SENSOR: a drinking water sampling day

Simona Retelletti, 13 March 2020

We are finally ready to start our samplings in the water purification plants to validate the functioning of our sensor. Now begins the ‘tour de force’ that will see us very busy for two full weeks in sampling, filtering, and measuring drinking water samples from Pisa, Empoli, Lucca, and Valdelsa areas.

Simona and Valter preparing the material for sampling.

Sampling at the Pisa’s purification plants

25/02/2020: Week 1, Day 2. The alarm clock rings at 6 am (Giovanni is not that happy at this time of the day), and at 7 am we are in the lab, ready to collect all the sampling tools and material. Luckily everything has been prepared the day before: big and small bottles, filters, syringes, gloves, cooler to preserve the samples, and all the necessary PPEs (safety shoes, safety helmet, and high-visibility jacket). We load everything in the car and in no time we are on our way to the first sampling plant: “Padueltto” water purification plant in Vecchiano. At 7:45 am we are ready to start (even though Giovanni is already asking for a coffee break). At the purification plant Andrea, a technician from the water company, is waiting for us. He will patiently accompany us in several drinking water treatment plants around Pisa. After showing us around, we start the sampling procedure. First, put on the gloves. Label the bottles (a small one and a big one). Fill up the syringe and rinse it 3 times. Wash the filter. Now filter 60 ml of water in the small bottle (after rinsing it 3 times with the filtered sample). Fill up the big bottle wit the same unfiltered sample. Write everything down on the logbook. Repeat the procedure for all the taps.

Giovanni and Stefano filtering a sample at the “Paduletto” treatment plant in Vecchiano.

The sampling at the first purification plant goes smoothly and at 8:10 am we already have 3 untreated water samples (the water that needs to be purified in the plant) and 1 drinking water sample (the water that goes into the drinking water pipes). We quickly jump back in the car and we follow Andrea to the secondo water purification plant. He drives so fast, I have some difficulties to keep up but in no time we are at the second plant in Avane. Before moving to the third sampling location, Andrea explains to us that the next plant receives water that is already partially treated, so we have to add one more station where the water is completely untreated. Why not? One more station to go to. In the meantime we’ve lost Stefano, we decided we’ll wait for him later on. We stop at this newly added sampling location, collect a couple of untreated water samples and in no time we are back on the road, trying to follow Andrea in a very narrow street. Once we arrived in the “Orzignano” treatment plant, which is a bit uphill, an astonishing view opens in front of us and we realize that the building looking like a castle that we’ve always seen from the road is actually one of the water purification plants. The following plant in San Giuliano Terme is also hiding a surprise, Andrea brings us underneath the building where we find a pool of warm water naturally flowing from the subsoil.

The inside of the “castle”, the drinking water treatment plant in Orzignano.
Water naturally flowing through the subsoil in San Giuliano Terme.

At 10:20 am we stopped for a coffee break (Giovanni is finally having his breakfast) and then straight to the ‘Gabella’ plant. The following sampling is in Pisa, here Stefano leaves us to go back to the lab and start with the measurements. I, Giovanni, and Andrea finally move to the final sampling of the day in San Piero a Grado. At 11:40 we thank and say goodbye to Andrea, who is finally able to go on with his actual job, and we go back to the lab.

Daily catch: 36 samples, of which 7 treated drinking water samples and 11 untreated water samples, 18 filtered samples, 18 unfiltered. All that needs to be measured in the lab.

The SENSOR’s first test in the lab

Finally back to the lab we organize the samples, wash the sampling material, turn on all the instruments, and have lunch (we are starving!). In the afternoon I measure all the samples with 2 instruments: the sensor prototype that we’ve developed, and the spectrofluorimeter that we have in the lab. These measurements will be used to compare the results from the two instruments and see if the prototype of the sensor is working properly.

Valter in the lab, while measuring some of the samples with the sensor.

36 samples are a lot, I finish measuring them all at 6:30 pm. Luckily Valter helps me! I turn everything off, prepare the sampling material for the day after (Chiara and Valter will sample tomorrow) and at 7:30 pm I am finally back home!

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