In 2003, the District of Columbia Water and Sewer Authority published an Odor Control Master Plan (OCMP) for the Blue Plains Advanced Wastewater Treatment Plant with the intent of developing a longterm strategy for further odor mitigation. Facility modifications have been made over the past ten years that incorporated odor mitigation measures within new Capital Projects as recommended in a previous odor study. Actual gains of these mitigation measures versus prediction, and need to establish a revised baseline for odor prompted a subsequent OCMP study in 2011. The goals of the OCMP study were to develop a strategy to minimize offsite impacts and facilitate selection of effective odor mitigation measures and process changes.Using an air dispersion model as a way to estimate impacts and improvements, multiple control and dispersion strategies were developed for a variety of source categories around the Plant. The control strategies and engineering solutions evaluated for the Facility's Primary Sedimentation Tanks are discussed and a cost / benefit analysis is provided for each option considered.
Comprehensive odorous emissions sampling programs were recently conducted at the Blue Plains Advanced Wastewater Treatment Plant. Liquid and air emission samples were simultaneously collected at each of the wastewater treatment processes and the solids processing facilities. Air emission samples were analyzed for sulfur-containing compounds and olfactory parameters. Liquid samples were analyzed for a variety of parameters such as dissolved hydrogen sulfide, pH, dissolved oxygen (DO), oxidation reduction potential (ORP) and many other parameters.The results showed that the high rate activated sludge treatment process emits substantial quantities of odorous emissions and the main odorous compound is methyl mercaptan. The results also showed that the highest total reduced sulfur (TRS) and odor mass emissions occur when primary clarifier effluent is added to activated sludge mixed liquor in low DO and low ORP conditions and subsequently aerated. Long mixed liquor retention time in the secondary clarifiers also create conditions that are related to the high quantities of odorous emissions. However, continuous aeration can increase oxidative conditions in the activated sludge process and these conditions reduce the emissions of sulfur-containing compounds by 95 to 99%.
A decrease in the nitrogen discharge from wastewater effluent has been mandated by the U.S. Environment Protection Agency (EPA) under the National Pollutant Discharge Elimination System (NPDES) program to minimize the nitrogen loading into the Chesapeake Bay. Meeting this regional objective requires increasing the denitrification treatment capacity at the District of Columbia Water and Sewer Authority's (DC Water) wastewater treatment plant by constructing a new Enhance Nitrogen Removal Facilities (ENRF). This will increase methanol usage during denitrification, requiring regulated air permitting prior to construction and facility operation. It also requires implementation of O&M practices that mitigate methanol emissions, and periodic compliance filing to regulatory agencies. This paper discusses design, construction, and operating considerations including: a) implications on equipment and process design and operation b) integration of permit conditions into design and operation of ENRF system, and c) emissions mitigation and management through monitoring, O&M programs and software tools.
In 2003, the District of Columbia Water and Sewer Authority (DC Water) published an Odor Control Master Plan (OCMP) for the Blue Plains Advanced Wastewater Treatment Plant (Blue Plains) with the intent of developing a long-term strategy for mitigating odor. While facility modifications have been made over the past ten years, continued concerns of offsite odor impacts prompted a subsequent OCMP study in 2011. The goals of the OCMP study were to estimate offsite impacts and facilitate selection of odor mitigation measures and process changes.Assessment of potential odor on the surrounding community was conducted through a dispersion modeling analysis using the US EPA's AERMOD program. The dispersion environment surrounding Blue Plains varies from residential communities and commercial establishments to the north and west to tidal wetland and residential areas to the south and east. The plant terrain is generally flat to gently rolling with an elevation of 2-5 meters above sea level. The river to the east combined with elevated terrain to the west influence the wind patterns that influences the odor transport from sources the plant.Detailed model set-up is presented and discussed. Example unit-level and facility-wide modeling results are also presented in order to demonstrate the power of dispersion modeling as a tool for estimating odor reduction potentials of various engineering solutions.
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