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Separating algae from water from a raceway pond - Page 4

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Posted by Michael B on December 13, 2009, 7:19 pm

This may have some info of value.
Including the reasons for clumping, and how to facilitate

Posted by Curbie on December 13, 2009, 8:10 pm


Thanks, it is on two levels, the information and I didn't even think
of searching on algae for waist-water treatment.

Chemical flocculation is a proven commercial concept, although I'm
hoping for a sustainable process without chemicals.



Posted by Jim Wilkins on December 13, 2009, 2:45 pm

In the fall of 1965 the brook that runs through the middle of the
University of New Hampshire campus clogged up with foul smelling
algae. It ran conveniently under the Biology building where they soon
discovered the cause to be phosphate runoff from the experimental
agricultural field upstream. IIRC the smell was from anaerobics in the
oxygen-depleted water.

Several of us set up silly protests, mine was a small water wheel
powered by the stream that ostensibly metered Chlorox into the water
with a scoop run by a wooden gear train. Really it was just a kinetic

Algae grew very quickly on the paddles and other wetted parts, faster
than it grew on the rocks, possibly because it received fresh CO2 from
the air. Within a week it was too smelly and disgusting to touch
without rubber gloves.

It ran for a month, much longer than I expected for wooden gears and
bearings, until someone stole it. By then the nights fell below
freezing and ice was thick on the blades in the morning, though the
stream was still ice free. The algae decreased as the weather cooled
and the fertilizer washed away.


Posted by Curbie on December 13, 2009, 6:06 pm


Generally, as Michael points out, smelly algae come from anaerobic
digestion of bio-mass producing hydrogen sulfide (think rotten eggs),
the purpose of the paddle-wheel is to keep the algae in motion during
peak sunlight hours for CO2 sequestration and shading (depth of algae
in pond, algae partially shaded by algae above it).

Since the paddle-wheel is necessary to maintain algae at a higher
exponential growth rate and to help prevent smelly anaerobic digestion
in the raceway pond anyway, I'm trying to use the paddle-wheel to also
concentrate the algae (think replacement of high volume pumps, feeding
a centrifuge). A DIY translation of the commercial process.


Posted by Jim Wilkins on December 15, 2009, 2:43 pm

The only successful methane digester I've seen was at the treatment
plant in Heilbronn Germany.
I googled Heilbronn Klaeranlage and Klaerwerk but didn't find
technical details and all results were in German, which is barely
comprehensible when automatically translated into English. I subscribe
to the Daimler research journal in German and have a hard time with
the technical terms, for which I don't have an adequate dictionary.

They digested the sludge in an egg-shaped pressure vessel and ran a
very large, low speed Diesel engine off the gas to generate enough
electricity to run the plant, the guide said. IIRC it was barely
enough and sometimes they took power from the nuclear power plant
directly across the river.

I was the token enlisted man whom the Army sent whenever the local
Germans offered get-to-know-our-Kultur events. Some were interesting,
like the banquet in Heidelberg Castle with all our half-drunk senior
officers and their bored, boisterous wives.

I visited a US wastewater plant with an EPA lady friend and got a
closer look at the machinery, which seemed designed to minimize
maintenance and electricity demand. The German plant was in a built-up
area and minimized odor, though we were still too eager to leave to
ask questions.

The solids separator in the US plant was wire screen conveyer belt
that dipped into the inlet trough on one end, similar to the
Fourdrinier paper-making machinery I mentioned earlier. In Germany I
flew to remote comm sites frequently, and just past the end of our
runway there was a wastewater pumping station with what looked like
several exposed Archimedian screws to raise and aerate the water. I
suggested tubing for yours because a more efficient sheet metal one
would be quite difficult to fabricate, unless you have access to scrap
stainless and a plasma cutter and TIG welder.

Even having those it's tricky, stainless doesn't conduct heat well so
the heated area expands and warps, and the back side oxidizes. Type
316L is recommended, but unmarked scrap is often 304 sheet and 303


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