pumped, via pump 52 and pipe 54, to a waste sump tank 56. If the waste is not of the required minimum quality, it is recycled, via the recycle pipe line 58, back to the inlet of either the first, second or third marsh, where it undergoes further purification.

A bypass system 60, to direct waste directly from the anaerobic holding tanks to either the second or the third marsh, is also provided, in the event that maintenance or replanting is underway in one or more marsh module(s) . Additionally, if the waste is of a higher purity than normal and does not require treatment in all three marshes, waste may be directed not into the first marsh but into the second or third marsh, or directly into the waste sump tank.

Waste from the system waste sump tank is either pumped via pump 62 to filter cartridges 64 or it may be channeled to a bypass system 66, to bypass the filter cartridges, if desired. The waste is then pumped to ultraviolet-light (UV) sterilization units 68 or, alternatively, the waste may be pumped to a bypass system 70 around the UV light, if desired.

Irradiation of the waste with UV light is included to kill bacteria or to reduce the number of bacteria contained in it. Preferably, the wavelength of the UV light is about 260 nm, since this wavelength is most effective for bactericidal effect. To ensure that it is free of bacterial contamination, the waste, which has been purified via the waste-treatment systems, may be treated with agents such as hydrogen peroxide, in addition to the UV light treatment. Hydrogen peroxide or ozone treatment is preferred over treatment with chlorine, since it does not contaminate the closed system. After such additional treatment, the waste is considered to be fit for use as irrigation water.

After the "sterilization" procedures, the waste is then pumped to a utility storage tank 72, to rice paddies 74, or back to the marshes or holding tanks, as desired. In addition, an emergency waste-storage tank

73 is provided for overflow when needed.

The total volume, including the volume taken up by the gravel and soil, in the three-marsh system of the human waste-treatment system, is about 12,800 liters for up to eight people, or about 1,600 liters per person. This volume is considerably less than the

20,000 liters per person that is currently being used in other types of marsh treatment facilities. The marsh is constructed of fiberglass or other suitable material. Also, the marshes are modular and may be transported separately. Due to the relatively small volume and size of the marshes, the waste-treatment systems may be moved and relocated as may be necessary to serve changing waste-treatment requirements. The marshes, soil, and plants can be transplanted separately and assembled on site.

The animal collection areas 75 include animal stalls, and industrial waste collection areas 83 include laboratories where wastes such as organic and inorganic chemicals are generated, and mechanical workshops where wastes containing heavy metals may be generated.

Waste from the animal area is collected into three holding tanks 76, about 1.1 meters long, about 0.9 meter wide, and about 0.8 meter high, having a capacity of about 850 liters. Animal waste is handled in a fashion similar to that for human waste, although holding the waste for 24 hours, to undergo anaerobic digestion, may not be necessary. Waste from the holding tanks is piped, via pipe 78 and pump 80, to a fourth waste marsh 90. Alternatively, the contents of the animal waste holding tank can be piped to a utility tank 72, where it is combined with water for irrigating crops, or to the human waste holding tanks via pipe 81.

Waste from the workshop and laboratory areas is also collected into three holding tanks 84, about 1.1 meters long, about 0.9 meter wide, and about 0.8. meter high, having a capacity of about 800 liters. From the holding tanks, the waste is piped, via pipe 86 and pump 88, to the fourth waste marsh 90.

The flow rate from the animal and workshop/laboratory holding tanks is at a maximum rate of about 19 liters per minute. The maximum flow through the marshes is about 1,200 liters per day, with about 800 liters per day being derived from the animal waste holding tanks, and about 400 liters per day being derived from the workshop/laboratory holding tanks.

The fourth marsh, the first marsh of the animal/shop/laboratory waste-treatment system, is about 2.4 meters long by about 2.4 meters wide. The water level in the marsh varies from a maximum high of about 0.4 meter to a minimum low of about 0.15 meter. Two diffusers 92 are provided at the inlet 94 of the fourth marsh and run for a length of about 1.8 meters, along the 2.4-meter length of the marsh. The diffusers comprise eight-centimeter-diameter piping, with a plurality of one-centimeter holes along the bottom of the piping. The diffusers are provided to distribute the waste as it enters the marshes, to foster the even growth of plants and aerobic microorganisms in the marsh.

The fourth marsh is sectioned with baffles 96 and

98, which direct the flow of waste back and forth along the width of the marsh. The use of baffles in the marsh results in a total distance of 7.3 meters over which the waste flows.

The fourth marsh includes a 0.3-meter-thick layer of gravel, which is evenly distributed over the floor of the fourth marsh. A 0.1-meter-thick layer of soil is layered over the gravel. This soil-and-gravel layer provides a medium for the marsh plants to establish their root system. A small open water area is provided at the outlet of the fourth marsh. The soil and gravel layers are retained by a mesh layer. The volume of gravel and soil is about 1,800 and about 600 liters respectively. The total volume of the fourth marsh is about 2,900 liters at the high water level.

When the flow completes its passage through the end of the fourth marsh, it is directed out of the fourth marsh and into a fifth marsh 100. The fifth marsh is identical to the fourth marsh, except the diffusers are not present at the inlet of the marsh and the gravel and soil layers are arranged to leave an open water channel 102 within the marsh. The gravel is layered on the floor of the fifth marsh to a depth of about 0.3 meter around baffles 104 and 106 and the edges of the marsh. A 0.1-meter-thick layer of soil is layered over the gravel. The volume of gravel and soil is about 900 and about 300 liters, respectively. The total volume of the fifth marsh is about 2,900 liters at the high water level. Flow from the fifth marsh is directed to a sixth marsh 108. The sixth marsh is identical to the fifth marsh, with the gravel and soil layers arranged around the baffles 109 and 111 and the walls of the marsh, to leave a water channel 110 within the marsh.

The gravel is layered on the floor of the sixth marsh, to a depth of 0.3 meter, and covered with a 0.1-meter layer of soil. The volume of gravel and soil is about 1,000 and about 300 liters respectively. The total volume of the sixth marsh is about 2,900 liters at the high water level. The water areas in the fifth and sixth marshes are planted with aquatic plants such as Azola, . Lemna (Duckweed) , Eichornia crassipe (Water Hyacinth) , and Nv phaea odorata (Fragrant Water Lily) . The gravel and soil areas in the fourth, fifth, and sixth marshes are planted with marsh plants such as Iris versicolor. Equisetum hvemale. Typha latifolia. Scirpus validus. Phragmites communis. Sagittaria latifolia , Canna edulis, and Acorus calamus.

Waste from the sixth marsh is tested for its purity. If the purity is of sufficient quality, the waste is pumped, via pump 112 and pipe 114, to a waste sump tank 116. If the waste is not of sufficient quality, it can be recycled, via pipe 118, back to the inlet of either the fourth, fifth, or sixth marsh, where it will undergo further purification. A bypass system 120, which directs water to the fifth and sixth marshes, is also provided in the event that maintenance or replanting is underway in one or more marsh module(s) . Waste from the waste sump tank 116 is either pumped, via pump 122, to filter cartridges 124 or it may be channeled to a bypass system 126 around the filter cartridges, if desired. The waste is then pumped to UV sterilization units 128, or, alternatively, the waste may be pumped to a bypass system 130 around the UV light, if desired. The waste is then pumped to a utility storage tank 72.

While the wastes from the animal and industrial holding tanks are described as both feeding into the fourth marsh, it is also possible to direct the waste from each of the holding tanks to the fourth marsh independently of each other.

The present invention is described generally in relation to only one embodiment and is for illustrative purposes. Variations will be apparent to those skilled in the art. For example, although the systems are described with three sequential marshes, an additional marsh or two may be added in parallel or in series, for increasing the average residence time of wastes in the system. Such additional marshes may be useful, for example, when temperatures or solar illumination are reduced and digestion reactions thereby slowed. The sizes of the waste-treatment system marshes could be varied to accommodate more or fewer people or greater or smaller volumes of waste. Plants other than those described could be used, which would still result in degradation of the contaminants in the waste and also provide fodder and compost. Methods other than UV irradiation could be used to sterilize the waste after treatment. Hydrogen peroxide or other chemicals could be used as a method of sterilizing the waste, in addition to or in place of the UV irradiation. Different piping methods could be used which would still result in adequate treatment of the waste. The waste-treatment systems could be used in conjunction with each other or they may be used separately. Additional waste-treatment system modules could be added to the system to accommodate other types of waste. Therefore, the present invention is not intended to be limited to the embodiment described above. The scope of the invention is defined in the following claims.

Claims

WHAT IS CLAIMED IS :

1. Aportable waste-treatment system comprising: anaerobic holding tanks for anaerobic digestion of collected waste; a plurality of aerobic marshes connected to an outlet of the holding tanks and connected to each other in series for aerobic digestion of the anaerobically digested waste, such a marsh comprising: a liquid waste diffuser at an inlet of a first marsh for.distributing the waste; gravel and soil beds in which marsh plants are grown and through which the waste flows; water channels in which aquatic plants are grown and through which the waste flows; and a plurality of baffles within the marshes, which direct waste flow back and forth across the marsh, for increasing the length of the flow path of the waste in the marsh; a waste sump tank for collecting the aerobically digested waste; and means for recycling the waste between the holding tanks, each of the marshes, and the sump tank of the waste-treatment system as desired.

2. A portable waste-treatment system as recited in claim 1 further comprising means for disinfecting the aerobically digested waste.

3. A portable waste-treatment system as recited in claim 1 further comprising means for collecting waste from a plurality of sources and conveying the collected waste to a single waste-treatment system.

4. A portable waste-treatment system as recited in claim 1 further comprising means for collecting waste from a plurality of sources and conveying the collected waste to a plurality of different waste-treatment systems.

5. A portable waste-treatment system as recited in claim 1 further comprising a marsh having a volume of from about 1,000 liters to about 2,000 liters for each person using the waste-treatment system.

6. A portable waste-treatment marsh comprising: a plurality of baffles within the marsh which direct waste flow back and forth across the marsh; gravel and soil layers piled around the baffles and sides of the marsh to form an open water channel along the length of the marsh; marsh plants growing in the gravel and soil layer; and aquatic plants growing in the open water channel.

7. A portable waste-treatment marsh as recited in claim 6 further comprising waste flowing through the marsh along a sinusoidal path around the baffles.

8. A portable waste-treatment marsh comprising: a rectangular marsh; a plurality of baffles within the marsh for directing waste along a sinusoidal path through the marsh; gravel and soil layers piled within the marsh; an open water area within the marsh; marsh plants growing in the gravel and soil layer; and aquatic plants growing in the open water area.

9. Aportable waste-treatment system comprising: means of anaerobically digesting waste; a plurality of marshes; means for passing a liquid waste stream through each marsh along a path several times as long as it is wide; and means for aerobically digesting the waste in the waste stream.

10. A portable waste-treatment system as recited in claim 9, wherein the means of anaerobically digesting the waste comprises anaerobic digestion using microorganisms.

11. A portable waste-treatment system as recited in claim 9, wherein the means for passing the aste through each marsh comprises a plurality of baffles.

12. A portable waste-treatment system as recited in claim 9, wherein the means for aerobically digesting the waste comprises marsh plants, aquatic plants growing in the marsh, and microorganisms which are associated with the plants.

13. A portable waste-treatment system as recited in claim 9 further comprising a marsh having a volume of from about 1,000 liters to about 2,000 liters for each person using the waste-treatment marsh.

14. In an improved waste-treatment system having anaerobic digestion tanks and means for aerobically digesting waste, the improvement comprising: a plurality of portable marshes connected in series; means for introducing air into a first marsh; and means for recycling the waste between the portable marshes and the anaerobic digestion tanks.

15. An improved waste-treatment system as recited in claim 14 further comprising marsh plants growing in the portable marshes that are suitable for utilizing waste.

16. An improved waste-treatment system as recited in claim 14 further comprising aquatic plants growing in the portable marshes that are suitable for utilizing waste.

17. An improved waste-treatment system as recited in claim 14 further comprising a marsh having a volume of from about 1,000 liters to about 2,000 liters for each person using the waste-treatment system.

18. A method for treating waste comprising: collecting waste from a variety of sources; anaerobically digesting the collected waste; aerobically digesting the anaerobically digested waste in a plurality of serially connected portable marshes, comprising the steps of: diffusing air into the anaerobically digested waste to aerate the waste at the entrance of a first marsh; growing marsh plants in gravel and soil beds within the marshes through which the waste flows; growing aquatic plants in a water channel within the marshes through which the waste flows; and directing waste flow back and forth across each marsh by means of a plurality of baffles within the marshes which increase the distance the waste flows in the marsh; and discharging the digested waste from the marsh.

19. A method for treating waste as recited in claim 18 further comprising the step of disinfecting the treated waste.

20. A method for treating waste as recited in claim 18 further comprising the steps of collecting waste from multiple sources and conveying the collected wastes to a plurality of different treatment systems.