The Cleanest Effluent In The Country?

The Maryland Environmental Service (MES) operates the Eastern Correctional Institution Wastewater Treatment Plant (ECI WWTP) located in Westover, Maryland. The Maryland Department of Environment (MDE) issued a revised discharge permit which imposed extremely strict nitrogen and phosphorus limits in accordance with the Chesapeake Bay Total Maximum Daily Load requirements. In addition, the permit required combining the waste stream from the onsite reverse osmosis drinking water purification system with the WWTP effluent in a single discharge point to the Manokin River which was still subject to the total nutrient loading limits. These new permit conditions required a complete upgrade of the existing advanced wastewater treatment facility. Major project challenges included fitting all the new treatment processes within the existing plant footprint which is extremely tight; bordered on one side by a prison and the other by a road. Further there were budgetary constraints. When the original design went out for bid, the low bid was $34 million, while the budget was $22 million. The contractor and engineer presented four treatment options to MES ranging in cost from $22 million to $26 million. The selection of precast post-tensioned process tanks greatly enhanced the project schedule and shaved nearly 9 months of schedule versus cast-in-place concrete. The new discharge limitations presented a significant technical challenge to MES and the design team. The term 'enhanced nutrient removal' (ENR) is generally considered to be the highest goal for any facility resulting in discharges at or below 3.0 mg/l for total nitrogen and 0.3 mg/l for total phosphorus. MDE set fixed loading limits (lbs/day) for each of these nutrients in the new discharge permit, while requiring the waste streams from the adjacent drinking water purification system be combined with the WWTP effluent. The result of these new requirements is that the nutrient concentrations needed to be reduced well beyond the ENR level (1.26 mg/l TN; 0.13 mg/l TP). During design, research performed by the team revealed several facilities which have documented performance at the reduced nutrient levels for either nitrogen or phosphorus, but no facilities which were reaching both levels simultaneously. Based on this information and dynamic process modeling, the team developed a treatment process sequence to allow operators to focus on driving each nutrient concentration down to the lowest levels possible, while maintaining flexibility in seasonal operation. The team applied several existing technologies to produce treated effluent which may be the cleanest in the nation. The primary biological treatment utilized a four-stage Bardenpho process with membrane filtration which is capable of meeting ENR levels and is frequently the only nutrient removal process required. However, to meet the extremely low nitrogen levels required, post-denitrification filters were installed. A ballasted flocculation system was installed to allow separate phosphorus removal as well as additional organic nitrogen removal. These processes were followed by ultraviolet disinfection and post-aeration to ensure full permit compliance. To support the project, the design team incorporated professionals from almost every major engineering discipline. Multi-media collaboration through site visits, in person meetings, conference calls, virtual meetings and data sharing sites allowed for coordination among the disciplines as well as between the owner, engineer, and contractor. The design team put great effort into documenting existing infrastructure (above and below grade), understanding operating limitations, and developing a proposed solution that would not only meet the treatment requirements but would also physically fit on the site and could be phased to allow for construction. In addition to addressing the technical issues associated with the discharge limits, the project faced significant challenges relating to schedule and budget constraints. Initial attempts to complete the project using a traditional design-bid-build approach were not successful. MES was willing to adjust the scope to align with the available budget but needed some form of price surety to allow for informed decisions to be made. KCI assisted MES to evaluate several options including alternate-delivery methods such as Design/Build and Construction Manager at Risk (CMAR). After careful consideration, MES selected CMAR as the preferred method while retaining KCI as the owner's agent and engineer of record. The major advantage of the CMAR approach is that the owner secures a guaranteed maximum price early in the project and the owner, engineer, and contractor are all able to work collaboratively through the final design, permitting, and construction. During construction, constant communication through progress meetings, weekly calls, site visits, etc. facilitated a true sense of teamwork moving to a common goal. In addition, over 540 shop drawings and 123 RFIs were processed to ensure project requirements were met. The project was constructed on time (728 calendar days) with no increase in budget from the Guaranteed Maximum Price ($24M) established by the CMAR team. As a result of the project, the new treatment process has an expanded capacity just under 1.0 MGD and is consistently producing effluent with less than 1.0 mg/l total nitrogen and 0.15 mg/l total phosphorus. The performance of the newly upgraded facility is proving that it is possible to reach extremely low levels of nitrogen and phosphorus at the same time. However, the reduced nutrient levels also require a significant capital and operations cost. The upgraded facility could provide a case study for future TMDL decisions as well as a testing facility for the unique combinations of treatment processes. The comprehensive control and monitoring system will allow real time performance review and analysis. This project provides a real-life cost/benefit analysis opportunity to allow broader infrastructure investment decisions to be better evaluated. In addition to the wastewater treatment value, the project performance also supports the viability of alternate delivery methods such as CMAR even for technically specialized and complex projects such as WWTP upgrades. The collaboration between the owner, engineer, and construction team, maintained control of the schedule and budget, avoiding possible delays and change orders.
Construction Costs: 24.4M
Design Team Total Fees: 2.5M (includes design and construction administration)
Construction Schedule: NTP–June 17, 2019 |
Substantial Completion–May 13, 2021