In contrast to bacterial degradation, nutrient assimilation by plants is limited by surface, as photosynthesis is dependent on solar radiation. Therefore, to achieve maximum nutrient recycling rates, trickling filter systems should provide
a large surface area for plant growth and photosynthesis in relation to their volume. In theory, a planted trickling filter could double its nutrient recycling capacity when constructed halve as deep and with a surface twice as large. Given this, possible applications of the concept would not be in the classic wastewater treatment
disciplines where land use is regarded as loss of efficiency, but rather in industry sectors already using large surfaces for plant production. In other words, the idea is not to replace existing filter techniques in municipal wastewater treatment
but to recruit producers of hydroponic vegetables as recipients and users of nutrient-rich wastewaters. This approach reflects postulations that suggested to re-integrate agronomic production forms nowadays separated in monocultures to combined production systems [6].