Water Sampler

The Need

Shellfish aquaculture is a critical industry in many coastal areas, but when located near high population densities, it can face significant challenges due to pollution events, such as sewage overflows during heavy rainfall. New Bedford Massachusetts, has a history of shellfish closures due to such events, managing 27 combined sewer overflow (CSO) outfalls, releasing millions of gallons of potentially contaminated water with every heavy rainfall. Each significant CSO discharge not only impacts general water quality, but also requires precautionary shellfish bed closures for up to 31 days after each weather event under their “Conditionally Approved” classification, greatly disrupting production. However, if samples are collected and shown to be safe after 7 days, then the closure can be lifted. Addressing these challenges requires improving the frequency and accuracy of water quality and CSO discharge measurements, ensuring that shellfish beds are only closed when necessary. To support this goal, I designed a multi-container water sampling system integrated with a preexisting autonomous underwater zip-line robot.

Design

This modular sampler unit is designed to collect five unique water samples during a single deployment, offering the ability to get an accurate picture of the water quality across different depths and locations. These samples are collected using solenoid pumps and valves, a two-part fluidic manifold/electronics housing end cap, an array of syringes, and an electronic housing. All five solenoid valves are connected to the pump via a single channel in the manifold. At the user’s desired location/depth, one valve is opened and water is pumped into the valve’s attached syringe. Using a pump based mechanism instead of a mechanically actuated system such as Van Dorn and Niskin bottles increases the user’s control and allows for many samples to be collected at various times and locations. The two-part manifold allows for much easier manufacturing and maintenance, meaning the mechanism is more serviceable in the field. The robot’s limited mobility along a zip line allows for targeted sampling over time, ensuring that the user can collect a sample at the exact same location repeatedly.

Preliminary Testing

This video shows the first test of the sampler in water. The collection syringe on the far right can be seen filling with water from the container the sampler is placed in for this test. This test proves the functionality of the fluidic manifold/enclosure end cap to sample water from its surroundings. It also validates the gasket seal at shallow depths, while vacuum tests have validated this at further depths.

Next Steps

With a working prototype, testing will continue in multiple environments such as a test tank and field tests in Buzzards Bay. Other applications for this project have also been brought to my attention, so I'll continue discussions with other possible clients including marine biologists at MIT. I submitted this project to the OCEANS conference, where it will be presented in June and published in September. Also, I've submitted this project to a few MIT award programs that will be released in May.

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