configuration for flushing and increased salinity in the tank

the salinity of the seawater we transported from the sea is around 37000 mg/l.
finally yesterday we completed the whole setup,tanks and modifications in tanks and placed a 200 L tank (for permeate storage) above the 1m3 tank. The plan was that while running the system, the permeate would fill the 200 L tank and the concentrate would return back to the 1m3 tank. When the 200 L tank was full, permeate would overflow back to the 1m3 tank.

We ran the system yesterday in this configuration. As a result, the salinity in the 1 m3 tank increases during the whole "running" (since around 150 L permeate didn't return in the 1m3 tank but was stored in the 200 L tank).
So the fact now is that after 150 L permeate is stored in the 200 L tank, the salinity in the 1m3 rises to 43000 mg/l, and this is the salinity that our membranes are required to desalinate during the whole "running".

We thought that after we flush the system, we should return the 2 streams back to 1m3 tank to decrease the salinity back to around 37000 mg/l.
We are not really sure if this is the right way to run the system.

The question is: Should we continue in this configuration, even though we run the system in extremely high salinity, which doesn't correspond to the real salinity of the seawater used? (The system can handle maximum 45000 mg/l).

One alternative would be to dilute the seawater contained in the 1 m3 tank, so that when the system reaches steady state after filling up the "permeate tank", the final concentration is 37000 mg/l as the real seawater of the region.

One extra problem we face right now is the high salinity of the permeate.
We ran the system yesterday for 2 hours using the above configuration, but we found out that the permeate quality was really high (1230 mg/l). If we run it for more time, we hope that the permeate quality will decrease. But if this is not the case, then we have to consider other issues.

Filling up the tanks!

It was both fun and complicated to bring seawater from the sea. Mostly because we had to transfer the water with my small car, which could hardly fit a 200 l barrel.

Andres enjoyed some nice moments in the sea while keeping the pump at the right position :)

In order to fill the 1 m3 tank, we had to repeat some times the whole procedure. If we consider that one complete trip (from pumping seawater from the sea, to transporting, pretreating and storing it in the 1m3 tank) was taking a little bit more than 1 hour, it is understandable why we finished late at night!

Photovoltaics look good on the roof!

Our Photovoltaics got installed yesterday :) Yeahh!

At the end of the afternoon the last installations of the electrical connections finished, and the photovoltaics were giving 32 Voc at 16:00 in the afternoon :) 

 

We are so looking forward to start testing the panels with our system!

We didn't manage to run the system yesterday, because we had underestimated the time needed to prepare the room (was not used the last 10 years, and we were cleaning for more than 2 hours), and to install the system in the room. The bulky 150 kgs "wardrobe" proved to be too tall to fit from the door! The only solution was to remove the wheels from it!We used jacks to lift it, and Andres and Nikos proved to be really strong!

Our small room, looked even smaller after the tank, the feedpump and all tubes and equipment were placed inside. 

We have the feeling that the pearson pump will get too hot in the room, since there is no ventilator or window. We have to think how to tackle this.

The day today will start with flushing the system with demineralised water produced in our lab :) 

then finally we will visit the beach to start bringing the seawater. Pyranometer and datalogger have also to be connected, cables do not seem long enough, we have to think where to put them.

nothing happens when you are expecting it to happen!

First two days on site passed mostly expecting for things :P

Expecting the desalination system and the rest boxes which came only today afternoon instead of yesterday morning, expecting the Photovoltaics company to confirm that no further delays will happen and expecting also for the rector of the university to give authorisation to use a recently -vacant room to set up the system. (The rector had to be involved, since the room was claimed by two different departments and prof.Diamantopoulos had to fight for it).

Monday was mostly the welcoming day and the day to settle down. Lots of administration work, meeting the people of the lab, planning the next steps and procedures, but also settle down in the office, configure computers, netIDs and doing lots of phone calls to trace the membranes-pumps and photovoltaics! 

The good news came today when we finally received our system!  Following Murphy's law, news cannot be only good; We noticed that the boxes didn't arrive in good order, at least on surface. One wheel of the main-system-box was broken, and all the oil from the pump crankcase had leaked out to the wooden support frame.. from down to up! It seems that the box had been turned upside-down! Unfortunately, we didn't have time to test it today since it arrived late, we have to wait until tomorrow to be sure that there is no further damage.

We got also our 1 m3 tank today to store the seawater, cleaned it and modified it with required fittings and valves. We will fill it in tomorrow with real seawater brought from a perfect location. The beach of Agios Onoufrios is 10 min away from the university and is also awarded with the "blue flag" (www.blueflag.org). This may be very useful with respect to fouling of the filters and membranes, since it is one of the cleanest beaches  in crete! 

For pumping the seawater tomorrow, we will use a submersible pump which will be powered using the facilities of a friendly owner of a cantine just 40 metres away from the coast  :)

It is interesting to note that the seawater here has 39000 ppm of TDS (highest number in the interconnected system of the earth's oceanic waters) which makes our desalination effort quite challenging and of course energy costly.

Whats next for tomorrow?

-The PV company will start the installation of the panels early in the morning, and promised to finish in one day (never trust the greeks!).

-Fortunately, we will get the keys of the room where we will set up the system, and we have to start by cleaning the place (it looks like it has not been used the last 10 years), then connect  electronics, tubes and pumps, and then flush the system with Demiwater. Hopefully, there is no damage from the transport (i try to win my pessimism)..

-If everything goes well, we will pump and bring the seawater in the afternoon and fill our tank.

Andres and me have to note that we get a lot of help and advice from the people at the lab people and prof.Diamantopoulos. Especially we are very grateful to Nikos Vakondios, a phD student who is greatly involved in our project and gives great help in practical things.

PS: Next days will be busier and more tiring and i will not have the time to write long posts like this, luckily for you :)

Tomorrow seems to be a very busy day ..

Goodnight from Crete,

Valia