Water Environment Federation (WEF) Discussion Forums / WEF Discussion Forums / Collection Systems / Duckweek Removal / Latest Posts

RE: Duckweek Removal

nutbush — Mon, 14 Jan 2008 10:31:42 GMT

Thanks guys for the info.

RE: Duckweek Removal

John Sansalone — Sat, 12 Jan 2008 16:42:50 GMT

I've seen situations where the duckweed (and other algae) ends up getting measured as TSS - at least that is what the operators claimed was the cause for permit violations. That led to having to do all sorts discussions about special permit conditions concerning chlorophyll, etc., to distingish between that, and possible other crud. Its not that there was a problem with having duckweed in the lagoon, but rather it going out the pipe. It can also mess up measurements for nitrogen.

In some cases, simple baffling - say, a pressure treated 2X10, could keep the weed inside, and avoid problems. In other cases, not doable, and a continuing headache. You may want to clarify with the regulator if that is the real problem (it appearing in the effluent), rather than it merely being present in the lagoon.

RE: Duckweek Removal

Jerry — Sat, 12 Jan 2008 11:34:30 GMT

The State has no business telling you to get rid of your duckweed unless they have scientific proof that the duckweed is indeed causing effluent problems. In most cases duck weed in the final cells have a benificial value. I suggest the State look up the "Lemna Treatment Process". You may have to control the duck weed to make sure it doesn't completely smother( delete O2) your lagoon. A good way to improve any smothering is to add a recirculating pump or aspirator type pump to cause a circulating effect. Otherwise you may have to get a pumper (vacuum) truck or trash pump to skim the duck weed off the surface. Heaven forbid, hand rakes. Anyway,it has good agricultural value.

Duckweek Removal

nutbush — Fri, 11 Jan 2008 16:55:06 GMT

Hey guys, new to this forum. It's nice, I like it. Got a question. I have 3 lagoons. The first lagoon is about 4 acres and is the first treatment, and this lagoon has no duckweed. The second lagoon is about 2.5 acres and is the second pond in line of treatment and it has a blanket of duckweed. The third is about 1 acre and is the final stage of treatment before being discharged to a river, it also has a blanket of duckweed. The state is making me rid my lagoons of this duckweed. The first question is: Why does number 2 and 3 ponds have duckweed and number 1 doesn't? The second question is: What is the best way to rid of the duckweed? I know that you can use nets, but I was mainly wondering about the best and cheapest chemical to use to rid of it quick.