Quantifying treatment system resilience to shock loadings in constructed wetlands and denitrification bioreactors.

Wastewater treatment ecotechnologies such as constructed wetlands and denitrifying bioreactors are commonly perceived as robust and resilient to shock loading, but this has proved difficult to quantify, particularly when comparing different systems. This study proposes a method of quantifying and comparing performance resilience in response to a standard disturbance. In a side-by-side study we compare the treatment performance of four different configurations of wetlands and denitrifying bioreactors subjected to hydraulic shock loads of five times the standard inflow rate of primary treated sewage for five days.

Microbial Transport, Retention, and Inactivation in Streams: A Combined Experimental and Stochastic Modeling Approach.

Long-term survival of pathogenic microorganisms in streams enables long-distance disease transmission. In order to manage water-borne diseases more effectively we need to better predict how microbes behave in freshwater systems, particularly how they are transported downstream in rivers. Microbes continuously immobilize and resuspend during downstream transport owing to a variety of processes including gravitational settling, attachment to in-stream structures such as submerged macrophytes, and hyporheic exchange and filtration within underlying sediments.

Retention and remobilization dynamics of fine particles and microorganisms in pastoral streams.

Both microbial metabolism and pathogen retention and remobilization are dependent on downstream transport of fine particles, which migrate in a series of deposition and resuspension events. All fine particles, including clay minerals, particulate organic carbon, nutrients and microbes, are often considered to be transported similarly in the environment because of a lack of specific observations comparing their relative transport. We conducted a tracer injection study to compare the transport and retention of the fecal indicator bacterium Escherichia coli, synthetic inert fluorescent fine particles, and a dissolved conservative tracer.

Multiyear nutrient removal performance of three constructed wetlands intercepting tile drain flows from grazed pastures.

Subsurface tile drain flows can be a major s ource of nurient loss from agricultural landscapes. This study quantifies flows and nitrogen and phosphorus yields from tile drains at three intensively grazed dairy pasture sites over 3- to 5-yr periods and evaluates the capacity of constructed wetlands occupying 0.66 to 1.