Density, Salinity, and Entry Depths of Municipal Wastewater in an Urban Lake

Abstract

The depths of entry of municipal wastewater into receiving lakes importantly affects associated impacts on water quality. The plunging behavior of two negatively buoyant inflows that carry municipal waste, an urban tributary and an effluent discharge, in Onondaga Lake, NY, is characterized and quantified based on an integrated program of monitoring, density calculations, and modeling. In-lake signatures of plunging from the two inflows are differentiated according to constituents in which each is enriched. Under common contemporary conditions, the summer averages of the fraction of the urban stream and effluent discharge inflows plunging to stratified depths is predicted, with a calibrated hydrodynamic model, to be approximately 0.7 and 0.35, respectively. Recent short-term increases in salinity levels from construction site dewatering caused greater plunging of the effluent discharge and interfered with normal complete fall turnover in the lake.

Coupling Suspect and Nontarget Screening with Mass Balance Modeling to Characterize Organic Micropollutants in the Onondaga Lake–Three Rivers System

“…For example, the majority of wastewater-derived OMPs (e.g., pharmaceuticals) formed distinct concentration spikes in the metalimnion (i.e., at 7 m depth) when the lake was strongly stratified in July 2017; however, such concentration spikes diminished as the lake became weakly stratified in October 2017 (Figure b). Considering the plunging inflow phenomenon in Onondaga Lake, − the concentration spikes observed in July likely developed as a result of the plunging of negatively buoyant inflows (i.e., cooler and denser WWTP effluent and tributary waters relative to the epilimnetic lake water; see temperature data in Table S3) into the metalimnion. Hypothetically, the depth-resolved concentration profiles of OMPs confirmed by suspect screening could be leveraged to filter and prioritize nontarget mass spectral features for structural elucidation.…”

“…Mass balance modeling was first implemented in AQUASIM to evaluate the fate of OMPs in Onondaga Lake given its relatively short hydraulic residence time . Onondaga Lake was strongly stratified in July 2017, during which the negatively buoyant inflows plunged to the metalimnion as interflows to varying extents, − and the fraction of each inflow entering the metalimnion varied from 10 to 40% according to the specific conductance data measured in situ by rapid profiling instrumentation . On the other hand, the metalimnion descended to lower depths as the lake became weakly stratified in October 2017, during which 100% of the inflows entered the well-mixed epilimnion.…”

Coupling Suspect and Nontarget Screening with Mass Balance Modeling to Characterize Organic Micropollutants in the Onondaga LakeThree Rivers System

“…On July 25, 2017, varying fractions of the negatively buoyant inflows (i.e., those with a density greater than that of the epilimnetic water) from the regional WWTP outfall and the four tributaries plunged into the metalimnion as interflows. [37][38][39][40] Using S50 the specific conductance data measured in situ, the fraction of each inflow entering the metalimnion in July was estimated to be 40%, 10%, 30%, 10%, and 10% for the WWTP effluent, Ninemile Creek (T1), Onondaga Creek (T2), Harbor Brook (T3), and Ley Creek (T4), respectively. On October 16, 2017, 100% of the inflows were estimated to enter the well-mixed epilimnion (i.e., as overflows over the metalimnion).…”