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The onsite treatment plant at a private gated community produces near-drinking-quality water suitable for irrigating the golf course grounds and residents’ private landscaping.
By Lori Lovely
Onsite wastewater treatment is fast becoming a major issue in Georgia. Despite being known for humid cypress swamps and moss-draped trees fed by 40 to 50 inches of rainfall every year, the southern coastal state now endures sustained periods of unusually dry weather and a rapidly growing population that puts a strain on available water resources. Adding to the cumulative problem was five years of drought and increasing water demand from development that produced a 13-foot drop in water level of Lake Lanier and led to water scarcity in 2003. The state responded by implementing a drought management plan that included water-use restrictions. During the drought, some small water treatment plants along Chattahoochee River tributaries closed because the waterways virtually dried up.
Near the capital, the push for water resource management included 16 counties around Atlanta. The counties entered into a new water planning initiative in 2001, creating the Metropolitan North Georgia Water Planning District (MNGWPD), with the intention of overseeing development and implementation of regional and watershed-specific plans for preserving water quality and extending the supply in the area whose population is expected to double by 2030. According to a statement by Tim Equels, assistant director of the Fulton County, GA, Public Works Department Water Services Division, “Conservation initiatives are expected to reduce demand by about 11%,” although he outlines plans to provide an additional 10% savings in potable water demand through reuse strategies.
One way to conserve water is by regulating irrigation days. “Georgia is on an odd/even water day for irrigation,” says John Machisko, chief operating officer of The Manor Golf Country Club in North Fulton County, GA.
Thanks to an onsite wastewater treatment plant, Manor residents can water their lawns any day they choose.
OWT As Amenity
Developed by Brooks Land Inc. in partnership with the Phoenix Corp. of Georgia, the Manor Golf and Country Club is a private gated community stretching across 731 acres. The luxury community features 1-acre lot sizes (or bigger), limiting the capacity to 399 homes, with home prices ranging from $800,000 to $1.5 million. In addition to breathtaking views, attractive amenities include a clubhouse with a spa and athletic facilities, outdoor Olympic-sized swimming pool, indoor family pool, outdoor and indoor tennis courts, basketball court, a Junior Olympic pool, additional tennis courts with a smaller satellite clubhouse, and a 180-acre Tom Watson signature golf course.
A less obvious but nevertheless significant feature is disguised as a utility shed: a Z-MOD packaged membrane bioreactor system for gray and black water treatment, manufactured by GE Water & Process Technologies. Graywater typically comes from laundry and sink wastewater; blackwater comes from toilet wastewater. The Z-MOD system, which treats 100% of the community’s wastewater, achieves a treatment level classified by the Georgia Environmental Protection Division as urban reuse—near drinking quality, suitable for irrigating the golf course, grounds, and residents’ private landscaping.
Membrane bioreactors (MBRs) provide a highly compact, fully automated, low-odor alternative for wastewater treatment. MBRs also contribute toward the earning of Leadership in Energy and Environmental Design (LEED) certification in categories that include water-use reduction, water-efficient landscaping, innovative wastewater treatment technologies, and innovation in design. Although LEED certification is currently available only for commercial buildings, Machisko says water reuse was “the way to go. Reuse water is the thing of the future. Florida is already doing a lot with it.” In fact, he lists it as an amenity. “Every home has sewer and unlimited use of reuse water. That’s a selling point. It’s a real issue. We sold the reuse as an amenity.”
To ensure the system remains a selling point instead of a detraction, the pre-engineered Z-MOD system was “disguised in a barn building so it would be discrete, undetectable,” explains Donna Hartman, commercial manager of packaged plant systems for GE Water & Process Technologies. Luckily, the system has a small footprint—about 3,000 square feet. “We had to put it in the middle of the subdivision, so we needed something that fit in a small footprint and produced no odor and no noise,” Machisko elaborates. The bioreactor remains outside, but the rest of the unit is housed in a barn-like structure that he says looks like a maintenance shed.
Plug and Play
“They knew exactly what they wanted,” Hartman recalls. “Ron Green had prior experience at Cauley Creek [Water Reclamation Facility] in treating wastewater, so he contacted us. They commissioned the system in June 2005.”
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Photo: GE Water & Process Technologies |
| Above diagram illustrates how solids and bacteria are removed via the membrane fiber. Below: The main control room of the system in place at The Manor. |
As Machisko explains, The Manor Golf and Country Club was originally owned by Innovative Water Systems, where he served as chief operations officer. It was sold to the county late last year. Innovative Water Systems also owned Cauley Creek, the first distributor of reuse water in Georgia, built in 2002. “We looked at a lot of technology there. Membranes were in their infancy. But way back then, Ron Green decided it was the way to go.” They never looked back. A GE ZeeWeed MBR system has been operating at Cauley Creek for nearly five years with no violations.
The Cauley Creek Water Reclamation Facility in North Fulton County was completed in 2002. Originally designed to provide 9,500-cubic-meter-per-day average daily flow rate of high-quality reuse water to the local community for agricultural and residential irrigation, within two years the plant was expanded to its current capacity of 19,000-cubic-meter-per-day average daily flow rate.
The effluent exceeds the MNGWPD standard for water reuse and discharge, thanks to MBR technology. And because the footprint is small, there is no odor or noise. The plant—disguised as a barn—is located near customers, reducing distribution costs due to proximity. With the cost of reuse irrigation water significantly lower than for treated potable water, demand continues to increase and North Fulton County has plans to build a larger water reclamation facility.
Their success at Cauley Creek with the ZeeWeed MBR system set the stage for Machisko’s and Green’s decision about what to install at The Manor. “The experience was very positive,” Machisko recalls about Zenon Environmental, which was recently acquired by GE Water & Process Technologies. “Zenon had a great track record with follow-up maintenance.” Zenon was also able to meet The Manor’s timing needs, installing the system quickly—about 10 months.
Other determining factors include the quality of the water the Z-MOD system produces and the compactness of the system and its longevity. “The size of the subdivision and the number of homes determined the size of the plant we needed,” Machisko explains. The installation was completed with no surprises. “For this size system, the pumping rack comes pre-fabricated. We just had to pour a base and a crane dropped it on. The contractors didn’t have to hook it up; it was pre-tested. All the pumps were aligned. It’s very efficient. It was easy to install because we had the infrastructure set up from the beginning.”
Working the System
MBRs combine conventional activated sludge processes with the physical barrier of hollow-fiber ultra filtration membranes to treat wastewater for reuse in municipal or industrial applications such as irrigation, groundwater recharge, or process water. This allows communities to substitute the reuse water for potable water, thereby reducing the demand on natural water resources and municipal infrastructure.
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| The pumping rack on the system is prefabricated. The only required assembly is
that the foundation be connected to the structure onsite. |
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Photo: GE Water & Process Technologies |
| The barn-like style blends in with the rest of The Manor. |
ZeeWeed immersed ultra filtration membranes are hollow fibers developed specifically for the high-solids environment of a bioreactor. Each plastic membrane fiber contains billions of microscopic pores with an average diameter of 0.04 micron. The membranes remove virtually all fine, suspended particles, including 99.99% of bacteria and viruses.
Thousands of membrane fibers are bundled and suspended in modular cassettes connected to collection pipes, forming a physical barrier against suspended solids and colloidal material. The cassettes are immersed into the mixed liquor of the bioreactor where slight vacuum creates suction with the fiber, drawing clean water inside through the pores of the membrane fiber while blocking contaminants.
Wastewater is screened before being diverted to an anoxic chamber for denitrification, to the bioreactor for nitrification, and then to the ZeeWeed membrane process tank for filtration. Permeate pumps pull the wastewater through thousands of membrane fibers, each of which is filled with billions of microscopic pores that physically block suspended solids, bacteria, and viruses in order to provide high quality and clarity continuously. Once inside the membrane, the permeate flows to a central permeate collection header and on to a permeate storage tank. The water is further disinfected with ultraviolet lights, ozone, and chlorine before entering purple pipes on its way to home sites or the golf course for irrigation.
Because the system removes solids by filtration rather than settling, the process is more effective than traditional treatments and can operate at a higher mixed-liquor suspended solids-concentration.
Membrane filters are automatically cleaned with a clean-in-place back-pulsing process that reverses the flow of filtration and forces permeate water back through the membrane pores to dislodge particles. Aeration removes debris from the fibers and provides mixing inside the process tank to maintain solids in suspension. Chemical cleaning can be performed if necessary. Permeation, cleaning, and monitoring are automatically performed.
Z-MOD MBR systems can handle flows from 5,000 gallons per day (gpd) to over a million gpd. Currently, the Z-MOD system is treating 500,000 gpd, but it’s capable of treating up to 600,000 gpd with the additional membrane cassettes in the membrane process tank. A flow of 1 million gallons per day can be treated during peak wastewater production.
The system features full process redundancy so it can operate at full capacity during cleaning or maintenance. The Manor Golf and Country Club is handling maintenance on the system. “It’s designed to run automatically,” Hartman says, adding that only trained and licensed wastewater operators can work on it. Maintenance duties are eased by the remote capabilities of the system. “We can adjust the parameters and do other things remotely by computer.”
Machisko confirms that the system requires a minimal amount of maintenance, which to date has been preventive only. In addition to maintaining the biological system, the 10 pumps and blowers need only routine oil and grease. The membranes require a recovery clean with chlorine every six to eight months. “By permit, we need only one person here four hours a day.”
He remains pleased with the choice. “We were able to produce high-quality water from the start. Replacing septic tanks is also a positive.” Although he says he can’t break down the cost savings, just the fact that residents and groundskeepers will have water all summer is enough of a benefit to justify the expense. “It’s nice that we’re not withdrawing water from the Chattahoochee.” The Chattahoochee River is only a few feet deep in some areas, making it susceptible to pollution—particularly during hot summers. A drought-proof supply of sustainable water that is not susceptible to the same kind of ownership disputes some aquifers and surface-water sources endure is a decided benefit to a community.
Growing Trend
Four of the 16 counties in Georgia’s MNGWPD are currently using or constructing MBR treatment plants, but it’s California leading the way. The state’s stringent water reuse regulations are being used as the basis for water reuse programs throughout the country. California’s Title 22 regulations specify the bacteriological water-quality standards for treated effluent based on the potential for human contact, with treatment varying in degree, based on the intended application for the water: indirect potable reuse, irrigation, or industrial processes.
As awareness of the issue of water reuse increases, so does emphasis on guidelines. The EPA released a revised version of its 1992 guidelines for water reuse. Twenty-five states used the guidelines to establish regulations for water reuse in non-potable urban, industrial, and agricultural applications. Most have documented treatment guidelines that specify effluent-quality requirements for reuse, and some even stipulate the specific treatment technology. The EPA recognizes MBR technology as an advanced treatment process with additional advantages over conventional systems. The high-quality effluent produced by MBRs meets the requirements of National Pollutant Discharge Elimination System permits granted by the EPA. The permits apply restrictions to the pollutants that can be released into bodies of water from point sources. Each discharging facility must monitor effluent quality and pollutants such as five-day biochemical oxygen demand, total suspended solids, pH, fecal coliform, chemical oxygen demand, ammonia, nitrogen, and phosphorus.
In addition, MBRs are being used by municipal and industrial dischargers in order to meet new standards mandated by the EPA’s total maximum daily load (TMDL) program that supports section 303(d) of the Clean Water Act requiring all states to develop a list of bodies of water that don’t meet water-quality standards. Classified as impaired, the bodies of water incorporate a TMDL program to restore quality. According to the EPA, more than 218 million people live within 10 miles of an impaired body of water, contaminated by excessive nutrients, harmful microorganisms, and other sources of pollutants that impede the water body’s ability to assimilate pollution. Point dischargers including municipal and industrial wastewater treatment plants frequently have to upgrade their technology to comply with EPA regulations.
Regulations drive MBR technology, and many communities are turning to them to ensure compliance with increasingly stringent water-quality regulations. Recycling is another driver. High-quality effluent, a compact footprint, ease of operation, low odor and noise, and customizable architecture make MBRs appealing to an increasing number of wastewater treatment plants.
The technology isn’t exactly new, says Hartman. The first ZeeWeed MBR system was commissioned 12 years ago and there are currently 300 MBR systems in operation, with about 40% of those for water reuse applications. “As the discharge requirements become more stringent, people are looking ahead. The City of Atlanta is building a purple pipe network.” Purple pipes indicate reused wastewater. The MNGWPD predicts that within 20 years, Atlanta will rely heavily on recycled water and will be able to reduce its reliance on traditional water resources by 10% to 15%.
Some people are also looking at the bottom line. MBR systems are cost-effective, reducing utility bills. A few communities have taken the economics of it one step further. Hartman refers to Marco Island, FL, a community that sells its recycled water back to the city. “Because it’s about half the cost of potable water, it saves a lot of money. It’s a source of revenue for the city. It’s also a source of pride. People like the idea of recycling water. This is water that’s usually dumped: Nobody used it. Marco Island has turned it into a situation where everyone wins.”
Some communities are considering an even bigger step. Direct potable reuse is not uncommon in many Latin countries but is not widely accepted in the US. However, some cities such as San Diego and Tucson have considered the use of recycled water to meet future drinking-water needs. Often, the water is indirectly reused in potable water supplies through groundwater recharge or by being blended into surface-water sources like lakes, rivers, and reservoirs. In addition, groundwater supplies along the coast can be protected from seawater intrusion by injecting recycled water into coastal aquifers. The Manor Golf Course and Country Club is using recycled water for irrigation only, but with growing populations straining the natural resources of many communities, the use of MBRs is anticipated to expand.
MBR technology has been tabbed as an efficient and cost-effective alternative to treating wastewater for recycling and environmental stewardship. “Our approach is a holistic one,” Tony Kobilnyk, marketing specialist for Zenon Membrane Solutions, summarizes. “Conservation and responsible use are one aspect, but where it is necessary, technology can play a larger role in recycling water for many uses—irrigation, industry, and even drinking water.”
Residing in Indianapolis, IN, Lori Lovely writes authoritatively on transportation and technical subjects.
OW - July/August 2007 |
