80% of all municipal wastewater treatment plants are affected with bulking sludge problems sometime. In particular, Microthrix parvicella and Nocardia are the most dominant bacterial species that cause issues with a high sludge volume index SVI value (see picture of sewage sludge below).

Thus, sludge flotation from the secondary clarifier in the receiving water can occur.

With the C-ION techology these filamentous sludge bacteria can be combated successfully.

NTP will improve the sludge conditions in two ways.

First, the ionized air will change the charge of sludge flocks and by that sludge flocks will coagulate more efficiently.

Second, NTP will destroy filamentous bacteria without affecting flock-forming microorganisms. The NTP will be introduced in the return sludge stream with less than 20 min. retention time.

There are several other reported positive impacts. For instance, flocculation chemicals for bulking sludge can be omitted or at least strongly reduced; the destruction of filamentous bacteria increases the BOD/COD ratio and improves the denitrification step and enhanced dewatering behavior can be expected.

The effect of NTP on the sludge flock is shown in the following scheme:

In Wörgl wastewater treatment plant (Austria) the filamentous bacteria could be successfully reduced by treatment with the C-ION technology:

SVI of 250 ml/g (left) to SVI of 75 ml/g (right)