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Operating and Troubleshooting

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FReTA

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Clay Stock Preparation, Clay Stock Valve, and Raw Water:

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Common Problems: Make sure that the alum pump is functioning; it is possible that the yellow cable connecting it to the stamp box may have come loose. Additionally, it is not uncommon for bubbles to form in the tubing leading to the alum pump when it is first connected to the stock bucket. If you find that there are large bubbles, they could restrict the flow and you may need to flush them out. Additionally, if you find that the pump is not delivering the correct dosage, it may need to be recalibrated in Process Controller.

Connector Joining Alum line to Main raw water line

One significant problem we encountered during our research was the precipitation of aluminum hydroxide in the connector joining the alum line to the main raw water line of the flocculator. The problem occurred because our stock alum is mixed in distilled water. Distilled water has a lower pH than the tap water the raw water is mixed with. Alum is more at lower pH values; when the stock alum hits higher pH and alkalinity of the raw water, it quickly begins to precipitate as aluminum hydroxide(it is the precipitation of aluminum hydroxide that makes flocculation possible). However, as we ran more experiments over the course of the semester, more aluminum hydroxide built up in the connector joining the two lines. At its worst it almost entirely blocked the alum feed and caused a significant back pressure in the raw water line. (Since the precipitation occurred in the T connector joining the alum and raw water lines, it was able to block both). This problem caused significant setbacks for our research until we were able to locate it. Future teams should consider redesigning this section of FReTA to avoid the problem. Additionally, until a solution is implemented it is important to check the connector for the buildup of aluminum hydroxide regularly. A blockage can begin to form in as little as a week or two of experiments.

Tube Flocculator:

The flocculator can be run at one of three lengths, either 2796 cm, 5592 cm, or 8388 cm. Occasionally it may need to be cleaned by running a piece of sponge through it during backwash.

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