Patent Application
20230132622
The disclosure relates to greywater treatment systems and more specifically to modular greywater treatment systems including two-stage filtration.
As human population increases, ever greater demands are being put on natural resources. Food production and energy production systems are being taxed, resulting in food and power shortages. Another natural resource that is becoming scarce is safe fresh water. Water shortages have been experienced worldwide in recent years as population centers exhaust their supplies of fresh water. Water shortages have a destabilizing effect on local economies and may even lead to national or international conflicts.
Approximately 80% of the world’s population lives in areas having vulnerable water supplies. Excessive human water use can detrimentally affect wildlife, such as migrating fish, and can cause depletion of fresh water sources. Furthermore, dense population centers require extensive water delivery infrastructure. Good management of fresh water resources can protect wildlife while increasing water security.
Increases in population can result in water crises during droughts when water demand exceeds natural water replenishment of fresh water supplies. Generally, rainfall comes from complicated internal processes in the atmosphere that are very hard to predict. As population increases, naturally occurring periods of lower rainfall may result in water shortages as demand exceeds supply.
Although an overwhelming majority of the planet surface is composed of water, 97% of this water is saltwater. The fresh water used to sustain humans is only 3% of the total amount of water on Earth’s surface. Therefore, there is a limited supply of fresh water, which is stored in aquifers, in surface reservoirs and in the atmosphere. While seawater may be desalinated to render the water potable or useable by humans, only a very small fraction of the world’s water supply derives from desalination because desalination is an expensive, energy intensive process.
Fresh water supplies may be better managed through conservation efforts, such as water reclamation and water recycling. In some cases, demand on fresh water supplies may be reduced by reclaiming water that would otherwise go unused. One reclamation process is collecting rainwater in containers and storing the collected rainwater for later use. Water recycling, on the other hand, may be used by virtually any population, even those located in areas that receive little rainfall. Water recycling includes reusing or repurposing water that is used during human activities.
Generally, daily human water use produces two categories of wastewater, which are known as “greywater” and “blackwater.” Blackwater is wastewater that includes biological waste, such as feces and urine or is water heavily loaded with other contaminants such as food waste or wash water discharge from the wash cycle of a clothes washing machine. Blackwater is produced by toilets and other human waste collectors and requires extensive treatment before being released back into the environment due to its high organic content, dissolved solids, and contamination by various pathogens. Greywater, which is generated from domestic activities such as the rinse cycle of clothes washing machines, lavatory use, and bathing, requires less treatment as greywater generally contains fewer organic compounds than blackwater and generally includes less pathogen contamination. Greywater is produced by lavatory sinks, showers, the rinse cycle of clothes washing machines, and some industrial light use processes, etc.
Greywater may be used for many purposes that would otherwise use fresh, potable water. For example, greywater may be used for flushing toilets and irrigating outdoor plants. Using treated greywater to flush toilets, for example, instead of using fresh, potable water, can reduce the daily use of fresh, potable water by up to 30% in a typical family home.
As demands for potable water increase, communities will rely more heavily on water conservation efforts that include water recycling. Greywater recycling may become a key component of a water recycling system. In fact, some governments are incentivizing water conservation efforts by legislating tax breaks for programs that result in a reduction in fresh potable water usage from the community water supply. Recycling or repurposing greywater is often one component of such programs.
Current greywater recovery systems are generally limited to repurposing untreated greywater for irrigation purposes. Such systems are relatively simple, only requiring a separation of the greywater from the blackwater before the two are mixed. Then, the greywater is diverted outside for irrigation. These systems require that any irrigation be done through subsurface methods to minimize risks to public health and such systems are generally prohibited from storing greywater for extended periods. Most current greywater recovery systems do not treat greywater for indoor reuse.
Untreated greywater is heavily regulated by local health regulations, which generally restrict the uses for untreated greywater due to potential public health issues. In many localities, contact of untreated greywater with humans is prohibited and thus, using untreated greywater for indoor or above ground irrigation use is not currently allowed in most countries.
According to a first embodiment, a greywater treatment system includes a first modular greywater processing apparatus having a raw greywater inlet, a mechanical (MTF) filter connected to the raw greywater inlet, and a first ultrafine (UF) filter connected in series downstream of the mechanical filter. The UF filter includes a UF filter inlet, a filtrate outlet, and a cross-flow outlet. The filtrate outlet is connected to a processed water outlet. A modular base supports the mechanical filter and the UF filter.
The foregoing first embodiment of a greywater treatment system may further include any one or more of the following optional features, structures, and/or forms.
In some optional forms, a second UF filter is connected in parallel with the first UF filter, and in series with mechanical filter.
In some optional forms, the mechanical filter filters out particulate matter 200 microns or larger.
In some optional forms, the mechanical filter includes a backwash outlet that is adapted to be fluidly connected to a sewer.
In some optional forms, a differential pressure monitor is connected to the mechanical filter.
In some optional forms, a first control valve is disposed between mechanical filter and the UF filter.
In some optional forms, the filtrate outlet is fluidly connected to a processed water holding tank.
In some optional forms, the cross-flow outlet is fluidly connected to a raw greywater tank.
In some optional forms, an ultraviolet (UV) sterilizer is disposed downstream of the UF filter.
In some optional forms, a backwash line is disposed between the UV sterilizer and the UF filter.
In some optional forms, the UF filter removes particulates 0.02 microns and larger.
In some optional forms, a first backwash valve is disposed downstream of the UF filtrate outlet.
In some optional forms, a first control valve is disposed between the MTF filter and the UF filter.
In some optional forms, a second control valve is disposed downstream of the UF filtrate outlet.
In some optional forms, a third control valve is disposed between the UV sterilizer and the UF filtrate outlet.
In some optional forms, a second modular greywater processing apparatus is operatively connected to the first modular greywater processing apparatus.
In some optional forms, the second modular greywater processing apparatus includes a third UF filter connected in parallel to a fourth UF filter, both the third UF filter and the fourth UF filter being connected in series to the mechanical filter.
In some optional forms, a third modular greywater processing apparatus is operatively connected to the second modular greywater processing apparatus.
In some optional forms, the third modular greywater processing apparatus includes a fifth UF filter connected in parallel to a sixth UF filter, both the fifth UF filter and the sixth UF filter being connected in series to the mechanical filter.
In some optional forms, a chemical backwash system is fluidly connected to the UF filter.
In some optional forms, the chemical backwash system comprises a mixing tank and a chemical supply.
In some optional forms, the chemical backwash system further comprises a mixing venturi upstream of a chemical supply inlet.
In some optional forms, the mixing tank comprises a processed greywater inlet.
According to a second embodiment, a method of operating a greywater treatment system includes backwashing an MTF filter and a UF filter based on a zero flow reading from a flow sensor for a minimum period of time, and emptying raw greywater from a raw greywater tank.
The foregoing second embodiment of a method of operating a greywater treatment system may further include any one or more of the following optional features, structures, and/or forms.
In some optional forms, the minimum period of time is between 16 and 24 hours, preferably about 18 hours.
In some optional forms, the flow sensor is disposed downstream of the UF filter.
In some optional forms, the UF filter is continuously cleaned with a crossflow circuit and the waste from the crossflow circuit is returned to the raw greywater tank or to a sewer.
In some optional forms, the UF filter is backwashed based on a minimum flow input from the flow sensor.
In some optional forms, the minimum flow reading is between 1000 gallons of processed water and 3000 gallons of processed water, preferably between 1500 gallons of processed water and 2500 gallons of processed water, and more preferably at approximately 2000 gallons of processed water.
In some optional forms, the MTF filter is backwashed based on one of a maximum differential pressure input from a pressure sensor and a minimum flow input from the flow sensor.
In some optional forms, the maximum differential pressure is between 0 psi and 10 psi.
In some optional forms, the minimum flow input is between 35 gallons per minute and 80 gallons per minute
In some optional forms, the UF filter is chemically backwashed with a high pH solution based on a minimum flow input from the flow sensor.
In some optional forms, the minimum flow input for the chemical backwash is between 30,000 gallons of processed water and 50,000 gallons of processed water, preferably about 40,000 gallons of processed water.
In some optional forms, a processed water backwash is completed after the chemical backwash.
While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter, which is regarded as forming the present invention, the invention will be better understood from the following description taken in conjunction with the accompanying drawings.
The disclosed greywater treatment systems generally collect greywater from a greywater source, such as sinks, showers, or the rinse cycle of clothes washing machines, the systems then treat and store the greywater and distribute the treated greywater for reuse. The treated greywater may be used indoors, for example, to flush toilets, thereby reducing consumption of potable fresh water. The treated greywater may be used for other purposes, such as for water in clothes washing machines, or for above-ground spray irrigation systems, and some light industrial processes.
The benefits of collecting or harvesting greywater, treating the collected greywater, and reusing the treated greywater go far beyond fulfilling a desire to be “green.” Collecting, treating, and reusing greywater can have lasting economic benefits for building owners and for communities in general. By reusing treated greywater to flush toilets or urinals, to irrigate landscaping, or to support other water-intensive operations, municipal water charges can be significantly reduced. Wastewater treatment fees and environmental impact fees can also be reduced. Additionally, large scale reuse of greywater may stretch supplies of potable freshwater for communities, which extends the natural resource of water while simultaneously reducing individual water costs.
In high density buildings, the greywater treatment and reuse systems advantageously provide a relatively constant supply of treated greywater for flushing toilets. In some cases, the supply of treated greywater can meet 100% of toilet flushing requirements for a particular building. Because the disclosed greywater collection and treatment system provide a supply of greywater that is steady and predictable, storage requirements are reduced, saving storage space and cost. In other words, the predictable nature of greywater production in high density buildings allows the disclosed greywater treatment and reuse systems to be tailored in capacity for a particular building so that the supply of treated greywater generated by the greywater treatment and reuse systems closely match the demand for treated greywater (i.e., so that supply virtually matches demand), which reduces the need for extended storage of the treated greywater. Other uses for treated greywater include makeup water for evaporative cooling towers.
Greywater (also referred to as grey water, gray water and greywater), as used herein, refers to water that is produced by human domestic operations and that does not include significant concentrations of human biological waste (i.e., urine and feces) or food waste. Greywater is generally produced by sinks, showers, baths and light industrial applications, such as the rinse cycle of clothes washing machines and, and has not yet been treated (e.g., filtered and/or chemically treated) for pathogens.
When properly filtered and stored, greywater can be a valuable source of water to flush toilets, to flush urinals, or to irrigate landscaping. Toilet flushes can account for 25-65% or more of the total water use in a commercial building, even when low-flush fixtures are used.
Turning now to
The MTF filter 122 is a self-cleaning mechanical filter that captures relatively large particulates in the greywater stream. The MTF filter 122 captures particulates larger that about 200 microns, such as lint, hair, and other large debris. The MTF filter 122 includes a backwash outlet 140 that is adapted to be fluidly connected to a sewer (or to a raw greywater holding tank) by a wastewater outlet 142 so that backwash water may be directed to the sewer after a backwash cleaning cycle. A backwash valve 144 opens to allow backwash water to flow to the wastewater outlet 142 during the backwash cycle, which will be discussed further below. A differential pressure monitor 146 (
A first backwash valve 170 is disposed between the MTF filter 122 and the UF filter 124. The first backwash valve 170 directs backwash water from the MTF filter 122 to the wastewater outlet 142 during a backwash cycle.
The UF filter 124 is an ultrafine membrane filter with a cross-flow cleaning circuit. The ultrafine membrane filter comprises both flat sheet and capillary membranes. The UF filter 124 removes particulates 0.02 microns and larger, which includes pathogens (such as bacteria and viruses) and suspended solids. In some embodiments, a second UF filter 125 may be connected in parallel with the first UF filter 124 and in series with the MTF filter 122, as illustrated in
Turning now to
The raw greywater holding hank 200 is fluidly connected to sources of greywater, such as plumbing fixtures, washing machines, etc., by a raw greywater inlet line 202, which directs raw greywater into a raw greywater tank body 204. The raw greywater tank body 204 includes a raw greywater pump 206 that pumps raw greywater out of the raw greywater tank body 204 through a raw greywater output line 208, which leads to the MTF filter 122. The cross-flow outlet 130 from the UF filter 124 is connected to an internal cross-flow circuit (not shown) that continuously removes loading from the membrane and returns the loading to the raw greywater holding tank 202 through a cross-flow line 158.
From the MTF filter 122, the filtered greywater flows to the UF filter 124 through a mechanical filtrate line 160. After passing through the UF filter 124, the filtered greywater exits the UF filter 124 through a filtrate line 162 to a UV sterilizer 302. After sterilization in the UV sterilizer 302, the sterilized greywater is directed to a processed water tank body 402 in the processed water holding tank 400. In embodiments without a UV sterilizer 302, the filtrate outlet 132 may be directly fluidly connected to the processed water holding tank 400. A processed water pump 404 pumps the processed water from the processed water tank body 402 to downstream users of the processed water through a processed water exit line 406.
A processed backwash pump 408, which is activated during a standard backwash cycle, pumps processed water through backwash line 410, part of which connects the UF filter 124 to the UV sterilizer 302, to clean the UF filter 124, the MTF filter 122, and the UV sterilizer 302 during a standard backwash cycle. Generally, the standard backwash cycle is initiated after about 2000 gallons of greywater have been processed by the UF filter 124, although in other embodiments, other thresholds of processed greywater may be used to initiate the standard backwash cycle. The standard backwash cycle may also be initiated as a function of differential pressure across the MTF filter 122.
When more thorough cleaning is needed, the chemical backwash unit 500 supplies a chemically enhanced cleaning solution (normally a high pH solution) through a cleaning line 502 to the UF filter 124 during a chemical backwash cycle. The chemical backwash cycle is normally initiated after about 40,000 gallons of greywater have been processed by the UF filter 124, although in other embodiments, other thresholds of processed greywater may be used to initiate the chemical backwash cycle.
The backwash operations are controlled by the first backwash valve 170 disposed downstream of the UF filtrate outlet 128, a first control valve 172 disposed upstream of the raw greywater inlet 120, a second control valve 174 disposed downstream of the UF filtrate outlet 128, and upstream of the first backwash valve 170, and a third control valve 176 disposed between the UV treatment apparatus 302 and the UF filtrate outlet 128. The first, second, and third control valves 172, 174, 176, in the illustrated embodiment, are three-way motorized valves. The first backwash valve 170, in the illustrated embodiment, is a solenoid valve.
In the embodiments illustrated in
The modular nature of the modular greywater processing apparatus 100, enables multiple modular greywater processing apparatus 100 to be connected in parallel to one another so that the greywater treatment system 10 may be scaled appropriately for the needs of a particular project. For example, turning now to
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As discussed above, the standard backwash cycle is initiated after about 1000-3000 gallons, preferably between about 1500 and about 2500 gallons, and more preferably between about 1500-2000 gallons of greywater have been processed by the UF filter 124. Greywater flow through the UF filter 124 is monitored by a flow transmitter 180 connected to the filtrate line 162. The standard backwash cycle keeps the membranes in the UF filter 124 relatively clean so that they operate at optimum levels. Operation of the greywater treatment system 10 is controlled by the controller 600 that is normally disposed on the modular greywater processing apparatus 100. Although electrical connections between the controller 600 and various components of the greywater treatment system 10 are not illustrated, where the controller 600 is discussed as communicating with a component, such as a control valve, the controller 600 is communicatively connected to that component. The communicative connections may be electrical connections, pneumatic connections, or wireless connections, or any other type of connection that allows communication between the controller 600 and the various components of the system. During the normal backwash cycle, the first backwash valve 170 is closed, preventing fluid flow between the UF filter 124 and the UV sterilizer 302 through the filtrate line 162, the first control valve 172 is in a drain position, which allows backwash fluid (which is taken from the processed water holding tank 400) to flow out of the UF filter 124 through the raw greywater inlet 120 to a sewer (or to the raw greywater holding tank 202), and the second control valve 174 and the third control valve are in a normal backwash position, which allows backwash fluid to flow from the processed water holding tank 402 through the backwash line 410 to the filtrate outlet 128 so that the UF filter 124 is backwashed. The normal backwash cycle is between approximately 30 and 120 seconds long, preferably between 40 and 100 seconds long, more preferably approximately 45 seconds long. In some embodiments, the length of the backwash cycle may be adjustable to account for differing cleaning requirements.
The chemical backwash cycle is activated after between approximately 30,000 gallons and 100,000 gallons, preferably between about 30,000 and 50,000, and more preferably about 40,000 gallons, of greywater have been processed by the UF filter 124. Similar to the normal backwash cycle, greywater flow through the UF filter 124 is monitored by the flow transmitter 180. The purpose of the chemical backwash is to circulate a high pH solution of NaOCL and NaOH the UF Filter 124 to remove scale and/or to kill any biological agents that may have collected on the UF filter 124 membranes. The chemical backwash cycle lasts between 4 and 10 minutes, preferably between 4 and 8 minutes, and more preferably about 5 minutes. During the chemical backwash cycle, the chemical backwash pump 514 is activated to pump chemical backwash solution from the chemical backwash tank 516 through the chemical backwash line 502. The first backwash valve 170 is closed, the first control valve 172 is in a chemical backwash position in which chemical backwash fluid is directed from the chemical backwash line 502 into the raw greywater inlet 120. The second control valve 174 is in a chemical backwash position in which chemical backwash fluid is directed from the filtrate outlet 128 to the chemical backwash tank 516 through a chemical backwash return line 550. The raw greywater pump 206 and the processed backwash pump 408 are off during the chemical backwash cycle.
After the chemical backwash cycle is complete, a standard backwash cycle is activated, as outlined above, to remove any traces of the chemical backwash fluid from the UF filter 124 and the flow lines.
As described above, the modular greywater processing apparatus 100 must be properly shutdown after use so that any remaining greywater inside the filters and piping doesn’t become blackwater. There are two ways to initiate a full system shutdown. First, the full system shutdown may be manually initiated by a button on a control touchscreen that will start an automatic shutdown sequence. Second, if the flow sensor 180 that monitors the volume of processed water does not see any change over a programmable time period (typically set to 18 hours), the system will automatically force a shutdown sequence if the shutdown push button had not been previously manually activated.
In either shutdown instance, the system performs a standard backwash of both the MTF Filter 122 and the UF Filter 124. Additionally, a drain pump 220 on the raw greywater tank 204 may be activated to empty the raw greywater holding tank 202 to a sanitary sewer at least once per every 24 hours. The automatic shutdown sequence is based on a zero flow reading from the flow sensor 180 for a minimum period of time, such as every 18 hours. In some embodiments, the minimum period of time is between 16 and 24 hours.
The disclosed greywater treatment systems have been tested to advantageously produce excellent water quality, which meets or exceeds the NSF 350 standards as listed below in table 1. In most cases, turbidity will be less than 0.5 NTU with 0 levels of E.coli and CBOD and crystal clear water with less than 1 ppm of Total Suspended Solids. Turbidity is measured at various locations throughout the system, for example in the filtrate line 162.
The dimensions and values disclosed herein are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as “40 mm” is intended to mean “about 40 mm.” Moreover, any dimension disclosed in one embodiment is equally applicable in other embodiments.
Every document cited herein, including any cross referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
