Filter materials - a possible method to optimise the reduction and recycling of phosphorus in smallscale wastewater treatment systems?

Abstract

One of the environmental goals adopted by the Swedish Parliament concerns the reduction
and extended recycling of nutrients, especially phosphorus (P). Phosphorus is discharged into
the environment through poorly treated wastewater, especially in sparsely populated areas
where few people are connected to the municipal sewer-system. In these areas, small-scale
wastewater treatment systems such as constructed wetlands and infiltration systems have been
used as treatment facilities. These systems have shortcomings and the recycling of phosphorus is very limited. New methods have therefore been searched for. One interesting
method is the use of filter materials that efficiently sorb high amounts of phosphorus and,
when P-saturation is achieved, could be used as soil conditioner or P-fertilisers. The criteria
such materials have to fulfil are that they have a high P-sorption capacity, are available and
that sorbed phosphorus is available for uptake by plants. Different filter materials, natural
materials as well as anthropogenic ones have been tested in different kinds of investigations.
Most materials have been tested in batch experiments, others have been selected for further
studies in column experiments and a few materials have also been tested in field experiments.
A few materials have also been investigated with regard to plant availability of sorbed
phosphorus. The results from the different investigations are promising, even though the
knowledge still is scarce. In order to learn more about these materials, further studies are
suggested.