Peat sludge problem in pipe

[Vortechs]

I have a Pelton wheel micro-hydro setup that has been running for nearly 9 years. It's in the mountains where the ground is peat over bedrock. My filter is made from a stainless steel washing machine drum and works well to stop anything going down the pipe that would block the nozzle but it doesn't stop the very fine particles of peat that are in the water, any filter that did would have to be huge and would clog up really quickly. These tiny bits of peat build up in the slight dips in the pipe over time. To deal with this I have a T junction just before the turbine with a 2" lever valve to vent the water fast enough to clear it from the pipe. The problem is over the years this peat sludge has been gradually coating the inside of the pipe and causing the pressure to slowly drop. Today I vented the pipe for half an hour then went up the mountain and took apart one of the connectors, the inside of the pipe is covered with about half an inch of sticky black peat goo. How do other people in these circumstances deal with this problem? Any help gratefully received.
Thanks.

My Setup:
Head 33.5m on 250m 0f pipe (150m of ID 2" pipe and 100m of ID 3"
pipe), through a 13.5mm nozzle for winter use and 9mm for summer use.
3 l/s through the 13.5mm nozzle and 1.5 l/s through the 9mm nozzle.
(I need the turbine to be able to run at 1.5Ltrs/Sec as that is the
lowest the stream goes in dry summer spells.)
20M of 10mm cable to the battery housing, where I have eight 12V
120ah batteries (wired to 24v), then 10M of 10mm cable to
the house. Air resistive dump load. Xantrex C40 Controller.  2.3KW Studer inverter.
**************

[dbcollen]

may try flushing some golf balls through the pipe to knock some of it loose followed by something thet is near pipe dia and will still fit through the connectors. The water pressure should have no problem driving it through.

[birdhouse]

welcome aboard!

i don't have a hydro system, so my info may be lacking.  a simple mechanical cleaning comes to mind.  fish some string/rope through the pipe, then attach a heavy duty sponge to the string, and tug it through.  maybe have a little water flowing while doing it?

i'd think a few passes with the sponge would remove most of the build up.  it would be a pain, but if you only have to do it every five years or so, doesn't sound all that bad. 

adam

[DanG]

Type of pipe?

[Mary B]

Sewer cleaner and lots of extensions comes to mind...

[southline]

I have injected compressed air with the water to clean soil from drains.  If you allow the air to go in at the right rate it will mix with the water and "hammer" and rattle the pipes.  Might be a long way for an air hose though..

Adam

[thirteen]

Maybe use an electircail fish tape that they pull wire threw conduet. Just like cleaning a gun barrel.  You can get them in several lenght's.  Back flush the system. A small brush on a rod would work like a chimney brush. pull it threw with the fish tape or make up some rods that connect together and every couple of years clean the piping.  Just a few ideas.
 How about a Blue Smerf with a brush and shovel just send him down the pipe. 13

[hydrosun]

Others have given ideas of mecanically removing the sludge. At this point that will have to be done first. To keep the small particles out you either need to settle them out  by slowing the water before it enters the pipe. Or keep water moving faster in the pipe so it doesn't settle out inside the pipe. So you would need to use more water whenever it is available. Sort of a continuous flushing. I realize that might not be posible. Or try using a coanda hydro screen. A large settlinig tank used to be the only way to deal with this problem. A hydro screen is set at an angle and the water flows over it. Most of the debris keeps flowing past but the water follows the surface of each wire and into the c catchment below. Talk to Bob Weir at hydroscreens.com to see what spacing to get to take out fine particles. I know it is used for water supply inlets to get particles down to the 2 micron size out of the water. The systems i've put in with the hydroscreen hae worked well with the larger particles but don't have to deal with peat. I also used larger 4 inch pipes to keep pressure losses down. So I don't have direct experience with your problem. That's why i reconmend talking to bob Weir who sells the screen. He will know from others experiences what works.
Chris

[Vortechs]

Thanks for all the suggestions. The pipe is plastic, the type that comes on a big roll.
I've considered most of the mechanical ways of cleaning it and dismissed them. Feeding a string or rope down a quarter kilometre of pipe just isn't going to happen. If something got stuck in the pipe it would be a nightmare to get out. The connectors haven't been opened in 9 years and are all hidden under the bushes that have grown over the pipe.
I figured that other people must have come up against this problem before so I tried phoning a few people who install hydros and windmills in this area and eventually got to speak to someone who had dealt with it, he said he first tried putting a rope down the pipe but gave up on it and ended up filling the pipe with dilute caustic soda (sodium hydroxide) and left it overnight, said it worked great.
As for filtering, a large settling tank would do it but it would be very difficult to construct where the inlet is high up in the mountain, the stream is in the bottom of a narrow rocky gorge so getting materials there would be real challenge.
Thanks Chris, I'll talk to Bob.

[keithturtle]

High strength bleach or Calcium hypochlorite (HTH) pool chlorine in a very strong mix will kill the vegetation.  Calculate the volume of the pipe and fill it.  Problem is, after the turbine you will want  to capture  it before it enters the stream and plays havoc with the living creatures downstream.

Let the recovered stuff sit for several days for the chlorine to off-gas, then pour it out on a gravel drive.  You can also neutralize it instantly with sodium bisulfite.  These are common wastewater treatment chemicals and your local sewer works may be able to help, as could any pool supplier.

I don't think I'd use caustic if chlorine is available.

Turtle