Dynamic Fish Manure Extractor System

Cleanliness in fish hatchery raceways is of the utmost importance when it comes to healthy fish. As an engineering team, our purpose is to design a system that can effectively reduce the build-up of fish manure on the bottom of the raceways without causing re-suspension of the manure in the water.

Background
Current techniques used to clean fish hatchery raceways take an unnecessary amount of time. Minimum wage workers spend hours upon hours cleaning fish manure out of the raceways, but are ineffective in doing so due to problems with re-suspension of fecal particles. Therefore, the lack of an efficient way to collect fish feces causes hazardous living conditions for the fish in the raceways as well as for the ecosystem where the hatchery discharges its water: the Snake River.

Previous Designs

 * A screen that is pushed across the bottom of the raceways to collect manure (see photo)
 * A vacuum that cleans waste in the quiescent zone (see photo)
 * Quiescent Zone: area of the raceway designed to help the re-suspended particles have time to settle in the settling basins.
 * Last 20 feet of the raceway
 * No fish in this area
 * Settling basins emptied by hand

Last Year's Design
Our design team is continuing a project that began last year. Last year's team designed a moving baffle that would help to eradicate the manure problem. The essence of the design was to create a high velocity (relative to the raceway's flow rate) stream of water that moved underneath the baffle, thereby "pushing" the fish manure downstream. As seen in the video below, the baffle design caused the manure to move downstream, but this did not solve the problem. Benefits and drawbacks are listed below.

Pros

 * Pushed manure downstream with nearly 100% effectiveness
 * Did not require an external power source
 * Could be adjustable based on the flow rate present

Cons

 * Re-introduction of the high velocity stream to the slower-moving water caused re-suspension of the manure particles
 * Detrimental effects when fish breathe in manure
 * Manure did not settle in the Quiescent Zone, but rather was pushed into the next raceway; problem was pushed downstream and not solved.
 * Baffle may cause stress in fish, as they will need to either jump over the top of the baffle or swim underneath
 * Fish are cornered at the back of the raceway where dissolved oxygen is lowest
 * Disrupts the feeding routine at the raceway
 * Very heavy- not portable
 * Still needs people to restart the baffle at the top of the raceway or transport to the next one.

The model and dimensions of the previous design are shown below.

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 * Movable baffle design, tested with 0" baffle gap and 9" horizontal baffle

All in all, the client stated that the use of a baffle system such as the one proposed last year was not feasible or practical for his needs.

Client Needs
Our client requests a design that will accomplish the following needs:
 * Remove feces from the bottom of raceways without re-suspension of particles
 * Be durable (minimal maintenance)
 * Be easy to use (anyone can operate)
 * Be cost effective (less than our budget of $750)
 * Be simple (be replicable)
 * Cause a net decrease in labor

Goals
Design a system that:
 * Meets client specifications
 * Is automated and more efficient than the current method
 * Increases overall productivity and health of the fish
 * Increase dissolved oxygen levels
 * Lowers phosphorous levels

Modified Baffle
This design extrapolates upon last year's design. The idea is to create a velocity gradient by cutting another slit in the baffle, which will essentially make two higher velocity jets (the "old" and the "new"). Since the velocity of the jet depends upon the hydrostatic pressure and the flow rate in the raceway, the velocity of the "upper" jet will be slower than the "lower" jet. However, the velocity in the new jet may help to alleviate some re-suspension of particles, since the difference in water velocity causes the turbulence needed to re-suspend the particles. We hope that the feces will become trapped between the two jets and then carried downstream where settling will occur in the Quiescent Zone.

Siphon Filtration
Description

Pump Filtration
Description