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What's eating my biomass? - Red Worms, Blood Worms & Midge Fly Larvae

10/13/2014

9 Comments

 
PicturePicture - TPO Magazine
Call them red worms, blood worms, or midge fly larvae, all are names for chiromid larvae are not welcome in your wastewater treatment plant. These larvae can thrive in a lightly loaded pond or wastewater treatment unit with oxygen levels above 2.0 mg/L. The adult midge lay eggs which then hatch producing larvae that consume bacterial floc as they grow. After several days, the larvae undergo metamorphosis resulting in adult midge flies that start the cycle all over again. In addition to "eating" the active biomass, the larvae can cause effluent TSS problems and loss of ammonia removal efficiency (nitrifiers grow more slowly than other bacteria and "wash out"). While the adult flies do not bite, they are annoying as they swarm in areas near the wastewater plant.

Control Options
I have seen numerous ways people have tried to control midge flies from using pesticides to dosing hypochlorite to the system. The above control attempts can actually cause more problems! Research has found two methods for excellent control of a midge larvae infestation - they are also US EPA approved for control of midge in wastewater.

Option 1 - Use Bacillus thruringensis (AquabacXT) - Becker Microbial Products
Bt slurry produced from the spores of a common bacteria works effectively to kill larvae. Dosed at 10-50 ppm over a few day period, the Bt slurry will be consumed by the larvae which damages their gut .... thereby killing the larvae.

Option 2 - Use Strike an insect growth regulator - Adapco
While not as "natural" as the Bt, strike only impacts the growth/reproductive cycle of the midge larvae. Strike is added near the influent at a rate of 5 ounces per million gallons flow. By adding this dose for 10 - 14 days the midge larvae will be brought under control.

What if I have lost substantial amounts of my biomass and see increased effluent ammonia?
The first step in stopping biomass loss from midge larvae is to use one of the control options to eliminate the infestation. After commencing the control option, I would wait 24 hours. You can wait for biomass to naturally regrow, or to speed up the process seed the system commercial bacterial bioaugmentation product. We have been able to restore normal biological activity and increase MLSS to needed levels within 3 - 4 days.

9 Comments
Dan ward
4/30/2016 10:34:01 am

Well Red Worms have any effect on D.O.? have a real challenge, no D.O.even after extensive adding a D.O. additivery .any help would be greatly appreciated.

Reply
Erik Rubaugh
5/2/2016 12:03:09 pm

Red Worms (midge larvae) are only found in areas with abundant dissolved Oxygen. This is why find them in lightly loaded systems.

So while red worms consume oxygen, they would not be found in a low DO system.

Reply
Dennis Buccella
9/26/2016 01:21:35 pm

Since the worms are found in high DO, would dropping the DO down below 2 upset the worms life cycle enough to control them? Dennis

Reply
Erik Rumbaugh
9/29/2016 11:19:39 am

While lowering DO below 2 mg/L may gradually disrupt the larvae life cycle, it comes at the risk of damaging the aerobic biomass especially when it comes to ammonia oxidation - converting ammonia into nitrate. So, we usually just use the Bt or Strike solutions.

Reply
Aneesh Basheer
3/22/2018 09:52:22 am

We reside in the campus of a hospital that has a wastewater treatment plant. There are blood worms in our potable water since many months. We haven't been able to trace the source. Can you suggest a systematic approach to identifying the source and eliminating?

Erik Rumbaugh
3/22/2018 07:46:37 pm

For blood worms to grow in potable water, there must be a biofilm somewhere for the larvae to eat. Biofilms start to grow when the chlorine residual is insufficient. I would investigate if you have biofilm in the holding tank and a way for the midge flies to lay eggs in the tank. My solution would be to use a heavy chlorine, bleach, or chlorine dioxide dose to kill all the biomass. Then keep a chlorine residual in the system.

Reply
Kim
5/16/2018 12:32:33 pm

I have the worms on the surface of my clarifies. This is the first time I have had them. I looked at the website for Strike. They have 3 different options. Not sure which to get but in any case, this product won't affect my good bugs?

Reply
Erik Rumbaugh
5/17/2018 05:40:05 am

All of the Strike products are based on insect growth regulators similar to those used for flea control in pets. They will not harm your wastewater bacteria. Another option is to use a Bacillus thuringiensis (Bt) based product - this is completely natural using a harmless Bt spore. You can get dosing information and EPA approved Bt wastewater product from Aquafix - https://teamaquafix.com/products/midge-flies/aquabac-xt-midge-flies/

Priyanka
1/3/2020 01:31:07 am

I live in a society having waste water treatment plant and treated wateris used for toilet flush. From last few months I am noticing some red & cream worms in my toilet bowl. Initialy I thought that are from inside my body. I have been treated twice and now also they are visible. Asked the management they showed me the clear water from filter plant. Don't know from where they are coming.

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    Author

    Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater  facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.

    View my profile on LinkedIn

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