Sustainable wastewater separation treatment systems coupled with nutrient and water reducing greywater reuse technologies

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Nationally and internationally, pressure is increasing to introduce nutrient reducing, water conserving and recycling measures for sustainable residential and small community water/wastewater systems. Reports of inadequate water quality and quantity are being reported daily. Over the past thirty years the federal government and State of Alaska have invested over 4 billion dollars installing piped water and sewer systems in remote Native Alaskan Bush Villages (averaging over $80,000 per household) with a ninety percent failure rate because of the high operation, maintenance and replacement costs. In Minnesota alone it is estimated that $1.8 billions dollars is required to upgrade existing community sewer and onsite septic systems. At the World Summit on Sustainability, United Nations, World Bank and certain key professionals stated that the current way in which wastewater is handled in the developed world is probably not sustainable, and hence the technologies in use are, in their present form, not appropriate for transfer to the developing world.

Systems utilizing separation technology represent a logical option for reducing and eliminating these pressures. Northern Testing Laboratories, Inc., the University of Alaska Fairbanks (Fairbanks, AK) and the Olmsted County Water Resources Center (Rochester, MN) have tested and documented that the Equaris BMRC (BioMatter ReSequencing Converter) and Greywater Treatment Systems can reduce water consumption by 40%, CBOD & TSS by 90%, nitrates by 99% and bacteria by 1000 fold when compared to septic tank effluent. The further treated, filtered and disinfected greywater effluent for reuse either within the household or for safe discharge to ground or surface water is possible with the use of the Household Water and Wastewater Treatment and Recycling System. This type of sustainable technology has the capability of eliminating the need for sewer collection systems by reducing water usage and pollution loading to levels sufficient and acceptable for onsite disposal with dramatically reduced subsurface absorption system sizing. Total recycle of wastewater is possible with far reaching implications for sustainable development, conservation of water, protection of the environment, lakes and groundwater in particular, building on difficult lots, urban sprawl and annexation.

Financing of water conserving and pollution preventing wastewater systems for homes and small communities is available through the commercial banking system associated with this technology. To provide incentive to the wastewater treatment industry and the public, legislation has been introduced in the State of Minnesota, which, if passed, will provide zero interest loans for wastewater treatment technologies other than standard that can reduce water consumption and pollution.

Introduction

During the mid 1980's, under contract with the Alaska Army National Guard, Equaris Corporation (formerly AlasCan of Minnesota, Inc.) manufactured and installed over 50 non-automated, waterless composting toilet systems for remote Alaska Native Village Army National Guard Armories. These villages were predominately located on Alaska's west coast, above and below the Arctic Circle, and lacked any form of conventional running water and wastewater treatment systems. As a result of those experiences, the Equaris Corporation developed an automated version for the composting process to help reduce maintenance requirements and increase its efficiency. This version was named the 'AlasCan Composting Toilet System'.

Water supply and wastewater treatment problems are not unique to Alaska's Bush Villages but exist throughout Alaska because of its climatic conditions and soil constraints (frozen soils - permafrost - and/or frigid air and soil temperatures). In the late 1980's and early 1990's various residential and commercial operations installed Equaris BMRC Systems but needed a greywater system to treat the remaining wastewater. As a result the Equaris Greywater Treatment System was developed with grant funding from the US Department of Energy and the Alaska Science and Technology Foundation and tested by Northern Testing Laboratories and the University of Alaska Fairbanks under actual residential and commercial conditions as well as simulated laboratory conditions. The documentation from that testing period concluded that a BMRC and greywater treatment system combination reduced water consumption and produced a treated compost and greywater effluent that was of superior quality compared to conventional septic system effluent. For installations in the remote Bush Native Alaskan villages a prefabricated, insulated building was constructed and attached to the existing home. Utilizing the SeaLand VacuFlush Toilets, the Equaris equipment can be located on the same level as the toilets. Figure 1 depicts the entire Equaris System in the basement of a typical home in the Midwest. The entire System occupies less than 120 square feet. In new construction or retrofits with basements and sufficient room for the System, it is recommended that they be designed and installed in a room, like the mechanical room, where the furnace and water conditioning equipment are already located.

For existing homes that do not have basements or for homeowners who do not want or do not have a location where an above ground building can be located, an underground structure or concrete vault is recommended. The structure can be insulated and heated for cold climate installations.

In addition, maintenance personnel can easily service the Systems without having to enter the home. Locating the Systems outside the home maintains that 'out-of-sight, out-of-mind' mentality for wastewater treatment.

System Description

BMRC (BioMatter ReSequencing Converter)

This system biologically converts 90 to 95 percent of all toilet and kitchen garbage disposal organic wastes into odorless carbon dioxide and water vapor. In the double walled tank, aerobic organisms (oxygen consuming) thrive in a media to which air and a carbon source are supplied. In this environment, the remaining solid waste portion is converted to a readily useable soil amendment. Aerobic organisms do not produce the methane gas and hydrogen sulfide odors common with anaerobic (non-oxygen consuming) septic systems.

The aerobic/composting environment kills 90 to 99 percent of viruses and pathogens utilizing time and temperature. Approximately 10 to 15 gallons of finished compost, similar to potting soil in texture, are produced by a family of 4 per year and are easily removed by the homeowner or maintenance personnel with the auger system designed for this purpose. Programmable timer driven agitators gently distribute the fresh wastes on the top surface of the tank to aid the organisms in the natural decomposition process.

This system can serve up to 12 adults full-time and can accommodate larger numbers for brief periods. Unlike septic systems, it is highly recommended that a garbage disposal be installed on a small separate sink and plumbed to the BMRC. This also eliminates kitchen organic refuse, thereby reducing the total amount of garbage, which lowers the cost of garbage disposal and removal.

Greywater Treatment System

Greywater is plumbed to a series of separate wastewater treatment and filtration tanks. This system consists of a surge tank for flow control, an aeration tank for aerobic treatment and a clarification tank for separation of the settleable solids, which are air lifted and returned to the surge tank.

Air, which is continuously circulated to aerate the wastewater, is supplied by an extremely energy efficient (67 watts), off-the-shelf, linear air compressor. The standard wastewater treatment technology of extended aeration is employed in this part of the system. For ease of maintenance, a sludge removal system pumps solids from the bottom of each tank to the BMRC for final treatment. Minimizing water use utilizing separation technology revises the estimate for water consumption and greywater treatment to 40 gallons of wastewater per person per day. Based upon 24-hour retention for treatment of the greywater, the estimated treatment capacity of each system is 250 gallons per day. For flows over 250 gallons per day, additional systems can be added and installed in parallel.

The extended aeration process produces a treated wastewater effluent quality that can then be efficiently and economically filtered and disinfected for reuse. The quality of the treated water is compared to septic effluent in Table 5.

Potable Water Recycling System

The Equaris Recycling System provides a closed loop capability for treating the effluent from the greywater treatment system for household reuse in a total recycle mode. Water for drinking and cooking is provided by a dedicated well, a rainwater catchment cistern system or municipality. To guarantee the quality of this water, it is recommended that the water be pretreated utilizing filtration, ultraviolet light and ozone disinfection and reverse osmosis.

The effluent from the greywater treatment system is automatically pumped through filters to remove sediment, cysts, objectionable taste and odor prior to being treated by ultraviolet light, ozone and a reverse osmosis system. Water purified by reverse osmosis is then continuously disinfected utilizing a small circulation pump and ultraviolet light/ozone system. The filtered and treated water may also be discharged to a subsurface absorption area reduced in size by 70 - 90% based upon flow reduction and quality.

By increasing the size of the reverse osmosis unit, the system is capable of various flow rates of treated water by incorporating larger sized FDA approved water storage tanks for the filtered and disinfected water. The entire system can be controlled and monitored to automatically shut the system off and alert the homeowner and/or maintenance personnel if any problems are detected.

Toilet Fixtures

The systems are installed utilizing stylish one-cup-of-water-per-flush, or less, porcelain toilet fixtures from SeaLand Technology, Inc. SeaLand, an Ohio based company, manufactures a line of toilet fixtures that are designed for recreational vehicles and the luxury marine vessel marketplace. These ceramic toilet fixtures are available in a wide range of color options. The toilets utilize a foot pedal operating flushing mechanism that rotates a ball/trap device. The toilet pedal can also be lifted with the foot, allowing more water into the toilet bowl, thereby totally eliminating any toilet staining problems usually associated with low water flushing toilets.

The SeaLand Model 510 utilizes gravity and a steeper plumbing angle (25 degrees from horizontal or 2 1/2 inches per foot drop) to transport the toilet refuse and paper to the BMRC. The marine VacuFlush toilet incorporates the same toilet fixture but utilizes a small vacuum tank and a twelve-volt bellows type pump to create a vacuum, which is capable of lifting the toilet refuse 10 feet vertically and transporting it horizontally 100 feet to the BMRC. This allows flexibility in locating the BMRC instead of having to design the house or facility around the system. Both models meet appropriate codes.

Kitchen Garbage Disposals

Two thirds of all of the organic refuse that is produced in the household comes from the kitchen. On standard septic or sewer types of wastewater treatment systems the garbage disposal adds additional load and requires additional maintenance and pumping costs. With the BMRC, a separate bar type sink with a garbage disposal is installed next to the standard kitchen sink. With a small amount of water from a sprayer, this new kitchen fixture grinds up and transports all of the organic refuse to the BMRC.

Research And Development

Alaska

During the spring of 1987 Northern Testing Laboratories, Inc., Fairbanks, Alaska began a 4-month greywater-testing program for the inventor's first Equaris greywater treatment prototype system located at his full time occupied single-family residence (2 people) located in Healy, Alaska. The testing program monitored the influent and effluent of the treatment system for organic and solids loading and the effluent for fecal coliform bacteria. The test data was to determine the system loading and efficiency and to document fluctuations in equipment performance. Results of the monthly composite samples are presented in Table 1. Microscope exams performed on the Converter samples showed only a few small flocs present (note Converter TSS data in Table 1), with large numbers of active bacteria. No higher protozoans or nematodes were observed.

BOD and TSS values are mg/l, except % removals. BOD and TSS averages are arithmetic. Fecal coliform values are colonies/100 ml. Fecal coliform average is geometric. The average monthly flow was estimated from potable water meter flow measurement to be 2,750 gallons (92 gpd).

During the performance test, the greywater system was successful in removing approximately half of the organic strength (BOD) and solids (TSS) from the weak greywater influent, although a significant improvement in removal occurred following an upgrade in the aeration system after the June 2 sample was collected. Northern Testing Laboratory, Inc.'s Conclusions and Recommendations:

  1. This performance test of the first prototype Equaris greywater treatment system demonstrated that under aerobic conditions, the plant was able to remove approximately one half of the organic (BOD) loading and solids (TSS) loading from an influent flow of approximately 90 gallons of water per day. With the upgraded aerator, the plant removed approximately 80% of the BOD and TSS.
  2. The aerobic treatment process produced effluent containing fecal coliform bacteria ranging in concentration from 10 to 1000 colonies per 100 ml averaging 116 colonies per 100 ml without disinfection. The lowest coliform levels were achieved following the upgrading of the aeration system after the third laboratory sample was collected.
  3. An influent flow control basin (surge tank) should be added to the treatment system in order to dampen the hydraulic surges to the plant.
  4. The flat bottom of the clarifier was not effective in directing the solids to the inlet of the sludge return airlift pump. A sloping bottom has since been retrofitted into the clarifier to correct this.

Overall, this performance test has demonstrated that an aerobic biological process is capable of reducing the BOD and TSS levels of household greywater to approximately secondary effluent quality. The Equaris greywater plant, with the minor modifications noted above, should prove to be an effective system for containing and optimizing this process on a household size scale. In regard to the downsizing factors comparing the Equaris greywater treatment system with conventional septic tank treatment, based on the results of the performance test, using information derived from the following publications, we can conclude the following:

  1. Reduction in total wastewater flow of up to 36% per (US EPA, 1980) and 39% per (Winneberger, 1974) can be achieved by using blackwater/greywater separation. The total greywater flow remaining can be expected to be in the range of approximately 30 to 40 gpcd. (Alaska Department of Environmental Conservation, 1982).
  2. An even more dramatic difference is noted in the quality of the wastewater. The EPA design manual, which is cited in the ADEC regulations for onsite system sizing, lists the organic strength of conventional domestic wastewater as 200 - 290 mg/L BOD5, and the total suspended solids (TSS) also as 200 290 mg/L. The influent greywater data from the 1987 study averaged 93 mg/L for BOD5 and 37 mg/L for TSS. The average influent greywater strength (BOD5) was only 38% and the solids loading (TSS) only 15% of conventional domestic wastewater. (Pollen, 1987).

Minnesota

Because of the karst geology and problem soils for standard onsite soil based wastewater treatment systems, Olmsted County Officials decided to investigate alternative wastewater treatment technologies to reduce nitrate pollution to its aquifers during the early 1990's. In 1993, a new recreation park, Chester Woods, was being developed and the Olmsted County Officials decided that the Park Manager's house at the park would provide an excellent opportunity to install and test an alternative wastewater treatment technology. Olmsted County directed its environmental staff to research and locate an advanced technology for wastewater treatment that could demonstrate a better way to safeguard the groundwater from nitrate and bacterial contamination. The staff researched available nitrogen reducing wastewater treatment technologies and contracted to have an Equaris System installed.

In 1993, Olmsted County installed an Equaris BMRC and greywater treatment system at the park manager's fulltime residence at the park to demonstrate waste load reduction and downsizing of drainfield area. During the summer and fall of 1997, Olmsted County Water Resources representatives conducted a monitoring and testing program for the system for a range of chemical and physical wastewater parameters. Grab samples were taken from the clarifier chamber of the greywater system each week for four weeks and then each month for four months. Table 2 presents the data for treated greywater.

Values for parameters related to the organic components (BOD, TOC, COD) indicate that the effluent from the system is of typical domestic origin (Eckenfelder, 1970). Table 3 compares BOC/TOC and COD/TOC ratios in the treated greywater to those of typical domestic wastewater. The comparison suggests that some degree of biological treatment has occurred. The effluent COD/TOC ratio is consistent with the more refractory (resistant to bio-oxidation) nature of organics in greywater compared to toilet wastes.

Calculated Reduction in Pollutant Loadings

For purposes of comparing the Equaris system to other treatment systems, the data from Tables 2 and 3 have been converted to loadings in grams/capita/day (gcd). Results are shown in Table 4 with published values for per-capita waste generation for greywater, blackwater, and combined raw domestic waste. Based on these generic loading rates, the Chester Woods system is calculated to achieve greater than a 94% reduction for TSS and BOD5, greater than 83% reduction in total organics, and over 90% reduction of total-N. The calculated removal rates were largely due to the separation and retention of the solids and the nitrogen in the compost mass, and through nitrogen loss to the atmosphere as ammonia, and possibly through denitrification.

Table 5 illustrates the degree of reduction calculated for TSS, TKN, BOD5 and coliform compared to reported septic tank effluent (in mg/L). While these concentration comparisons may not exactly relate 'one-to-one' to per capita loadings, they do show the same general pattern of nitrogen and organics reduction as described above. Calculated reductions for the Chester Woods site are less when compared to septic tank effluent (Table 5) than when compared to raw domestic wastes (Table 4), as would be expected since some settling and removal of nitrogen and organics occurs in septic tanks.

Based on this monitoring data, the system is calculated to have achieved a 90% reduction in loadings of total nitrogen, BOD and suspended solids to the drainfield compared to primary treated wastewater effluent from a septic tank. Fecal coliform levels are calculated to be up to 1,000 fold less than effluent from conventional septic tank effluent. Measured water use, measured pollutant loadings and the lack of ponding in drainfield trenches are consistent with the original design of a 40% downsized soil disposal area.

Recycling Greywater Development

In 1998, Equaris Corporation began researching water filtration and disinfection technologies that could be utilized to treat the greywater effluent to meet the standards for a National Pollution Discharge Elimination System (NPDES) permit. The research resulted in the development of a prototype water purification unit. During January 2000 the 'Recycling' System prototype was tested by the Olmsted County Public Health Services Environmental Water Well Testing Lab. The lab only tested for fecal coliform and E. Coli. Test results for three samples were zero for both parameters. Even though the tested prototype performed very well, Equaris Corporation subcontracted the development of a new Recycling System that would reduce maintenance requirements and provide a higher level of performance. As of this writing, a new prototype has been developed and a 1-year testing program is scheduled to begin in February 2002.

Evaluation Of On-Site Drainfields For The Treated Greywater

Chester Woods, MN Site

The requirements from Olmsted County were that the system would be installed utilizing conventional construction practices and that if it failed to meet the nitrate reduction requirements or aesthetic acceptability of the occupants it would be removed by the manufacturer. Because of the reduced volume of wastewater generated with the elimination of the traditional multi-gallon flush toilet, the disposal field was designed and installed with a 40% reduction in drainfield size in accordance with the prescriptive standards of Minn. Rule 7080. Each of five 5-trenches, 50 feet in length were arranged with drop boxes so that the flow to the field would go only to the first trench until it no longer handled the flow, at which time the flow would be directed to the second trench.

After 6 years of continuous use by the first residents, (2 adults) then 2 more years by the second residents, (2 adults and 3 preschool children), Olmsted County officials, the drainfield designer and the manufacturer examined the drainfield. Each of the drop boxes was checked for standing water and water was only found in the first drop box. The edge of the first trench was identified and hand excavation was done adjacent to the trench. When the excavation reached to approximately the depth of the trench, soil adjacent to the trench was carefully removed so as not to disturb the trench. It was noted that this area had been receiving treated greywater for disposal. Soil from the excavation adjacent to the rock of the drainfield trench, where one would normally find discoloration, was removed and sliced with a pocketknife to identify soil discoloration or biomat. None were observed.

Summary and Conclusions Based On The Observations:

  1. Only 1 of 5 drainfield trenches has actively received treated greywater over the 8 years of continuous use.
  2. Treated greywater to the field was significantly cleaner than blackwater from a septic tank.
  3. No biomat had formed anywhere in the observation area.
  4. No soil discoloration was observed in the area of observation.
  5. All of the water went to the first drainfield trench for absorption and disposal and 4 trenches of the drainfield are still available to absorb and dispose of water.
  6. At the present rate of drainfield use, its life expectancy is 30 years, not counting the useful life of the first trench, which is judged to be substantial even at this time.
  7. The useable life of this system is due to the quality of the water coming to it therefore, the useable life may be indefinite.

Judson, MN Site

In August of 1997, a complete Equaris BMRC and Greywater Treatment System was installed at a remodeled home located in Judson, Minnesota. The homeowners chose this system for its environmental benefits and also because the house is located on a site that has less than one foot of soil on top of limestone. Following the Minnesota Pollution Control Agency onsite wastewater treatment system requirements for Type IV dwellings (greywater only) a 40% reduced sized mound was constructed.

To meet the required 3-foot separation distance from bedrock, which was 1 foot below the surface of the soil, a sand mound was constructed containing 'Infiltrator' chambered units with pressure distribution. To determine if the mound could be reduced further in size, the mound was divided into 3 zones with valves to control the flow to each zone. Only one of the zones has been utilized and inspections of the first zone have shown neither standing water nor evidence of biomat formation. Because of the increased treated greywater quality being discharged it can be assumed that further reductions in the design and sizing of mounds accepting high quality greywater can be implemented.

Financing, Monitoring And Maintenance Program

The majority of homeowners do not want to service or 'deal' with their own wastewater treatment equipment. Recognizing society's and the local approving health authority's values and sometimes requirements to have some form of monitoring and service organization in place for onsite types of systems, Equaris Corporation offers a monitoring, service and warranty program for a small monthly fee for a local plumbing company to perform the service and the professional maintenance required, thereby keeping the systems operating efficiently.

Monitoring

If a problem should arise this system will automatically alert the main office and up to 8 other locations (i.e. homeowner, county and state health departments, maintenance personnel) that it needs to be serviced. The monitoring equipment can range from simple auto-dialers for reporting problems to sophisticated reporting and recording devices that can provide limitless information and remote service capabilities with security system options. Anticipating this requirement and the customer's needs, systems can be continuously monitored utilizing a small computer unit with a modem that is hooked up to the customer's phone line. It will not interfere with the customer's phone service and reports the data at night. The computer is continuously checking the systems to insure that they are running smoothly.

Maintenance and Financing

The systems need some monthly maintenance. The BMRC system requires the addition of pine bedding as the carbon source. Sludge is pumped from the greywater treatment system to the BMRC. The filtration and disinfection system maintenance consists of back flushing and disinfecting the filtration system, changing the filter cartridges and replacing ultraviolet light lamps. For homeowners not wanting to do the maintenance, a certified technician will inspect the systems and provide the necessary maintenance for peak operating efficiency on a monthly basis for a fee.

If financing is a problem, Equaris Corporation offers a financing program to make it easier for homeowners, developers, communities and local units of government to purchase and install these systems. This applies to new construction as well as existing homes and businesses. The financing program is based upon the implementation of a monitoring, maintenance and warranty program. Typically, a certified plumbing company provides the service. Equaris Corporation then finances the purchase of the equipment and installation for the customer.

Future Work

In a recent report, according to Professor Richard Ashley, Chairman of the Sewer Systems and Process Working Group, IAWQ/IAHR Joint Committee on Urban Drainage:

'The techniques currently used to dispose of wastewater have been utilized for several millennia. However, it was only in the last century that explicit linkages were made between reliable wastewater systems and the maintenance of public health, and formalized methods were developed for sewer design and construction. The adoption worldwide of the concept of sustainability, following the world summit in 1992, poses a major challenge to water and wastewater system owners, operators and users. Many commentators at all levels (for example, the United Nations, World Bank and certain key professionals) have stated that the current way in which wastewater is handled in the developed world is probably not sustainable, and hence the technologies in use are, in their present form, not appropriate for transfer to the developing world.

The sustainability perspective requires a fundamental paradigm shift, which affects all stakeholders: governments, institutions, regional authorities, local authorities, non-government organizations, pressure groups, professionals and citizens. A future scenario in the developed world may be postulated in which:

  1. water demand (for WC flushing) is considerably reduced, and hence so are wastewater flows;
  2. storm drainage is largely handled locally - even in established cities (source control retrofitting is under trial in number of countries), and storm water re-use has become more economic;
  3. industrial effluents are pre-treated onsite, with little discharge into 'municipal' wastewater systems; and
  4. 'domestic' sanitary wastewater is much reduced in volume (greywater is re-used) and the nature of the solids is very different - no plastics or textiles.' (Ashley, 2000).

According to the November 2000 Vol. 44, No. 11 issue of the AWWA periodical, 'The US General Accounting Office has confirmed what water conservation proponents already know: conserving water saves money. Reducing water consumption and wastewater flows may allow local communities to save money by deferring or avoiding investments in water or wastewater infrastructure.' (AWWA, 2000).

Conclusions

Separation technology systems can reduce water consumption by 40% in residential and up to 80% in commercial applications. It has the capability for treating greywater to near secondary standards, thereby enabling filtration and disinfection systems to further purify water for irrigation or for reuse within the home or facility. If disposal is the option, fields can be downsized without shortening life expectancy. Field design can be based upon the soil's saturation rate and its ability to absorb clean water. Field sizing does not need to be predicated upon the soil's structure, biomat formation or its ability to treat septic tank effluent qualities. When used in conjunction with community water supply and wastewater treatment systems, separation technologies can prolong the life and capabilities of both. Nitrogen and phosphorous reducing capabilities make separation technologies ideal for use where soil based systems cannot be installed or where nutrients in groundwater are a concern. Separation technology is sustainable for developed countries as well as third world applications.

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