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Most cold-climate biological nutrient removal facilities experience poor settling mixed liquor during winter, resulting in treatment capacity throughput limitations. The Metro Wastewater Reclamation District in Denver, Colorado, operated two full-scale secondary treatment trains to compare the existing biological nutrient removal configuration (Control) to one that was modified to operate with an anaerobic selector and with hydrocyclone selective wasting (Test) to induce granulation. Results from this evaluation showed that the Test achieved significantly better settling behaviour than the Control. The difference in the mean diluted SVI30 between the Test and Control were statistically significant (P < 0.05), with values of 77 ± 17 and 135 ± 25 mL/g observed for the Test and Control respectively. These settling results were accompanied by differences in the particle size distribution, with notably higher settling velocities commensurate with increasing particle size. The degree of granulation observed in the Test train was between 32 and 56% of the mass greater than ≥250 μm in particle size whereas 16% of the mixed liquor in the Control was ≥250 μm over the entire study period. The improved settling behaviour of the Test configuration may translate into an increase of secondary treatment capacity during winter by 32%. HIGHLIGHTS Inducing granulation in a full-scale continuous flow activated sludge system was possible with the application of both biological and physical selection pressures.; Observations in this study could translate to a cost effective intensification solution versus traditional expansion for WRRFs evaluating capacity needs.

Disinfection is one of the most critical processes for municipal wastewater treatment. However, traditional chemical dosing approaches do not consider how changes in water quality and process opera...

While the impact of suspended solids on chemical disinfection kinetics has been widely recognized, a detailed modeling framework for assessing their contribution on disinfection efficiency in municipal contact tanks is yet unavailable. In this paper, we conducted experimental and modeling studies to mechanistically describe the interplay between suspended solids (not removed by gravity settling in secondary clarifiers) and disinfection performance of an emerging disinfectant, peracetic acid, operated in a municipal contact tank. Specifically, we developed an integrated computational fluid dynamics (CFD) model to simultaneously predict the fate and transport of suspended solids, Escherichia coli and peracetic acid in a hypothetical reactor using an exposure-based (i.e., CT-based) inactivation rate expression. The integrated CFD model, calibrated against laboratory data, was used to gain insights on the vertical distribution and local PAA decay effect associated with solids settling and their impact on disinfectant decay and microbial inactivation. Results indicated that: (a) solids settling in contact tanks is a significant phenomenon that cannot be neglected, which can substantially impact disinfection efficiency under low flow conditions; (b) vertical solids distribution and stratification in contact tanks can strongly affect Escherichia coli inactivation by peracetic acid, as highlighted by the CFD modeling studies; (c) Escherichia coli settling is experimentally measurable, and strongly correlated with solids settling. These phenomena can be successfully integrated into a CFD model to obtain a comprehensive description of the PAA disinfection process in presence of changes in secondary effluent quality and flow, a situation typically encountered in municipal contact tanks operated in full scale wastewater treatment plants.

The DEMON treatment process is rapidly becoming an established technology for sidestream treatment due to its low energy use and no requirement for carbon addition to remove nitrogen completely through deammonification. A new filtrate treatment facility (FTF) based on the DEMON process and currently under design for the Blue Plains Advanced Wastewater Treatment Plant (AWTP) has several unique design aspects and treatment challenges due to its large scale and the fact that it will treat liquors from a digestion system that includes the CAMBI thermal hydrolysis process. This paper outlines the design, highlighting the unique features and the approach taken to overcome design constraints to meet the desired treatment performance, including consideration of: (1) space constraints, (2) multiple-reactor operation, (3) potential toxicity, (4) high temperatures, and (5) the aeration/mixing system. Design of the Blue Plains FTF is due to be completed in 2013.

Monod kinetics were used to recalibrate published sets of soil microcosm data that document the aerobic biodegradation of calcium magnesium acetate in a highway shoulder. The natural attenuation is important because acetate can exert an appreciable oxygen demand on ground-water if it persists from the ground surface to the water table. Biomass dynamics were modeled, as well as acetate degradation, in the assumed abundance of oxygen and nutrients. The maximum specific growth rate (μM) and half saturation constant (KS) quantify the ability of an individual aerobe to degrade acetate and accordingly calibrate microcosm data from all locations in the shoulder. Thirty-two microcosm sets from SR-25 in southeastern Massachusetts yielded a calibrated μM of 0.00133 h[minus]1 and a KS of 0.087 kg acetate/m3 soil moisture. Calibrated (not measured) initial biomass concentrations varied from 10 to 1,000 μg biomass/g dry soil, with the largest values near the surface of the loamy sand cover layer and the smallest values above the capillary fringe consisting of uniform sand. The initial biomass concentrations and Monod kinetics yielded reaction rates consistent with field scale estimates of acetate degradation.