W: Good evening everyone, and welcome. As you'll already know, this is the first of a series of talks about environmental issues. And tonight I'm going to be telling you about various developments in the field of water engineering.
Today one of the biggest challenges facing rural communities in many parts of the world is the difficulty of getting a reliable source of water. People need water for both domestic use and for farming. The problem is that in many parts of the world people do not have access to a constant supply of water. Any long-term solution to this problem has to take into account the impact on the environment, in addition to the needs of water users. So for example, any method of getting water that uses pumps powered by gasoline or diesel fuel creates new problems. For one, using these fuels creates more air pollution. And the costs of running equipment powered by these fuels are very high. So it's better to find ways of providing water that do not rely on fossil fuels. So. ..now let me give you some examples of ways of supplying water which meet these requirements, starting with a type of pump called the ram pump. Ram pumps aren't new. They've been around for a very long time, in fact. But the design of them has been steadily improving, so now the performance of the pumps is better, and they're also much more reliable. Their use is spreading, but they're already very popular in Asia and parts of Central America.
Just to give you some idea of cost — a ram pump that supplies a community of around 300 people in the Philippines typically costs between $4,000 and $5,000, which is very cost-effective compared to the alternatives. As for maintenance, well to make sure the pumps operate reliably, they have to be checked every day, and the valves have to be replaced every 3 to 6 months. But as this is not particularly difficult, it's possible to train community members as pump technicians, and the families who receive the water only have to be charged a small monthly fee to pay the technicians and the cost of the replacement parts. The ram pump can be used wherever there's a stream which flows quickly enough. You can get ram pumps in different sizes - the smaller ones deliver around sixty liters of water each day, while the biggest ones can deliver thousands of liters. And the biggest ones can pump water uphill, for up to 200 meters.
So how does a ram pump work? Well I have a diagram here. It's simplified a bit, but it shows you the main parts. You'll see that water has to be moved from the stream to that village in the distance, which is at a higher level. The stream in the picture is flowing from west to east, and on the west side a small dam has been built to divert some of the water into a canal alongside the stream there. The pump itself is a little bit further downstream, and there's a drop of several meters between the dam and the pump. A delivery pipe carries water from the pump to the village — up there to the north - and there's a pipe between the dam and the pump called the drive pipe. Before the water flows down the slope to the pump it's collected in a catchment tank, where any debris is removed. At the beginning of the operation cycle, the water flowing downhill exits straight from the waste pipe at the other end and goes back into the stream. There's a valve at the end of this pipe called the waste valve. As the water flows faster this valve is suddenly forced shut by the pressure. And when this happens, water pressure forces open the other valve that you can see at the base of the air chamber. This one is known as the check valve. It allows the water to flow through the air chamber and then out into the delivery pipe. But as the water pressure lowers again, the check valve is forced shut by air pressure, and the water from the stream is routed once again out through the waste valve. Then the whole operation cycle begins again.
So that's one type of. |
