The WEF Sustainable Utilities Task Force presents a resource for utility managers seeking examples of succesful sustainability practices

Cold Weather Design and Operational Considerations for Deep-bed Denitrification Filters to Achieve Limit-of-Technology Nutrient Removal

Back River Wastewater Treatment Plant
Baltimore, Maryland

For several decades deep bed downflow denitrification filters have proven reliable as tertiary
treatment for achieving low effluent nitrogen levels. The majority of these facilities are operating
in the southeastern region where wastewater temperatures are generally warmer. In recent years,
a number of facilities have also been installed in the mid-Atlantic region to meet nutrient
reduction requirements. While wastewater temperatures are comparably colder in this region
most of these facilities are either operating in seasonal denitrification mode (low flow, warm
period), or operating in filtration mode only (no external carbon addition) where the plant’s
upstream process is capable of meeting current total nitrogen requirements. Also, it is found that
many of these facilities are operating at lower loading conditions and therefore reported
performance data may not be representative of design conditions. In an effort to confirm the
design criteria for typical mid-Atlantic cold weather operation and year-round performance to
meet limit-of-technology (LOT) levels (TN < 3 mg/L, TP < 0.3 mg/L) required for treatment
plants in Maryland, as well as other jurisdictions within the Chesapeake Bay watershed, the
Maryland Department of the Environment (MDE) and the City of Baltimore collaborated on a
denitrification filter pilot testing program. Testing was conducted at the Back River WWTP
from January through July of 2009 and the results are presented in this paper, and compared with
performance observed at full-scale facilities.
In summary, the cold weather testing demonstrated the system’s ability to achieve effluent
objectives (for nitrate removal) at loading rates from 40-50 lbs nitrate/1,000 ft3/day. The average
hydraulic loading rates were up to 3.0 gpm/ft2, with 80-90% removal efficiency at average
wastewater temperatures of about 13 oC. During warmer weather testing the nitrate mass removal
capacity increased and the system was able to achieve lower effluent concentrations at loadings
similar to or higher than those for cold weather testing. The filter system was also hydraulically
tested during warmer weather at peak-day loading rates up to 9 gpm/ft2 (at a loading near 100 lbs
nitrate/1,000 ft3/day) while still achieving about 80% nitrate removal, demonstrating the system’s
ability to handle peak flows and loads without significant reduction in effluent quality.

Metric Used:
Posted: May 20th, 2011 | Filed under: 500K-1M, Waste Water Treatment | Tags: , , | No Comments »

Energy Sustainability and Nutrient Removal from Municipal Wastewater

The state of energy sustainability in wastewater treatment and especially nutrient removal has improved rapidly with development of new technologies and increased concerns for the environment. The ultimate goal of the wastewater treatment industry could be achieving energy self-sufficiency within a facility. The progress that has been made toward this goal with nutrient removal technologies was investigated and the challenges and opportunities facing our industry are identified in this paper. A benchmark for energy sustainability was recently achieved in Strass, Austria, where the energy usage of 1000 kwh/million gallons (MG) treated was achieved, which was actually less than the energy generated by digester gas, . This paper presents a comparison between the U.S. and Austria of potential energy use and generation, and offer approaches that could lead to similar U.S. success in the future. The selection of technologies and their operation impact the sustainability of facilities in two ways; energy management and carbon management. On energy management, the current U.S. energy usage ranges between 600 and 2,600 kwh/MG treated when operated with internal carbon sources. When carbon is imported, the energy usage increases by approximately 600 kwh/MG treated or more, which needs to be either reduced or supplied from the outside sources. For the purpose of energy generation, key factors include, in-plant generation of volatile fatty acids(VFA), increased biogas yield from both enhanced primary settling with chemical addition and conditioning of feed sludge and co-digestion, where feasible . For the purpose of energy conservation, key factors included ability to operate the swing zone, step feed mode of activated sludge , sidestream treatment of recycle loads, and automation with on-line sensors. A list of challenges and opportunities are suggested for reaching a long term goal of energy self-sufficiency. Source: WEFTEC 2009 Proceedings

Metric Used:
Posted: August 27th, 2010 | Filed under: Waste Water Treatment | Tags: , , | No Comments »

Incorporation of an Intentional Struvite Precipitation Model Into a Whole-plant Process Simulator

West Boise WWTP
Boise, Idaho

An intentional struvite precipitation model is incorporated into a whole-plant process simulator allowing for the quantification of impacts to the overall mass balance and associated phosphorus recovery from a wastewater treatment system. The intentional struvite precipitation model predicts the overall struvite quantities generated (as magnesium ammonium phosphate, MgNH4PO4ยท6H2O) and the associated reduction of phosphorus and ammonia across the reactor. The results are incorporated into the overall wastewater treatment facility (WWTF) mass balance, quantifying the impact intentional struvite precipitation has on the nutrient removal performance of the facility. The use of this model in a whole-plant process simulator allows the direct comparison to other nutrient removal alternatives, providing a basis for the selection of the appropriate treatment process configuration. The incorporation of an intentional struvite precipitation model into a whole-plant simulator proved to be a valuable tool in evaluating a number of treatment configurations to meet total effluent phosphorus goals. This technology was compared to traditional treatment configurations, allowing a quantification of overall plant performance. This tool was part of the evaluation process that ended up recommending the use of an intentional struvite reactor at the West Boise WWTF to help improve total phosphorus removal at the facility. Performance from the simulation shows a significant decrease in effluent total phosphorus with the use of an intentional struvite reactor. The simulation indicates a 77-percent reduction of effluent total phosphorus from the use of EBPR only to that with a system that incorporates intentional struvite precipitation. This, along with the sustainable features of the technology, prompted the recommendation of continuing with the implementation into the design of the WWTF expansion. Source: WEFTEC 2009 Proceedings

Metric Used:
Posted: June 23rd, 2010 | Filed under: Waste Water Treatment | Tags: , | No Comments »