Synthesis review on groundwater discharge to surface water in the Great Lakes Basin

Groundwater in the Great Lakes Basin (GLB) serves as a reservoir of approximately 4000 to 5500 km³ of water and is a significant source of water to the Great Lakes. Indirect groundwater inflow from tributaries of the Great Lakes may account for 5–25% of the total water inflow to the Great Lakes and in Lake Michigan it is estimated that groundwater directly contributes 2–2.5% of the total water inflow. Despite these estimates, there is great uncertainty with respect to the impact of groundwater on surface water in the GLB. In terms of water quantity, groundwater discharge is spatially and temporally variable from the reach to the basin scale. Reach scale preferential flow pathways in the sub-surface play an important role in delivering groundwater to surface water bodies, however their identification is difficult a priori with existing data and their impact at watershed to basin scale is unknown. This variability also results in difficulty determining the location and contribution of groundwater to both point and non-point source surface water contamination. With increasing human population in the GLB and the hydrological changes brought on by continued human development and climate change, sound management of water resources will require a better understanding of groundwater surface–water interactions as heterogeneous phenomena both spatially and temporally. This review provides a summary of the scientific knowledge and gaps on groundwater–surface water interactions in the GLB, along with a discussion on future research directions.     

A tanks-in-series bioreactor to simulate macromolecule-laden wastewater pretreatment under sewer conditions by Aspergillus niger

Sewers are typically a means of transporting wastewater to a treatment facility, with little biotransformation of the soluble polymeric organic matter by suspended biomass. In the interest of providing an effective pretreatment of wastewater in a sewer network, it is necessary to design an accurate tool simulating sewer conditions and introduce an appropriate biomass for macromolecular pollutant degradation. Such a model reactor was built using a tanks-in-series design and the degradation of a polysaccharide (starch) by Aspergillus niger MUCL 28817 was studied. Starch degradation and the accumulation of intermediates (hydrolysis fragments) in the individual reactors were quantified under transient conditions, at a mean hydraulic residence time of 17 h. Starch was degraded by 90% in this reactor system and an accumulation of oligosaccharides with molecular weight lower than 1,000 Da was observed. These results may be helpful in the development of wastewater treatment in sewers and in the alleviation of the burden on undersized wastewater treatment systems.