Stressed again! Equipment failure! Hurray?

Just days before we needed to start our equipment failure test, the electronics that control the sewer, emptying of the greywater holding tank, to our shower failed- including the control board that opens and closes the valves.

What seemed like a disappointment was actually an important discovery. First, it’s important to be reminded while doing research that mistakes and failures like this are learning opportunities.  The shower sewer system crashing turned into a great opportunity for our stress test and to prepare for our stress test all we had to was let it stay broken. Second, we learned that while printing our own circuit boards in the lab is fun, buying manufactured circuit boards is more reliable and will be incorporated into our final system design.

Left: UAA lab designed valve control board
Right: manufactured board designed by UAA


Since the stress test design was already done for us as well, we didn’t need to simulate anything. We really had an equipment failure! Great timing!

Here’s what else we did:

The stress test ran November 7th till November 14th.

For the first day we kept the system running at 40% of our regular loading, 40% of the greywater went down the bathroom sink, kitchen, and laundry drains for recycling. We treated greywater to wash water. The next 2 days the system was shut off leaving our treated wash water in its tank to sit.

During the 2 day “break” we had a chance to do maintenance to the cabin shower electronics, and our system was operating again by day 4.  Day 4 the wastewater that sat for 2 days flowed into the cabin as we began operating on a 60% loading cycle for days 4-6.

By days 7 and 8, the system was back to operating at 100% loading of greywater. The shower was operating well and the holding tank was emptying like it should!

On day 7 our Nanofiltration membrane had had enough and needed to be swapped out. However, It was more of a coincidence than a result of the stress test.

We collected certified samples November 7th the day the stress test began and on November 10th, after the system was off for 2 days with the wash water sitting. Again, our internal water quality samples did not change. Our certified lab samples can back negative for total coliform bacteria. Follow the link to our certified water quality results:

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