AlexRenew

In April the Potomac Watershed Roundtable met at AlexRenew in Alexandria, Virginia. In the morning meeting Karen Pallansch, the Chief Executive Officer of Alexander Renew spoke about AlexRenew, one of the most advanced waste water treatment plants in the United States. AlexRenew has more than 100 employees at their advanced waste water treatment plant that covers 35-acres in Alexandria. AlexRenew calls their plant a “Water Resource Recovery Facility” because it is far advanced of the sewage treatment plants of the past. The plant processes about 13 billion gallons of wastewater each year into clean water and reusable resources- Class A Biosolids.

During the past eleven years under the leadership of Ms. Pallansch, the waste water treatment plant was rebranded Alex Renew and saw significant treatment upgrades. Ms. Pallansch oversaw the implementation of a strategy that incorporated a successful public-developer partnership, creating a neighborhood from an area that once served as a City of Alexandria landfill. The new site, which opened in 2016, includes a LEED Platinum Environmental Center with an educational lobby. The building uses AlexRenew’s reclaimed water and is powered in part by solar energy and is where our meeting was held. Next to the building is an Envision Platinum Nutrient Management Facility topped with a multipurpose artificial turf field operated and maintained by The City’s Parks Department.

In short, AlexRenew is an innovative and inoffensive (it really doesn’t smell) waste water treatment plant and I had wanted to tour the facility since I read about it in Rose George’s excellent book “ The Big Necessity; the unmentionable world of Human Waste and why it matters.” I was not disappointed. You can take a virtual tour or sign up for an actual tour.

Before the tour Ms. Pallansch briefly spoke to the group about the history and operations of Alex Renew and in broad strokes of how they will help Alexandria meet the state legislative mandated timeline for solving the combined sewer overflow problem in Alexandria. There is an area of the City, mostly around Old Town that has a Combined Sewer System. This combined system is a piped sewer system in which there is one pipe that carries both sanitary sewage and stormwater to the local wastewater treatment plant. This was how sewer systems were commonly built in the days when sanitation was simply moving sewage out of the city to the rivers and streams. Back then one piping system was cheaper and adequate for the job.

However, today when sewage is treated by waste water treatment plants, the rain water that falls in the street and enters the storm water drains is combined with the sanitary waste water entering the sewers from homes and businesses. The combined flow can overwhelm the waste water treatment plant. So, to protect the sewage system as a whole, the combined sewage and rainfall is released into the local creeks in a controlled and planned fashion out of the “Combined Sewer Overflows” which are release locations permitted and monitored by the regulators.

Now Alexandria is under mandate from the state legislature to eliminate this problem by 2025. Though the state issued a mandate, they did not offer any funding to Alexandria or the right solution. In order to accomplish this, Alexandria has transferred ownership of the outfalls and the interceptor lines (the sewer mains transporting to the raw sewage to the treatment plant) to AlexRenew.

AlexRenew has taken the lead and based on feedback received during the Stakeholder Group process, they developed a plan that includes building a tunnel system with:

• Storage tunnels 
• Conveyance tunnels 
• Diversion facilities (diversion chambers and drop shafts) 
• Dewatering pumping stations 

AlexRenew upgrades including:

• Wet weather pumping station 
• Increase treatment peak capacity from 108 to 116 million gallons a day 
• Wet weather treatment utilizing existing and improved facilities at the AlexRenew plant. 

Unfortunately, without funding from the state Alexandria residents will have to pay for the full project costs which are estimated to cost between $22-$40 per sewer connection per month to finance a project that is estimated at over $340 million.

Recycled Water in Fairfax, Virginia

All the water that ever was or will be on earth is here right now. More than 97% of the Earth’s water is within the in oceans. The remaining 2.8% is the water within the land masses, as groundwater, rivers, streams, lakes, and within the ice caps and glaciers (over 77% of fresh water is currently frozen). Only a fraction of water falls as rain each year to make the rivers flow, recharge lakes and groundwater. The water on earth never rests, it is constantly moving within the hydrologic cycle along various complex pathways and over a wide variety of time scales. Water moves quickly through some pathways -rain falling in summer may return to the atmosphere in a matter of hours or days by evaporation. Water may travel through other pathways for years, decades, centuries, or more. As the demand for water grows in our population centers, we are straining to meet the demand. Even in generally water rich areas there are limits to the availability of water and United States has slowly and quietly begun to address the availability of water by recycling the water.

Direct water recycling is reusing treated wastewater for beneficial purposes such as agricultural and landscape irrigation, industrial processes, toilet flushing, and replenishing a ground water basin (referred to as ground water recharge) and less commonly returning the water directly to reservoirs. Since 1978, the upper Occoquan Sewage Authority has been discharging recycled water into a stream above Occoquan Reservoir, one of the two potable water supply sources for Fairfax County, Virginia. Recycled water has been part of the Occoquan supply for 34 years and chances are if you are in Fairfax, parts of Prince William and Loudoun counties you have been regularly drinking recycled water. Noman M. Cole, Jr., a very forward thinking engineer, developed the Occoquan Watershed Policy in 1971. This policy was the acknowledgment that to continue supplying the region with drinking water, the Occoquan Reservoir would be used both for wastewater disposal and public water supply. To do this and protect public health the Occoquan Watershed Policy not only specified the type of waste treatment practices that would have to be adopted on a basin-wide scale, but it provided for an on-going program of water quality monitoring to measure the success (or failure) of the waste water treatment. This resulted in the construction of the Upper Occoquan Service Authority, UOSA, advanced wastewater treatment plant with tertiary treatment to replace the eleven small secondary treatment plants.

Wastewater treatment within the basin would have three stages of treatment, primary, secondary and tertiary or advanced treatment.  Primary Treatment consists of sedimentation and screening of large debris using screens and large settling tanks. Until 1960’s primary treatment was the only form of sewage treatment in most places. Secondary treatments usually include biological and/or chemical treatment. One of the most common biological treatments is the activated sludge process; in which primary wastewater is mixed with bacteria that break down organic matter and cleans the water. Oxygen is pumped into the mixture. A clarifying tank allows sludge to settle to the bottom and then the treated wastewater moves on for tertiary treatment. Coagulation, filtration and disinfection take place in tertiary treatment. A coagulant is added, UOSA uses the high-lime process to reduce phosphorus to below 0.10 mg/L. This process also serves as a barrier to viruses, captures organics leaving secondary treatment, and precipitates heavy metals and other suspended particles. The UOSA permit requires total suspended solids, TSS, below 1 mg/L and chemical oxygen demand, COD, below 10 mg/L. To meet these stringent levels, multimedia filtration and activated carbon are used. Filtration removes organic matter, microorganisms and mineral compounds, and excess nutrients. The final barrier to pathogens is a chlorination and dechlorination process. UOSA uses sodium hypochlorite and sodium bisulfite. UOSA is has an expansion program underway to expand capacity to 54 million gallons a day, but according to 2012 Fairfax County disclosures, the plant currently operates closer to an average of just over 13 million gallons a day.

After disinfection the reclaimed water is released to the watershed cleaner than the rest of the river, according to Dr. Tom Gizzard ofthe Occoquan Watershed Laboratory. Financed by the wastewater treatment plants and Fairfax Water, the Occoquan Watershed Laboratory (OWL), was established by the Virginia Polytechnic Institute Department of Civil Engineering. The laboratory began its Fairfax operations in 1972, and has conducted comprehensive studies of receiving water quality, and effects of the waste water treatment effluents for 40 years. The current Director of the Laboratory is Dr. Tom Grizzard, professor of Civil Engineering at Virginia Polytechnic Institute and State University (Virginia Tech). When I spoke to Dr. Grizzard he pointed out that the water released into the Occoquan is “highly reclaimed wastewater” and not sewage effluent. There is a difference and Dr. Grizzard and the OWL staff make sure of it.

The Occoquan Watershed Policy is the oldest and largest reservoir augmentation program in the county and the second largest water recycling program in the country. The largest water recycling or reclamation program in the country and in the world belongs to the Orange County Water District and the Orange County Sanitation District jointly owned and developed the Groundwater Replenishment (GWR) system, the world’s largest water purification plant for groundwater recharge. The GWR System diverts secondary treated sewer water and purifies it through a series of tertiary treatments: microfiltration, reverse osmosis, ultraviolet disinfection and hydrogen peroxide. The cleaned water is returned to the groundwater basin to increase both the water supply and quality rather than discharging the treated sewer water to the ocean. The additional treatment of the wastewater is much cheaper that desalinization and makes the groundwater use sustainable-utilizing the groundwater basin as a reservoir.

In Fairfax County Virginia, water is withdrawn from the Potomac River and the Occoquan Reservoir and filtered, cleaned, disinfected and delivered as drinking water to the homes and businesses throughout the county (and in parts of Prince William and Loudoun Counties). Waste water from toilets, sinks, drains is collected by the sewer systems and six waste watertreatment plants that serve some portion of Fairfax County.  On average, Fairfax County uses 160 million gallons of drinking water per day from both the Corbalis plant and the Griffith plant drinking water plants. The combined total capacity of both plants is 345 million gallons/day. The drinking water systems are sized to deliver the peak demand on a 100 degree day when everyone is doing laundry and watering their lawns and everything else we do with water on hot summer days.  Most of that water (except what is used to irrigate landscaping) finds its way to a waste water treatment plant within the region. The wastewater processed in Fairfax County is fully treated and released into the river and streams of the Potomac watershed. (We will ignore the issues currently being addressed at Blue Plains.) To ensure the continuation of water supply during droughts, Fairfax is party to a low flow allocation agreement with the members of the Interstate Commission on the Potomac River Basin, ICPRB. In addition, Fairfax bought the rights to 14 billion gallons of water from the Jennings Randolph Reservoir. On an ongoing basis ICPRB coordinates Fairfax Water’s low flow water withdrawals between the Potomac and Occoquan. The Occoquan Reservoir contains 11 billion gallons that receives both natural river flow and about 13 million gallons of reclaimed water daily.

From Fairfax County

Noman M. Cole, Jr. Pollution Control Plant (named in honor of the engineer) is now engaged in a direct water recycling program, reusing treated wastewater for landscape irrigation and industrial processes. The Noman Cole plant releases its reclaimed water to Pohick Creek. Now the plant is engaged in the Water Reuse Project also known as the Purple Pipe Project, to directly reuse some of the water. (The pipes are colored purple to designate the water as non-potable.) The Purple Pipe project has completed the first phase of the project and is delivering 1.4-1.6 million gallons of fully treated waste water to the Covanta Fairfax, Inc. Resource Recovery Plant and Laurel Hill Golf Course via a recently constructed 5 mile purple pipeline, two large pumps, instrumentation and hypochloride disinfection. The Laurel Hill Golf Course will use the water to augment the on-site irrigation lake during the summer. Due to recent rains, the demand for water by the golf club is limited, but according to Michael McGrath the Director, Wastewater Treatment Division, Department of Public Works and Environmental Services, for Fairfax County, the Laurel Hills Golf Club can draw up to 27 million gallons a year of reclaimed water from the Noman Cole Plant. The Covanta Resource Recovery Plant is allowed to use up to 560 million gallons a year of Purple Pipe Water to irrigate the adjacent athletic fields and other purposes. The Noman Cole plant discharges and average of 45 million gallons a day to Pohick Creek, so this is just a small fraction of the daily flow.  The reclaimed water from Noman Cole makes up a significant flow to Pohick Creek so that there is a minimum environmental flow that should continue, but there is opportunity for growth in the Purple Pipe Project.

The project, which began in 2009, cost $16 million for the first phase (or about $600 per foot) with $6.5 million in funding coming from the federal stimulus funds through the American Recovery and Reinvestment Act, and the remainder was paid for by Fairfax county through a loan from the Virginia Department of Environmental Quality Clean Water Revolving Fund Loan Program. In the first partial year of operation the project will produce about 20,000 credits for Noman Cole Plant in the Virginia Nutrient Trading Program in addition to the reduced cost water. Nutrient trading programs provide wastewater treatment plants with flexible options for meeting and maintaining permitted nutrient load limits, but also could be used to meet the approximately 25% reduction in nutrients required under the federally mandated Chesapeake Bay TMDL. A nutrient credit is a reduction of one pound of nitrogen and worth (at the current time) $2. Though the first phase of the Purple Pipe Project will generate more credits next year, still at $2 per credit plus the price received for water and costs or $600 per foot there is virtually no way for Fairfax to utilize Purple Pipe to meet the TMDL goals or increase water supply without a significant rate increases for water and large volume users. If using reclaimed water is necessary for the region to maintain its quality of life, the cost of water will have to rise to cover the costs because we are already using all the cheap water.

The numbers break down like this: this project would have to produce cash flow of about $918,000 per year (rather than the projected under $200,000 for water and nutrient credits) to pay for the $16,000,000 cost at 3% interest (current AAA interest for 20 year bonds is above 3%) over 25 years.  (Though for this project the $6.5 million from the federal stimulus funds does not have to be repaid.) The Purple Pipe project is a very cool project, but at the current cost of water the capital costs are prohibitive. Or maybe, we've just had a glimpse of the marginal cost of water.

  

Blue Plaines From the Past to the Future

AECOM Picture

The District of Columbia's sewage system, one of the oldest in the United States, began its story around 1810, when the first sewers and culverts were constructed to drain storm and ground water from the streets of Washington D.C. In 1815 the canal system was built and included the Washington Canal that ran down what is now Constitution Avenue. The canal system provided a convenient way to transport goods, provide access to water and also dispose of waste. Residents drew their water from a series of city owned springs. In the first half of the 1800’s streets in Washington began piping in spring or well water for residents' use, and sewage was discharged into the nearest body of water- often the canals.

The Washington Aqueduct bringing river water for potable use citywide was built in the 1859 when population growth required a dedicated clean drinking water supply. Lieutenant Montgomery C. Meigs, is credited with planning and building the Washington Aqueduct. The surge in population during the Civil War, quickly created a human waste problem in the city and there were epidemics of smallpox, typhoid and malaria, which took many thousands of lives during the war years. From 1871 to 1874, the city’s Board of Public Works built an estimated 80 miles of sewers to remove the human waste from the city. Although the amount of construction was impressive, sewer engineering and hydrology were in their infancy and much of the work was poorly planned, structurally unsound and hydraulically inadequate, but the vitrified clay and brick sewers remain part of the sewer system to this day. In the early 1880s when the Washington City Canal was covered over because it had become nothing more than a stagnant open sewer, the problem of open sewage was transferred to the marshes along the Potomac and Anacostia Rivers.

Up to this time, the sewer canals and pipes that served DC were a combined system that merely carried and discharged (without treatment) both sanitary sewage and stormwater into local creeks and rivers. In the 1890s, it was decided that the existing combined system should be retained (due to the costs of rebuilding the sewers as separate systems), but that any extensions of the system would be built using the more expensive system of separate lines to carry stormwater and sewage flows. In order to protect the health of city residents, who were drinking the river water provided by the Washington Aqueduct, all the sewage discharges would be extended away from the city to a point far enough down the Potomac River to prevent being taken up in the Aqueduct for drinking water. The discharge point selected was Blue Plains, the southernmost tip of the District of Columbia. Pumping raw sewage into rivers was state of the art in the 1800’s. Washington DC did not start treating the sewage waste until 1937 when the Blue Plaines sewage treatment plant was built.

Today, sitting on the southernmost tip of Washington DC, across the river from Alexandria is the Blue Plains Advanced Wastewater Treatment Plant. While there are larger sewer treatment plants, that remove the solids and bacteria, the modern day Blue Plains also has Tertiary Treatment to remove nitrogen and phosphorus making Blue Plains the largest advance treatment plant in the United States at 150 acres and with a rated annual average day capacity if 370 million gallons per day (mgd) and a peak wet weather capacity of 1,076 mgd. The system needs such a large storm rated capacity to accommodate the old central city section which accounts for one third the area of the District and still has the old combined sewer system that overflows with predictable regularity during large storms. The system has released excess storm flows averaging 54 million gallons per year to the Anacostia River. In addition, Blue Plains is under a consent order from the Environmental Protection Agency, EPA, to meet new effluent limits for total nitrogen released and better control of the system during storms.

Being an advanced waste water treatment plant is not as modern as it sounds. At Blue Plains and other sewer treatment plants primary treatment screens wastewater, and performs some rudimentary treatment to remove crude solids of human waste and skim off grease, oil and fat. Wastewater sits in settling tanks, which are designed to hold the wastewater for several hours. During that time, most of the heavy solids fall to the bottom of the tank, where they become a thick slurry known as primary sludge. The material that floats is also skimmed from the surface of the tanks. Secondary (or biological) treatment involves feeding oxygen to bio-organisms that break down any organic matter still in the wastewater.

Tertiary treatment further treats the effluent water to remove nitrogen, phosphorus, fine suspended particles and microbes, and to kill or slowdown disease-causing organisms and viruses. It is the tertiary treatment that makes Blue Plains an Advanced Wastewater Treatment Plant. At this time, Blue Plains cannot remove enough nitrogen (on average over the year including storm periods) from the waste stream to meet the EPA mandated limit for nitrogen of 4.689 million pounds of nitrogen per year. In addition, when it rains and the Blue Plains AWWT plant tries to provide complete sewage treatment to flows of 600-740 million gallons a day the performance of the clarification units deteriorates because of the large flow of water, turbulence and not enough time to settle the solids and scum. The deterioration in performance cascades from the primary treatment to the secondary and onto the advanced treatment. This results in a reduced treatment for the sewage that lasts not only during the rain, but can last for several weeks. Blue Plans is currently engaged in a $7.8 billion 20 year improvement program called the Clean Rivers Project that will meet the reduced total nitrogen released requirements of their operating permits and increase the control of the system during rain storms in addition sludge treatment will be improved and sewer piping improved in many areas.

The sludge is separated from the wastewater during the primary treatment is further screened and allowed to gravity thicken in a tank. Then the sludge is mixed with the solids collected from the secondary and denitrification units. The combined solids are pumped to tanks where they are heated to destroy pathogens and further reduce the volume of solids. With treatment sludge is transformed (at least in name) to biosolids. Blue Plaines biosolids are Class B; however, after the completion of the improvement project in 2014 utilizing thermal hydrolysis (heating to over 160 degrees under high pressure) followed by anaerobic digestors, the biosolids produced by the plant will be Class A and the methane captured will provide 20% of the power for Blue Plains. To ensure that biosolids applied to the land as fertilizer do not threaten public health, the EPA created the 40 CFR Part 503 Rule in 1989 that is still in effect today. It categorizes biosolids as Class A or B, depending on the level of fecal coliform and salmonella bacteria in the material and restricts the use based on classification. The biosolids are tested for fecal coliform and salmonella and composite sampling is done for metals and hydrocarbons; the presence of other emerging contaminants in the biosolids is not tracked.

The Clean Rivers project will maintain the peak flow rate of 1,076 mgd from the collection system to Blue Plains. Peak flow rates to Complete Treatment would be reduced to 555 mgd for the first 4 hours, 511 mgd for the next 24 hours and 450 mgd thereafter. A tunnel would be constructed between Poplar Point and Blue Plains, and flows exceeding the complete treatment capacity would be diverted to the tunnel and that tunnel connected to the other tunnel storage. The storage provided by the new tunnel would be an additional 31 million gallons for a total storage in the system of 157 million gallons spread over the Anacostia River tunnels system and the new Blue Plains Tunnel. This facility will allow flow from the collection system that exceeds the complete treatment capacity of the plant to overflow to the tunnel. Flow captured in the tunnels would be dewatered through a new enhanced clarification facility, ECF, with a capacity of 225 mgd. Operating provisions would include arrangements to dewater the tunnels during and following rain and to convey ECF effluent to a direct outfall (after disinfection) and/or through the complete treatment facilities depending on the capacity available at the time.

The Clean Rivers project will also include the construction of Enhanced nitrogen removal, ENR, facilities. The new ENR facilities will have the capacity to provide complete treatment for flow rates up 555 million gallons per day for the first 4 hours, 511 million gallons per day for the next 24 hours and at a rate of 450 mgd thereafter to meet the new total nitrogen effluent limit mandated by the EPA. When completed, the Blue Plains Advanced Waste Water Treatment Plant will be able to meet the nitrogen release standard under the operating permit, reduce the number of uncontrolled storm related releases of waste.