Here is a link to our design proposal: MDProposalPCER
Without Greg’s bag we have not been able to start sieving sand for the biosand filter, but we have still been keeping busy. Our days 6/20-6/24 have been filled with a wide variety of activities related to the building of the school and the water systems in particular. For the building we have been digging holes and trenches, mixing concrete and laying bricks. The worksite is coming along nicely. Our water systems work during the day has included constructing a ceramic water filter to use until the biosand filter is functional, creating a temporary wastewater system to be used for the existing house until it can be integrated with the school’s system, and cleaning up the old waste system, which is located on the site of one of the buildings. Other work done at night has included calculating flowrates, and updating designs for the well, storage tank, and wastewater system. Hopefully Greg’s bags will come soon so we can get going on the biosand filter. Here are some pictures of our work so far. More pictures documenting the progress of building the school can be found on the PCER blog (link on the left).
Over the past few weeks we have made progress on the waste water system. Recently, in cooperation with the architects, we have changed the designs to better fit the need and simplicity of the waste water design. The changes include making the path to the respective septic tanks (one for each phase,) as short and as straight as possible. This involves locating the toilets on a direct route to the septic, whereas the grey water from the showers and sinks will have elbows and junctions (the necessity for these exits to be straight isn’t as pressing.) Each septic will have somewhere around 15-20 people using it, so we originally specified the septic to be 10 feet long 4.5 feet wide and 6 feet deep. This was done, and ready for brick laying, but the Pedreiro (construction manager) came and made a circular motion- so our design changed to a circle. Now our septic holes are close to 3 meters in diameter and about 2 meters deep – a gross overestimation of the demand on either system. Regardless, we will be finishing them. The interesting thing about the design of the septic tanks in the region is that they act both as a septic and leach field in one. After the Pedreiro told us of the circle, he also showed us the brick layout for the walls. How they do it here is they stagger the bricks so that the liquid can leach into the soil after the solid particulates have settled to the bottom. This seems like a rather ingenious method of treating their waste because of the composition of the soil. The layers of earth before the groundwater consist of sand and clay – which act as a natural filter and purifier before the liquids reach the aquifer in the ground below. We will be implementing this local methodology. An area for future research is the effectiveness of this design compared to the more standard separation of the two.
After a week without the baggage which had our designs and tools for the slow sand filter, that part of our design is a week behind schedule. Sadly, we may be hard pressed to fully implement our initial design. Today we will be looking for materials – of which include more sieves and fine sand – that will hopefully speed up the completion of the filter.
Positives within the past week is that we have put in our hand pump, and have been pumping away, clearing out the stagnant water from the well and seeing if the well will hold enough water for our demand levels and if it has clean water. The most likely long term source of water will be tapping into the jaguar lodge across the street – which is also servicing a house already on site. Or another option is to drill a new, more modern well.
More to come on the design system when we return to the U.S.