July 2008, Vol. 20, No.7
Blazing the Nutrient-Removal Trail
One state’s efforts to stay ahead of the compliance curve
Brian L. Book
Like many other professionals involved in the water quality industry associated with Pennsylvania, I find many of my days focused on what to make of the Pennsylvania Department of Environmental Protection (DEP) Chesapeake Bay Tributary Strategy (CBTS). The professional community of operators, engineers, scientists, and regulators throughout Pennsylvania has been studying, planning, fighting, and embracing the future — and the need to one day perform biological nutrient removal. Now it appears this day is upon us, and we find ourselves frustrated, challenged, and confused.
Our current situation began with Gov. Tom Ridge’s June 2000 commitment to the Chesapeake Bay Partners (Maryland, Virginia, Pennsylvania, the U.S. Environmental Protection Agency [EPA], and Washington, D.C.) that we would work to remove Chesapeake Bay from EPA’s Clean Water Act Sec. 303(d) list of impaired waterways. His pledge in part requires us by 2010, to “correct the nutrient- and sediment-related problems in the Chesapeake Bay and its tidal tributaries sufficiently to remove the Bay and the tidal portions of its tributaries from the list of impaired waters under the Clean Water Act.”
The Chesapeake 2000 Agreement forms the basis for our current goals under CBTS. But, as a community, we have struggled with the meaning of this commitment.
Kathleen McGinty, DEP secretary, required cap loads on all major wastewater treatment plants in the Susquehanna River Basin. (In Pennsylvania, we consider all plants permitted at or greater than 1514 m³/d [400,000 gal/d] to be “majors” for this program.) When first announced, these cap loads were to be based on 2010 projected flows at an effluent quality of 8 mg/L total nitrogen (TN) and 1 mg/L total phosphorus (TP).
These announcements were met with shock and, at times, objections from segments of our industry. In response, DEP created six stakeholder committees to review and ultimately propose changes to the strategy while still meeting the overall goals of nutrient reduction as measured by the total mass load in the Susquehanna River where it crosses the Mason–Dixon line. In spring 2006, a revised CBTS — which changed the cap load calculation to 6 mg/L TN at permitted and designed flow and 0.8 mg/L TP on the same flow basis — was presented. These cap loads, along with a nutrient trading program, now dominate the landscape of our industry.
When announcing the nutrient cap loads, McGinty referenced several pilot nutrient-removal programs in Pennsylvania that already have demonstrated success:
- Towanda Borough was able to reduce its TN contribution by making operational changes, which also reduced its overall operational costs.
- Operational changes to the Wyoming Valley facility for a period of approximately 7 years produced consistently higher-quality effluent than required while reducing electrical and chemical costs.
- The City of Sunbury completed an upgrade to address various issues, including combined-sewer overflows, dwindling capacity, and aging infrastructure. In the process, the city included nutrient reduction.
- Eastern Snyder County Regional Sewer Authority included nutrient reduction technology as part of a scheduled general upgrade. According to the manufacturer, the facility will be capable of producing TN concentrations at design flows of 3 mg/L.
While these case histories are valid, they are not necessarily representative of other municipalities’ experiences. We have had more recent successes in Pennsylvania that merit consideration as we struggle with accomplishing the overall goals of the Chesapeake 2000 Agreement.
University Area Joint Authority
The University Area Joint Authority (UAJA) began its “2002 Stage 6 Additions & Modifications Beneficial Reuse” project to accomplish local goals. Specifically, UAJA faced the need to expand its water pollution control facility to support the robust economy in and around Pennsylvania State University (State College). These economic demands were made more complex by the fact that the only local waterbody is a rather small, high-quality trout stream known as Spring Creek.
During the 1998–2000 planning of the 2002 expansion, UAJA participated in a pilot study in which biological activity meters were used to fine-tune the blower systems and maximize denitrification in the authority’s existing tanks. This pilot project demonstrated that the plant could reduce the operational blower horsepower by approximately 25% while reducing the overall TN discharge to the bay to approximately 15 mg/L TN and maintaining biochemical oxygen demand (BOD) of less than 10 mg/L.
Building on the pilot study and community desires, UAJA implemented a 39,970-m³/d (10.56-mgd) advanced wastewater treatment plant with nitrification–denitrification and water reuse capabilities for 17,260 m³/d (4.56 mgd) to meet local requirements and overall efficiency goals. A benefit of the initial design was a TN discharge of 7 mg/L on the 22,710 m³/d (6 mgd) sent to Spring Creek (the portion not available for reuse), with TN below detectable limits on the reuse water. Having seen the final version of the Chesapeake Bay Tributary Strategy, UAJA has been testing carbon augmentation systems and plans to achieve a TN of 5 mg/L on the 22,710-m³/d (6-mgd) stream discharge.
At full scale, this project reduces the TN loading to the Chesapeake Bay watershed by 177,360 kg/yr (391,000 lb/yr). The project was almost totally financed by UAJA customers (full-scale cost is anticipated to be $75 million, and to date only a $950,000 grant from the U.S. Army Corp of Engineers was used), with a resulting user rate of less than $350 per household per year. Currently, the biological processes and systems are in place for the nitrification–denitrification treatment, and capacity exists to produce a nominal 3785 m³/d (1 mgd) of reuse water.
Berwick Area Joint Sewer Authority
Currently under construction, the Berwick Area Joint Sewer Authority (BAJSA) began planning a project concurrent with the initial presentation of CBTS in 2004. Unlike other examples cited previously, BAJSA decided that the best approach for its customers was to rush to the front of the line and maximize its share of available financial assistance offered in exchange for early compliance. In its current configuration, the BAJSA plant is permitted for 13,780 m³/d (3.64 mgd) from the Borough of Berwick and five adjoining municipalities. BAJSA operates an oxidation ditch but is required to meet secondary limits for BOD and total suspended solids.
BAJSA began operational modifications (a pilot program to test a potential modification) to reduce the overall dissolved-oxygen concentration in its oxidation ditches. As part of the pilot, the return activated sludge was controlled manually as well to encourage simultaneous nitrification and denitrification. The pilot demonstrated a reduction in the annual average TN discharge from approximately 20 mg/L to approximately 10 mg/L. While successful, this effort was difficult to maintain on a consistent basis, as the plant is staffed 5 days per week and two shifts per day.
Based on the pilot testing, BAJSA designed a plant upgrade to convert the two parallel oxidation ditches to series operation. The first oxidation ditch then was converted to an environment that encourages simultaneous nitrification and denitrification in an underloaded aerated environment. Internal recycles were added to provide the necessary carbon recycle, and the return activated sludge is also pretreated and conditioned in an anoxic tank before return.
Ultimately, BAJSA received a $500,000 Growing Greener Innovative Grant and a $2.2 million grant from PennVEST — an agency that funds sewer, stormwater, and drinking water projects throughout Pennsylvania — and the remaining costs were funded with loans from PennVEST on a total project cost of $7 million. This project, which at press time was operating on a limited basis and expected to be complete in June, will help the plant achieve TN of 5 mg/L and TP of 0.5 mg/L. This change will effectively remove 75,300 kg (166,000 lb) of TN and 10,000 kg (22,000 lb) of TP per year from the bay watershed while allowing BAJSA to maintain user fees within its multiple rate districts of approximately $300 to $540 per year per household.
At the same time that nutrient removal has become the focus in Pennsylvania, there has been a resurgence in alternative fuels nationwide. Several projects in Pennsylvania are designed to attack both issues at the same time.
For instance, a collective of dairy farms surrounding the Borough of Martinsburg has implemented a pilot program to capture and treat manure from approximately 6500 head of dairy cattle. These cattle are overloading the ecosystem, and groundwater in the area has TN in the range of 10 mg/L. The project, known as the Cove Area Regional Digester, aims to reduce the nutrient load stressing local groundwater sources and its impact on the surrounding drinking water supplies. It also has the goal of generating electricity to offset operational costs.
The pilot system, funded through a grant from the Chesapeake Bay Commission, has proven the validity of the design and energy production. It also has proven the system capable of reducing the TN to Chesapeake Bay by 358,344 kg/yr (790,000 lb/yr). This $30 million project is intended for full-scale operation before the 2010 deadline for removing Chesapeake Bay from the Sec. 303(d) list. It becomes financially self-sustaining at nitrogen credits of $1.10/kg•yr ($0.50/lb•yr) with electricity at $0.04/kW•h. With current credit projections of $20/kg•yr ($9/lb•yr), all the Cove Area Regional Digester needs is a willing buyer of credits to participate in the bay cleanup and also begin to generate renewable power.
Similar ideas have driven the Milton Regional Sewer Authority (MRSA) to consider a plant expansion and upgrade. MRSA receives more than half of its nutrient loading from the historic Chef Boyardee facility owned and operated by ConAgra (Omaha, Neb.). MRSA is permitted for 12,260 m³/d (3.24 mgd) and is considering a plant expansion to 17,030 m³/d (4.5 mgd). In part, this expansion will look at the potential to accept trucked-in waste from surrounding systems. It also would expand into a larger service area while rehabilitating the existing plant.
If regionalization is successful, four smaller plants that are not capable of nutrient removal could be eliminated. At the same time, the facility, which combines anaerobic treatment of wastewater with conventional technologies, will treat trucked-in liquid wastestreams that are not receiving any mechanical treatment. Finally, the effluent quality of the existing facility would be improved significantly. It is anticipated that this project, which costs approximately $35 million, will remove approximately 45,360 kg (100,000 lb) of nitrogen per year from the bay while producing more energy than it uses for that treatment.
There remain a great deal of concern and uncertainty about Pennsylvania’s Chesapeake Bay Tributary Strategy. Upgrading 186 major wastewater treatment plants between now and 2014 is a big challenge. Furthermore, meeting the mandate for upgrades — originally estimated at between $400 million to $1.5 billion and now suggested to be $10 billion or even $20 billion — will be difficult. In fact, the Pennsylvania Legislature is considering a new study to determine the estimated cost of CBTS, and several professional organizations have banded together to propose a $1 billion funding program. But, in spite of the fear of the unknown, a handful of trailblazers already have begun to show the Keystone State that point source nitrogen and phosphorus reductions can be implemented affordably.
Brian L. Book is vice president of Water and Energy Services at Herbert, Rowland & Grubic Inc. (Harrisburg, Pa.).