  Diffuse pollution in rural areas due to agricultural run-off is a widespread
and difficult problem to address due to the vast areas affected. Drainage
channels do receive these polluted waters, but its introduction in the
conventional treatment network is unfeasible. Within this context,
microalgae-based treatment systems could be used as alternative treatment
plants. In this study, a new design of semi-closed (hybrid) tubular horizontal
photobioreactor (HTH-PBR) with low energy requirements has been evaluated for
microalgae cultivation at full-scale (8.5 m3), using agricultural runoff as
feedstock. This novel system was tested in batch and continuous mode during a
total of 4 and 135 days. Considering a full-scale application in an
agricultural context, a batch test was carried out to evaluate the performance
of the system. An increase of 22% in the biomass concentration in 4 days was
registered, and all nutrients were consumed during the first two days. In the
continuous experiment (December- April), a productivity between 2-14 g TSS/m3d
was reached in winter, whereas values up to 76.4 g TSS/m3d were reached at the
end of the study in spring, despite the low nutrients concentration in the
feedstock. The elimination of emerging contaminants was also evaluated,
obtaining the highest removals for the fragrances tonalide and galaxolide (73%
and 68%), and the antiinflamatory diclofenac (61%).
