The key active in RootOut, diquat, has a long history of effective herbicide activity in the agricultural arena. Using diquat in a complex formulation has resulted in a product with a low hazard profile, high effectiveness in controlling tree roots in sewers and a very low potential to harm sewage treatment plants.

At application strength RootOut is not classified as a Dangerous Good as per the Australian Dangerous Goods Code of Practice, nor is it classified as a Hazardous Substance as per the criteria of the Australian Safety and Compensation Council (formerly NOHSC). The product may therefore be used with minimal health risk to operators applying the product to sewer lines and also low health risk to the general public.

The low health risk of RootOut at the application strength is attributed to the physical properties of diquat in an aqueous solution. Diquat has similar physical properties to table salt; it is an ionic molecule that completely dissolves in water to form a stable solution that does not generate hazardous vapours.

Like table salt, diquat in an aqueous solution has a very long shelf life. Analytical tests have demonstrated the product’s shelf life to be greater than two years when in its dilute form. When compared to alternative root foaming products, the extended stability of the diquat molecule eliminates the potential application of out-of-specification foam:

* Metham sodium based products need to be used within 16 hours once diluted as the metham sodium converts to MITC gas in the charge tank, reducing the level of active delivered to the roots in the sewer lines; * Once mixed with water for application, dichlobenil based products need to be constantly agitated until used. If not, the material settles out of solution, resulting in a lower dichlobenil level available for foaming.

The reduction of available active ingredient, due to extended storage or the lack of charge tank agitation, results in a decreased level of active delivered to the tree roots, potentially resulting in minimal tree root removal.

RootOut has been registered in Australia since 2002 and has already demonstrated remarkable results. In the USA, RootOut is known as Razorooter II, and has been used for approximately 10 years with results that have made it the product of choice for managing otherwise chronic choke problems caused by tree roots.

The success of sewer maintenance programs utilising RootOut has been attributed to the resulting three year period between treatments, with cost reductions of greater than 60 per cent being consistently being reported. In addition to the three year application cycle, a further benefit of a proactive RootOut sewer maintenance program is the eradication of the need to mechanically cut roots prior to foaming. Mechanical root cutting is only implemented with severe chokes that prevent the travel of the foaming nozzle up the sewer line.

When compared to the alternative methods of root removal (both chemical foaming and physical cutting) the application of RootOut is relatively quick and easy, resulting in the better utilisation of resources.

In addition to tangible cost savings, significant reductions in choke rates are observed when RootOut has been incorporated into proactive sewer maintenance programs. In the USA, 70 and 90 per cent choke reductions have been observed over three and ten year usage periods respectively.

Historically, the use of chemicals in sewerage systems has resulted in environmental and treatment plant concerns. With approximately ten years of extensive use as a root foaming agent, RootOut has demonstrated its suitability as an agent for the removal of tree roots from sewer lines.

• RootOut is a contact herbicide that kills tree roots on contact, but is not translocated through the tree; therefore, the product may be used to remove tree roots from sewers without damaging aboveground foliage.

• RootOut acts only as a herbicide, so unlike metham sodium based products, it does not kill essential sewer bacteria required for the decay of dead tree roots; this eliminates the ‘petrifaction’ of tree roots that often cause the choking of lines soon after treatment.

• The active in RootOut, diquat, is adsorbed (deactivated) by sewage and clay-based materials. Therefore, active material that is not consumed in killing tree roots in the sewer is deactivated as the foam collapses and is mixed with the sewage. This removal mechanism results in extremely low concentrations of active reaching waste water treatment facilities. No adverse effects have been recorded in small treatment plants (2 ML/d) treating approximately 800 metres of 150 mm line per day.

• No impacts have been observed where treatment plant residues have been used for crop fertilisation and irrigation, or the common practice of discharging to ocean outfalls.

Although RootOut is one of the newest products introduced to the global sewer root control market, its success in the USA and to a limited extent in Australia is rapidly positioning RootOut as the product of choice in proactive root maintenance programs.