Honduras Interns Progress Report
Date: 9/28/07
Location: Ojojona
Work Completed This Week
¿ Improvements to Plant
o All sed tank influent pipes now have pins securing them.
¿ Progress in Problem Solving
o Sed Tanks
¿ On Monday September 25th while cleaning sed tank 3 during the re-filling process the laminas were not replaced. During the refilling process all of the entrance tubes into the sed tank rose up because there was air trapped in the tubes. The longest sed tube was not under the cage and so lifted up more than the others. This was fixed by drilling two small 3/16" holes in the top to let the air escape while re-filling.
¿ For some reason the distance between the top of the lamina and the water surface is considerably less in tank 3. This is a problem when we send the water to waste because the water level in the sed tanks drop and some of the holes in the exit tube are no longer submerged. The cages under the lamina seem to be about the same height so we are not sure what the difference is, but it should be easy to determine.
¿ We think the plant can run on 2 sed tanks with flow of about 260 L/min. This is equivalent to the design flow of the plant. We tried running the plant on one sed tank with a flow of 230L/min and had poor results. Flocs rose up through the lamina.
o Sulfate
¿ The new sulfate does not settle and we have not had problems with it clogging the doser hose or float valve.
¿ We have never been able to get truly linear results with the doser hose. If the flow is laminar, every centimeter we drop the doser hose should be a set increase in flowrate. We're finding that this increase is more or less constant, but that there is always a little extra flowrate (see attached data). Thus flow per cm of head is greater at lower doses than at higher doses. We thought this could be because the flow is going turbulent, but this doesn't fit well with the data and the Re is still really low. Could it be that the surface tension of the water dripping out of the end of the hose is providing and extra driving force that pulls the water through the tube? There is a certain mass of water that is always hanging from the end of the tube and this mass might be able to pull on the water still in the tube due to surface tension. This would explain why there seems to be some sort of constant driving force in addition to the head that we're accounting for.
o Chlorine
¿ The chlorine doser hoses clogged the other day. We think that chlorine chrystalizes in the tubes. It also crystallizes in the pipe between the doser and where the chlorine is added. Every time that the chlorine barriles are filled the tubes should be purged with water to clean them.
o Problems with operation during the night
¿ We're still having problems with rain coming during the night and turbidity increasing.
¿ This afternoon we tried shutting off sources 2 and 3 when we left for the day. This left only source 1 running at 30 gal/min. Since source 1 is very clean (5NTU today when the other sources were about 40 NTU) we can just run it through the plant without adding sulfate. We're hoping that if the distribution tank is full when we leave that there will be enough water with source 1 to last until the fontanero arrives at 5 or 6 am to get the plant working again. This feels like cheating, but if it gets the job done it will be great.
¿ Capacitation of plant operators, Sustainability in Ojojona
o Juan is in charge of the plant this week and has done a very good job. Nearly every day when we get there at 8:15am he has been there since 6am and already has the plant working and has written down what he has done.
o They will continue to have the fonteneros change every week up until January when they will find a permanent operator. Right now the other two fontaneros are covering the responsibilities of the fontanero who is at the plant. Under this system, each fontanero is paid about 700L extra a month (in addition to their 2600L salary)
o We are meeting with Martin Thursday, Sept 26 to discuss a campaign to publicize the plant and justify a raise in the tariff.
¿ Moroceli
o Engineer Serrano has looked over the information we have on the conduction line and is has come up with a plan to improve it.
Questions, work for Cornell Team
Plant Improvement Ideas
¿ Holes in the top of the sed tank tubes
Moroceli
¿ We will have a meeting today to talk with the Junta and hopefully the Alcalde de Moroceli to discuss their situation with the conduction line. We will send more information next week on how the meeting went.
Plans for the Future
¿ New Laminas
o We bought the new polycarbonate modules to replace one at the end of the module. We will use the laminas in the module that we replace to replace damaged lamina in other modules.
o At the junctions between modules, we will use 1.5" pvc caps to accept the spacers from the adjacent module. This allow us to actually connect the modules and still keep the spacers in place. We will try to find a way to divert the inlet flow downward without taking up so much space at the beginning of the tank.
o Also need to buy materials to make a "cage" at the end of the tank to help support the force and minimize buckling of the connections at the end.
¿ Sedimentation tank
o Also try to find another way to design the cages, need to have support in the middle so that the lamella don't fold over and fall in between.
o Glue parts of the cages together (the bottom so that they don't come apart)
¿ Get materials to take the water from the overflow chamber away from the plant. The Junta plans on providing this and we are waiting for the materials to arrive from them.
¿ Trips:
o Trip to La 34 - not scheduled
o Trip to Marcala - not scheduled, plans to contact Fred to see when would be convenient for him.