Sphaerotilus natans/Type 1701

Identification

• Gram and Neisser negative
• Can have attached growths and false branching
• Both filaments have sausage/rod-shaped cells, within a thick sheath

Why Do I Have It?

• Low D.O. in system
• High BOD loads
• Can wash in from upstream sewer lines

Treatment

If your plant has S. natans/Type 1701, working to increase dissolved oxygen through aeration is best. If increasing aeration is not possible, Aquafix recommends the addition of OxyFresh to the site of the S. natans growth. OxyFresh is designed to help combat low dissolved oxygen conditions. Chlorinating can kill these filaments but will not degrade their problematic sheaths, so bulking may still occur after chlorination.

Under the Microscope and in Your Plant

Sphaerotilus natans/Type 1701 are Gram and Neisser negative filaments that commonly cause bulking to occur. Aquafix tends to group these filaments together as they have similar characteristics and appear in similar plant conditions. However, S. natans tends to be thicker (1.4-1.6 µm) in comparison to Type 1701 (0.8-1 µm). Type 1701 is more likely to have attached growth while S. natans is more likely to exhibit false branching (when two of the same filament get fused together by a sheath and continue to grow in opposite directions). S. natans/Type 1701 can be identified under 400x magnification by their sausage or rod-shaped cells and thick sheath. Even if the cells in these filaments are dead, bulking can still occur due to their difficult-to-degrade sheaths.

Sphaerotilus natans/Type 1701 frequently grow upstream from wastewater plants, anchoring to sewer line walls. If flow rate within the lines increases, these filaments can get broken off the walls and wash into the wastewater plant. Missing or damaged cells within its sheath is an indication that the filaments are not actively growing on-site and may be washing in from an upstream source. Low dissolved oxygen levels, high BOD load, and high flow rates tend to promote the growth/presence of S. natans/Type 1701.

Unique Experience in the Field

During an annual sewer line cleaning, S. natans/Type 1701 were being washed into a municipal wastewater plant. By the time these filaments reached the sludge storage tank, almost all that was left of these filaments were their sheaths. These sheaths then started to accumulate within the storage tank and caused bulking to occur, reducing the amount of sludge that could be stored. The sludge storage tank was dosed with hydrogen peroxide and bleach. This did not solve the settling issue, so Aquafix recommended a 60% cationic polymer coupled with aluminum chlorohydrate to provide more density to the floc and make the sludge storage tank settle better. This improved the settling, preventing the need to pay another site to dispose of the excess sludge.