The developed technology is based on the natural capacity of streams to clean-up themselves from pollutants by utilizing a proper complex of biological, physical and chemical self-purification processes. If a stream does not have some of these conditions, the necessary complex could be created artificially. As a result, a wider spectrum of pollutants, including organic and inorganic polluting particles, and also pathogens could be eliminated from the entire water body as well as from the benthic soil.

The key factor in the development of the new long-term clean-up methodology which utilizes the natural self-purification processes in streams was the disastrous toxic spill in Etobicoke Creek (Ontario, Canada) in May, 1997. While investigating the heavy polluted sites of the creek during its self-restoration, ONCFEC discovered the new self-purification process (natural froth formation). A typical example of the latter is the froth on river surface downstream from Niagara Falls.

One of the important processes in stream self-purification is the decomposition of total organics by fungi, bacteria and other microorganisms. While the decomposition takes place, the entire water as well as the benthic soil is periodically enriched with biological surfactants and the generated dissolved biogases. Further, this system also contains dissolved air and all kinds of polluting particles, including man-made surfactants. Therefore, the next step in river self-purification, the generating of biogas and air bubbles, and the attaching of the polluting particles to the bubbles in the presence of surfactants should be considered. For the latter, the proper level of turbulence must exist. Water cascading over weirs, waterfalls and other obstacles, creating the shallow-turbulent character of water current, is the suitable condition.

The particle-bubble aggregates will rise to the water surface and concentrate in the froth as well as the surrounding thin top layer of surface water upstream from the collector. The resulting froth comprises a high concentration of polluting agents (organic and inorganic, including pathogens).

By testing a large number of the froth and the water samples (See Table 1 and Table 2), we proved our hypothesis that rivers possess their own environmental capacity to purify themselves from pollutants through the natural froth formation process (See Photo 1).

As a result, we can, without adding any chemicals, intervene directly on site in the clean-up of the stream that is heavily polluted from all kinds of polluting sources, including the non-point ones.

Table 1. Comparison Test Results for the Creek Samples.


Top layer of surface water downstream from the collector


Top layer of surface water upstream from the collector next to it


Filtered mixture from the froth



Zinc (Zn):


0.01 0.10 0.24



a) total Detection limit: 0.03mg/L

0.00 0.03 0.17


Ammonia (N):


0.14 4 20




0.03 0.35 1.01

Table 2. Comparison test results for E. coli and fecal coliforms.

Samples from Etobicoke Creek: E. coli Colonies Counted CFU/100mL Fecal coliforms 5TMPN/100mL


Water body:


10 920


Mixture from Froth:


700 >1600


Ontario Provincial Water Quality Objectives:


100 N/A

Photo 1. The froth collector, placed at the creek site.