what does the term 'BIODEGRADABILITY' mean and impacts on our waterways?

Biodegradability (Australian Standard AS(AS) 4351.-1996 provides standard test for determining biodegradability). A biodegradable substance is one which is capable of being broken down within 28 days, by chemical, natural or biological processes, into substances not harmful to the environment. Under the AS, biologically soft surfactants are those which break down within 21 days and as much as 80% of these surfactants are able to be broken down. Whereas biologically hard surfactants break down in the same time period but only 50% is achieved. So some labels on cleaning products for example, don’t make this distinction.  
Products are able to claim being ‘readily biodegradable’ (e.g. some of the products in Hunter Organics) under AS 4351 for just one of their ingredients, even if it makes up as little as 5% of the total product. Readily (or quickly) Biodegradability does not, in itself, make cleaning products low risk and low harm.  So it is important to look for ‘whole product readily biodegradable’ where possible, as this will indicate that ingredients will break down within 28 dys.
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Biodegradability is NOT an indicator of whether a detergent contains phosphate, which even after degrading can leave biologically available phosphates which act as nutrients in waterways.

To be truly biodegradable, a substance or material should break down into carbon dioxide (a nutrient for plants), water and naturally occurring minerals that do not cause harm to the ecosystem (salt or baking soda, for example, are already in their natural mineral state and do not need to biodegrade).